tag:theconversation.com,2011:/global/topics/krill-6834/articles Krill – The Conversation2020-03-31T14:05:01Ztag:theconversation.com,2011:article/1325272020-03-31T14:05:01Z2020-03-31T14:05:01ZNew discovery: penguins vocalise under water when they hunt<figure><img src="https://images.theconversation.com/files/319244/original/file-20200309-118881-1i3w8wb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">King Penguins at sea.</span> <span class="attribution"><span class="source">John Dickens</span></span></figcaption></figure><p>Penguins, like all seabirds, are known to be highly vocal on land where they come to breed. They use these vocalisations to help them <a href="https://royalsocietypublishing.org/doi/abs/10.1098/rspb.2000.1112">recognise</a> their mate and kin. </p>
<p>Outside of the breeding season, seabirds spend most of their life at sea and are adapted to the marine environment where they feed. Penguins are very unique among seabirds for their extreme diving abilities. They can perform series of dives to depths of between 20 and 500m (depending on the species) in search of fish, krill, or squid.</p>
<p>Given the penguins’ diving abilities, we wanted to know if they produced sound underwater. To do this, our Marine Apex Predator Research Unit <a href="https://mapru.mandela.ac.za">(MAPRU)</a> team at Nelson Mandela University (South Africa) attached small video loggers, with built-in microphones, on the back of three species of penguins: the King penguin, the Gentoo penguin and the Macaroni penguin.</p>
<p>Our study <a href="https://peerj.com/articles/8240/">provides</a> the first evidence that penguins emit sounds under water when they hunt.</p>
<h2>Recording penguins at sea</h2>
<p>Because of recording difficulties, very little was previously known about the vocalisations of penguins when they are at sea. However, thanks to recent developments in technology, such observation <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ibi.12806">becomes accessible</a>, in particular through the use of miniaturised penguin-borne video loggers.</p>
<p>We used video loggers and recorded 203 underwater vocalisations from all three species over almost five hours of underwater footage: 34 from two King penguins, a single one from a Macaroni penguin and 168 from Gentoo penguins. </p>
<p>These species were chosen because they reflect the diversity of feeding strategies in penguins. The King penguin is specialised to feed on fish at a substantial depth (<a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/0012-9658%281998%29079%5B1905%3AFSOKPA%5D2.0.CO%3B2">200m</a>), whereas the Macaroni penguin feeds mostly on schooling krill within the <a href="https://link.springer.com/article/10.1007/s00300-010-0950-5">first 10m of the water column</a>. In contrast, the Gentoo penguin displays a very diverse foraging strategy, feeding on <a href="https://link.springer.com/article/10.1007/s00227-017-3113-1">all sorts of prey</a> at <a href="https://link.springer.com/article/10.1007/s00227-016-3066-9">all depths</a>.</p>
<p>The birds were caught as they left their breeding colonies at Marion Island (a sub-Antarctic island off South Africa) on the way out to the sea. We then retrieved the cameras after a single foraging trip. </p>
<p>We found that all vocalisations were short and emitted during dives when the penguin was hunting. Most vocalisations (73%) happened during the bottom phase of the dives. This is where penguins <a href="https://jeb.biologists.org/content/213/22/3874.short">mostly</a> catch their food, as opposed to the descent and ascent. </p>
<p>Here is a video showing a full dive by a King penguin, as observed from the penguin-borne video loggers:</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/2qp_51XO4ao?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Here is a short clip showing only a few underwater vocalisations associated with prey capture:</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/024DafCNoIg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>More than 50% of the vocalisations were directly associated with a hunting behaviour: immediately after they had accelerated (<a href="https://link.springer.com/article/10.1007%2Fs00227-005-0188-x">chasing prey</a>) or immediately after an attempt at catching prey.</p>
<p>Because vocalisations were produced by all three species of penguins, it suggests that underwater vocal behaviour may exist in other penguin species. The vocalisations were also recorded in higher proportion when penguins were feeding on fish, compared to krill and squid. This suggests they could be more common in penguins that feed on fish.</p>
<h2>Unexpected?</h2>
<p>Our findings on their vocal behaviour were totally unexpected, though some of the penguin <a href="https://www.cb.universite-paris-saclay.fr/">acoustics experts</a> on our team in France had their suspicions about what we might discover.</p>
<p>We already knew that the use of vocalisations at the sea surface was related to group formation in the <a href="https://www.nationalgeographic.com/animals/birds/g/gentoo-penguin/">Gentoo penguins</a> and that African penguins vocalise from the sea surface <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ibi.12806">mostly when</a> commuting (possibly to keep contact with one another) and foraging on bait-balls (possibly to synchronise their behaviours). </p>
