tag:theconversation.com,2011:/ca/topics/food-webs-38231/articlesFood webs – The Conversation2023-12-19T13:16:50Ztag:theconversation.com,2011:article/2188992023-12-19T13:16:50Z2023-12-19T13:16:50ZWild ‘super pigs’ from Canada could become a new front in the war on feral hogs<figure><img src="https://images.theconversation.com/files/566082/original/file-20231215-23-irn2uo.jpg?ixlib=rb-1.1.0&rect=8%2C4%2C2986%2C1958&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Feral hogs' long snouts and tusks allow them to rip and root their way across the landscape in search of food. </span> <span class="attribution"><a class="source" href="https://flic.kr/p/ehmMiS">USDA/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>They go by many names – pigs, hogs, swine, razorbacks – but whatever you call them, <a href="https://www.invasivespeciesinfo.gov/profile/wild-boar">wild pigs</a> (<em>Sus scrofa</em>) are one of the <a href="https://www.washingtonpost.com/science/2019/08/06/think-feral-hogs-is-joke-millions-more-are-rampaging-across-us/">most damaging invasive species</a> in North America. They cause millions of dollars in crop damage yearly and harbor dozens of pathogens that threaten humans and pets, as well as meat production systems.</p>
<p>Although wild pigs have been <a href="https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/operational-activities/feral-swine/sa-fs-history">present in North America for centuries</a>, their populations have rapidly expanded over the past several decades. Recent studies estimate that since the 1980s the wild pig population in the United States has <a href="https://doi.org/10.1007/s10530-019-01983-1">nearly tripled</a> and <a href="https://doi.org/10.1002/wsb.808">expanded from 18 to 35 states</a>. More recently, they have <a href="https://www.cbc.ca/news/canada/british-columbia/invasive-pigs-canada-1.5136431">spread rapidly across Canada</a>, and these populations are <a href="https://apnews.com/article/wild-pigs-feral-swine-canada-minnesota-border-e59a542efb3c64d5f4b136fc137b7665">threatening to invade the U.S. from the north</a>.</p>
<p>The wild pigs in Canada are unique because they were originally crossbred by humans to be larger and more cold-hardy than their feral cousins to the south. This suite of traits has earned them the name “super pigs” for good reason. Adults can reach weights exceeding 500 pounds, which is twice the size of the largest wild pigs sampled across many U.S. sites in <a href="http://dx.doi.ORG/10.1002/ece3.9853">a 2022 study</a>. </p>
<p>As a <a href="https://www.researchgate.net/profile/Marcus_Lashley">wildlife ecologist</a>, I study how wild pigs alter their surroundings and affect other wildlife species. <a href="https://www.doi.gov/invasivespecies/early-detection-and-rapid-response">Early detection and rapid response</a> is of utmost importance in eradicating an invasive species, because invasions are more manageable when populations are small and geographically restricted. This is especially true for species like wild pigs that have a high reproductive rate, can readily move into new areas and can change their behavior to avoid being captured or killed.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/RpwHJT4t-Zo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Minnesota wildlife experts are keeping a wary eye on their northern border for signs of wild ‘super pigs’ moving down from Canada.</span></figcaption>
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<h2>Omnivores on the hoof</h2>
<p>Much concern over the spread of wild pigs has focused on economic damage, which was recently estimated at <a href="https://www.usatoday.com/story/news/nation/2023/11/21/which-states-have-the-worst-wild-hog-problem/71658126007/">about US$2.5 billion annually</a> in the United States.</p>
<p>Wild pigs have a unique collection of traits that make them problematic to humans. When we told one private landowner about the results from our studies, he responded: “That makes sense. Pigs eat all the stuff the other wildlife do – they just eat it first, and then they go ahead and eat the wildlife, too. They pretty much eat anything with a calorie in it.” </p>
<p>More scientifically, wild pigs are called extreme generalist foragers, which means they can survive on many different foods. A <a href="https://doi.org/10.1111/mam.12015">global review of their dietary habits</a> found that plants represent 90% of their diet – primarily agricultural crops, plus the fruits, seeds, leaves, stems and roots of wild plants.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A male lesser prairie-chicken inflates his orange throat sacs to call potential mates." src="https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=510&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=510&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566078/original/file-20231215-23-4f6gba.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=510&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lesser prairie chickens are a ground-nesting species – found in parts of Colorado, Kansas, New Mexico, Oklahoma and Texas – that is listed under the Endangered Species Act. Feral hogs prey on the birds and their eggs and damage the birds’ habitat by rooting up and consuming native plants and spreading invasive plant seeds.</span>
<span class="attribution"><a class="source" href="https://www.fws.gov/media/lesser-prairie-chicken-lek">Greg Kramos/USFWS</a></span>
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</figure>
<p>Wild pigs also eat most small animals, along with fungi and invertebrates such as insect larvae, clams and mussels, particularly in places where pigs are not native. For example, a 2019 study reported that wild pigs were digging up eggs laid by endangered loggerhead sea turtles on an island off the coast of South Carolina, <a href="https://doi.org/10.1016/j.actao.2019.103442">reducing the turtles’ nesting success to zero in some years</a>.</p>
<p>And these pigs do “just eat it first.” They compete for resources that other wildlife need, which can have <a href="http://dx.doi.org/10.1007/s10530-012-0229-6">negative effects on other species</a>. </p>
<p>However, they likely do their most severe damage through predation. Wild pigs kill and eat rodents, deer, birds, snakes, frogs, lizards and salamanders. This probably best explains why colleagues and I found in <a href="https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ece3.5360">one study</a> that forest patches with wild pigs had 26% fewer mammal and bird species than similar forest patches without pigs. </p>
<p>This decrease in diversity was similar to that found with <a href="https://doi.org/10.1016/bs.aecr.2016.10.002">other invasive predators</a>. And our findings are consistent with a global analysis showing that invasive mammalian predators that have no natural predators themselves – especially generalist foragers like wild pigs – <a href="https://doi.org/10.1073/pnas.1602480113">cause by far the most extinctions</a>. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1734983386941333818"}"></div></p>
<h2>Altering ecosystems</h2>
<p>Many questions about wild pigs’ ecological impacts have yet to be answered. For example, they may harm other wild species indirectly, rather than eating them or depleting their food supply. </p>
<p>Our work shows that wild pigs <a href="https://doi.org/10.1016/j.fooweb.2022.e00270">can alter the behavior of common native wildlife species</a>, such as raccoons, squirrels and deer. Using trail cameras, we found that when wild pigs were present, other animals altered their activity patterns in various ways to avoid them. Such shifts may have additional cascading effects on ecosystems, because they change how and when species interact in the food web.</p>
<p>Another major concern is wild pigs’ potential to spread disease. They carry numerous pathogens, including brucellosis and tuberculosis. However, little ecological research has been done on this issue, and scientists have not yet demonstrated that an increasing abundance of wild pigs reduces the abundance of native wildlife via disease transmission. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/vIHbFQFdyaM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Feral hogs can be seen rooting up the soil in this trail camera footage from Alabama.</span></figcaption>
</figure>
<p>Interestingly, in their native range in Europe and Asia, pigs do not cause as much ecological damage. In fact, some studies indicate that they may <a href="http://biozoojournals.ro/nwjz/content/v13n2/nwjz_e161706_Baruzzi.pdf">modify habitat in important ways</a> for species that have evolved with them, such as frogs and salamanders. </p>
<p>So far, however, there is virtually no scientific evidence that feral pigs provide any benefits in North America. One <a href="http://dx.doi.org/10.1007/s10530-012-0229-6">review of wild pig impacts</a> discussed the potential for private landowners plagued with pigs to generate revenue from selling pig meat or opportunities to hunt them. And it’s possible that wild pigs could serve as an alternative food source for imperiled large predators, or that their wallowing and foraging behavior in some cases could mimic that of locally eradicated or extinct species. </p>
<p>But the scientific consensus today is that in North America, wild pigs are a growing threat to both ecosystems and the economy. It is unclear how invading super pigs would contribute to the overall threat, but bigger pigs likely cause more damage and are generally better predators and competitors. </p>
<p>While efforts to control wild pigs <a href="https://www.nrcs.usda.gov/feral-swine-eradication-and-control-pilot-program">are well underway</a> in the U.S., incursions by Canadian super pigs may complicate the job. Invasive super pigs make for catchy headlines, but their potential effects are no joke.</p>
<p><em>This is an updated version of <a href="https://theconversation.com/feral-pigs-harm-wildlife-and-biodiversity-as-well-as-crops-120066">an article</a> originally published on Aug. 26, 2019.</em></p><img src="https://counter.theconversation.com/content/218899/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marcus Lashley receives funding from USDA Wildlife Services.</span></em></p>Feral hogs are one of the most destructive invasive species in North America, harming land, crops and wildlife.Marcus Lashley, Associate Professor of Wildlife Ecology, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1998262023-02-15T12:21:43Z2023-02-15T12:21:43ZInsects are vanishing worldwide – now it’s making it harder to grow food<figure><img src="https://images.theconversation.com/files/510040/original/file-20230214-28-nfrfs.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5657%2C3799&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-green-corn-growing-on-field-2012418830">Catherine_P/Shutterstock</a></span></figcaption></figure><p>Over the past 20 years a steady trickle of scientific papers has reported that there are fewer insects than there used to be. Both the combined weight (what scientists call biomass) and diversity of insect species have declined. Some studies were based on sightings by amateur entomologists, while others involved scientists counting the number of bugs splattered on car windshields. Some collected flying insects in traps annually for years and weighed them.</p>
<p>In the past six years, this trickle has become a flood, with more and more sophisticated studies confirming that although not all insect species are declining, many are in serious trouble. A 2020 <a href="https://www.science.org/doi/10.1126/science.aax9931">compilation</a> of 166 studies estimated that insect populations were on average declining globally at a rate of 0.9% per year. But the declines are uneven. Even within the same environments, populations of some insect species have waned, while others have remained stable and still some others increased. The reasons for these differences between insects are unknown, though evidently some are more resilient than others.</p>
<p>Until recently, much of the evidence has been drawn from protected areas in Europe and to a lesser extent North America. So what is the picture like elsewhere? <a href="https://www.science.org/doi/10.1126/sciadv.ade9341">A new study</a> offers fresh data on the seasonal migrations of insects in east Asia. These insects, many of them pest species, fly north in spring every year to take advantage of the new growing season, and fly south in autumn to escape the cold.</p>
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<img alt="A sky filled with monarch butterflies." src="https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=481&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=481&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510041/original/file-20230214-24-2yjxp1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=481&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Insects can travel thousands of miles in seasonal migrations.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/monarch-butterfly-biosphere-reserve-michoacan-mexico-1786064138">Javarman/Shutterstock</a></span>
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<p>A progressive fall in the enormous numbers of these migrants indicates that insect declines are indeed a global problem.</p>
<h2>Millions of migrating insects</h2>
<p>Between 2003 and 2020, scientists from the Chinese Academy of Agricultural Sciences in Beijing caught almost 3 million migrating insects from high-altitude searchlight traps on Beihuang Island off the coast of northeast China. A further 9 million insects were detected from radar records. In all, 98 species were identified and counted, most of which were either plant-eating crop pests or insects that are their natural enemies – predators and parasites. Over the whole 18-year period, the yearly tally of all identified insects fell by 7.6%, a steady downward trend of 0.4% a year.</p>
<p>Insect declines clearly are occurring on a large scale in Asia, just as they have been in Europe and North America. It seems reasonable to assume that the causes are the same. Although we don’t know for certain what those causes are, it seems likely that they operate all over the world.</p>
<p>The study also showed that pest insects such as the black cutworm moth, whose caterpillars attack a wide variety of vegetable crops, are as strongly affected by the global decline of insects as non-pest species such as bees and butterflies that were the subjects of most of the previous European and American studies.</p>
<p>We are so used to considering insects as pests that it is tempting to think that, in a world with fewer of them, agriculture might prosper as never before. This new study reveals why that is not the case. The researchers used detailed entomological records from the past to construct a complex food web showing how each of the insect pest species caught in the searchlight traps can be eaten by several kinds of insect predators and parasites, often termed “natural enemies”. As an example, black cutworm caterpillars are eaten by green lacewings, among others. </p>
<figure class="align-center ">
<img alt="A long, green insect with curved, transparent wings and small, red eyes." src="https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510043/original/file-20230214-22-5s7zav.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Green lacewings eat crop pests – but there are fewer of them in farm fields.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/extreme-magnification-lacewing-pest-control-465774065">Cornel Constantin/Shutterstock</a></span>
</figcaption>
</figure>
<p>The researchers compared how fast 124 pests had declined alongside each of their natural enemies. Over the 18-year study, the abundance of natural enemy species fell at a rate of 0.65% a year, while the plant-eating prey did not decrease in number at all, on average. This suggests that beneficial natural enemy species are more likely to decline than the pests that they feed on. As a result, farmers must either tolerate lower crop yields or use even more chemical insecticides to control pests, leading to still worse declines.</p>
<p>Although it is tempting to point a finger at <a href="https://theconversation.com/a-common-soil-pesticide-cut-wild-bee-reproduction-by-89-heres-why-scientists-are-worried-155985">pesticides</a>, <a href="https://theconversation.com/why-the-changing-colour-of-our-streetlights-could-be-a-danger-for-insect-populations-166470">bright streetlights</a> or <a href="https://theconversation.com/climate-change-triggering-global-collapse-in-insect-numbers-stressed-farmland-shows-63-decline-new-research-170738">climate change</a>, insect declines almost certainly have multiple causes that overlap. </p>
<p>The most frequently named suspect is agricultural intensification. This term covers a multitude of sins. Farm mechanisation, the eradication of hedges, crop monocultures, the increased use of chemical fertilisers and regular applications of pesticides are all intended to produce fields without weeds, pests or diseases. Only a reduced range of wild plants and animals can survive in the narrow field margins and neighbouring roadside verges that remain. Another way of putting it is that farmers have made fields unwelcoming to most insects.</p>
<p>Intensification is designed to ensure that as much as possible of the farm ecosystem’s energy flow is diverted into growing crops and livestock for human consumption. It has been estimated that <a href="https://www.pnas.org/doi/full/10.1073/pnas.0704243104">24% of all plant growth</a> annually is now appropriated by humans, and this rises to a staggering 69% on cropland. These figures roughly doubled over the 20th century. It’s no wonder that insects don’t do well in landscapes such as these, and farmland occupies <a href="https://www.fao.org/sustainability/news/detail/en/c/1274219/">almost 40%</a> of the land.</p>
<h2>Why you’ll miss bugs</h2>
<p>Insects are by far the most numerous of all animals on Earth. The estimated <a href="https://www.science.org/doi/10.1126/sciadv.abq4049#">global total</a> of new insect material that grows each year is an astonishing 1,500 million tonnes. Most of this is immediately consumed by an upward food chain of predators and parasites, so that the towering superstructure of all the Earth’s animal diversity is built on a foundation of insects and their arthropod relatives.</p>
<p>If insects decline, then other wild animals must inevitably decline too. There is already evidence that this is happening. In North America, insect-eating bird species experienced an <a href="https://academic.oup.com/condor/article/123/1/duaa059/6063623">average decline in population size</a> of almost 10 million over the past 50 years, while those for which insects are not essential prey did not decline at all. In Europe, parallel declines of insectivorous swallows, house martins and swifts have all been <a href="https://avianres.biomedcentral.com/articles/10.1186/s40657-021-00278-1">linked to insect declines</a>.</p>
<p>While it’s true that a few insects are a menace to humans (disease-carrying mosquitoes come to mind), the vast majority of insects are friendly: they pollinate crops, provide natural pest control, recycle nutrients and form soil by aiding the decomposition of dead animals and plants. All these processes will slow down if insects become scarce. The economic value of these services is incalculable – agriculture could not continue for long without them.</p>
<p>Our insect friends are being crowded out. Somehow, we must find ways to make more room for them.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Stuart Reynolds does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research from China shows how the loss of insects is destabilising food webs.Stuart Reynolds, Emeritus Professor of Biology, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1962862022-12-17T03:49:16Z2022-12-17T03:49:16ZChildren born today will see literally thousands of animals disappear in their lifetime, as global food webs collapse<figure><img src="https://images.theconversation.com/files/501198/original/file-20221215-15841-3aidkq.jpg?ixlib=rb-1.1.0&rect=23%2C23%2C5152%2C3422&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Frida Lannerstrom/Unsplash</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Climate change is one of the <a href="https://www.science.org/doi/10.1126/science.aaa4984">main drivers</a> of species loss globally. We know more plants and animals will die as heatwaves, bushfires, droughts and other natural disasters worsen.</p>
<p>But to date, science has vastly underestimated the true toll climate change and habitat destruction will have on biodiversity. That’s because it has largely neglected to consider the extent of “<a href="https://www.nature.com/articles/s41598-018-35068-1">co-extinctions</a>”: when species go extinct because other species on which they depend die out.</p>
<p>Our <a href="http://doi.org/10.1126/sciadv.abn4345">new research</a> shows 10% of land animals could disappear from particular geographic areas by 2050, and almost 30% by 2100. This is more than double previous predictions. It means children born today who live to their 70s will witness literally thousands of animals disappear in their lifetime, from lizards and frogs to iconic mammals such as <a href="https://theconversation.com/climate-change-and-wildlife-3-studies-that-reveal-the-devastating-toll-on-africas-animals-192412">elephants</a> and <a href="https://theconversation.com/stopping-koala-extinction-is-agonisingly-simple-but-heres-why-im-not-optimistic-141696">koalas</a>. </p>
<p>But if we manage to dramatically reduce carbon emissions globally, we could save thousands of species from local extinction this century alone.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500026/original/file-20221209-35163-sgmihk.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ravages of drought will only worsen in coming decades.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
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<strong>
Read more:
<a href="https://theconversation.com/this-is-australias-most-important-report-on-the-environments-deteriorating-health-we-present-its-grim-findings-186131">This is Australia's most important report on the environment's deteriorating health. We present its grim findings</a>
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<h2>An extinction crisis unfolding</h2>
<p>Every species depends on others in some way. So when a species dies out, the repercussions can ripple through an ecosystem.</p>
<p>For example, consider what happens when a species goes extinct due to a disturbance such as habitat loss. This is known as a “primary” extinction. It can then mean a predator loses its prey, a <a href="https://www.nature.com/articles/ncomms2723">parasite loses its host</a> or a <a href="http://doi.org/10.1126/science.1232728">flowering plant loses its pollinators</a>. </p>
<p>A real-life example of a co-extinction that could occur soon is the potential loss of the critically endangered <a href="https://www.zoo.org.au/fighting-extinction/local-threatened-species/mountain-pygmy-possum/">mountain pygmy possum</a> (<em>Burramys parvus</em>) in Australia. Drought, habitat loss, and other pressures have caused the rapid decline of its primary prey, the <a href="https://australian.museum/learn/animals/insects/bogong-moth/">bogong moth</a> (<em>Agrotis infusa</em>).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=605&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=605&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=605&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=760&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=760&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500021/original/file-20221209-26397-b9fnz3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=760&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">All species are connected in food webs. The spider shown here is an elongated St. Andrews cross spider <em>Argiope protensa</em> from Calperum Reserve, South Australia.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<p>Research suggests co-extinction was a <a href="https://www.sciencedirect.com/science/article/pii/S016953470800195X">main driver</a> of past extinctions, including the five previous <a href="https://theconversation.com/what-is-a-mass-extinction-and-are-we-in-one-now-122535">mass extinction events</a> going back many hundreds of millions of years. </p>
<p>But until now, scientists have not been able to interconnect species at a global scale to estimate how many co-extinctions will occur under projected climate and land-use change. Our research aimed to close that information gap.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500177/original/file-20221211-64867-ft8xxk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The unprecedented bushfires of 2019/2020 on Kangaroo Island killed thousands of individuals in many different wildlife populations.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/our-laws-fail-nature-the-governments-plan-to-overhaul-them-looks-good-but-crucial-detail-is-yet-to-come-196126">Our laws fail nature. The government’s plan to overhaul them looks good, but crucial detail is yet to come</a>
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<hr>
<h2>The fate of wildlife</h2>
<p>Using one of Europe’s <a href="https://www.csc.fi">fastest supercomputers</a>, we built a massive <a href="http://doi.org/10.1126/sciadv.abn4345">virtual Earth</a> of interconnected food-web networks. We then applied scenarios of projected climate change and land-use degradation such as deforestation, to predict biodiversity loss across the planet. </p>
<p>Our virtual Earths included more than 15,000 food webs that we used to predict the interconnected fate of species to the end of the 21st Century.</p>
<p>Our models applied three scenarios of projected climate change based on future pathways of global carbon emissions. This includes the high-emissions, business-as-usual scenario that predicts a mean global temperature increase of <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf">2.4°C by 2050, and 4.4°C by 2100</a>. </p>
<p>If this scenario becomes reality, ecosystems on land worldwide will lose 10% of current animal diversity by 2050, on average. The figure rises to 27% by 2100. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/worried-about-earths-future-well-the-outlook-is-worse-than-even-scientists-can-grasp-153091">Worried about Earth's future? Well, the outlook is worse than even scientists can grasp</a>
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<p>Adding co-extinctions into the mix causes a 34% higher loss of biodiversity overall than just considering primary extinctions. This is why previous predictions have been too optimistic.</p>
<p>Worse still is the fate of the most vulnerable species in those networks. For species highest in food chains (<a href="https://education.nationalgeographic.org/resource/omnivores">omnivores</a> and <a href="https://education.nationalgeographic.org/resource/carnivores">carnivores</a>), the loss of biodiversity due to co-extinctions is a whopping 184% higher than that due to primary extinctions.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500018/original/file-20221209-35075-n77srn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Without enough prey, predators like this African lion, will perish.</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<p>We also predict that the greatest relative biodiversity losses will occur in areas with the highest number of species already – a case of the rich losing their riches the fastest. </p>
<p>These are mainly in areas recognised as “<a href="https://www.conservation.org/priorities/biodiversity-hotspots">biodiversity hotspots</a>” — 36 highly threatened areas of the Earth containing the most unique species, such as <a href="https://www.cepf.net/our-work/biodiversity-hotspots/southwest-australia">Southwest Australia</a> and South Africa’s <a href="https://www.cepf.net/our-work/biodiversity-hotspots/cape-floristic-region">Cape Floristic region</a>. This is because the erosion of species-rich food webs makes biological communities more susceptible to future shocks.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/3IeU8L9CaFk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Tropical forest is the main ecosystem found in many biodiversity hotspots worldwide.</span></figcaption>
</figure>
<p>We also detected that these networks of interacting species themselves will change. We used a measure of “connectance”, which refers to the density of network connections. Higher connectance generally means the species in a food web have more links to others, thereby making the entire network more resilient.</p>
<p>Connectance, we learnt, will decline between 18% and 34% by the end of this century in the worst-case climate scenario. </p>
<p>This reduction in connectance was also driven by the loss of some key species occupying the most important positions in their local networks. These could be top predators such as wolves or lions keeping plant eaters in check, or an abundant insect eaten by many different insectivores.</p>
<p>When such highly connected species go extinct, it makes the network even less resilient to disturbance, thereby driving even more loss of species than would otherwise have occurred under a <a href="https://www.nature.com/articles/ncomms12462">natural ecological regime</a>. This phenomenon illustrates the unprecedented challenges biodiversity faces today.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500017/original/file-20221209-33845-ws570q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Adieu, koala?</span>
<span class="attribution"><span class="source">CJA Bradshaw</span></span>
</figcaption>
</figure>
<h2>Can we minimise the threat?</h2>
<p>As the <a href="https://www.unep.org/events/conference/un-biodiversity-conference-cop-15">United Nations Biodiversity Conference</a> winds up this week in Montreal, Canada, governments are trying to agree on a new set of global actions to <a href="https://www.unep.org/un-biodiversity-conference-cop-15">halt and reverse nature loss</a>. </p>
<p>It follows the recent <a href="https://unfccc.int/event/cop-27">COP27</a> climate change summit in Egypt, where the resulting agreement was <a href="https://theconversation.com/cop27-one-big-breakthrough-but-ultimately-an-inadequate-response-to-the-climate-crisis-194056">inadequate</a> to deal with the global climate crisis.</p>
<p>We hope our findings will, in future, help governments identify <a href="https://theconversation.com/avoiding-climate-breakdown-depends-on-protecting-earths-biodiversity-can-the-cop15-summit-deliver-195902">which policies</a> will lead to fewer extinctions.</p>
<p>For example, if we manage to achieve a lower carbon-emissions pathway that limits global warming to <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf">less than 3°C</a> by the end of this century, we could limit biodiversity loss to “only” 13%. This would translate into saving thousands of species from disappearing.</p>
<p>Clearly, humanity has so far underestimated its true impacts on the diversity of life on Earth. Without major changes, we stand to lose much of what sustains our planet.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cop27-one-big-breakthrough-but-ultimately-an-inadequate-response-to-the-climate-crisis-194056">COP27: one big breakthrough but ultimately an inadequate response to the climate crisis</a>
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<img src="https://counter.theconversation.com/content/196286/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corey J. A. Bradshaw receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Giovanni Strona does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research finds nearly 30% of land animals could disappear form their local area by 2100 due to climate change and habitat destruction. This is more than double previous predictions.Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityGiovanni Strona, Doctoral program supervisor, University of HelsinkiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1928952022-12-05T13:25:26Z2022-12-05T13:25:26ZWeasels, not pandas, should be the poster animal for biodiversity loss<figure><img src="https://images.theconversation.com/files/498335/original/file-20221130-20-3djrpi.jpg?ixlib=rb-1.1.0&rect=6%2C3%2C2037%2C1348&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A short-tailed weasel in Yellowstone National Park, Wyoming.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/2baqDL7">Jacob W. Frank, NPS/Flickr</a></span></figcaption></figure><p>At the <a href="https://www.unep.org/events/conference/un-biodiversity-conference-cop-15">United Nations biodiversity conference</a> that opens in Montreal on Dec. 7, 2022, nations aim to create a new global framework for transforming humanity’s relationship with nature. The <a href="https://www.cbd.int/conferences/2021-2022">conference logo</a> features a human reaching to embrace a panda – but from an ecological perspective, a weasel or badger would be a more appropriate choice.</p>
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<a href="https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphic of a girl reaching to embrace a panda" src="https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=925&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=925&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=925&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1162&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1162&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498319/original/file-20221130-8088-3h45m9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1162&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Logo for the COP 15 conference in Montreal, which was delayed from its original 2020 date due to COVID-19.</span>
<span class="attribution"><a class="source" href="https://www.cop15news.com/en/index.htm">Convention on Biological Diversity</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Large mammals with widespread appeal, also known as <a href="https://animals.howstuffworks.com/endangered-species/charismatic-megafauna.htm">charismatic megafauna</a>, often represent the highest achievement in biodiversity protection. As the logic goes, saving the tiger, polar bear, wolf or lion means saving an entire ecosystem, since these species often have large ranges and may sit at the top of food chains.</p>
<p>But research shows that, relatively speaking, many large charismatic species aren’t doing that badly in North America. Wolves are <a href="https://www.nytimes.com/2022/03/11/science/california-wolves-misinformation.html">repopulating California</a>, where their last wild ancestor was killed in 1924. Cougars could become <a href="https://doi.org/10.1016/j.ecolmodel.2015.09.026">reestablished across the Midwest</a> over the next several decades. Black bears have regained much of their range in the <a href="https://www.bearbiology.org/wp-content/uploads/2017/10/Scheick_and_McCown_2014_Ursus.pdf">eastern U.S</a>, to the point where many states have a <a href="https://www.outdoorlife.com/story/hunting/record-black-bear-hunting-harvest/">bear hunting season</a>. Similar stories are playing out across Europe, where even large carnivores like the lynx and wolverine are <a href="http://dx.doi.org/10.1126/science.1257553">recovering</a>. </p>
<p>For small carnivores like weasels, skunks and foxes, it’s a different story. These species and their relatives have equal or greater impacts on the ecosystems they inhabit than larger species like wolves. They even provide benefits for humans by preying on rodents that eat crops and infest our houses. Yet small carnivores are of increasing conservation concern because their populations are declining dramatically in many places.</p>
<h2>Many threats but no single cause</h2>
<p>While small carnivores don’t typically get as much public attention as larger species, conservation biologists have been trying to arrest their decline for decades. </p>
<p>For example, the black-footed ferret, a member of the same family as weasels and minks, has been <a href="https://www.fws.gov/species/black-footed-ferret-mustela-nigripes">on the U.S. endangered species list</a> since the list was created in 1973. As recently as the early 1900s there were thousands of black-footed ferrets across western prairies. Today scientists estimate there are <a href="https://blackfootedferret.org/">fewer than 400 left in the wild</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two ferrets with black feet and eye masks, one peeking out of a pipe" src="https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498333/original/file-20221130-22-dzg6n4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The U.S. Fish and Wildlife Service is breeding black-footed ferrets in captivity in northern Colorado. Restoring the endangered ferret is considered a key step in reviving prairie ecosystems.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/oct-29-there-are-48-outdoor-pre-conditioning-pens-that-news-photo/186801918">Kathryn Scott Osler/The Denver Post via Getty Images</a></span>
</figcaption>
</figure>
<p>Recent evidence suggests that even the most common and widespread small carnivores are in decline. A 2005 study estimated that eastern spotted skunks, which are rarely seen today but historically occurred across much of the U.S. east of the Rocky Mountains, had <a href="https://doi.org/10.1017/S1367943005001964">declined in number by 90% over the preceding 50 years</a>. </p>
<p>I led an effort in 2021 to determine the status of the most widespread of small carnivores in North America – <a href="https://doi.org/10.1371/journal.pone.0254387">weasels</a>. We found range-wide decreases dating back to the 1960s that paralleled the decline of spotted skunks. </p>
<p>Scientists have a very poor understanding of what has caused losses of weasels and most other small carnivores. We suspect that many stresses may be involved, including changing farming practices, diseases and new carnivores like house cats, domestic dogs, raccoons and striped skunks that follow human development and outcompete or eat native small carnivores. </p>
<p>What we do know is that North America is not unique. Small carnivores are declining globally at an alarming rate. A 2021 review suggests that over the past couple of decades <a href="https://doi.org/10.1016/j.biocon.2021.109005">over half of all small carnivores have declined in number</a>, and a quarter are at risk of extinction. Proportionally, these are the same levels of decline and endangerment as the better-publicized threats to large carnivores. </p>
<h2>Short-legged ecosystem indicators</h2>
<p>We also know that compared with larger species, small carnivores have shorter lives and use smaller areas. This allows them to respond quickly to even minor fluctuations in temperature, habitat change and food availability. In my <a href="https://scholar.google.com/citations?user=CjwvzoIAAAAJ&hl=en&oi=sra">research over the past 23 years</a>, I have learned that these attributes make small carnivores sensitive indicators of even minor shifts in how well their ecosystems work. </p>
<p>A prime example comes from the Channel Islands off the coast of California, home to the diminutive <a href="https://www.nps.gov/chis/learn/nature/island-fox.htm">island fox</a>, a species found nowhere else on earth. In the late 1990s land and wildlife managers noticed a decline in island foxes, which coincided with the decline of bald eagles and arrival of golden eagles on the islands. Golden eagles preyed on the foxes, as well as on non-native wild pigs. At one point the fox population was reduced to fewer than 100 individuals. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2AVRSGkartg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Saving California’s island foxes required reconstructing an ecosystem that human actions had drastically altered.</span></figcaption>
</figure>
<p>Restoring island foxes was a complex initiative that involved reintroducing bald eagles – which prey on fish, not mammals – to the islands to chase off golden eagles; eradicating introduced pigs, which served as food for the golden eagles and altered the vegetation where the foxes sheltered; restoring shrubs and grasses; and breeding foxes in captivity, then releasing them. This effort is one of the most prominent examples of biologists intervening to <a href="https://www.nps.gov/chis/learn/nature/island-fox.htm">reverse a species’ slide toward extinction</a>. </p>
<p>More broadly, the island fox story shows that small carnivores can provide unique insight into the structure of ecosystems, because they are at the centers of <a href="https://www.nature.com/scitable/knowledge/library/food-web-concept-and-applications-84077181/">food webs</a>. Look at the diet of a fox or weasel and you have a great snapshot of <a href="https://doi.org/10.1002/fee.2407">how many species are present in that ecosystem</a>. </p>
<p>Losing small carnivores can change ecosystems. Many small carnivores typically prey on small seed-eating rodents like mice and gophers. This reduces rodent impacts on plants and <a href="https://doi.org/10.1016/j.ecoser.2017.12.006">farm crops</a>. It also helps to reduce the <a href="https://doi.org/10.1016/j.ecoser.2017.12.006">spread of tick-borne diseases</a>, since small rodents can serve as <a href="https://doi.org/10.1186/s13071-020-3902-0">hosts for infected ticks</a>.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/Cld5PUMrvno/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<p>For these reasons, I and other ecologists argue that it makes sense to use small carnivores as <a href="https://doi.org/10.1111/mam.12300">barometers of ecosystem health</a>. This would mean replacing polar bears with weasels as global warming poster animals, and keying in on <a href="https://doi.org/10.1111/btp.12635">ocelots</a> rather than jaguars to understand how rainforest destruction is affecting wildlife. </p>
<p>While lions and polar bears are important, I believe ferrets, weasels and foxes deserve the same kind of protection and are a more precise tool for measuring how ecosystems are responding to a rapidly changing world.</p><img src="https://counter.theconversation.com/content/192895/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Jachowski does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Polar bears and wolves may get the glory, but small predators like weasels, foxes and their cousins play outsized ecological roles. And many of these species are declining fast.David Jachowski, Associate Professor of Wildlife Ecology, Clemson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1934582022-11-30T04:04:10Z2022-11-30T04:04:10ZCurious Kids: What would happen if all animals on Earth were herbivores?<figure><img src="https://images.theconversation.com/files/498154/original/file-20221130-24-h6m8zw.jpg?ixlib=rb-1.1.0&rect=14%2C14%2C4969%2C3303&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><blockquote>
<p>What would happen if all animals on Earth were herbivores? – Molly, age 9, Melbourne</p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Thanks for the great question, Molly! </p>
<p>We hear a lot about how humans eating meat is bad for the planet. That’s because making room for the animals that produce meat leaves less space for us to farm plants, and less natural habitat for wildlife. And when all those farm animals burp, it releases methane into the atmosphere and contributes to climate change.</p>
<p>So it’s natural to wonder if all animals, including humans, should be herbivores – in other words, only eat plants.</p>
<p>To answer this question, we first need to understand a little about animals, and herbivores. </p>
<figure class="align-center ">
<img alt="Deer in a field" src="https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498155/original/file-20221130-12-62zblj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Should every animal be like deer, and eat only plants?</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Where do animals fit into life on Earth?</h2>
<p>The animal kingdom is one branch of life on Earth, alongside plants, fungi, and two (or three, depending on which textbook you read) types of tiny organisms called bacteria.</p>
<p>Animals can be categorised by the main type of food in their diet. Herbivores eat plants or algae. Carnivores eat other animals. And omnivores eat both plants and animals. </p>
<p>But some omnivores and carnivores would die if they had a completely plant-based diet. For example, <a href="https://education.nationalgeographic.org/resource/carnivore">cats need meat</a> for the nutrients it contains and because they can’t digest plants well. This is true for all cats, from a terrifying tiger to a teeny tabby cat. </p>
<p>So if all animals on Earth only ate plants, millions of carnivore and omnivore species would die out. That’s a problem, because meat-eating animals play an important role on our planet. </p>
<p>Take, for example, scavengers such as vultures, ravens, dogs and flies. They eat other animals that are already dead – and when they poo it out they put important nutrients into the soil so plants can grow. </p>
<p>Without these scavengers, the job of breaking down dead animals would be left to fungi and bacteria. That would mean a lot of dead animals lying around for a lot longer.</p>
<p>There aren’t many things smellier than dog poo – but a rotting kangaroo is one!</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-much-meat-do-we-eat-new-figures-show-6-countries-have-hit-their-peak-172507">How much meat do we eat? New figures show 6 countries have hit their peak</a>
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</em>
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<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=588&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=588&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=588&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=740&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=740&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498165/original/file-20221130-26-jvoss5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=740&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A food web diagram. Energy from the sun is captured by plants which are eaten by herbivores, which in turn are eaten by carnivores. Not pictured are the scavengers and decomposers, which complete the cycle by turning organic matter into healthy soil for plants again.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Carnivores actually help the planet – including humans</h2>
<p>The absence of carnivores in an ecosystem can also mean herbivores start taking over an area, making it unlivable for other species. This occurred when <a href="https://education.nationalgeographic.org/resource/wolves-yellowstone">wolves were removed</a> from Yellowstone National Park in the United States. </p>
<p>Wolves used to eat deer in the wild. When wolves disappeared, deer populations got too big. They ate too many plants near streams, which caused riverbanks to crumble into the water. Deer also damaged trees used by beavers to build dams. This muddied the water even more, and other animals such as fish couldn’t live there any more.</p>
<p>But the absence of meat-eating animals could also bring benefits.</p>
<p>For example, many native species are endangered because they’re being eaten by introduced predators. Without carnivores, these endangered animals would have more of a chance. </p>
<p>The fate of farm animals is less obvious. If all humans were herbivores then there would be no need to raise animals for meat. That would mean we’d only ever see cows, sheep, chickens and pigs at the zoo. </p>
<p>And what about pets? Cats and dogs need meat to survive. So in a world of herbivores, the biggest animal at the pet shop would probably be a plant-eating guinea pig!</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/from-foe-to-friend-how-carnivores-could-help-farmers-92190">From foe to friend: how carnivores could help farmers</a>
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</em>
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<figure class="align-center ">
<img alt="hand holds bowl of meat over small dog" src="https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498156/original/file-20221130-20-o53nm0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cats and dogs need meat to survive.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>There are human health aspects to consider, too. </p>
<p>We humans require a few micrograms of <a href="https://www.hsph.harvard.edu/nutritionsource/vitamin-b12/">vitamin B12</a> each day, and the best source of this is meat. </p>
<p>If humans only ate plants, we’d need to eat a lot of the primary plant sources of B12 – seaweed, algae and some mushrooms. We’d also probably need to take B12 tablets or other man-made “supplements” containing B12. Making these would require farming a lot more algae and bacteria that naturally produce this essential vitamin. </p>
<p>Of course, many vegans – people who don’t eat animal products – already manage to keep up their B12 levels. But I daresay others would struggle. And a lot of people simply enjoy eating meat. I’d hate to come between a bodybuilder and his or her steak! </p>
<h2>Life finds a way</h2>
<p>Losing carnivores would clearly have far-reaching consequences. Earth would soon look dramatically different. </p>
<p>But the more I study evolution, the more I realise life finds a way to achieve what seemed impossible.</p>