<p>There is also evidence which shows that other air-breathing marine predators – such as <a href="https://link.springer.com/chapter/10.1007%2F978-1-4612-1150-1_4">dolphins</a>, <a href="https://books.google.co.za/books?hl=fr&lr=&id=McNEUgU8Q58C&oi=fnd&pg=PR9&dq=Riedman+M.+1990.+The+Pinnipeds:++Seals,+Sea+Lions,+and+Walruses.+Berkeley:+University+of+California+Press.&ots=hq3uwPw1kM&sig=Wg_UlpgzOHAYF1zJ3eriPUxU-44&redir_esc=y#v=onepage&q=Riedman%20M.%201990.%20The%20Pinnipeds%3A%20Seals%2C%20Sea%20Lions%2C%20and%20Walruses.%20Berkeley%3A%20University%20of%20California%20Press.&f=false">seals</a> and <a href="https://bioone.org/journals/Copeia/volume-105/issue-1/CE-16-407/First-Evidence-of-the-Pig-nosed-Turtle-Carettochelys-insculpta-Vocalizing/10.1643/CE-16-407.short">marine turtles</a> – produce sound under water. So why not penguins as well?</p>
<h2>Door open for future research</h2>
<p>From our observations, new questions have arisen. For example, how are penguins able to produce such sound under water, given the high pressure at depth? And why are they vocalising under water? Are all these vocalisations signalling the same information? Do they produce other underwater vocalisations in different contexts? Are they related to physiological needs for a predator diving and feeding in apnoea – to <a href="https://jeb.biologists.org/content/205/9/1189">adjust buoyancy</a>? Could they have a function in <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ibi.12806">social interactions</a>? Could they be part of a hunting technique and be used to <a href="https://afspubs.onlinelibrary.wiley.com/doi/abs/10.1577/1548-8675%281992%29012%3C0667%3AROBHTH%3E2.3.CO%3B2">startle prey</a>? </p>
<p>We hope recent developments in technology will continue to provide more insights into the penguins’ fascinating behaviour.</p><img src="https://counter.theconversation.com/content/132527/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andréa Thiebault receives research funding from South Africa's National Research Foundation.</span></em></p><p class="fine-print"><em><span>Pierre Pistorius receives research funding from South Africa's National Research Foundation. </span></em></p><p class="fine-print"><em><span>Isabelle Charrier and Thierry Aubin 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>This study provides the first evidence that penguins emit sounds underwater when they hunt.Andréa Thiebault, Postdoctoral fellow, Nelson Mandela UniversityIsabelle Charrier, Chercheuse CNRS en bioacoustique, Université Paris-SaclayPierre Pistorius, Professor , Nelson Mandela UniversityThierry Aubin, Senior Scientist, Centre national de la recherche scientifique (CNRS)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1282222019-12-12T19:03:00Z2019-12-12T19:03:00ZWhy are whales big, but not bigger?<figure><img src="https://images.theconversation.com/files/306633/original/file-20191212-85417-hq31z6.JPG?ixlib=rb-1.1.0&rect=0%2C0%2C5176%2C3437&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Minke whale.</span> <span class="attribution"><span class="source">Jeremy Goldbogen</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Both toothed and baleen (filter-feeding) whales are among the largest animals ever to exist. Blue whales, which measure up to 100 feet (30 meters) long and can weigh over 150 tons, are the largest animals in the history of life on Earth. </p>
<p>Although whales have existed on this planet for some 50 million years, they only evolved to be truly gigantic in <a href="https://doi.org/10.1098/rspb.2017.0546">the past five million years or so</a>. Researchers have little idea <a href="https://doi.org/10.1073/pnas.1804077115">what limits their enormous size</a>. What is the pace of life at this scale, and what are the consequences of being so big?</p>
<p>As scientists who study <a href="https://scholar.google.com/citations?user=uo1sSBwAAAAJ&hl=en">ecology</a>, <a href="https://scholar.google.com/citations?user=CBjDcy8AAAAJ&hl=en">physiology</a> and <a href="https://scholar.google.com/citations?user=TPY3-ccAAAAJ&hl=en">evolution</a>, we are interested in this question because we want to know the limits to life on Earth, and what allows these animals to live at such extremes. In a <a href="https://science.sciencemag.org/content/366/6471/1367">newly published study</a>, we show that whale size is limited by the largest whales’ very efficient feeding strategies, which enable them to take in a lot of calories compared to the energy they burn while foraging.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306194/original/file-20191210-95149-1orahti.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">A humpback whale approaches scientists in the Antarctic.</span>
<span class="attribution"><span class="source">Goldbogen Laboratory, Stanford University / Duke University Marine Robotics and Remote Sensing, taken under permit ACA / NMFS #14809</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Ways to be a whale</h2>
<p>The first whales on Earth had four limbs, <a href="https://ocean.si.edu/through-time/ancient-seas/evolution-whales-animation">looked something like large dogs</a> and lived at least part of their lives on land. It took about 10 million years for their descendants to evolve a completely aquatic lifestyle, and roughly 35 million years longer for whales to become the giants of the sea. </p>