<p>If all animals on Earth were herbivores, sooner or later a species of herbivore or fungus would evolve into a new form of life that knows how to turn its herbivorous neighbours into a tasty meal. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/most-large-herbivores-now-face-extinction-our-study-shows-41102">Most large herbivores now face extinction, our study shows</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/193458/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mitchell G. Nye-Wood works in a lab group that receives funding from the Australian Research Council. </span></em></p>We hear a lot about how humans eating meat is bad for the planet. But if every animal only ate plants, Earth would look dramatically different.Mitchell G. Nye-Wood, Research Fellow, Edith Cowan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1888462022-08-24T14:53:55Z2022-08-24T14:53:55ZJellyfish alert: increased sightings signal dramatic changes in ocean food web due to climate change<figure><img src="https://images.theconversation.com/files/480835/original/file-20220824-14-7td2j9.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4928%2C3260&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lionsmane-jellyfish-seas-inner-hebrides-on-386531131">Joost van Uffelen/Shutterstock</a></span></figcaption></figure><p>Did you see a jellyfish on a recent trip to the seaside? UK beachgoers are <a href="https://theconversation.com/why-holidaymakers-are-seeing-giant-jellyfish-off-the-uk-coast-and-what-to-do-if-you-are-stung-165652">more likely to spot one</a> now than in the past, as rising sea temperatures due to climate change have ushered more of these gelatinous animals into the waters around northern Europe.</p>
<p>Jellyfish don’t swim like fish. They belong to the plankton: a diverse group of marine creatures that drift through the sea, floating wherever the currents take them. Jellyfish are among the few types of plankton visible to the human eye. Most plankton are tiny (smaller than 2mm) and can only be seen with a microscope.</p>
<p>Although largely invisible, plankton are the base of the ocean food web, eaten by fish, seabirds and even whales. Species that don’t eat plankton, like seals, will eat organisms that do. Globally, phytoplankton (single-celled algae which, like trees and shrubs on land, are mostly green in colour and use chlorophyll to photosynthesise) <a href="https://theconversation.com/inside-the-world-of-tiny-phytoplankton-microscopic-algae-that-provide-most-of-our-oxygen-159955">produce half of the oxygen</a> we breathe.</p>
<p>Increasingly abundant jellyfish are just one example of the many ways that plankton are reflecting climate change’s influence on the ocean. My research team has found that the species making up North Atlantic plankton communities are also <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.15066">shifting as sea temperatures rise</a>.</p>
<p>We analysed <a href="https://essd.copernicus.org/articles/13/5617/2021/">plankton data</a> collected using nets and bottles throughout the northeast Atlantic over the past 80 years. <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.15066">We found</a> that the larvae of crabs, starfish, sea urchins and lobsters are becoming more common, while shrimp-like crustaceans called copepods (a critical food source for fish, seabirds and even basking sharks) are declining.</p>
<figure class="align-center ">
<img alt="Translucent, microscopic creatures on a black background." src="https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480841/original/file-20220824-4729-sdo0s6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Copepods are a rich food source for a variety of fish.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/plankton-organisms-drifting-oceans-seas-zooplankton-1356428912">Choksawatdikorn/Shutterstock</a></span>
</figcaption>
</figure>
<p>These are big changes among some of the smallest forms of life, and they will affect the entire marine food web, as well as humans. We must understand these changes in order to adapt to them. That could mean new fishing practices – and even diets.</p>
<h2>In a jellyfish’s wake</h2>
<p>Zooplankton (the animal subset of plankton) consists not only of copepods and jellyfish, but also the larval stages of fish, crustaceans and echinoderms (the “spiny skin” group that starfish and sea urchins belong to) which later settle to the sea floor and mature into their familiar adult forms. Both zooplankton and phytoplankton communities are highly diverse, containing species of all sorts of weird and wonderful shapes.</p>
<p>Since the 1960s, colder-water zooplankton species have been <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2009.01848.x">retreating</a> towards the Arctic, followed by warmer-water species that are also tracking rising sea temperatures northwards. The warmer-water zooplankton species which now dominate northern European waters are generally smaller and less nutritious than the cold-water species they have replaced.</p>
<p>The seasonal timing of when plankton are abundant in the North Sea has also <a href="https://www.nature.com/articles/nature02808">shifted</a>, including around the UK. While the seasonal cycle of phytoplankton is driven by sunlight and so hasn’t changed, the point in the year when some zooplankton species are most abundant now arrives earlier, as shorter and warmer winters cause the eggs of some species to hatch sooner. This has meant a mismatch between the spring phytoplankton bloom and the annual peak abundance of the zooplankton that gorge on it.</p>
<figure class="align-center ">
<img alt="A satellite image of the ocean with a turquoise plume." src="https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480839/original/file-20220824-14-c7wdy8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Phytoplankton blooms are usually so vast they can be seen from space.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aerial-turquoise-ocean-photo-clear-sky-2102266519">GizemG/Shutterstock</a></span>
</figcaption>
</figure>
<p>These shifts have meant the quantity and type of food available to larval fish (which are zooplankton themselves but eat smaller zooplankton) is changing in the North Atlantic. Warm-water species such as bluefin tuna and anchovies are now <a href="https://www.mccip.org.uk/fisheries">commonly found</a> in northern European waters, while cod, herring, whiting and sprat, all important commercial fish species, have declined in number.</p>
<p>Fishery managers need to work with scientists to set quotas that ensure these new species are fished sustainably, while coastal fishing communities may have to catch new species as familiar ones decline. The public may have to adapt their diets too as traditional species, such as cod in the UK, become scarcer.</p>
<p>The jellyfish you now see in UK waters might have once been a rarity, but it’s following a (largely invisible) crowd that is upending marine food webs and changing the kind of fish you might buy and eat locally. The next time you watch the hypnotic motion of one of these beautiful creatures as it pulses through the water, think of the changes its arrival portends, both for the ocean and yourself.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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<p class="fine-print"><em><span>Abigail McQuatters-Gollop receives funding from NERC, EMFF and Defra. </span></em></p>Plankton, some of the smallest organisms on Earth, are leading big changes in the ocean.Abigail McQuatters-Gollop, Associate Professor of Marine Conservation, University of PlymouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1851182022-07-20T18:33:22Z2022-07-20T18:33:22ZMegalodon sharks ruled the oceans millions of years ago – new analyses of giant fossilized teeth are helping scientists unravel the mystery of their extinction<figure><img src="https://images.theconversation.com/files/474715/original/file-20220718-72671-te0fb6.png?ixlib=rb-1.1.0&rect=133%2C118%2C2944%2C2035&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Megalodon would have dwarfed today's great white sharks.</span> <span class="attribution"><span class="source">Christina Spence Morgan</span></span></figcaption></figure><p>Millions of years ago, giant sharks three times larger than today’s great whites stalked the world’s ocean. They’re long gone now, but occasionally, someone walking on a beach <a href="https://www.bbc.co.uk/news/uk-england-suffolk-61378018">spots an odd triangular shape in the sand</a>. On closer inspection, they realize it’s a fossilized tooth as large as a human hand, with sharp serrated edges. And they have to wonder: What was that beast eating?</p>
<p>These fossilized teeth hold clues to a mystery about a legend of the seas, a mammoth creature that was at the apex of the food chain – and then vanished. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An adult hand holds a giant shark tooth that covers it from the palm to the fingertips." src="https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=737&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=737&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=737&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=926&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=926&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474347/original/file-20220715-12-dfgdi0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=926&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A megalodon tooth found on the North Carolina coast.</span>
<span class="attribution"><span class="source">Harry Maisch</span></span>
</figcaption>
</figure>
<p>It’s known as the megalodon, believed to be the largest shark species to ever exist. Evidence in the teeth and bite marks found on fossilized bones suggest these ancient sharks were swimming the ocean between 23 million and <a href="https://doi.org/10.7717/peerj.6088">3.5 million years ago</a>. Scientists have estimated they reached <a href="https://www.theguardian.com/environment/2020/sep/03/researchers-reveal-true-scale-of-megalodon-shark-for-first-time">lengths upwards of 50 feet (15 meters)</a> – longer than a city bus.</p>
<p>The megalodon was the last species of a group of sharks called the megatooth sharks. We study the chemistry of fossils to better understand ancient animals, and while many mysteries remain about megalodon’s life and eventual extinction, its teeth are revealing some answers.</p>
<h2>What did ancient sharks eat?</h2>
<p>There are tantalizing clues about the diet of ancient sharks in the fossil record. </p>
<p>The shape and structure of their teeth can indicate general eating styles. Broad serrated megalodon teeth are thought to be particularly well adapted to gnawing on marine mammals, while the sharp and pointy teeth of other sharks lend themselves to piercing and tearing fish.</p>
<p>In some exceptional cases, fossil marine mammal bones have been found with the <a href="https://chesapeakebaymagazine.com/megalodon-bite-marks-found-on-calvert-cliffs-fossil/">bite</a> <a href="https://doi.org/10.1016/j.palaeo.2017.01.001">marks</a> <a href="https://www.popsci.com/science/megalodon-diet-sperm-whale-head/">of a megalodon</a>. Some <a href="https://doi.org/10.1098/rspb.2022.0774">sperm whale bones</a> have evidence of megalodon attacks on their foreheads, a part of the whale that would have been rich in fats. <a href="https://chesapeakebaymagazine.com/megalodon-bite-marks-found-on-calvert-cliffs-fossil/">Dolphin tailbones</a> have also been found with deep megalodon tooth marks. Each of these incredible fossils offers a snapshot of one megalodon’s meal on one day millions of years ago. </p>
<figure class="align-center ">
<img alt="Large bite marks on part of a whale backbone." src="https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=461&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=461&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=461&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=579&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=579&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474352/original/file-20220715-20-zth067.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=579&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This whale vertebra was bitten in half by a megalodon.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Meg_bitten_cetacean_vertebra.jpg">Jayson Kowinsky via Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Were marine mammals a part of megalodon’s regular diet, or just a special snack that day? And what else may have fallen prey to this massive shark?</p>
<h2>Finding answers in the chemistry of fossil teeth</h2>
<p>Using newly developed tools, we have been able to analyze the chemical composition of these fossil teeth, including samples from the United States, western Europe and Japan. </p>
<p>The results, published in two recent studies, tell us about the diet of each ancient shark and about the environment it lived in long before humans walked the Earth.</p>
<p>When animals eat, they acquire <a href="https://organismalbio.biosci.gatech.edu/nutrition-transport-and-homeostasis/nutrition-needs-and-adaptations/">nutrients</a> from their meals, including nitrogen and zinc. Because of this, nitrogen and zinc are passed up the food web from prey to predator.</p>
<p>Both nitrogen and zinc have multiple stable <a href="https://theconversation.com/explainer-what-is-an-isotope-10688">isotopes</a>, forms whose atoms contain the same number of protons but different numbers of neutrons. For nitrogen, the ratio of the 15-nitrogen isotope to the 14-nitrogen isotope <a href="https://thefisheriesblog.com/2017/06/04/determining-trophic-position-everyone-gets-a-trophy-but-only-the-top-doesnt-get-eaten/">increases with each step up the food web</a> because animals tend to discard more of the 14-nitrogen isotope in their waste. On the other hand, the ratio of 66-zinc to 64-zinc decreases within animals higher up in the food web.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration shows different sharks by period when they lived. Maglodon is the largest and an apex predator" src="https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=318&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=318&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=318&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=400&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=400&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474661/original/file-20220718-69569-2vdqzi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=400&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When megalodon and its megatooth ancestors lived, and their position in the food web as apex predators compared with sharks that primarily eat fish.</span>
<span class="attribution"><span class="source">Christina Spence Morgan</span></span>
</figcaption>
</figure>
<p>Very small amounts of nitrogen and zinc are preserved deep inside the mineral layers of fossil teeth. We can extract and purify these elements from the teeth, measure the isotope ratios, and then estimate the position in the food web, for each ancient shark. </p>
<p>While nitrogen isotopes are often measured in modern protein tissues, these decompose rapidly and cannot be measured in the fossil record. This new method of measuring nitrogen isotopes can analyze the trace amount of nitrogen preserved in the mineral layers of fossil teeth over millions of years. The zinc isotope method is also new; this study marks the first time it has been applied to sharks and fossils more than 86,000 years old.</p>
<p>Together, the isotopes of nitrogen and zinc in fossil teeth tell us about the diet of extinct animals living in ecosystems that vanished millions of years ago. In our studies, we used <a href="https://doi.org/10.1126/sciadv.abl6529">nitrogen</a> and <a href="https://doi.org/10.1038/s41467-022-30528-9%22%22">zinc</a> isotopes to reconstruct the diets of sharks. </p>
<h2>Megalodon’s extinction: Competition with the white shark?</h2>
<p>Understanding the diet of the megalodon can help us unravel the mystery of its extinction, and the possible ripple effects of its disappearance on marine ecology.</p>
<p>Both measurements show that the megalodon – and its slightly smaller megatooth ancestors – were feeding at an extraordinarily high position in ancient food webs. In fact, at least according to the nitrogen isotopes, they may have been higher than any apex predator existing today.</p>
<p>To be in such a high position they may have been eating now-extinct marine mammals, such as predatory sperm whales. Megalodon might also have been cannibalistic, maybe with larger adults eating juveniles. It’s very likely that the megalodon was a true apex predator, not targeted as prey by any other marine animal. </p>
<figure class="align-center ">
<img alt="A pile of very large shark teeth" src="https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474351/original/file-20220715-12-eypa2y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Megalodon was here. Several of the shark’s giant teeth have been found along the North Carolina coast.</span>
<span class="attribution"><span class="source">Harry Maisch</span></span>
</figcaption>
</figure>
<p>The emergence of the modern white shark around 5 million years ago has been hypothesized as one factor that could have contributed to megalodon’s extinction. </p>
<p>White sharks were believed to have fed on similar prey. There are similarities in tooth shape, and <a href="https://doi.org/10.1038/s41467-022-30528-9">fossil bite marks on similar species</a> also suggest that the white sharks <a href="https://www.abc.net.au/news/science/2022-06-01/megalodon-extinction-great-white-shark-pliocene-diet-zinc/101112348">may have outcompeted</a> megalodon, or <a href="https://doi.org/10.1126/sciadv.abl6529">outcompeted juvenile megalodon</a>.</p>
<p>The isotopes offer conflicting answers. The comparison of nitrogen isotopes between great whites and megalodon from around the same time period placed these predators at different positions in the food web, meaning that they were not competing for the same prey. The zinc isotopes, however, <a href="https://www.abc.net.au/news/science/2022-06-01/megalodon-extinction-great-white-shark-pliocene-diet-zinc/101112348">do not reject the competition hypothesis</a>, placing these two sharks at similar positions in the food web instead. </p>
<p>The disappearance of the giant sharks could have been caused by other factors, too, such as temperature changes, the loss of shelf environments due to sea-level fall, or, likely, a combination of influences.</p>
<p>Future research combining both methods may help resolve this conundrum and finally solve the mystery of why the largest shark on Earth vanished.</p>
<p><em>Michael Griffiths of William Paterson University and Kenshu Shimada of DePaul University contributed to this article.</em></p><img src="https://counter.theconversation.com/content/185118/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sora Kim receives funding from the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Emma Kast and Jeremy McCormack do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Megalodon, the world’s largest known shark species, swam the oceans long before humans existed. Its teeth are all that’s left, and they tell a story of an apex predator that vanished.Emma Kast, Postdoctoral Research Fellow in Geosciences, University of CambridgeJeremy McCormack, Specialist in Geoscience, Goethe University Frankfurt am MainSora Kim, Assistant Professor of Paleoecology, University of California, MercedLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1599552021-04-29T15:21:35Z2021-04-29T15:21:35ZInside the world of tiny phytoplankton – microscopic algae that provide most of our oxygen<figure><img src="https://images.theconversation.com/files/397791/original/file-20210429-19-8lbh7j.jpg?ixlib=rb-1.1.0&rect=115%2C115%2C5396%2C3999&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/volvox-polyphyletic-genus-chlorophyte-green-algae-558059725">Shutterstock/Choksawatdikorn</a></span></figcaption></figure><p>Phytoplankton are microscopic algae living throughout the ocean’s surface waters. They can’t swim and are at the mercy of the currents and tides. Despite their small size, phytoplankton enable life in the oceans – and throughout the planet – to exist.</p>
<p>There are two types of plankton – zooplankton, which are animals, and phytoplankton, which are algae. Phytoplankton are filled with chlorophyll which gives them a green colour, just like land plants. And like land plants, phytoplankton play a critical role, converting carbon dioxide and energy from the sun into food through photosynthesis, producing oxygen. </p>
<p>These tiny organisms have been producing oxygen for the world for hundreds of millions of years. But most people know very little about them, what they do for the rest of the world and the threats they are facing.</p>
<p>Phytoplankton are thought to have made an appearance in the Bible’s Book of Revelation, which says: “A third of the sea turned into blood, a third of the living creatures in the sea died, and a third of the ships were destroyed”. Modern scientists think this must be a reference to a harmful algal bloom, or red tide, that can be cause by phytoplankton and can discolour that water. These can also produce toxins, causing illness and even death in animals – <a href="https://www.sciencedirect.com/science/article/pii/S1568988321000160">fish</a>, <a href="https://peerj.com/articles/3123/">whales</a>, <a href="https://www.sciencedirect.com/science/article/pii/S1568988308001571?casa_token=px7Q1iYbEI0AAAAA:qdcWssl9s6eowloHuz4OgBaTKyLo8wf_gcSFPuXCm5tShlz5QaBjxcAF3ELWfIv90QmcbfWdAw">manatees</a>, <a href="https://www.sciencedirect.com/science/article/pii/S1568988312001175?casa_token=XT7ZylxInu0AAAAA:b0SLek_vefPziV7dRiuawt1dlOe6U6tABXyS8toMTYkdFfZzzRbKJ_QMnDh8ZqqoYjiwTeLxYg">birds</a>, and even <a href="https://bioone.org/journals/african-journal-of-wildlife-research/volume-50/issue-1/056.050.0149/Mass-Die-Off-of-African-Elephants-in-Botswana--Pathogen/10.3957/056.050.0149.full">elephants</a> – and people. </p>
<p>They’ve made their way into modern culture, too. Alfred Hitchock’s movie the Birds, where birds attack residents of a California town, was inspired by birds behaving erratically due to toxic phytoplankton.</p>
<p>Despite being a source of cultural inspiration, there are many things about phytoplankton most people don’t know – such as the fact they can be seen from space. Unlike land plants which can grow 100 metres (380 feet) in height, phytoplankton individuals consist of a single cell. Individual phytoplankton can usually only be seen with a microscope, but when phytoplankton bloom, the aggregations are so large that they can be seen from satellites.</p>
<figure class="align-center ">
<img alt="An image of the ocean with a swirling blue pattern, caused by a phytoplankton bloom." src="https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397608/original/file-20210428-17-11tgoy9.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A phytoplankton bloom seen from space.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/ContentFeature/Phytoplankton/images/newzealand_amo_2009298.jpg">NASA/Robert Simmon and Jesse Allen</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Although they’re microscopic, phytoplankton are wonderfully diverse, with thousands (or maybe even millions) of different species and hundreds of body shapes. Some have spines or form chains to help them maintain buoyancy, while others have flagella – tiny whip-like appendages – to enable them to orient themselves in the water. Some phytoplankton are covered in CaCO₃ plates, called liths, giving them the appearance of tiny footballs, which play <a href="https://www.nature.com/articles/nclimate1753">an important role</a> in carbon sequestration.</p>
<h2>The lungs of the sea</h2>
<p>Rainforests get much of the credit for oxygen production, but phytoplankton produce at least <a href="https://science.sciencemag.org/content/291/5513/2594">50% of the Earth’s oxygen</a>. Phytoplankton are <a href="https://theconversation.com/tiny-plankton-drive-processes-in-the-ocean-that-capture-twice-as-much-carbon-as-scientists-thought-136599">the lungs of the sea</a> – the oxygen from one out of every two breaths we take comes from plankton.</p>
<p>Climate change would be <a href="https://www.pnas.org/content/117/18/9679">much more extreme</a> without phytoplankton. They use carbon dioxide from the atmosphere to fuel photosynthesis. When they die, they sink to the sea floor, locking away that carbon. Phytoplankton absorb up to <a href="https://www.nature.com/articles/s41467-020-18203-3#Sec2">50% of anthropogenic CO₂</a>, which, without them, would cause higher atmospheric CO₂ levels.</p>
<p>Nevertheless, climate change is causing changes <a href="https://www.nature.com/articles/nclimate1388">in phytoplankton communities</a>. In some places, like the North Atlantic, oceans are experiencing tropicalisation – when warming waters enable warm water plankton species to move northwards while colder water species are squeezed towards the pole. </p>
<figure class="align-center ">
<img alt="A few different types of phytoplankton under a microscope, in various shapes, with a black background." src="https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397869/original/file-20210429-18-q06gxr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Under the microscope.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/diatoms-photosynthesising-algae-they-have-siliceous-1537841030">Shutterstock/Choksawatdikorn</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tiny-plankton-drive-processes-in-the-ocean-that-capture-twice-as-much-carbon-as-scientists-thought-136599">Tiny plankton drive processes in the ocean that capture twice as much carbon as scientists thought</a>
</strong>
</em>
</p>
<hr>
<p>Some plankton in the North Atlantic have shifted northwards by over 1,000km (620 miles) in <a href="https://science.sciencemag.org/content/296/5573/1692/tab-figures-data">the past 50 years</a>. Warming seas can cause some phytoplankton to change the timing of their blooms. These changes can affect food webs, as the phytoplankton may bloom too early or late to feed the zooplankton that depend on them.</p>
<p>This is why it’s important to monitor them. There are many ways to monitor plankton, including sampling with bottles or nets, or estimating phytoplankton biomass from space using satellites. The Continuous Plankton Recorder survey has monitored plankton in the North Atlantic since 1931, using commercial vessels such as ferries and cargo ships on their normal routes to tow a one metre long recording device through the sea behind the boat.</p>
<p>The devices filter seawater through a moving band of silk, trapping the plankton. The silks are then sent to a laboratory in Plymouth, UK, to identify and count the plankton. The survey has recorded almost <a href="https://www.sciencedirect.com/science/article/abs/pii/S0272771415001596">800 taxa of plankton</a>, around 300 of which are phytoplankton. It’s created a 90-year-old record of North Atlantic plankton, allowing us to better understand the marine food web and detect changes in the marine environment caused by pollution, fishing and climate change.</p><img src="https://counter.theconversation.com/content/159955/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Abigail McQuatters-Gollop is an Associate Professor in Marine Conservation at the University of Plymouth. She is also the managing director of Ecosystem Approaches, Ltd. </span></em></p>These tiny organisms play a huge role in fighting climate change, but they’re under threat.Abigail McQuatters-Gollop, Associate Professor of Marine Conservation, University of PlymouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1441802020-09-15T11:55:28Z2020-09-15T11:55:28ZWhen hurricanes temporarily halt fishing, marine food webs recover quickly<figure><img src="https://images.theconversation.com/files/356588/original/file-20200904-18-saqn8y.jpg?ixlib=rb-1.1.0&rect=5%2C916%2C4000%2C3233&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hurricane Harvey set up a rare natural experiment to study the effects of fishing.</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Hurricane_Harvey#/media/File:Harvey_2017-08-25_2231Z.png">NOAA via Wikipedia</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>Fishing has a strong impact on coastal marine food webs, but it’s a hard effect to measure. When Hurricane Harvey hit Texas in 2017, it temporarily halted fishing in one area of the Gulf Coast and set up a natural experiment for our team. We found that when the hurricane halted recreational fishing, populations of sport fish rebounded almost immediately, causing a cascade of effects throughout marine food webs in the area.</p>
<p>In August 2017, Hurricane Harvey <a href="https://www.cnn.com/2017/08/26/us/rockport-texas-hurricane-harvey/index.html">made landfall in Aransas Bay, Texas</a>. The high winds and storm surge destroyed docks, piers and boats in addition to homes and businesses. With fishing infrastructure destroyed, fishing in this area declined significantly <a href="https://doi.org/10.1016/j.cub.2020.06.048">the following year</a>.</p>
<p>The storm then moved north, dropping <a href="https://www.npr.org/sections/thetwo-way/2018/01/25/580689546/harvey-the-most-significant-tropical-cyclone-rainfall-event-in-u-s-history">record setting rainfall</a> near Houston, Texas, in the Galveston Bay watershed. In both Aransas and Galveston bays, rainfall significantly reduced salinity and altered water quality. But, Galveston Bay was <a href="https://www.galvnews.com/news/free/article_6cde66ef-500b-5bd5-9fb4-3b38c340cca0.html">spared from the worst wind damage</a> and <a href="https://doi.org/10.1016/j.cub.2020.06.048">fishing continued as normal</a>.</p>
<p><iframe id="X9ReM" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/X9ReM/1/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>This set up a natural experiment: Fishing was reduced in one area – Aransas Bay – but not in another – Galveston Bay – allowing us to assess how the ecosystems recovered under high or low fishing pressure. </p>
<p>After the storm reduced fishing in Aransas Bay, populations of sport fish – many of which are top predators – boomed the next year and we saw a trophic cascade throughout the food web. With more predators around, populations of shrimp, crabs and smaller fish that sport fish commonly eat, <a href="https://doi.org/10.1016/j.cub.2020.06.048">all declined</a>. On oyster reefs, mud crabs that commonly eat small oysters were hard to find because of higher predation by fish. </p>
<p>Although Galveston Bay experienced similar rainfall and water conditions, very little fishing infrastructure was damaged, and fishing continued as normal after the storm passed. Sport fish populations remained steady, and we <a href="https://doi.org/10.1016/j.cub.2020.06.048">didn’t see any serious changes to the food webs</a> of Galveston Bay. </p>
<p>The hurricane, by curtailing fishing, showed just how much of an effect fishing has not only on the targeted species, but on entire food webs. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dozens of boats scattered and sunk in a marina in the aftermath of Hurricane Harvey." src="https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/356590/original/file-20200904-16-41whbx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Harvey destroyed docks and boats and fishing infrastructure in Aransas Bay, but not Galveston Bay.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Hurricane_Harvey#/media/File:Hurricane_Harvey_(2017)_170828-Z-FG822-026_(36127995543).jpg">U.S. Department of Defense via Wikipedia</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>Researchers know that humans are important components of food webs, but measuring these effects is challenging. The hurricane occurred in the midst of ongoing studies on fish populations and afforded us a unique opportunity to measure its effects, including reduction of fishing.</p>
<p>In Texas, fish populations bounced back quickly after fishing activity ceased, suggesting that these fisheries are well managed and that fishing regulations are being followed. This is in stark contrast to many fish stocks that have been historically overfished, leading to <a href="https://science.sciencemag.org/content/293/5530/629.abstract">collapse of coastal ecosystems</a>. The results highlight that science-based fishing regulations and conservation planning need to be maintained, as well as how important it is for fishermen to follow the rules. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of an uncovered oyster reef at low tide." src="https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/356589/original/file-20200904-18-1tr3p37.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Oyster reefs are important habitats for a variety of species in the Gulf of Mexico and the food webs found on these reefs changed dramatically after fishing was reduced.</span>
<span class="attribution"><span class="source">Dr. Lee Smee</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>What still isn’t known</h2>
<p>The oceans face many challenges from <a href="https://oceanconservancy.org/">fishing, pollution and climate change</a>. Food webs are inherently complex and difficult to study – especially when the conditions that affect them are constantly changing – and there is a lot scientists don’t yet know about how they might change with so many variables in flux. Understanding these relationships is critical if conservationists want to better protect marine resources.</p>
<h2>What’s next</h2>
<p>Studies that examine how multiple factors affect individual species and the food webs they are a part of will improve conservation planning. We believe these studies should also investigate how changes to one species can affect not only other animals but plants and nonliving systems too. It is also important to study how these changes affect humans and vice versa.</p>
<p>Finding the right balance between the needs of people and the needs of healthy ecosystems is difficult but important work. Hurricane Harvey was destructive, but it gave us an opportunity to learn valuable information about these complicated systems.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p><img src="https://counter.theconversation.com/content/144180/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Hurricane Harvey destroyed the fishing infrastructure of Aransas Bay and reduced fishing by 80% over the following year. This removed humans from the trophic cascade and whole food webs changed.Lee Smee, Assistant Professor of Marine Science, Texas A&M University-Corpus ChristiJoseph W. Reustle, SPIRE Postdoctoral Scholar, University of North Carolina at Chapel HillLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1384052020-06-03T12:15:15Z2020-06-03T12:15:15ZParasitic worms in your shellfish lead a creepy but popular lifestyle<figure><img src="https://images.theconversation.com/files/336189/original/file-20200519-152344-gc94zt.jpg?ixlib=rb-1.1.0&rect=1%2C2%2C697%2C520&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Parasites do very well for themselves, which is why they are so common in the animal kingdom.</span> <span class="attribution"><a class="source" href="http://www.marinespecies.org/introduced/aphia.php?p=image&pic=99515">Geoffrey Read</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>If you’re an oyster lover, seeing a shaggy worm slither across your appetizer is revolting – even though such worms are harmless to people. An internet search using the keywords “oyster” and “worm” will bring up a large cache of images, each one less palatable than the next. </p>
<p>As a <a href="https://scholar.google.com/citations?user=DtgT_YIAAAAJ&hl=en">biologist</a>, I study invasive species including these mud blister worms. Despite their high gross-out factor, their parasitic lifestyles are fascinating. While parasites do cause harm to their hosts, they are also a crucial piece of the planet’s ecosystem.</p>
<h2>Shell-boring worms</h2>
<p>Mud blister worms belong to a larger group of segmented worms, collectively known as <a href="https://www.smithsonianmag.com/science-nature/14-fun-facts-about-marine-bristle-worms-180955773/">polychaetes</a>. “Poly” means many and “chaete” means bristles in ancient Greek. Mud blister worms are one of many species that burrow into the shells of animals like oysters, abalone and scallops, where they spend their entire adult life.</p>
<p>Considering the shells of oysters and scallops are made up of calcium carbonate, which has limited nutritional value, it might seem an odd location for a worm infestation. But rather than feeding on the shell itself, these worms create an amazing network of tunnels within the shell’s matrix, using it as a house rather than a food source. </p>
<figure>
<img src="https://cdn.theconversation.com/static_files/files/1045/vl6Q3M.gif?1589988051" width="100%">
<figcaption><span class="caption">This worm, <i>Polydora cornutanhas</i>, uses tentacles to snag passing algae and food particles, while its body remain safely ensconced in the shell of its host organism.</span></figcaption>
</figure>
<p>The worms feed by protruding their tentacles out of tiny openings in the shell, where they capture food particles from the surrounding seawater. Unlike other parasites, which feed directly on their hosts, mud blister worms invade their hosts’ outer covering and must have food delivered to them for survival.</p>
<p>How many worms can a single shell harbor? I once counted more than 120 worms emerging from the shell of a heavily infested Pacific oyster. The surface of the oyster looked like any other, but once it was immersed into a special irritating solution, a stunning number of worms began to rise up, just like a creature in a zombie film. </p>
<h2>Sibling cannibalism</h2>
<p>Adult worms are sedentary, meaning they remain within the tunnels they create and do not actively leave their quarters. The offspring of these worms, however, are free-swimming larvae, which are released into the water column after birth and <a href="https://doi.org/10.1007/s00227-013-2388-0">disperse the species throughout the ocean</a>. </p>
<p>After mating, females produce an egg case containing thousands of eggs, some of which hatch into larvae and some of which do not hatch at all. The latter become “nurse eggs,” or food that <a href="https://doi.org/10.1007/s00227-013-2388-0">nourish the developing offspring</a>. This is where things get interesting. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zqXuh82_D6c?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">It’s ‘eat or be eaten’ among larvae.</span></figcaption>
</figure>
<p>In one of my earliest <a href="http://hdl.handle.net/10019.1/96594">studies of these worms</a>, my colleagues and I found that in situations where nurse eggs were depleted, larger larvae often viciously attacked and cannibalized their siblings within the egg case. In other situations, the cannibalism occurred even in the presence of nurse eggs. </p>
<p>The mother is in charge of releasing the larvae, using a <a href="https://doi.org/10.1016/j.jembe.2014.07.012">pair of tentacles to rupture the egg</a> cases at a time of her choosing. Because she is solely responsible for liberating the offspring from the egg case, she has complete <a href="https://doi.org/10.1016/j.jembe.2014.07.012">control over which siblings live and which die</a>. </p>
<p>Sibling cannibalism, as brutal as it sounds, is actually quite common across the <a href="https://doi.org/10.1016/j.aaf.2016.12.001">animal</a> <a href="https://doi.org/10.1111/j.1439-0310.2010.01792.x">kingdom</a>. Sand tiger sharks, for example, exhibit a similar behavior where <a href="https://doi.org/10.1098/rsbl.2013.0003">siblings fight each other to the death</a> in the womb although, in this case, the mother shark does not exert as much control as a mud blister worm matriarch does. </p>
<p>The evolutionary significance of sibling cannibalism – and why it seems to have emerged in animals as far apart on the tree of life as worms and sharks – is still not fully known and remains an <a href="https://doi.org/10.1073/pnas.1911677117">active area of evolutionary biology research</a>. </p>
<h2>Threats to humans and the aquaculture industry</h2>
<p>Luckily, shell-boring worms pose no threat to humans. Aside from an unexpected protein boost, accidental consumption will not lead to any health problems. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Oysters under siege.</span>
<span class="attribution"><a class="source" href="https://youtu.be/zqXuh82_D6c">Federal University of Recôncavo da Bahia and State University of Santa Cruz</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>However, these worms are <a href="https://www.adfg.alaska.gov/static/species/disease/pdfs/bivalvediseases/shellboring_polychaetes.pdf">notorious pests in the aquaculture industry</a>. Heavy infestations can cause reduced growth in shellfish, because the mollusk must <a href="https://www.int-res.com/abstracts/aei/v7/n2/p147-166/">divert energy from growth to shell repair</a>. In addition, the meat of infested oysters has been reported as having a <a href="http://masgc.org/projects/details/maximizing-the-return-on-investment-of-oyster-aquaculture-by-managing-mud-b">more “watery” consistency</a> than uninfested oysters. Together, these effects result in a commercial loss for aquaculture farms. </p>
<p>In past years, scientist have proposed the <a href="https://doi.org/10.1016/j.aquaculture.2010.10.031">use of chemical compounds</a> and the <a href="https://doi.org/10.1016/0044-8486(95)01212-5">heat-shocking of oysters</a> to control the worms, but there has yet to be a silver bullet for eradication. </p>
<p>Perhaps one of the most overlooked facts in zoology is that parasitism is the <a href="https://doi.org/10.1016/j.biocon.2010.10.025">most predominant lifestyle on Earth</a> and plays an important role in maintaining ecosystems by <a href="https://doi.org/10.1007/s10393-004-0028-3">stabilizing food webs and regulating population sizes</a>. Like many marine invertebrates, the larvae of these worms serve as planktonic food for animals higher up in the food chain, thereby <a href="https://doi.org/10.1093/icb/icq037">contributing to the overall structure of the marine community</a>. </p>
<p>So next time you are at a seafood restaurant and you order a couple of raw oysters, try breaking apart the shells – perhaps after you’ve finished eating. You might discover a few hidden freeloaders. </p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/138405/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Davinack does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Mud blister worms make their homes in the shells of oysters and other shellfish, where they weaken their hosts.Andrew Davinack, Assistant Professor of Biology, Clarkson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1384362020-05-18T20:04:31Z2020-05-18T20:04:31ZClimate change threatens Antarctic krill and the sea life that depends on it<figure><img src="https://images.theconversation.com/files/335616/original/file-20200518-138639-1fyvvg1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5458%2C3641&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Brett Wilks</span></span></figcaption></figure><p>The Southern Ocean circling Antarctica is one of Earth’s richest marine ecosystems. Its food webs support an abundance of life, from tiny micro-organisms to seals, penguins and several species of whales. But climate change is set to disrupt this delicate balance.</p>
<p>Antarctic krill – finger-sized, swarming crustaceans – might be small but they underpin the Southern Ocean’s food web. Our research <a href="https://www.nature.com/articles/s41558-020-0758-4">published today</a> suggests climate change will cause the ocean habitat supporting krill growth to move south. The habitat will also deteriorate in summer and autumn.</p>
<p>The ramifications will reverberate up the food chain, with implications for other Antarctic animals. This includes humpback whales that feed on krill at the end of their annual migration to the Southern Ocean.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=535&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=535&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335617/original/file-20200518-138606-1yj761h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=535&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Changes in krill habitat could affect species up the food chain including the humpback whale.</span>
<span class="attribution"><span class="source">Mike Hutchings/AAP</span></span>
</figcaption>
</figure>
<h2>What we found</h2>
<p>Antarctic krill are one of the most abundant animal species in the world. About 500 million tonnes of Antarctic krill <a href="http://www.antarctica.gov.au/about-antarctica/wildlife/animals/krill">are estimated</a> to exist in the Southern Ocean.</p>
<p>Antarctic krill play a critical role in the ocean’s food webs. But their survival depends on a delicate balance of food and temperature. Scientists are concerned at how climate change may affect their population and the broader marine ecosystem.</p>
<p>We wanted to project how climate change will affect the Southern Ocean’s krill “growth habitat” – essentially, ocean areas where krill can thrive in high numbers.</p>
<p>Krill growth depends largely on ocean temperature and the abundance of its main food source, phytoplankton (microscopic single-celled plants).</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anatomy-of-a-heatwave-how-antarctica-recorded-a-20-75-c-day-last-month-134550">Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month</a>
</strong>
</em>
</p>
<hr>
<p>Under a “business as usual” climate change scenario, future changes in ocean temperature and phytoplankton varied depending on the region and season.</p>
<p>In the mid-low latitudes, our projections showed temperatures warmed towards the limits krill can tolerate. For example, by 2100 the waters during summer around South Georgia island warmed by 1.8°C. </p>
<p>Warming water was often accompanied by decreases in phytoplankton; in the Bellingshausen Sea during summer a 1.7°C rise halved the available phytoplankton.</p>
<p>However, phytoplankton increased closer to the continent in spring and summer – most dramatically by 175% in the Weddell Sea in spring.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334549/original/file-20200513-82375-1wsg43x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antarctic krill habitat will shift south under climate change.</span>
<span class="attribution"><span class="source">Simon Payne, Australian Antarctic Division</span></span>
</figcaption>
</figure>
<h2>Shifting habitat</h2>
<p>Across all seasons, krill growth habitat remained relatively stable for 85% of the Southern Ocean. But important regional changes still occurred.</p>
<p>Krill growth habitat shifted south as suitable ocean temperatures contracted towards the poles. Combined with changes in phytoplankton distribution, growth habitat improved in spring but deteriorated in summer and autumn. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-antarctic-krill-fertilise-the-oceans-and-even-store-carbon-all-with-their-poo-125362">How Antarctic krill fertilise the oceans and even store carbon – all with their poo</a>
</strong>
</em>
</p>
<hr>
<p>This early end to the growth season could have profound consequences for krill populations. The krill life cycle is synchronised with the Southern Ocean’s dramatic seasonal cycles. Typically this allows krill to both maximise growth and <a href="http://www.antarctica.gov.au/news/2011/krill-do-it-deep-in-the-southern-ocean">reproduction</a> and store reserves to survive the winter.</p>
<p>A shift in habitat timing could create a mismatch between these two cycles. </p>
<p>For example, female krill need access to plentiful food during the summer in order to spawn. Since larger females produce exponentially more eggs, a decline in summer growth habitat could result in smaller females and far less spawning success. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335619/original/file-20200518-138615-elci8r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antarctic predators including penguins rely on krill for survival.</span>
<span class="attribution"><span class="source">Royal Navy</span></span>
</figcaption>
</figure>
<h2>Why this matters</h2>
<p>Krill’s significant role in the food chain means the impacts of these changes may play out through the entire ecosystem.</p>
<p>If krill shift south to follow their retreating habitat, less food would be available for predators on sub-Antarctic islands such as Antarctic fur seals, penguins and albatrosses for whom krill forms a significant portion of the diet.</p>
<p>In the past, years of low krill densities has coincided with declines in reproductive success for these species.</p>
<p>Shifts in krill habitat timing may also affect migratory predators. For example, each year humpback whales migrate from the tropics to the poles to feed on the huge amount of summer krill. If the krill peak occurs earlier in the season, the whales must adapt by arriving earlier, or be left hungry.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=361&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=361&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=361&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=454&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=454&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335654/original/file-20200518-83384-nsx4pe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=454&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Krill predators. a. crabeater seal (Lobodon carcinophaga), b. Adelie penguins (Pygoscelis adeliae), c. Antarctic fur seal (Arctocephalus gazella), d. humpback whale (Megaptera novaeangliae).</span>