<p>Once whales became completely aquatic some 40 million years ago, the types that succeeded in the ocean were either <a href="https://en.wikipedia.org/wiki/Baleen_whale">baleen whales</a>, which fed by straining seaweater through baleen filters in their mouths, or <a href="https://en.wikipedia.org/wiki/Toothed_whale">toothed whales</a> that hunted their prey using <a href="https://en.wikipedia.org/wiki/Animal_echolocation">echolocation</a>. </p>
<p>As whales evolved along these two paths, a process called <a href="https://en.wikipedia.org/wiki/Upwelling">oceanic upwelling</a> was intensifying in the waters around them. Upwelling occurs when strong winds running parallel to the coast push surface waters away from the shore, drawing up cold, nutrient-rich waters from the deep ocean. This stimulates plankton blooms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=235&fit=crop&dpr=1 600w, https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=235&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=235&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=295&fit=crop&dpr=1 754w, https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=295&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/305967/original/file-20191209-90609-10zz2b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=295&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Upwelling occurs when winds displace surface waters, which are replaced by cold, nutrient-rich water that wells up from below.</span>
<span class="attribution"><a class="source" href="https://oceanservice.noaa.gov/facts/upwelling.html">NOAA</a></span>
</figcaption>
</figure>
<p>Stronger upwelling created the right conditions for baleen whale prey, such as <a href="https://en.wikipedia.org/wiki/Krill">krill</a> and <a href="https://en.wikipedia.org/wiki/Forage_fish">forage fish</a>, to become concentrated in dense patches along coastlines. Whales that fed on these prey resources could forage efficiently and predictably, allowing them to grow larger. <a href="https://doi.org/10.1098/rspb.2017.0546">Fossil records</a> showing that baleen whale lineages separately became gigantic all at the same time support this view. </p>
<h2>Really big gulps</h2>
<p>Is there a limit to how big whales can become? We tackled this question by drawing on animal energetics – the study of how efficiently organisms ingest prey and turn the energy it contains into body mass. </p>
<p>Getting large is based on simple math: If a creature can gain more calories than it spends, it gets bigger. This may seem intuitive, but demonstrating it with data collected from free-living whales was a gargantuan challenge. </p>
<p>To get the information, our international team of scientists attached high-resolution tags with suction cups to whales so that we could track their orientation and movement. The tags recorded hundreds of data points per second, then detached for recovery after about 10 hours. </p>
<p>Like a Fitbit that uses movement to record behavior, our tags measured how often whales fed below the ocean’s surface, how deep they dove and how long they remained at depth. We wanted to determine each species’ energetic efficiency – the total amount of energy that it gained from foraging, relative to the energy it expended in finding and consuming prey. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=335&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=335&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=335&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=422&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=422&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306466/original/file-20191211-95153-rnostz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=422&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tagged blue whale off the coast of Big Sur, California.</span>
<span class="attribution"><span class="source">Duke Marine Robotics & Remote Sensing under NMFS permit 16111</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Data in this study was provided by collaborators representing six countries. Their contributions represent tens of thousands of hours of fieldwork at sea collecting data on living whales from pole to pole.</p>
<p>In total, this meant tagging 300 toothed and baleen whales from 11 species, ranging from five-foot-long <a href="https://www.fisheries.noaa.gov/species/harbor-porpoise">harbor porpoises</a> to <a href="https://www.fisheries.noaa.gov/species/blue-whale">blue whales</a>, and recording more than 50,000 feeding events. Taken together, they showed that whale gigantism is driven by the animals’ ability to increase their net energy gain using specialized foraging mechanisms. </p>
<p>Our key finding was that <a href="https://en.wikipedia.org/wiki/Rorqual">lunge-feeding baleen whales</a>, which engulf swarms of krill or forage fish with enormous gulps, get the most bang for their buck. As these whales increase in size, they use more energy lunging – but their gulp size increases even more dramatically. This means that the larger baleen whales get, the greater their energetic efficiency becomes. We suspect the upper limit on baleen whales’ size is probably set by the extent, density and seasonal persistence of their prey.</p>
<p>Large toothed whales, such as <a href="https://en.wikipedia.org/wiki/Sperm_whale">sperm whales</a>, feed on large prey occasionally including the fabled <a href="https://ocean.si.edu/ocean-life/invertebrates/giant-squid">giant squid</a>. But there are only so many giant squid in the ocean, and they are hard to find and capture. More frequently, large toothed whales feed on medium-sized squid, which are much more abundant in the deep ocean.</p>
<p>Because of a lack of large enough prey, we found that toothed whales’ energetic efficiency decreases with body size – the opposite of the pattern we documented for baleen whales. Therefore, we think the ecological limits imposed by a lack of giant squid prey prevented toothed whales from evolving body sizes greater than sperm whales. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=486&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=486&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=486&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=611&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=611&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306463/original/file-20191211-95125-1g2hvmg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=611&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scaling of energetic efficiency in toothed whales and baleen whales.</span>
<span class="attribution"><a class="source" href="http://www.alexboersma.com">Alex Boersma</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>One piece of a larger puzzle</h2>
<p>This work builds on previous research about the <a href="https://doi.org/10.1098/rsbl.2016.0186">evolution of body size in whales</a>. Many questions remain. For example, since whales developed gigantism relatively recently in their evolutionary history, could they evolve to be even larger in the future? It’s possible, although there may be other physiological or biomechanical constraints that limit their fitness. </p>
<p>For example, <a href="https://doi.org/10.1073/pnas.1914273116">a recent study</a> that measured blue whale heart rates demonstrated that heart rates were near their maximum even during routine foraging behavior, thereby suggesting a physiological limit. However, this was the first measurement and much more study is needed.</p>
<p>We would also like to know whether these size limits apply to other big animals at sea, such as sharks and rays, and how baleen whales’ consumption of immense quantities of prey affect ocean ecosystems. Conversely, as human actions alter the oceans, could they affect whales’ food supplies? Our research is a sobering reminder that relationships in nature have evolved over millions of years – but could be disrupted far more quickly in the <a href="https://en.wikipedia.org/wiki/Anthropocene">Anthropocene</a>. </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/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklysmart">You can get our highlights each weekend</a>. ]</p><img src="https://counter.theconversation.com/content/128222/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Savoca receives funding from the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Jeremy Goldbogen receives funding from the National Science Foundation and the Office of Naval Research. </span></em></p><p class="fine-print"><em><span>Nicholas Pyenson receives funding from the Smithsonian Institution.</span></em></p>How did whales that feed on tiny prey evolve into the largest creatures on Earth? And why don’t they get even bigger?Matthew Savoca, Postdoctoral researcher, Stanford UniversityJeremy Goldbogen, Assistant Professor of Biology, Stanford UniversityNicholas Pyenson, Research Geologist and Curator of Fossil Marine Mammals, Smithsonian InstitutionLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1253622019-10-18T13:20:50Z2019-10-18T13:20:50ZHow Antarctic krill fertilise the oceans and even store carbon – all with their poo<figure><img src="https://images.theconversation.com/files/297600/original/file-20191017-98670-1jodhod.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">I. Noyan Yilmaz / shutterstock</span></span></figcaption></figure><p>Krill are best known as whale food. But few people realise that these small, shrimp-like creatures are also important to the health of the ocean and the atmosphere. In fact, <a href="https://islandpress.org/books/curious-life-krill">Antarctic krill</a> can fertilise the oceans, ultimately supporting marine life from tiny plankton through to massive whales and, through their faeces, they can increase the store of carbon in the deep ocean.</p>
<p>In a review we recently published in <a href="https://www.nature.com/articles/s41467-019-12668-7">Nature Communications</a>, we highlighted this less well-known role of Antarctic krill.</p>
<p>Krill are able to fertilise the oceans and help store carbon because they release essential nutrients, including ammonium and iron, into the surrounding water, either excreted as a waste product or in solid faecal pellets. These nutrients can then be used by tiny ocean plants at the base of most marine food webs (phytoplankton) to photosynthesise and grow. This is much the same process as humans adding nutrients to a field through a fertiliser. </p>
<p>The Southern Ocean surrounds Antarctica and is a long way from landmasses from which nutrients are washed into the ocean. As a result, nutrient concentrations can be low, particularly of iron which is essential for phytoplankton to grow. Concentrations tend to be highest near the Antarctic continent itself, its sea-ice and a few remote islands. </p>