<span class="attribution"><span class="source">Photo credits (in order a-d): Kevin Neff, Australian Antarctic Division; Mark Hindell, Institute for Marine and Antarctic Studies; Colin Lee Hong, Australian Antarctic Division; Anthony Hull, Australian Antarctic Division.</span></span>
</figcaption>
</figure>
<h2>Looking ahead</h2>
<p>Changes to krill growth habitat may damage more than the ocean food web. Demand for krill oil in health supplements and aquaculture feed is on the rise, and krill are the target of the Southern Ocean’s largest fishery. Anticipating changes in krill availability is crucial to informing the fishery’s sustainable management. </p>
<p>Many environmental drivers interact to create good krill habitat. More research is required, including better models, and an improved understanding of what drives krill to reproduce and survive. </p>
<p>But by examining changes in phytoplankton, we’ve taken significant strides towards predicting climate change impacts on krill and the wider Antarctic marine ecosystem.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-air-above-antarctica-is-suddenly-getting-warmer-heres-what-it-means-for-australia-123080">The air above Antarctica is suddenly getting warmer – here's what it means for Australia</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/138436/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Climate change is changing Antarctic krill habitat. The repercussions for the Southern Ocean food web are huge.Devi Veytia, PhD student , University of TasmaniaStuart Corney, Senior lecturer, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1330512020-03-09T19:02:08Z2020-03-09T19:02:08ZMalnourished bugs: Higher CO2 levels make plants less nutritious, hurting insect populations<figure><img src="https://images.theconversation.com/files/319431/original/file-20200309-118881-1bbmkgn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">These grasshoppers, like many insects around the world, are declining. </span> <span class="attribution"><span class="source">Dave Rintoul</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>The Research Brief is a short take on interesting academic work.</em></p>
<h2>The big idea</h2>
<p>Grasshopper populations, like those of many other insects, <a href="https://doi.org/10.1146/annurev-ento-011019-025151">are declining</a>. My colleagues and I identified a new possible culprit: The plants grasshoppers rely on for food are becoming less nutritious due to increased levels of carbon dioxide in the air.</p>
<p><a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/">Ever-increasing levels of carbon dioxide</a> in the atmosphere tend to <a href="https://doi.org/10.1038/s43017-019-0001-x">promote plant growth by supplying them with extra carbon</a>. But all that added carbon is <a href="https://doi.org/10.7554/eLife.02245">squeezing out other nutrients</a> that plant feeders – like insects and people – need to thrive. These fast-growing plants end up less dense in nutrients like nitrogen, phosphorus and sodium – more like iceberg lettuce than kale.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/319430/original/file-20200309-118960-sq3cff.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Konza Prairie, a protected grassland in Kansas, is a unique research area: decades of data and minimal human influence.</span>
<span class="attribution"><span class="source">Ellen Welti</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>On our study site in a Kansas prairie, my colleagues and I show that across more than 40 species of grasshoppers, <a href="https://www.pnas.org/content/early/2020/03/03/1920012117">total populations are falling at more than 2% a year</a>. This led to an overall reduction in grasshopper numbers over the past two decades of about one-third. These population declines parallel the <a href="http://doi.org/10.6073/pasta/2cf2858e0a8cf82c99f91cfcf191bc14">decline in grassland nutrients</a>. Grasshopper populations vary year to year for many reasons, but my colleagues and I believe that the dilution of plant nutrients caused by elevated CO2 is the most likely reason for the decline.</p>
<p>It adds up to what we call the “nutrient dilution hypothesis”: Increased CO2 is making plants less nutritious per bite and insects are paying the price.</p>
<h2>Why it matters</h2>
<p>Ecologists have thus far focused on pesticide use and the loss of native habitats as causes for insect declines.</p>
<p>These factors aren’t likely at the <a href="http://lter.konza.ksu.edu/konza-prairie-long-term-ecological-research-lter">large native prairie reserve</a> where I work. Yet the 2% per year decline in grasshoppers our study found is eerily similar to the 2% declines reported from long-term studies around the globe of <a href="https://doi.org/10.1371/journal.pone.0216270">moths and butterflies</a>, whose young – caterpillars – are also voracious plant feeders.</p>
<p>Other factors, like pesticide use and habitat destruction, are certainly <a href="https://doi.org/10.1111/icad.12367">hurting insect populations in many places</a>. But since CO2 is increasing globally, my colleagues and I suspect that nutrient dilution is likely bad news for plant-eating insects across a huge variety of habitats, in both pristine and degraded ecosystems. And since insects are crucial parts of all terrestrial food webs, their loss <a href="https://www.nationalgeographic.com/news/2017/08/insect-bug-medicine-food-macneal">affects many other organisms from plants to birds</a>.</p>
<h2>How we do our work</h2>
<p>Konza Prairie is a large protected prairie in northeastern Kansas, and researchers have been collecting data on the grasses, insects, and animals there since the early 1980s. My colleagues and I relied on this long-term data and physical samples from years past to perform our study. </p>
<p>Grasshopper numbers fluctuate on a roughly five-year cycle that follows changes in the climate, like the <a href="https://theconversation.com/what-north-america-can-expect-from-el-nino-51959">El Niño</a> Southern Oscillation. Having a decades-long data set allowed my colleagues and me to clearly separate these cycles from the long-term population decline and see how increasing CO2 levels played a part.</p>
<p>This kind of data is surprisingly rare, which has led to a good deal of controversy regarding the ubiquity of insect declines. Sites like the Konza Prairie (part of the NSF-funded <a href="https://lternet.edu/">Long-Term Ecological Research Network</a>) are on the front lines in documenting Earth’s changing ecosystems.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=614&fit=crop&dpr=1 754w, https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=614&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/318922/original/file-20200305-106584-15xc07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=614&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Block print of a Showy grasshopper (<em>Hesperotettix speciosus</em>) eating a sunflower leaf.</span>
<span class="attribution"><span class="source">Ellen Welti</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>What still isn’t known?</h2>
<p>Nutrient dilution by CO2 is a compelling hypothesis for why widespread insect declines are happening. Our data jibes with other experiments that pump CO2 into ecosystems and <a href="https://doi.org/10.1111/j.1365-2486.2007.01392.x">drive down both plant nutrients and insect growth</a>.</p>
<p>But solid data on insect numbers over time is still quite rare, and there are still more questions than answers. How widespread is nutrient dilution in ecosystems worldwide? Are plant-feeding insects suffering the greatest declines? Which ecosystems will be hardest hit?</p>
<p>At present, we ecologists lack even basic population estimates for most of Earth’s invertebrate species, which comprise the vast majority of animal diversity.</p>
<p>I suspect that if nutrient dilution by CO2 is indeed widespread, it will likely be affecting Earth’s ecosystems and organisms – including humans – for generations to come, at least as long as fossil fuels burn and CO2 levels continue to rise.</p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/133051/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ellen Welti receives funding from the National Science Foundation (NSF) Division of Environmental Biology (DEB) grants 1556280 and 1440484.</span></em></p>Insect populations are falling as what they eat becomes more like iceberg lettuce and less like kale.Ellen Welti, Postdoctoral Researcher of Biology, University of OklahomaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1264842020-01-22T13:37:24Z2020-01-22T13:37:24ZStoneflies and mayflies, canaries of our streams<figure><img src="https://images.theconversation.com/files/308426/original/file-20200103-11900-2fldm.jpg?ixlib=rb-1.1.0&rect=214%2C118%2C1913%2C1275&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The presence of mayflies and stone flies indicates clean water is nearby.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/andrew_ww/7275127502">Andrew/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Experienced anglers recognize that for a trout, the ultimate “steak dinner” is a stonefly or mayfly. That’s why fly fishing enthusiasts will go to extreme lengths to imitate these graceful, elegant and fragile insects. </p>
<p>I share their passion, but for different reasons. As a an entomologist who has <a href="https://bspm.agsci.colostate.edu/people-button/faculty/boris-kondratieff/">studied stoneflies and mayflies</a> for over 40 years, I’ve discovered these insects have value far beyond luring trout – they are indicators of water quality in streams and are a crucial piece of the larger food web. And they are in trouble.</p>
<h2>Collecting bugs</h2>
<p>I have served as director of the <a href="https://bspm.agsci.colostate.edu/gillette-museum/">C. P. Gillette Museum of Arthropod Diversity</a> since 1986. The greatest thrill of my career has been collecting and adding mayflies and stoneflies to our collection.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/309127/original/file-20200108-107219-1r624aq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Boris Kondratieff collecting aquatic insects in Oregon with former student Chris Verdone.</span>
</figcaption>
</figure>
<p>To find specimens, I have traveled to pristine streams in every U.S. state, Canada, Mexico, Central America, Brazil, Ecuador, the Arabian Peninsula and Europe. My collecting trips have yielded more than 100 new species of mayflies and stoneflies.</p>
<p>One of my favorites literally fell into my lap as I was beating lush foliage along a pristine stream in southern Oregon during May 2014. The beating sheet is an efficient means of sampling dense, streamside vegetation, where adult insects hide. The sheet itself is made of sturdy canvas stretched over two wooden cross members. A stick is used to knock the insects from the vegetation onto the canvas, where they are collected.</p>
<p>When I saw a large yellow and black insect drop onto my sheet, I knew immediately it was a new stonefly species, previously unknown to science. I was ecstatic. My colleagues and I <a href="https://www.researchgate.net/publication/315373464_KATHROPERLA_SISKIYOU_A_NEW_STONEFLY_SPECIES_FROM_CALIFORNIA_AND_OREGON_USA_PLECOPTERA_CHLOROPERLIDAE">subsequently described it as <em>Kathroperla siskiyou</em></a>, after the Siskiyou mountains of southern Oregon. </p>
<p>Mayflies and stoneflies thrive in unpolluted water – a fact my colleagues and I have witnessed firsthand on our numerous expeditions. Not only do we see greater overall abundance of these insects in clean streams, but more diversity of species, as well. In polluted areas, we observe the exact opposite. Without a doubt, the presence or absence of mayflies and stoneflies in a stream <a href="https://www.epa.gov/national-aquatic-resource-surveys/indicators-benthic-macroinvertebrates">is a reliable indicator of the quality of its water</a>. </p>
<p>The role of mayflies and stoneflies in the food chain is fundamental, as well. Immature mayflies and stoneflies consume algae, living plants, dead leaves, wood and each other. In this nymph phase, when they have gills and live exclusively underwater, they are an important food source for many animals further up the food chain, including fish and wading birds. When the mayflies and stoneflies emerge from the water as adults, they are essential food for spiders, other insects such as dragonflies and damselflies, and many kinds of birds and bats.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308425/original/file-20200103-11914-1yaa33q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mayflies are on the menu for this hungry fledgling.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/keithmwilliams/48561842382/">Keith Williams/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Currently, scientists estimate that <a href="https://doi.org/10.1016/j.biocon.2019.01.020">33% of all aquatic insects</a> are threatened with extinction worldwide. Many of these species are mayflies and stoneflies. The mayfly species <a href="https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=101536#null"><em>Ephemera compar</em> has already gone extinct in Colorado</a>, and several <a href="http://cnhp.colostate.edu/ourdata/trackinglist/arthropods_insects/">other species of aquatic insects are threatened in my home state</a>.</p>
<h2>Life drains into a stream</h2>
<p><a href="https://www.ngwa.org/what-is-groundwater/About-groundwater/information-on-earths-water">Less than 1% of Earth’s water is potable</a> and available for human use. Maintaining water quality has become an ever increasing challenge because of the large number of chemicals people use in everyday life and in commerce. Common contaminants such as sediment, organic enrichment including fertilizers and animal waste and heavy metals are constantly <a href="https://www.environmentalpollutioncenters.org/water/causes/">making their way into the waters</a>, as well. Declining water quality is like a police siren alerting humanity to current, ongoing and emerging pollution problems.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308428/original/file-20200103-11914-jlv768.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Native plantings along a waterway can reduce storm water runoff.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/native-plantings-along-riparian-zone-waterway-1122153395">Sheryl Watson/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>One of my great passions is to enlighten others on how to protect the most valuable natural resource of the planet: streams and rivers. Individually, citizens can make a difference. <a href="https://www.epa.gov/npdes/npdes-stormwater-program">Storm water is the number one water quality problem</a> nationally. Enhancing and planting <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/home/?cid=nrcs143_023568">riparian buffers</a> – that is, planted areas near streams – can help to prevent precipitation and sprinkler runoff. People can also prioritize using only native plants; decreasing mowing areas; recycling or composting yard waste; using less or no fertilizer; avoiding the use of pesticides; and bagging pet waste. Insisting that environmental laws be enforced and strengthened will also help reduce water pollution.</p>
<p>Without clean water, life on Earth will become difficult or impossible for mayflies and stoneflies, not to mention people.</p>
<p>[ <em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/126484/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Boris Kondratieff receives funding from National Park Service, Agricultural Experiment Station, and National Science Foundation.. </span></em></p>Mayflies and stone flies are extremely vulnerable to water pollution, which has implications for the larger food chain.Boris Kondratieff, Professor of Entomology and Curator of the C. P. Gillette Museum of Arthropod Diversity, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1209392019-07-25T15:06:16Z2019-07-25T15:06:16ZShark Week looms, but don’t panic<figure><img src="https://images.theconversation.com/files/285622/original/file-20190724-110166-10lkqop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's OK, I'm a filter feeder: Whale shark off Indonesia.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/8jtUkk">Marcel Ekkel/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Sharks elicit outsized fear, even though the risk of a shark bite is infinitesimally small. As a <a href="https://scholar.google.com/citations?user=FKrC4FYAAAAJ&hl=en">marine biologist</a> and director of the <a href="https://www.floridamuseum.ufl.edu/sharks/">Florida Program for Shark Research</a>, I oversee the <a href="https://www.floridamuseum.ufl.edu/shark-attacks/">International Shark Attack File</a> – a global record of reported shark bites that has been maintained continuously since 1958. </p>
<p>We are careful to emphasize how rare shark bites are: You are 30 times more likely to be struck by lightning than be bitten by a shark. You are more likely to die while <a href="https://theconversation.com/why-do-people-risk-their-lives-for-the-perfect-selfie-55937">taking a selfie</a>, or be <a href="https://www.floridamuseum.ufl.edu/shark-attacks/odds/compare-risk/nyc-biting-injuries/">bitten by a New Yorker</a>. In anticipation of the anxiety that’s typically generated by the Discovery Channel’s <a href="https://www.discovery.com/shark-week">Shark Week programming</a>, here are a few things about sharks that are often overlooked.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/Bz_foeEj4D0/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<h2>A big, diverse family</h2>
<p>Not all sharks are the same. Only a dozen or so of the roughly 520 shark species pose any risk to people. Even the three species that account for almost all shark bite fatalities – the <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharodon-carcharias/">white shark</a> (<em>Carcharodon carcharias</em>), <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/galeocerdo-cuvier/">tiger shark</a> (<em>Galeocerdo cuvier</em>) and <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharhinus-leucas/">bull shark</a> (<em>Carcharhinus leucas</em>) – are behaviorally and evolutionarily very different from one another. </p>
<p>The tiger shark and bull shark are genetically as different from each other as a dog is from a rabbit. And both of these species are about as different from a white shark as a dog is from a kangaroo. The evolutionary lineages leading to the two groups split 170 million years ago, during the age of dinosaurs and before the origin of birds, and <a href="https://www.ck12.org/book/CK-12-Human-Biology/section/7.2/">110 million years before the origin of primates</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=339&fit=crop&dpr=1 600w, https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=339&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=339&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=426&fit=crop&dpr=1 754w, https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=426&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/285713/original/file-20190725-136764-1xsdvll.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=426&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">White, tiger and bull sharks are distinct species that diverged genetically tens of millions of years ago.</span>
<span class="attribution"><span class="source">Gavin Naylor</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Yet many people assume all sharks are alike and equally likely to bite humans. Consider the term “shark attack,” which is scientifically equivalent to “mammal attack.” Nobody would equate dog bites with hamster bites, but this is exactly what we do when it comes to sharks. </p>
<p>So, when a reporter calls me about a fatality caused by a white shark off Cape Cod and asks my advice for beachgoers in North Carolina, it’s essentially like asking, “A man was killed by a dog on Cape Cod. What precautions should people take when dealing with kangaroos in North Carolina?” </p>
<h2>Know your species</h2>
<p>Understanding local species’ behavior and life habits is one of the best ways to stay safe. For example, almost all shark bites that occur off Cape Cod are by white sharks, which are a large, primarily cold-water species that spend most of their time in isolation feeding on fishes. But they also aggregate near seal colonies that provide a reliable food source at certain times of the year. </p>
<p>Shark bites in the Carolinas are by warm-water species like bull sharks, tiger sharks and <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharhinus-limbatus/">blacktips</a> (<em>Carcharhinus limbatus</em>). Each species is associated with particular habitats and dietary preferences. </p>
<p>Blacktips, which we suspect are responsible for most relatively minor bites on humans in the southeastern United States, feed on schooling bait fishes like menhaden. In contrast, bull sharks are equally at home in fresh water and salt water, and are often found near estuaries. Their bites are more severe than those of blacktips, as they are larger, more powerful, bolder and more tenacious. Several fatalities have been ascribed to bull sharks. </p>
<p>Tiger sharks are also large, and are responsible for a significant fraction of fatalities, particularly off the coast of volcanic islands like Hawaii and Reunion. They are tropical animals that often venture into shallow water frequented by swimmers and surfers. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/yDqzGOa-adc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Sharks are important predators that play critical roles in ocean food chains.</span></figcaption>
</figure>
<h2>Humans are not targets</h2>
<p>Sharks do not “hunt” humans. Data from the International Shark Attack File compiled over the past 60 years show a tight association between shark bites and the number of people in the water. In other words, shark bites are a simple function of the probability of encountering a shark. </p>
<p>This underscores the fact that shark bites are almost always cases of mistaken identity. If sharks actively hunted people, there would be many more bites, since humans make very easy targets when they swim in sharks’ natural habitats.</p>
<p>Local conditions can also affect the risk of an attack. Encounters are more likely when sharks venture closer to shore, into areas where people are swimming. They may do this because they are following bait fishes or seals upon which they prey.</p>
<p>This means we can use environmental variables such as temperature, tide or weather conditions to better predict movement of bait fish toward the shoreline, which in turn will predict the presence of sharks. Over the next few years, the Florida Program for Shark Research will work with colleagues at other universities to monitor onshore and offshore movements of tagged sharks and their association with environmental variables so that we can improve our understanding of what conditions bring sharks close to shore. </p>
<h2>More to know</h2>
<p>There still is much to learn about sharks, especially the 500 or so species that have never been implicated in a bite on humans. One example is the tiny <a href="https://www.newsweek.com/one-worlds-rarest-sharks-also-one-most-adorable-325280">deep sea pocket shark</a>, which has a strange pouch behind its pectoral fins. </p>
<p>Only two specimens of this type of shark have ever been caught – one off the coast of Chile 30 years ago, and another more recently in the Gulf of Mexico. We’re not sure about the function of the pouch, but suspect it stores luminous fluid that is released to distract would-be predators – much as its close relative, the <a href="https://sharkdevocean.wordpress.com/2015/04/23/second-ever-pocket-shark-discovered-in-gulf-of-mexico/">tail light shark</a>, releases luminous fluid from a gland on its underside near its vent. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/UTO5debfmsg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The goblin shark, found mainly off Asia, can project its jaw forward to pull prey into its mouth.</span></figcaption>
</figure>
<p>Sharks range in form from the bizarre <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/mitsukurina-owstoni/">goblin shark</a> (<em>Mitsukurina owstoni</em>), most commonly encountered in Japan, to the gentle filter-feeding <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/rhincodon-typus/">whale shark</a> (<em>Rhincodon typus</em>). Although whale sharks are the largest fishes in the world, we have yet to locate their nursery grounds, which are likely teeming with thousands of <a href="https://www.earthtouchnews.com/oceans/sharks/baby-whale-shark-rescued-from-gillnet-in-india-video/">foot-long pups</a>. Some deepwater sharks are primarily known from submersibles, such as the giant <a href="https://twitter.com/gavinnaylor/status/1146144452681113601">sixgill shark</a>, which feeds mainly on carrion but probably also preys on other animals in the deep sea.</p>
<p>Sharks seem familiar to almost all of us, but we know precious little about them. Our current understanding of their biology barely scratches the surface. The little we do know suggests they are profoundly different from other vertebrate animals. They’ve had 400 million years of independent evolution to adapt to their environments, and it’s reasonable to expect they may be hiding more than a few tricks up their gills.</p>
<p><em>This is an updated version of an article originally published July 25, 2019.</em></p>
<p>[ <em><a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=expertise">Expertise in your inbox. Sign up for The Conversation’s newsletter and get a digest of academic takes on today’s news, every day.</a></em> ]</p><img src="https://counter.theconversation.com/content/120939/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gavin Naylor receives funding from the National Science Foundation and the Lenfest Ocean Program.</span></em></p>Media coverage of sharks often exaggerates risks to people, but more than 500 shark species have never been known to attack humans, and there’s lots to learn about them.Gavin Naylor, Director, Florida Program for Shark Research, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1117492019-02-26T19:10:51Z2019-02-26T19:10:51ZWe can ‘rewild’ swathes of Australia by focusing on what makes it unique<figure><img src="https://images.theconversation.com/files/260362/original/file-20190222-195853-ux6kqn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Eastern quolls have been introduced in Booderee Nation Park as part of a rewilding project.</span> <span class="attribution"><span class="source">Oisin Sweeney</span></span></figcaption></figure><p>Since colonisation, a dizzying array of Australia’s native species and ecosystems have been <a href="https://www.pnas.org/content/112/15/4531.abstract">altered or removed altogether</a>. It therefore seems natural to consider the idea of restoring what’s been lost – a process termed “rewilding”.</p>
<p>Now a global trend, rewilding projects aim to restore functional ecosystems. The rationale is that by reactivating the often complex relationships between species – such as apex predators and their prey, for example – these ecosystems once again become able to sustain themselves. </p>
<p>Rewilding has successfully captured the public interest, particularly overseas. Conservation group <a href="https://rewildingeurope.com/">Rewilding Europe</a> has a network of <a href="https://rewildingeurope.com/european-rewilding-network/">eight rewilding areas</a> and a further 59 related projects, covering 6 million hectares in total. </p>
<p>The <a href="https://www.sciencedaily.com/releases/2018/11/181108134136.htm">reintroduction of wolves</a> to Yellowstone National Park in the United States remains the most recognised example of rewilding. The wolves reduced elk numbers and changed their behaviour, which allowed vegetation to grow and stabilise stream banks.</p>
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Read more:
<a href="https://theconversation.com/from-feral-camels-to-cocaine-hippos-large-animals-are-rewilding-the-world-83301">From feral camels to 'cocaine hippos', large animals are rewilding the world</a>
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<p>It’s not hard to see why rewilding is popular, given that it sounds a note of <a href="https://www.theguardian.com/environment/2018/jun/03/rewilding-conservation-bison-wolves-beaver-giant-tortoise-tigers">hope and inspiration</a> amid the seemingly endless stories of <a href="https://www.theguardian.com/environment/2017/oct/18/warning-of-ecological-armageddon-after-dramatic-plunge-in-insect-numbers">despair over ecological disaster</a>. </p>
<p>But in Australia, we need to do rewilding differently. The particular challenges we face with issues such as introduced species mean that, like Vegemite, our rewilding future must have a unique flavour.</p>
<h2>Australian values</h2>
<p>Our recently published <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/cobi.13280">paper</a> builds on findings from a <a href="https://npansw.org/npa/campaigns/statewide-campaigns/rewilding/">rewilding forum</a> held in Sydney in late 2016. Academics, government and non-government agencies met to discuss some of the outstanding issues around rewilding in Australia. Despite the large, diverse audience and wide-ranging views, the forum succeeded in identifying some <a href="https://npansw.org/npa/campaigns/statewide-campaigns/rewilding/">key themes</a>.</p>
<p>Peninsulas often make good locations for rewilding in Australia because their geography allows the impacts of introduced predators to be minimised. Booderee National Park at Jervis Bay has reintroduced <a href="https://blog.parksaustralia.gov.au/2015/02/09/potoroos-settling-in-at-booderee/">long-nosed potoroos</a>, <a href="https://www.australiangeographic.com.au/news/2017/06/bandicoot-born-in-booderee-national-park-for-the-first-time-in-a-century/">southern brown bandicoots</a> and <a href="https://rewildingaustralia.org.au/articles/eastern-quoll-joeys-leave-pouch-november-2018-update">eastern quolls</a>.</p>
<p>A much bigger Peninsula, Yorke, in South Australia, is the site of an <a href="https://www.wwf.org.au/news/news/2019/australia-launches-largest-ever-rewilding-project#gs.h9154oig">ambitious project</a> to reintroduce 20 species currently extinct in the area. </p>
<p>The widespread removal of dingoes has reduced natural control on introduced species such as foxes and cats. This in turn has <a href="http://dx.doi.org/10.1111/j.1469-185X.2011.00203.x">allowed</a> feral cats and red foxes to prey on small digging native mammals in the absence of a larger competitor. Meanwhile, declines in Tasmanian devils <a href="http://dx.doi.org/10.1111/cobi.12152">have been mirrored</a> by declines in smaller predators like eastern quolls, and changes to <a href="https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2018.1582">cat behaviour</a>, suggesting devils indirectly affect other species. </p>
<p>Many of these digging mammals have declined continent-wide and disappeared completely from other areas. This in turn has resulted in <a href="https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1442-8903.2003.00145.x">knock-on effects</a>, such as altered fire regimes and changes to plant diversity.</p>
<p>It’s no surprise, then, that our workshop identified restoring predators and small mammals as priorities in Australia. Lots of work is already going on to restore small mammal populations, such as via <a href="http://www.australianwildlife.org/sanctuaries.aspx">Australian Wildlife Conservancy’s</a> and <a href="http://www.aridrecovery.org.au/">Arid Recovery’s</a> fenced exclosures, from which foxes and cats have been eliminated. </p>
<p>But exclosures are also contrary to the aims of rewilding, because they need ongoing maintenance and do not help the ecosystem inside to be self-sustaining. They can also <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721078/">exacerbate prey naïveté</a>, whereby the native mammals fail to recognise and avoid introduced predators. </p>
<p>It may therefore be useful to view fences as a stepping stone to restoring small mammal populations to broader landscapes, helped by a variety of means including <a href="http://dx.doi.org/10.1111/1365-2664.12947">promoting co-evolution</a> of native and introduced species, incentives to farmers, and the use of <a href="http://dx.doi.org/10.1111/cobi.12959">guardian animals</a>.</p>
<h2>Australia is different</h2>
<p><a href="https://link.springer.com/article/10.1007/s10021-012-9558-7">Passive rewilding</a> – the removal of human agriculture, resulting in the return of natural vegetation – has had positive impacts on biodiversity in Europe. It could have similarly positive impacts here, for example by increasing the density of tree hollows in previously logged forest and woodland. But a complete removal of management is unlikely to be effective because of, for example, the need to manage fire and the presence of introduced species like miner birds that exert influences on <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/ddi.12294">other species</a> and even <a href="https://www.environment.nsw.gov.au/resources/vegetation/bell-miner-associated-dieback-independent-review.pdf">entire ecosystems</a>. </p>
<p>In arid areas, simply removing agriculture is unlikely to halt the declines in biodiversity unless deliberate steps are taken to control pest plants and animals and to shift the ecosystem into a preferred state. In oceans, where rewilding is no less urgent due to declines in large predatory fish, passive rewilding may be more feasible, as marine protected areas can result in recovery of fish, provided <a href="https://www.nature.com/articles/nature13022">certain key criteria</a> are met.</p>
<p>Reintroducing large (bigger than 100kg) herbivores is part of rewilding efforts in <a href="https://rewildingeurope.com/rewilding-in-action/wildlife-comeback/bison/">Europe</a> and <a href="http://www.pleistocenepark.ru/en/">Asia</a>. Yet in Australia, all large herbivores are introduced and are generally perceived as having negative impacts. </p>
<p>“Natural” control of such species is not possible due to a lack of big native predators. Introducing “surrogates” of long-extinct predators (as are <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(11)00346-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982211003460%3Fshowall%3Dtrue">used elsewhere</a> in rewilding) would have predictable results in terms of human acceptance (farmers wouldn’t like it), but uncertain impacts on ecosystems.</p>
<h2>What about people?</h2>
<p>People can benefit from rewilding – either directly, through <a href="https://rewildingeurope.com/rewilding-europe-capital/">wildlife tourism income</a> or <a href="https://theconversation.com/why-do-some-graziers-want-to-retain-not-kill-dingoes-77457">reduced kangaroo grazing on farmland</a>, or indirectly such as via provision of services <a href="https://www.theguardian.com/environment/2017/dec/12/uk-to-bring-back-beavers-in-first-government-flood-reduction-scheme-of-its-kind">like flood control</a>. So rewilding should not, as has been <a href="https://www.sciencedirect.com/science/article/pii/S0016718514002504?via%3Dihub">suggested elsewhere</a>, necessarily separate humans from nature. Aboriginal owned and managed land offers huge opportunities in this regard because it covers <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0173876">52% of the country and is home to many threatened species</a>. In urban areas, rewilding will have to be a compromise between what is acceptable to humans and what benefits ecosystems most.</p>
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Read more:
<a href="https://theconversation.com/should-we-move-tasmanian-devils-back-to-the-mainland-16388">Should we move Tasmanian Devils back to the mainland?</a>
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<p>There is clearly an appetite among scientists and managers for bold interventions such as <a href="https://rewildingaustralia.org.au/devilfacts">trial reintroductions of Tasmanian devils</a> to mainland Australia to restore <a href="https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(12)00006-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0169534712000067%3Fshowall%3Dtrue">ancient food chains</a> or <a href="https://theconversation.com/lets-move-the-worlds-longest-fence-to-settle-the-dingo-debate-37155">allowing dingoes to return</a> to areas where they occur at low densities and are functionally extinct. Rewilding’s focus on restoration of ecosystem processes can complement, but not replace, existing conservation approaches. For example, we still need to achieve a comprehensive, adequate and representative reserve network on land and at sea. </p>
<p>Development of a rewilding vision and strategy would be a valuable first step towards maximising the potential of rewilding, tracking success, and persuading governments to fund it.</p>
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<p><em>The authors would like to gratefully acknowledge the contribution of Dr Andy Sharp, Natural Resources Northern and Yorke Manager Planning and Programs, to this article.</em></p><img src="https://counter.theconversation.com/content/111749/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Menna Elizabeth Jones receives funding from Australian Research Council and US National Institute of Health. </span></em></p><p class="fine-print"><em><span>Mike Letnic receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Thomas Newsome is a member of the Australian Mammal Society, Ecological Society of Australia, Royal Zoological Society of NSW, and is Treasurer of the Australasian Wildlife Management Society. He has received funding from National Geographic, Australian Geographic, The Australia & Pacific Science Foundation, and the Australian Government NESP Threatened Species Recovery Hub.</span></em></p><p class="fine-print"><em><span>John Turnbull and Oisín Sweeney do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Rewilding is gaining popularity around the world, as a means to restore ecosystems to their ancient state. But just like Vegemite, Australian rewilding projects need to have a unique flavour.Oisín Sweeney, Senior Ecologist at the National Parks Association of NSW, Research Fellow, University of SydneyJohn Turnbull, PhD Candidate, UNSW SydneyMenna Elizabeth Jones, Associate professor, University of TasmaniaMike Letnic, Professor, Centre for Ecosystem Science, UNSW SydneyThomas Newsome, Lecturer, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1034922018-09-26T11:23:57Z2018-09-26T11:23:57ZOmnivore sharks and cannibal hippos – the strange truth about dinnertime in the animal kingdom<figure><img src="https://images.theconversation.com/files/238101/original/file-20180926-48662-1ihwgwx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hippo-mouth-open-kruger-national-park-510400405?src=WchcNLAlxVcBVCBdBtDENg-1-1">Katy Foster/Shutterstock</a></span></figcaption></figure><p>Animals don’t always stick to traditional menus, and they certainly don’t read the descriptions of their diets we include in textbooks. When it recently emerged that a notorious carnivore (a shark) was <a href="http://www.theguardian.com/environment/2018/sep/05/bonnethead-omnivorous-shark-species-identified">actually selecting the vegetarian option</a>, scientists were intrigued. </p>
<p>We’ve known for some time that bonnethead sharks consume large quantities of seagrass, but this was <a href="http://rspb.royalsocietypublishing.org/content/285/1886/20181583?utm_source=yxnews&utm_medium=mobile">thought to be accidental</a> – pesky vegetation finding its way into their mouths while they were hunting crabs. Yet this new research has revealed that the bonnethead shark actually digests and draws nutrition from the seagrass – the first known omnivorous shark.</p>
<p>This finding isn’t just an interesting new fact about sharks, it’s an important acknowledgement that environments need to be protected for reasons we may not have even considered. Who’s to say there aren’t other examples of species interacting with their habitats in unexpected ways? </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/238097/original/file-20180926-48665-13kckft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A bonnethead shark contemplating its next meal.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bonnethead_new_orleans.jpg">Mills Baker/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The natural world is far from fully understood, and while new scientific discoveries continue to be made, these revelations aren’t keeping pace with the <a href="https://ourworld.unu.edu/en/rate-of-environmental-degradation-puts-life-on-earth-at-risk-say-scientists">rate of environmental destruction</a>. Equally, nature seems to have a habit of surprising us. Or perhaps it’s just that we forget that animals don’t read the books we write about them.</p>
<p>In the field of feeding ecology alone, there are multiple examples of animals breaking the “rules” we’ve set for them. If the plant-eating shark was a shock, what about supposedly strict vegetarians turning to meat? Although <a href="https://link.springer.com/article/10.1007/s10344-015-0980-y">carcass-eating bunnies</a> and <a href="https://news.nationalgeographic.com/news/2015/01/150123-hippos-cannibalism-animals-food-science/">cannibal hippopotamuses</a> may sound like something out of a horror movie, they aren’t restricted to the imaginations of screenwriters. </p>
<h2>The food chain’s grislier links</h2>
<p>Let’s take the case of the hippo first. These iconic African animals are described in most textbooks as strict herbivores, who only use their large tusks and teeth for <a href="https://www.livescience.com/27339-hippos.html">display and territorial fights</a>. However, the rotund vegetarians have been seen consuming animal carcasses, <a href="https://news.nationalgeographic.com/news/2015/01/150123-hippos-cannibalism-animals-food-science/">including other hippos</a>. This behaviour is not isolated to a single observation and scientists believe it may even help diseases such as <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/mam.12056">anthrax to spread more widely</a> throughout hippo populations.</p>
<p>As for the cute and fluffy bunnies, even these will choose meat over veg in some circumstances. In a mixed-species zoo exhibit, the chicken and mice offered to captive birds of prey were <a href="https://link.springer.com/article/10.1007/s10344-015-0980-y">actually consumed by domestic rabbits</a> sharing the enclosure.</p>
<p>More gruesome examples of erstwhile vegetarians abound. The poor table manners of sheep and deer were reported in the late 1980s, as they were seen biting the legs, wings and heads off <a href="https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1988.tb02451.x">fledgling chicks</a>. Only a few months ago, startling footage of rare <a href="https://twitter.com/nat_b_zielonka/status/1001555173859381248?lang=en">curlew nests</a> being raided by sheep in the UK caused a sensation on social media.</p>
<p>But the dining tables are turned in New Zealand, where it’s sheep who are the victims. The kea bird, New Zealand’s friendly “mountain clown”, is a native parrot with a taste for open wounds on livestock, and can often be seen plucking tissue and blood from the animals while perched on their backs. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/237928/original/file-20180925-149958-fw02du.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Don’t be fooled.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/keas-alpine-parrots-sitting-together-arthurs-163096301?src=x6q_ASLTTMfuVnWpdk7tRw-1-7">Shaun Jeffers/Shutterstock</a></span>
</figcaption>
</figure>
<p>As early as 1895, the <a href="https://www.nature.com/articles/052629b0.pdf">species’ feeding habits</a> were the subject of scientific interest. However, it was the interest of farmers in these birds that warranted the greatest concern, as the keas’ apparent thirst for blood prompted <a href="https://www.nzgeo.com/stories/kea-the-feisty-parrot/">a campaign to exterminate them</a>.</p>
<p>The jury may still be out as to whether keas are clowns or killers, but what does appear accurate is that they are highly <a href="https://www.nzgeo.com/stories/kea-the-feisty-parrot/">adaptable opportunists</a> who don’t play by any rules we may make for them.</p>
<h2>A fresh look at food choices</h2>
<p>These examples <a href="https://link.springer.com/article/10.1007/s10344-015-0980-y">force us to rethink</a> the notion that feeding habits are a simple reflection of gut anatomy. Perhaps feeding behaviour and strategies are driven more by opportunity than <a href="https://link.springer.com/article/10.1007/s10344-015-0980-y">physiology</a>.</p>
<p>Rabbits, hippos and keas don’t have anatomies which make them good at capturing prey, but that doesn’t mean to say they can’t, and won’t, make use of animal tissues if they get the chance. Likewise, not all carnivores may be as hungry for meat as we once thought. </p>
<p>Free-living animals must make the most of the opportunities presented in their environment. If that means tucking into a chum that’s just died, or taking a <a href="https://theflexitarian.co.uk/flexitarian-diet-2/">flexitarian</a> approach to one’s dietary regime, then that’s what they’ll do. </p>
<p>After all, as my colleague <a href="https://www.researchgate.net/profile/Ellen_Dierenfeld">Ellen Dierenfeld</a> pointed out, carnivores and herbivores are just two extreme ends of the scale, and it’s only humans that tend to think of the points on that scale as immovable. So until the animals learn to write their own textbooks, we should be prepared for the unexpected, and never take anything off the menu when it comes to understanding the natural world.</p><img src="https://counter.theconversation.com/content/103492/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katherine Whitehouse-Tedd does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Sharks eating seagrass? Sounds fishy, but the reality is that animals don’t conform to the strict categories we try to place on their diets.Katherine Whitehouse-Tedd, Senior Lecturer, School of Animal, Rural and Environmental Sciences, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/989982018-07-10T10:38:06Z2018-07-10T10:38:06ZRock ‘n’ roll is noise pollution – with ecological implications that can spread through a food web<figure><img src="https://images.theconversation.com/files/226364/original/file-20180705-122250-eoerm5.jpg?ixlib=rb-1.1.0&rect=274%2C203%2C2514%2C1735&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not interested in your new favorite band.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/tjgehling/33349047406">TJ Gehling</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Despite being <a href="https://www.riaa.com/gold-platinum/?tab_active=top_tallies&ttt=T1A#search_section">one of the best-selling albums of all time</a>, ideology from AC/DC’s “Back in Black” album has gone unchallenged for nearly 40 years. The album’s closing track posited a testable hypothesis, asserting with rock-star confidence that “Rock ‘n’ roll ain’t noise pollution.” Opinions may vary from person to person, but little scientific evidence has been evaluated to determine if rock music is noise pollution … until now. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/X_IWlPHMziU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">AC/DC – ‘Rock And Roll Ain’t Noise Pollution’</span></figcaption>
</figure>
<p>My research group <a href="https://doi.org/10.1002/ece3.4273">recently tested the “AC/DC hypothesis.”</a> Sadly, we report that, at least in some situations, rock ‘n’ roll in fact is noise pollution. </p>
<p>OK, yes, our experiment may sound silly or frivolous. But our hope is to focus a little more attention on how sounds – whether Angus Young’s guitar licks or the steady drone from a busy highway – can affect ecosystems. Our work demonstrates that the effects of noise pollution are not restricted just to the animals directly affected by the sounds, but can alter their behaviors and interactions with other animals and plants, spreading the effects throughout an ecosystem.</p>
<h2>Noise and nature</h2>
<p>Noise pollution has been recognized as an <a href="https://theconversation.com/human-noise-pollution-is-disrupting-parks-and-wild-places-78074">increasing threat for wildlife</a>. For instance, scientists have shown that the sounds of <a href="https://doi.org/10.2981/wlb.00225">mining can affect deer behavior</a>. Noise from <a href="https://e360.yale.edu/features/how_ocean_noise_pollution_wreaks_havoc_on_marine_life">ocean drilling affects marine life</a>. And sounds from recreational vehicles are a particular <a href="https://home.nps.gov/subjects/sound/noise-sources.htm">concern in natural places</a> – spawning an <a href="https://electrek.co/2018/03/03/tesla-inspired-taiga-electric-snowmobile/">industry of quieter electric alternatives</a>.</p>