<h2>The krill poo carbon sink</h2>
<p>Krill waste also influences the carbon cycle. Krill poo is in the form of relatively large, carbon-rich pellets which can sink quickly to the deep ocean where they may remain for many years. This means krill poo can lock carbon away from the atmosphere for long periods of time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=481&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=481&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297667/original/file-20191018-56238-1211iv2.png?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"></a>
<figcaption>
<span class="caption">Krill release ammonium (NH4) through excretion and iron in faecal pellets. Pellets also contain a lot of carbon which then sinks to the deep ocean.</span>
<span class="attribution"><span class="source">McCork Studios/Nature Communications</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p><a href="https://www.nature.com/articles/s41467-019-12668-7">Our synthesis</a> has highlighted that young krill who live near sea-ice may be particularly important in the carbon sink. This is because they live deeper in the water column than adult krill. So any pellets released by younger krill have a better chance of escaping any ocean currents that may return them to the surface, and instead sink further until eventually reaching the deep ocean.</p>
<h2>Human impacts to krill and the environment</h2>
<p>But what happens when humans disrupt these natural cycles, for example through fishing or causing climate change?</p>
<p>Humans also commercially fish for Antarctic krill – in fact, krill is the most fished animal in the Southern Ocean. Their oily bodies are either used in pharmaceuticals as an alternative source of omega-3, fed to livestock and aquaculture fish, used in pet food or a small amount are even prepared for humans to eat.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297668/original/file-20191018-56224-11mbtta.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&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 large size of krill, their high biomass in swarms and extensive vertical migrations over hundreds of metres each day, amplify their impact on their environment.</span>
<span class="attribution"><span class="source">McCork Studios/Nature Communications</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Warming over the past 90 years has meant Antarctic krill have <a href="https://www.nature.com/articles/s41558-018-0370-z">moved south toward sea-ice</a> and fewer juveniles are surviving to adulthood. Given the likelihood that juveniles are also important in the carbon sink it is crucial to ensure that in future fishing boats do not encroach on young krill habitats near the sea-ice.</p>
<p>The krill “fishery” is international, made up of companies from a number of different countries and managed sustainably by international convention – the <a href="https://www.ccamlr.org/en/organisation/home-page">Commission for the Conservation of Antarctic Marine Living Resources</a> – which sets limits so that only 0.5% of the population is fished in a given year. This ensures that there is enough food in Antarctic waters for whales and penguins, and safeguards the future catch. Scientists and the krill fishery need to work together though to protect nutrient cycles, the carbon sink and the environment. In fact, we believe it is unlikely that any fishery globally considers the impact that removing animals like krill or fish has on nutrient cycles.</p>
<p>We still don’t know exactly how removing krill from the oceans will impact the atmosphere and oceans, and how climate change will further exacerbate this. But one thing is for sure, krill are important in supporting life and storing carbon in the oceans. </p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1125362">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/125362/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Cavan received funding from The Pew Charitable Trusts to carry out the research discussed in the article. </span></em></p><p class="fine-print"><em><span>Anna Belcher and Lavenia Ratnarajah 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>These small shrimp-like creatures are more than just whale food.Emma Cavan, Postdoctoral Research Associate in Ecosystem Modelling, Imperial College LondonAnna Belcher, Ecological Biogeochemist, British Antarctic SurveyLavenia Ratnarajah, Postdoctoral research associate, University of LiverpoolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1194992019-07-22T10:55:31Z2019-07-22T10:55:31ZWaiting for an undersea robot in Antarctica to call home<figure><img src="https://images.theconversation.com/files/281448/original/file-20190626-76705-w53a62.jpg?ixlib=rb-1.1.0&rect=0%2C310%2C5184%2C3135&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One of two underwater gliders is deployed from a research ship into Antarctic waters.</span> <span class="attribution"><span class="source">NOAA</span></span></figcaption></figure><p>“Call! Just call!” I think loudly in my head. “Did something happen? Are you okay?”</p>