<p>Most existing studies focus largely on the direct effects of noise – an animal hears the noise in its environment and is affected. But of course, animals don’t live in isolation. They’re embedded within a tangle of food web interactions with other species. So by affecting even one species, noise pollution – or any other environmental change – may generate indirect effects that spread from individual to individual, and eventually may affect entire communities.</p>
<p>Studying noise pollution and its cascading indirect effects is difficult, especially on large free-roaming animals. To test these interactions, <a href="https://scholar.google.com/citations?user=NuXykqQAAAAJ&hl=en&oi=ao">my</a> <a href="https://www.bartonlab.net">research group</a> will often scale-down our experiments and use smaller model systems.</p>
<p>Specifically, we study lady beetles, including <em><a href="https://biocontrol.entomology.cornell.edu/predators/Harmonia.php">Harmonia axyridis</a></em>, the multi-colored Asian lady beetle. Unknown to many, lady beetles are among the most <a href="https://www.nytimes.com/2018/06/01/science/ladybugs-aphids-toxic.html">important predators of agricultural pests</a> such as soybean aphids. By voraciously consuming aphids in soybean fields, lady beetles provide natural <a href="https://theconversation.com/us/topics/biological-control-7766">biological control</a> of pests and minimize the amount of pesticides needed on crops. Lady beetles provide an important ecosystem service – anything that disrupts their ability to attack aphids could be perceived as having a negative effect on society.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=366&fit=crop&dpr=1 600w, https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=366&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=366&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=460&fit=crop&dpr=1 754w, https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=460&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/226395/original/file-20180705-122277-hm38fq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=460&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The plants in their listening setup.</span>
<span class="attribution"><span class="source">Brandon Barton</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Firing up the hi-fi in the ecology lab</h2>
<p>With the help of colleagues – and fellow AC/DC fans – <a href="https://www.biology.msstate.edu/people/staff.php?id=vk85">Vince Klink</a> and <a href="https://scholar.google.com/citations?user=G84D9fQAAAAJ&hl=en&oi=ao">Marcus Lashley</a>, my team of undergraduate and graduate students sought to determine if noise pollution would decrease lady beetle effectiveness at controlling aphids. Further, we suspected that reducing predation rates on aphids would allow the pest population to explode, which would in turn reduce soybean yield. </p>
<p>First we wanted to figure out what sounds affected lady beetle feeding rates. We placed lady beetle larvae within small enclosures with a known number of aphids to eat, and allowed them to forage either in silence or under loud conditions. We played sounds through computer speakers at maximum volume: 95-100 decibels, approximately equal to a lawn mower or outboard motor.</p>
<p>In addition to AC/DC, we queued up one of our favorite country music albums – “Wanted! The Outlaws” featuring Willie Nelson, Waylon Jennings and others. We DJ’d a mix of rock music, including Lynyrd Skynyrd, Guns ‘n’ Roses, The Supersuckers, the British folk band Warblefly, and a mix of city sounds such as jackhammers, car horns, and so on.</p>
<p>Our results were good news for country and folk fans – lady beetles agreed that those songs were not noise pollution and continued to attack aphids with the same vigor when serenaded by these genres as they did in silence. However, lady beetles were not fans of AC/DC, the rock mix or city noises, even when played at the same volume as the country and folk treatments. In fact, listening to the “Back in Black” album cut the amount of aphids being eaten during a 16 to 18 hour period almost in half.</p>
<p>At least according to lady beetles, it seemed that rock ‘n’ roll was noise pollution and indirectly benefited agricultural pests. But could it have an effect on soybean plants?</p>
<p>Many researchers have investigated <a href="https://doi.org/10.1016/S2095-3119(13)60492-X">how music affects plant growth</a> with mixed results. However, when we blasted soybean plants with two weeks of nonstop “Back in Black,” we didn’t see any effect on growth. Similarly, we found no effect of continuous AC/DC on pest abundance when we grew aphids on plants without their predators.</p>
<p>But we were interested in whether there was an interactive effect of rock music and predators on pest and plants. So for two weeks, we watched lady beetles attack aphids, while aphids reproduced and plants grew.</p>
<p>When the plants were grown without music, the predators reduced aphid density to nearly zero. As a consequence, the plants grew strong and healthy in the absence of their pest. In contrast, when plants were grown with “Back in Black” blaring, the lady beetles did not control aphids and the pests’ population size was more than 40 times larger than in the silent condition – from an average of about 4 aphids per plant to more than 180. As a consequences of high pest abundance, the plants in music treatments were 25 percent smaller. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/226388/original/file-20180705-122265-1611ax7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Without predators to keep pests in check, crops like soybeans would need to be sprayed more.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/unitedsoybean/10060153913">United Soybean Board</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Cascading effects of noise pollution</h2>
<p>While others have shown that noise pollution can have <a href="https://theconversation.com/how-noise-pollution-is-changing-animal-behaviour-52339">direct effects on organisms and alter their predation rates</a>, our study uniquely demonstrates that these <a href="https://doi.org/10.1002/ece3.4273">effects can cascade throughout a food web</a>.</p>
<p>We also showed that insects are affected by noise pollution, too. Most previous work in this area focused on large, “sexy” megafauna. But insects provide many ecosystem services that are essential for the healthy functioning of our planet. Disrupting insect behaviors such as pollination or predation can have drastic consequences.</p>
<p>Finally, our work empirically evaluated the AC/DC hypothesis for the first time since its inception in 1980. As fans of AC/DC and rock music, we sadly must disagree with the band and concede that rock ‘n’ roll is noise pollution, at least for lady beetles. Of course, rock music is not really a threat to ecosystems. But because loud music is similar to other real-world instances of noise pollution such as the hum of snowmobiles and the <a href="https://www.npr.org/sections/alltechconsidered/2015/08/13/431982136/drones-increase-heart-rates-of-wild-bears-too-much-stress">buzz of drones overhead</a>, our results serve as a proof-of-concept that sound pollution can have pervasive effects throughout an ecosystem.</p>
<p>What about AC/DC’s other hypothesis, that “rock n roll ain’t gonna die?” As rock lovers, we’re happy to report there’s no evidence to contradict that one.</p><img src="https://counter.theconversation.com/content/98998/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brandon Barton does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An AC/DC-loving biologist tests the band’s 1980 assertion that “rock ‘n’ roll ain’t noise pollution.” Turns out it can be – and the negative effects of noise can ripple through an ecosystem.Brandon Barton, Assistant Professor of Biological Sciences, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/978152018-06-07T10:52:33Z2018-06-07T10:52:33ZScientists are using DNA to study ocean life and reveal the hidden diversity of zooplankton<figure><img src="https://images.theconversation.com/files/222047/original/file-20180606-137318-vl23xg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Copepod with eggs (blue). Copepods are typically just a few millimeters long, but are important food sources for small fish.</span> <span class="attribution"><a class="source" href="http://www.photolib.noaa.gov/bigs/fish3260.jpg">NOAA</a></span></figcaption></figure><p>Marine zooplankton are tiny animals, roughly the size of insects you might see on a summer day, that drift with ocean currents. Many of them are lovely, but except for scientists who study them, few people are aware that they are among the most numerous – and important – animals on Earth. </p>
<p><a href="https://scholar.google.com/citations?user=LHN47rkAAAAJ&hl=en&oi=ao">My research</a> focuses on marine zooplankton, which I think of as “charismatic microfauna.” These minute organisms are key players in open ocean food webs and critical as they are the preferred food for many fish. Many species are thought to be found throughout the global ocean. </p>
<p>More than 7,000 species of zooplankton have been described, but we do not know how many total species exist. Since they are important food sources for larger fish, and respond rapidly to environmental shifts and climate change, knowing more about zooplankton is key for understanding the health of ocean ecosystems.</p>
<p><a href="https://bucklin.lab.uconn.edu/">My laboratory</a> has gained new insights into zooplankton diversity using <a href="http://dx.doi.org/%2010.1146/annurev-marine-120308-080950">inexpensive and easy-to-use DNA sequencing</a>. These approaches are providing new tools to identify species. According to some estimates, there could be as many as 70,000 unknown and overlooked zooplankton species yet to be discovered.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222080/original/file-20180606-137288-1apvpyz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Norwegian research vessel GO Sars arriving in Reykjavik, Iceland, on a plankton sampling trip.</span>
<span class="attribution"><span class="source">Ann Bucklin (UConn)</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Key links in ocean ecosystems</h2>
<p>The open ocean is the largest habitat by volume on Earth. Because marine zooplankton are so numerous and diverse, they help to create complex food webs with multiple pathways of who-eats-whom. But changes in environmental conditions, including global warming, can disrupt these systems by <a href="https://doi.org/10.1017/9781108186148.037">altering zooplankton diversity and distribution</a>. </p>
<p>Currently, key zooplankton species are shifting poleward in search of cooler waters in a warming ocean. This is causing major disturbances to ocean ecosystems. For example, the cod fishery in the North Sea crashed after the zooplankton species that was the fish’s preferred prey was <a href="https://doi.org/10.1073/pnas.0913855107">replaced by another closely related copepod species</a> that moved north in response to global warming. </p>
<p>Events like this show that zooplankton can play critical roles in ocean ecosystems, even though scientists know very little about them, and may not appreciate the importance of a given species until it is gone.</p>
<p>Many factors make it challenging to measure marine zooplankton diversity. First, collecting samples from the deep sea is hard work. Research vessels operate around the clock, with scientists on board usually working two six-hour watches each day. We sample zooplankton using electronically operated, highly complex net systems. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=212&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=212&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=212&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=266&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=266&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222041/original/file-20180606-137309-7ui9fv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=266&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sampling deep sea zooplankton using a MOCNESS Multiple Opening Closing Net and Environmental Sensing System.</span>
<span class="attribution"><span class="source">Peter H. Wiebe</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>When the net is recovered, the samples contain many different species and the animals are usually still alive. They are carefully moved into trays for observation and species identification. In spite of the demanding schedule and hard work, I have loved going to sea and have been on many cruises, including stunning explorations of the polar regions of the Arctic and Antarctic Oceans. </p>
<p>For my research, samples collected at sea are quickly preserved for genetic analysis, which is usually done back in the lab. This is painstaking work. Zooplankton as a group are taxonomically complex, meaning that they include many difficult-to-identify and rare species. Also, many important marine organisms, including fishes, lack diagnostic characteristics in their immature (larval) stages.</p>
<h2>Identifying zooplankton species with genetic markers</h2>
<p>To understand, assess and manage marine ecosystems, it is critical to have information about the diversity of species that make them up. But acquiring this information using traditional methods is tedious, expensive and slow.</p>
<p>The job falls to expert morphological taxonomists, who may spend years learning to recognize subtle characteristics that mark differences between species. Since there are 7,000 described species of zooplankton spanning 15 phyla and more than 30 different groups, this work can involve <a href="https://doi.org/10.1016/j.dsr2.2010.09.018">large teams</a>. </p>
<p>But molecular methods are providing important new insights. My laboratory group uses different molecular approaches to study population ecology, population genetics, species diversity and other questions about marine zooplankton. </p>
<p>One efficient approach is to use DNA barcodes – short sequences of DNA – to identify and distinguish species. To do this, we sequence the DNA from a genetic region that is known to occur in all zooplankton, but varies markedly from species to species. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=258&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=258&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=258&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=324&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=324&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222039/original/file-20180606-137285-1unyc74.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=324&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">DNA barcoding entails identifying the species by microscopic examination, taking a photograph of the specimen (ideally while alive), and sequencing the COI barcode gene region.</span>
<span class="attribution"><span class="source">Ann Bucklin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>My laboratory has determined DNA barcodes for many zooplankton species. We use a portion of the mitochondrial cytochrome oxidase I (COI) gene, which is the most commonly sequenced gene region for analysis of species diversity among marine animals. The growing barcode database has been likened to a <a href="https://doi.org/10.1016/j.dsr2.2010.09.025">Rosetta Stone for species identification</a> of global zooplankton. COI sequences for thousands of species of marine animals are now available. They create an invaluable reference library that can be used as a basis for next-gen environmental sequencing, also known as metabarcoding. </p>
<p>Using metabarcoding speeds up our work because we can sequence DNA from zooplankton samples without identifying individual specimens. This “high-throughput” DNA sequencing yields millions of sequences, or <a href="http://dx.doi.org/10.1093/plankt/fbw023">metabarcodes</a>, that represent the target gene region for the entire sample. The resulting sequences can be identified by matching to a database of sequences for known zooplankton species.</p>
<p>Using metabarcoding to analyze zooplankton diversity routinely and reliably poses many challenges. However, a growing community of researchers is working to build reference databases that link DNA barcodes to species names for zooplankton collected anywhere and everywhere throughout the global ocean. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222042/original/file-20180606-137322-qtf2v7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Schematic representation of the processes of DNA barcoding, left, and metabarcoding, right. Colored circles represent extracted genomic DNA, which is composed of the genome of one individual (barcoding) or of multiple copies of the genomes of all the species composing the samples (metabarcoding).</span>
<span class="attribution"><a class="source" href="https://www.researchgate.net/figure/Schematic-representation-of-the-processes-of-DNA-barcoding-left-and-metabarcoding_fig1_262235357">Corell and Rodriguez-Ezpeleta, 2014.</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>A global effort</h2>
<p>Scientists expect that DNA barcoding and metabarcoding will significantly revise global estimates of zooplankton diversity. But we can only realize the remarkable promise of these approaches through global-scale conversation, cooperation and collaboration. </p>
<p>Several international collaborative efforts have paved the way. They include the 2004-2010 <a href="http://www.cmarz.org/">Census of Marine Zooplankton</a>, which identified thousands of species and described hundreds of new species previously unknown to science. I am a member of the <a href="http://wgimt.net/">Working Group on Integrated Morphological and Molecular Taxonomy</a>, which is carrying this work forward. Deeper insights into zooplankton biodiversity will provide a foundation for future research, monitoring and management of the largest habitat on Earth – the open ocean.</p><img src="https://counter.theconversation.com/content/97815/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ann Bucklin receives funding from:
NOAA / Office of Ocean Exploration and Research,
NSF / Office of Polar Programs / Antarctic Research, and
Woods Hole Oceanographic Institution . </span></em></p>DNA sequencing is making it possible for scientists to identify thousands of species of zooplankton – drifting animals that are key links in ocean food webs.Ann Bucklin, Professor of Marine Sciences, University of ConnecticutLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/957492018-05-02T15:03:36Z2018-05-02T15:03:36ZMeet the ocean creatures that use a mesh of mucus to catch their food<figure><img src="https://images.theconversation.com/files/217155/original/file-20180502-153878-11dri19.png?ixlib=rb-1.1.0&rect=6%2C247%2C4017%2C2793&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A pelagic snail ensnares food with with a mucous web.</span> <span class="attribution"><a class="source" href="https://doi.org/10.1098/rspb.2018.0056">Linda Ianniello https://lindaiphotography.com</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>All animals must eat to survive. If you’ve heard the term “grazer” before, it may bring to mind familiar farm animals, such as cows or sheep munching on pastureland. But the ocean has its own suite of grazers, with very different — even bizarre — body forms and feeding techniques. Instead of teeth, one group of these invertebrates uses sheets of mucus to consume huge quantities of tiny plant-like particles. In our new paper, my colleagues and I suggest a new categorization for this overlooked group: “<a href="https://doi.org/10.1098/rspb.2018.0056">mucous-mesh grazers</a>,” in recognition of their unusual feeding strategy.</p>
<p>Unlike the mucus in our noses, which appears amorphous and blobby, the mucous sheets of these ocean grazers can be <a href="https://www.youtube.com/watch?v=dvFI8d6-0kg">structured into ornate meshes and nets</a>. These mucous sheets can function like a filter to ensnare food as small as bacteria. The grazers themselves are mammoth in comparison: up to 10,000 times bigger than their food. If people ate food that small, you’d be picking salt and sugar grains off your dinner plate.</p>
<p><a href="https://scholar.google.com/citations?user=xvnhpsAAAAAJ&hl=en&oi=ao">Marine biologists like me</a> used to think mucous grazing was a “catch-all” feeding strategy – the idea was these guys would just chow down on whatever their mucous sheet caught. But recent technological advances are helping us understand that <a href="https://doi.org/10.1098/rspb.2018.0056">mucous grazers can be picky eaters</a>. And what they consume — or don’t — influences ocean food webs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=482&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=482&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=482&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=606&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=606&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217123/original/file-20180501-135837-1ff687j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=606&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ornate filtering meshes (amplified 1,000 times and stained bright green in this image) capture particles much smaller than the grazers themselves.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1098/rspb.2018.0056">Kelly Sutherland</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>How does mucous-mesh grazing work?</h2>
<p>Mucous-mesh grazers include salps, pyrosomes, doliolids, pteropods and appendicularians. They are typically centimeters in length, roughly spanning the size of your fingernail to the size of your hand. Some form colonies comprised of many individuals in long chains that <a href="http://www.deepseanews.com/2013/08/the-60-foot-long-jet-powered-animal-youve-probably-never-heard-of/">can be much longer</a>. These creatures are large and watery compared to their hard-bodied planktonic counterparts. If you stepped on one, it would squish, not crunch. A mostly water body enables them to grow large quickly.</p>
<p>Mucous-mesh grazers are free floating and suited to the open ocean. They live far from shore, where food is scarce and often small. The tiny holes and fibers of their mucous meshes enable them to capture microscopic particles, which they subsequently swallow, sometimes along with the mucus. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/yG2hJoj8b3E?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A chain of salps filtering tiny food particles through an internal mesh.</span></figcaption>
</figure>
<p>Unlike spiders that spin their feeding webs, these grazers have a special organ, called an endostyle, that secretes their mucous mesh. Depending on the grazer, the mucous mesh can be located either inside or outside the body. One group, for example, secretes a mucous bubble big enough for the animal to live inside like a house. Another group, nicknamed sea butterflies, secrete mucous webs that attach to their wing-shaped feet. These mucous webs range in size from an inch to over 6 feet.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=769&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=769&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=769&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=966&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=966&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217177/original/file-20180502-153908-enwzcd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=966&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Location of the mucous mesh for different groups of grazers. The mucous mesh is colored according to the ways grazers drive flow through or across the mesh. ‘MW’ shows the mucous web of a sea butterfly, or thecosome pteropod.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1098/rspb.2018.0056">Caitlyn Webster/www.bywebbie.com</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Historically, scientists assumed mucous-mesh grazers ate anything that passed through the mucous sieve — similar to a strainer in the drain of the kitchen sink catching everything of a certain size that flows in. <a href="https://doi.org/10.1002/lno.10680">Recent research by my lab</a> and others challenges this assumption and shows that their feeding may be highly selective. The mucus might capture certain food particles perfectly, while completely rejecting other particles on the basis of their size, shape or surface properties.</p>