<p>I might seem like a worried parent waiting for a teenager to report in from an unsupervised outing. Rather, I’m a <a href="https://www.linkedin.com/in/jenmariewalsh">research biologist</a> with the Antarctic Ecosystem Research Division at the National Oceanic and Atmospheric Administration. It’s late February 2019, and I am waiting for an autonomous underwater glider in Antarctica to surface and call me via satellite, so I can give it new diving instructions. The longest it’s supposed to go without surfacing is eight hours, and it’s now been nine.</p>
<p>Did it get stuck under an iceberg? An underwater ledge? I feel so helpless; I’m 9,000 miles away in San Diego and all I can do is chew my fingernails and think, “No. This can’t happen. We can’t lose this glider so close to the end.” </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=565&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=565&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=565&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=711&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=711&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=711&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 survey area where gliders measured Antarctic krill populations.</span>
<span class="attribution"><span class="source">NOAA</span></span>
</figcaption>
</figure>
<p>Our research team is two-and-a-half months into a three-month-long mission just north of the Antarctic Peninsula. This is our first time deploying gliders so far from home, and our hope for a successful field season – not to mention a great deal of research – depends on recovering the two gliders our group deployed in December 2018. The gliders are now full of oceanographic data that will help us provide scientific advice on how best to conserve the Antarctic ecosystem as the area around the peninsula warms faster than almost any other region on Earth, which may adversely affect the animals that live there.</p>
<h2>9 hours, 30 minutes: No call</h2>
<p>For over 30 years, the <a href="https://swfsc.noaa.gov/textblock.aspx?id=551&ParentMenuId=42">NOAA group I’m part of</a> has conducted studies to estimate how many Antarctic krill, small shrimp-like creatures that support the diverse Antarctic food web, live around the Antarctic Peninsula.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=586&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=586&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=586&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Antarctic krill, <em>Euphausia superba</em>, can grow up to about 2.5 inches long.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Krill666.jpg">Uwe Kils/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Krill feeds penguins and seals that breed in this area every summer and whales and fishes that feed here year-round, while also supporting a major fishery. You may have seen bright-red dietary supplements made from krill oil prominently displayed at the pharmacy. Our data help establish catch limits for the krill fishery, ensuring enough krill remain in the ocean to maintain the population after all people and animals take what they need to make a living. Without good data to support fishery-management decisions, krill fishing could <a href="https://www.ccamlr.org/en/fisheries/krill-%E2%80%93-biology-ecology-and-fishing">undermine the food web</a> for which Antarctica is so well known, as demand for supplements and other <a href="https://bestmarketherald.com/krill-oil-market-demand-expected-to-raise-by-dietary-supplements-segment-in-upcoming-years/">krill products surges</a>.</p>
<h2>10 hours: No call</h2>
<p>Until three years ago, my program chartered a research vessel for a month each year to sail around the Antarctic Peninsula and <a href="https://swfsc.noaa.gov/contentblock.aspx?ID=14326&ParentMenuId=42">estimate the biomass of krill</a>. But after 2016, rising vessel costs eliminated our surveys. For our program to continue, we had to find a creative way to collect our data in Antarctica without actually going to Antarctica. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.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">An autonomous glider in the ocean.</span>
<span class="attribution"><span class="source">NOAA</span></span>
</figcaption>
</figure>
<p>Our solution was to use autonomous underwater gliders, which can be deployed in just a few hours by a small team from a ship in Antarctica, and then recovered months later. Gliders can dive to 3,000 feet, cover thousands of miles and follow commands from anywhere in the world with a laptop and an internet connection. Their batteries last six months, which means that they can collect much more data for much less money than a bunch of scientists on a research vessel. </p>
<p>The gliders resemble torpedoes in appearance, but contain three massive batteries and an array of scientific sensors that collect much of the same data we used to collect from a ship. Although the gliders are able to transmit small amounts of data via satellite throughout the deployment, the most valuable data are stored on the glider. If we lose a glider, which is always a possibility when you let something roam free in the ocean unattended for months, then we also lose the data.</p>
<p>We had effectively replaced ourselves with drones. But would they work?</p>
<h2>12 hours: No call</h2>