<p>For example, when presented with a mixture of rod-shaped and spherical food particles – differently shaped but otherwise similar in size – one species of mucous-mesh grazer <a href="https://doi.org/10.1371/journal.pone.0183105">preferentially swallows the spherical particles</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=569&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=569&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=569&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=715&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=715&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217174/original/file-20180502-153866-fold28.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=715&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Particles of different size and shape (spherical and rod) from the dissected gut of a mucous-mesh grazer, the appendicularian <em>Oikopleura dioica</em>.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1098/rspb.2018.0056">Keats Conley</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>That’s a bit like choosing tater tots over French fries: They’re both made of potatoes and are roughly the same size but they have different shapes. The mucous grazers’ food “choice” is passive, though, having to do with how differently shaped prey orient in seawater and <a href="http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0183105.s002&type=supplementary">intercept the mesh</a>.</p>
<p>Grazers can “pick” prey, but prey may also be able to have some say in the matter — either passively or actively. For instance, some bacteria have Teflon-like surfaces and <a href="https://naturemicrobiologycommunity.nature.com/users/62278-ayelet-dadon-pilosof/posts/20821-teflon-bacteria-sar11-evades-predation-by-tunicates">don’t stick to the mucous meshes</a>, so they’re almost never consumed. How all of the different prey properties might influence grazing has been underappreciated until recently. </p>
<h2>Understudied but not unimportant</h2>
<p>Oceanographers are interested in how material moves through the ocean and how the process could be mediated by organisms. Mucous mesh grazers might be an overlooked piece of the cycle.</p>
<p>The fact that they don’t capture all prey equally has important consequences for how carbon moves through the ocean. After mucous grazers feed, they package undigested food particles into mucus-bound fecal pellets or other castoff material. Repackaging prey particles with sticky mucus concentrates small prey into larger aggregates, which makes them sink more quickly. This ultimately moves organic material to the ocean depths, potentially storing it for years or even centuries. At depth, this material is unavailable to the majority of marine organisms that live near the surface. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217124/original/file-20180501-135840-40y1ow.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ‘salpatron’ allows researchers to conduct feeding studies underwater.</span>
<span class="attribution"><span class="source">Gitai Yahel/Ayelet Dadon-Pilosof (www.gitaiyahel.com)</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Until the past decade or two, scientists didn’t have technological tools to watch what was happening with mucous-mesh grazers in their native habitat at the appropriate tiny scales. Because these organisms are quite fragile, now researchers in <a href="https://www.sutherlandlab.org/">my lab</a> and others use scuba diving or robots to directly observe them underwater. These close, careful observations using high-speed cameras and underwater microscopes or doing feeding studies in the natural environment have shown us how they select certain particles and reject others. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=623&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=623&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=623&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=782&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=782&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217126/original/file-20180501-135806-17idfsn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=782&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">High-speed underwater camera.</span>
<span class="attribution"><span class="source">B. Gemmell, S. Colin, J. Costello</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Further advances will combine underwater methods with recent developments in imaging and genetic sequencing to shed light on the role of mucous-mesh feeders in shaping the structure of the ocean’s microbial community. <a href="http://jaffeweb.ucsd.edu/research-projects/keck-microscope/">Underwater imaging</a> allows for undisturbed observations of these fragile creatures. Researchers can watch how individual particles behave on the mesh and whether they are ultimately captured. <a href="https://doi.org/10.1038/s41564-017-0030-5">Genetic sequencing used in the context of feeding studies helps scientists identify and distinguish</a> the groups of tiny microbes that are often invisible to the naked eye.</p>
<p>Knowing which particles are consumed and which aren’t tells us about the impact that the mucous grazers have on ocean food webs. </p>
<h2>Changing oceans, changing impact</h2>
<p>Picky eating by mucous-mesh grazers may have profound implications for biogeochemical cycles, particularly in light of shifting ocean conditions. Environmental factors like ocean temperature, availability of nutrients and the type and amount of prey present influence when and where mucous grazers appear, how long they stick around and their impact on ocean food webs.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1340&fit=crop&dpr=1 754w, https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1340&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/216771/original/file-20180429-135810-1sspgtl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1340&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pyrosome bloom off the Oregon coast in February 2018. Image was taken at about 60 m depth where there was a layer of pyrosomes, probably actively feeding on small particles.</span>
<span class="attribution"><span class="source">K. Sutherland/H. Sorensen</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>A more tropical species of mucous-grazing pyrosomes (<em>Pyrosoma atlanticum</em>) provides a case study. Typical in warmer waters as far north as Southern California, they confounded scientists and fishermen alike when they <a href="https://www.researchgate.net/profile/Andrew_Thompson3/publication/322665037_An_unusual_gelatinous_plankton_event_in_the_NE_Pacific_The_Great_Pyrosome_Bloom_of_2017/links/5a6780a10f7e9b76ea8f0193/An-unusual-gelatinous-plankton-event-in-the-NE-Pacific-The-Great-Pyrosome-Bloom-of-2017.pdf">appeared off the Oregon coast in 2014</a>.</p>
<p>No one knows why the pyrosomes appeared, but <a href="https://news.nationalgeographic.com/2017/02/space-map-pacific-blob/">ocean temperatures warmed around the same time</a>. Like other mucous-mesh grazers, the fine pyrosome filter allows them to graze on the smaller particles that are associated with warmer, less nutrient-rich surface water – prey too small for most other animals to catch. <a href="https://www.nwfsc.noaa.gov/news/features/pyrosomes/">Along with other researchers along the West Coast</a>, my lab is actively working to understand why the pyrosomes appeared, how they might affect the marine ecosystem, and if they will persist.</p>
<p>Grazers in the ocean are inherently more challenging to study than those than on land; we continue to learn more about who they are through what they eat.</p>
<hr>
<p><em>This article was co-authored by <a href="https://scholar.google.com/citations?user=17TmpcgAAAAJ&hl=en&oi=ao">Keats Conley</a>, a research biologist for the <a href="http://www2.sbtribes.com/fish-and-wildlife/">Shoshone-Bannock Tribes’ Department of Fish and Wildlife</a>.</em></p><img src="https://counter.theconversation.com/content/95749/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kelly Sutherland receives funding from the National Science Foundation, Sloan Foundation and Oregon Sea Grant.</span></em></p>Biologists are finding new evidence that these ocean invertebrate grazers don’t just ingest whatever they catch. They can actually be picky eaters – and their choices might influence ocean food webs.Kelly Sutherland, Assistant Professor of Biology, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/816072017-08-16T01:37:27Z2017-08-16T01:37:27ZBait and switch: Anchovies eat plastic because it smells like prey<figure><img src="https://images.theconversation.com/files/181977/original/file-20170814-28423-i5knb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Plastic trash on San Francisco's Ocean Beach.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/7Hxy4a">Kevin Krejci</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>As you bite down into a delicious piece of fish, you probably don’t think about what the fish itself ate – but perhaps you should. Over 50 species of fish have been found to consume plastic trash at sea. This is bad news, not only for fish but potentially for humans who rely on fish for sustenance. </p>
<p>Fish don’t usually die as a direct result of feeding on the <a href="http://www.ready-for-the-resource-revolution.com/en/marine-plastic-debris-and-microplastics-a-new-unep-report-on-plastic-pollution-in-our-oceans/">enormous quantities of plastic trash</a> floating in the oceans. But that doesn’t mean it’s not harmful for them. Some negative effects that scientists have discovered when fish consume plastic include <a href="http://dx.doi.org/10.1021/es5053655">reduced activity rates and weakened schooling behavior</a>, as well as <a href="http://dx.doi.org/10.1038/srep03263">compromised liver function</a>. </p>
<p>Most distressingly for people, toxic compounds such as <a href="https://en.wikipedia.org/wiki/Polybrominated_diphenyl_ethers">PBDEs</a> that are associated with plastic transfer to and bioaccumulate in <a href="http://dx.doi.org/10.1021/acs.est.5b06280">fish tissues</a>. This finding is troubling because it means these toxic substances could further bioaccumulate in us if we consume fish that have eaten plastic. Numerous species sold for human consumption, including mackerel, striped bass and Pacific oysters <a href="http://dx.doi.org/10.1038/srep14340">have been found with these toxic plastics in their stomachs</a> too.</p>
<p>It is well-known that our plastic trash poses <a href="http://dx.doi.org/10.1073/pnas.1502108112">a serious threat</a> to marine animals, but we are still trying to understand why animals eat it. Typically, research has concluded that marine animals visually mistake plastic for food. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ieMXDlMP0b8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Sea turtles can starve to death because they feel full after swallowing plastic bags or other debris.</span></figcaption>
</figure>
<p>While this may be true, the full story is likely more complex. For example, in a recent study with colleagues at the University of California, Davis, we showed that <a href="http://advances.sciencemag.org/content/2/11/e1600395">plastic debris may also smell attractive to marine organisms</a>. That study focused on seabirds, but now my co-authors and I have found that plastic trash <a href="http://rspb.royalsocietypublishing.org/content/284/1860/20171000">has a similar effect on anchovies</a> – a critical part of ocean food chains.</p>
<h2>Sniffing out the role of smell</h2>
<p>Olfaction (smell) is a very important sense for marine animals, including fish. Sharks can smell minute quantities of blood <a href="http://www.amnh.org/learn/pd/sharks_rays/rfl_myth/myth_page5.html">over long distances</a>, which helps them find prey. And scientists believe that salmon’s sense of smell helps them <a href="https://www.sciencedaily.com/releases/2013/02/130207131713.htm">navigate up rivers</a> to the specific tributaries where they were born to spawn. Fish may use their sense of smell in behavioral contexts including mating, homing, migrating and foraging. </p>
<p>We tested the idea that <a href="http://rspb.royalsocietypublishing.org/content/284/1860/20171000">plastic debris might smell attractive</a> to the <a href="http://wdfw.wa.gov/fishing/forage_fish/northern_anchovy.html">Northern anchovy</a> (<em>Engraulis mordax</em>), a common schooling fish found off the West Coast of North America. Known as forage fish, anchovies are critically important species ecologically and economically. Unfortunately, they have also been found to <a href="http://dx.doi.org/10.1038/srep34351">eat plastic in the wild</a>. </p>
<p>Working with anchovies is challenging because they require very specific water conditions and school size to behave normally. They need to be in cold, fast-flowing water in schools of at least 100 individuals. When that happens, the anchovies display their contentment by swimming slowly and directly into the flow of water – a behavior known as positive rheotaxis. Luckily, we were able to collaborate with the <a href="https://www.aquariumofthebay.org/">Aquarium of the Bay</a> in San Francisco, where they have expertise in keeping these fish happy and healthy. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182105/original/file-20170815-5485-15exuec.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Schooling Northern anchovies.</span>
<span class="attribution"><span class="source">Matthew Savoca</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Our olfactory experiment</h2>
<p>When we started the experiment we did not know whether adult anchovies used their sense of smell to find food at all, let alone whether smell might lead them to consume plastic. To test our hypothesis that it would, we soaked <a href="http://www.nationalgeographic.com/animals/invertebrates/group/krill/">krill</a> (tiny shrimp-like crustaceans that anchovies eat) or plastic debris and clean plastic in seawater for several hours, allowing the water to take on the smell of the material steeping in it. We then filtered our krill or plastic “tea,” presented it to the anchovy schools, and observed their behavior. </p>
<p>When fish are searching for food in groups, their behavior changes in predictable ways: They clump together near the interesting stimulus and dart around, altering their body position relative to the water current. To compare how anchovies responded to the scents of krill and plastic, we hung a specially designed apparatus with a GoPro camera attached over their tank to film the school’s behavior from above. </p>
<p>In addition to analyzing what anchovies did when they detected these odors, we also filmed their anchovies’ behavior while feeding on krill and when they were presented with control treatments of unscented seawater. This gave us baseline information about the schools’ behavior, which we could compare to their responses when they were presented with the different odors.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182000/original/file-20170814-14751-w61yev.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Anchovies schooling in a tank before being exposed to the odor of plastic debris.</span>
<span class="attribution"><span class="source">Matthew Savoca</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Using a combination of automated computer analyses and diligent observer scoring, we evaluated how tightly the schools clumped together and how each fish’s body positioning relative to the direction of water flow changed before and after adding an odor solution to the tank. As we predicted, when the anchovies were feeding, schools became more densely clumped and changed their body positioning so that instead of all fish facing directly into the oncoming current, their bodies aligned more haphazardly as they searched for food morsels. In the control treatments, with no food or food odors present, we did not observe these changes. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182001/original/file-20170814-5720-1nwtbh3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The same anchovies displaying feeding behavior after being exposed to the odor of plastic debris.</span>
<span class="attribution"><span class="source">Matthew Savoca</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>When we injected seawater scented with krill into the tank, the anchovies responded as if they were searching for food – which in this case was not there. And, importantly, when we presented them with seawater scented with odors of plastic debris, the schools responded in nearly the same way, clumping together and moving erratically as they would if they were searching for food. This reaction provided the first behavioral evidence that a marine vertebrate may be tricked into consuming plastic because of the way it smells.</p>
<h2>Reducing plastic pollution</h2>
<p>This research confirms several things. First, we showed that Northern anchovies use odors to locate food. This may sound intuitive, but before we did this study there was scant behavioral evidence that adult <a href="https://en.wikipedia.org/wiki/Forage_fish">forage fish</a>, such as anchovies, sardines and herring used smell to find food. </p>
<p>Our main finding was that plastic debris is likely confusing for marine consumers because of both its appearance and its smell. That’s a problem, because if plastic looks and smells interesting to fish, it will be very hard for them to discern that is it not food.</p>
<p>This study also suggests that our consume-and-dispose culture is coming back to haunt us via the fish we eat. The next big question that it raises is whether plastic-derived contaminants can be transferred from plastic-eating fish to fish-eating humans. </p>
<p>One way to mitigate the problem is to figure out why animals confuse plastic for prey so frequently, and our research has helped to do that. However, everyone can do something right now about ocean plastic pollution by avoiding single-use plastic items and recycling plastic upon disposal. There is more work to be done, but we know enough now to make substantial headway on this global environmental issue.</p><img src="https://counter.theconversation.com/content/81607/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Savoca receives funding from the National Science Foundation and California Sea Grant. </span></em></p>A new study shows that anchovies – key food for larger fish – are attracted to plastic trash because it smells like food. This suggests that toxic substances in plastic could move up through food chains.Matthew Savoca, Postdoctoral fellow, National Oceanic and Atmospheric AdministrationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/767982017-04-30T20:01:01Z2017-04-30T20:01:01ZClimate change could drive coastal food webs to collapse<figure><img src="https://images.theconversation.com/files/167135/original/file-20170428-15117-bwwrjh.jpg?ixlib=rb-1.1.0&rect=5%2C16%2C3756%2C2132&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A tank can give a good idea of what will happen out in the wild.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>Coastal marine food webs could be in danger of collapse as a result of rising carbon dioxide levels, according to our <a href="http://onlinelibrary.wiley.com/doi/10.1111/gcb.13699/abstract">new research</a>. The study shows that although species such as algae will receive a boost, the positive effects are likely to be cancelled out by the increased stress to species further up the food chain such as predatory fish.</p>
<p>Food webs are essentially <a href="http://science.sciencemag.org/content/325/5939/416">networks of species that interact</a> with each other. The connection between them can stabilise systems, for instance by preventing particular species from becoming too common, thereby encouraging the presence of a wide range of species. </p>
<p>These pathways can be quite stable, but they are vulnerable to ocean warming and acidification. Such food webs are therefore sensitive to changing climates, through potential changes both to plant growth (bottom-up effects) and to predator abundance and behaviour (top-down effects). </p>
<p>Because of the sheer complexity of species interactions within these food webs, we <a href="http://www.nature.com/nclimate/journal/v5/n1/full/nclimate2456.html">struggle to understand what future food webs might look like</a> and how humans will be affected through changes in the services provided by the ocean, such as food, materials and energy.</p>
<h2>Test tank</h2>
<p>We used a self-contained ecosystem in a 2,000-litre tank to study the effects of warming and ocean acidification on a coastal food web. This approach can give us a good idea of what might happen to genuine coastal food webs, because the tank (called a “mesocosm”) contains natural habitats and a range of species that interact with one another, just as they do in the wild.</p>
<p>Our food web had three levels: primary producers (algae), herbivores (invertebrates), and predators (fish). </p>
<p>The results show that carbon dioxide enrichment can actually boost food webs from the bottom up through increased algal growth. This benefited herbivores because of the higher abundance of food, and in turn boosted the very top of the food web, where fish grew faster. </p>
<p>But while this effect of ocean acidification may be seen as positive for marine ecosystems, it mainly benefits “weedy” species – a definition that can be applied to some species of <a href="http://rspb.royalsocietypublishing.org/content/277/1686/1409">algae</a>, <a href="http://www.cell.com/current-biology/abstract/S0960-9822(16)31450-6">invertebrates</a>, and even <a href="https://www.nature.com/nclimate/journal/v6/n1/full/nclimate2757.html">fish</a>. </p>
<p>In contrast, habitat-forming species such as kelp forests and coral reefs are more likely to disappear with rising CO₂ emissions, and with them <a href="http://www.nature.com/nclimate/journal/v7/n1/full/nclimate3161.html">many associated species</a> that are deprived of their habitats and food.</p>
<h2>Detrimental effect</h2>
<p>Our results therefore showed that warming had a detrimental overall effect on the coastal food web we studied. Although higher temperatures boosted algal growth, herbivorous populations did not expand. Because herbivore abundances remained similar and elevated temperatures result in a higher metabolic demand, predatory fish consumed more herbivorous prey, resulting in a collapse of these prey populations. </p>
<p>These results show how the benefits of one human-induced effect (increased ocean CO₂) are cancelled out by the negative effects of a co-occuring stressor (ocean warming). More importantly, it also shows how interactions between species (predator and prey, in this case) can alter the outcome of climate stressors on individual species.</p>
<p>Such indirect effects within the web of life have remained largely unstudied, despite the fact that they may in many cases be more important than direct effects in terms of their future impacts. </p>
<p>For example, habitat loss and loss of predator species are key indirect effects that can alter species populations within food webs. However, these effects also offer the opportunity for some conservation wins. </p>
<p>First, humans are <a href="http://science.sciencemag.org/content/319/5865/948">altering marine ecosystems</a> in many other ways than just climate change, such as through pollution, habitat destruction, and eutrophication (an excess of nutrients, often caused by runoff from land). By reducing these effects we could reduce the overall burden on marine species, potentially buying them time to adapt to climate change across generations. </p>
<p>Second, by reducing habitat loss from other human impacts – by implementing well-designed sanctuary zones – we can also maintain the habitats, prey and other organisms on which species depend for their growth and survival. </p>
<p>Finally, studies suggest that the <a href="http://www.pnas.org/content/112/43/13272.abstract">top of food webs will be disproportionately affected</a> by climate change, and research has shown that <a href="http://science.sciencemag.org/content/333/6040/301">predators play important roles</a> in maintaining diversity and general ecosystem health. By reducing the ongoing global overfishing of predatory species worldwide, we might relieve some of the direct effects of climate change on food webs and ecosystems.</p><img src="https://counter.theconversation.com/content/76798/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ivan Nagelkerken receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Sean Connell receives funding from The Australian Research Council. </span></em></p><p class="fine-print"><em><span>Silvan Goldenberg does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new study suggests the benefits of a boost to marine plant growth from increased carbon dioxide will be cancelled out by the increased stress to fish species.Ivan Nagelkerken, Professor, Marine Biology, University of AdelaideSean Connell, Professor, Ecology, University of AdelaideSilvan Goldenberg, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.