<p>For most of our team, the transition just a year ago from annual research voyages to the aquatic versions of C-3PO and R2-D2 was exciting. Secretly, though, I was terrified. I had spent my career as a scientist collecting krill samples from research vessels for biochemical analyses of their tissues. Suddenly I found myself ousted by oceanographic robots full of cables, wires, circuit boards and all sorts of other technological gadgetry.</p>
<p>These are not what you’d call smart robots. A bit like human toddlers, they have some degree of self-awareness, but would destroy themselves without semi-constant monitoring and instructions on how deep to dive or where to go. Outside supervision is especially important in the Southern Ocean, which is full of seamounts, canyons, strong currents and, most importantly, icebergs. </p>
<p>You can’t glider-proof the ocean the way you can baby-proof a house, so I had to forget everything I knew about biochemistry and learn as much as I could about glider piloting in 10 short months.</p>
<h2>13 hours: No call</h2>
<p>All that training and practice felt like 10 minutes by the time we finally packed up the gliders and shipped them to the Southern Hemisphere for their first Antarctic deployments. The commands for how deep to dive and where to go seemed simple enough, but the gliders responded as unpredictably as the ocean itself. </p>
<p>A near-disastrous practice deployment in San Diego revealed how slowly they maneuver, particularly in strong currents. Piloting them felt like trying to drive a remote-control semi-truck through a go-kart course, which reinforced our apprehension about driving these things through the ocean all the way across the planet, in one of the most remote and treacherous oceans on Earth.</p>
<p>Never mind the wind and the currents and the icebergs. What made this deployment far scarier was that if things started to go horribly wrong, we had no way to get the gliders back. It was like dropping a toddler off at college on another continent: What if he needs you and you can’t get to him?</p>
<h2>14 hours: No call</h2>
<p>Almost exactly 10 months from our first day of glider training, we carried the gliders across the Drake Passage on a research vessel bound for the Antarctic Peninsula. The deployments were flawless, and over the next few days, our confidence began to build. We quickly learned that icebergs were enemy number one, and they were formidable opponents. Satellite images of icebergs were <a href="https://www.polarview.aq/antarctic">available every couple of days</a>, and we overlaid maps of planned glider tracks onto those images so we could steer the gliders around any ice in their way. The trouble was, even the newest images we received were already a day old, and the ice had already moved.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=312&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=312&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=312&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=392&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=392&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=392&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On this chart of the South Shetland Islands, one intended glider path is marked in straight gray lines. Circled in red in the middle is the iceberg the researchers called ‘Yacu.’</span>
<span class="attribution"><span class="source">NOAA</span></span>
</figcaption>
</figure>
<p>Smaller icebergs were usually avoidable, but around three weeks into the deployment, “Yacu” appeared on the scene. Inspired by a <a href="http://www.salem-news.com/articles/august162010/monster-amazon-ta.php">mythological South American snake</a> that eats everything in its way, that was the nickname we gave a 12.5-mile-wide iceberg from the Weddell Sea that drifted right into the path of one of the gliders. Yacu stuck around for the rest of the deployment, every few days spawning smaller (but still huge) icebergs that posed a constant and unpredictable threat to gliders already at the mercy of currents, tides and wind.</p>
<p>If a glider gets trapped under an obstacle and senses that it’s been underwater for too long, it drops an emergency weight to rocket itself to the surface for an immediate recovery. Once a glider drops its weight, it can’t dive anymore. So if it is trapped under ice, it’s likely to stay trapped under ice. And one way to know if a glider is trapped is that it stops calling in, because it can connect to satellites only when it’s at the surface.</p>
<h2>15 hours: No call</h2>
<p>And then…</p>
<p>Ding ding! Ding ding! My laptop screams at me after 16 long hours: The glider is at the surface.</p>
<p>It is well past 9 p.m., but every member of our five-person team has been glued to a computer since early afternoon, and we collectively sigh with relief. We now think the glider probably surfaced after the first eight hours, failed to connect to the satellite and resumed diving, which can occasionally happen. The reason for the gap is unimportant compared to our elation. A couple of weeks later, we successfully recovered both gliders on schedule and completed our first autonomous Antarctic field season. </p>
<p>One key finding is that we can, in fact, replace a vessel-based fishery assessment with a glider-based one in less than a year. With gliders, we can get krill biomass estimates comparable to those we would expect from a ship. That means we can use gliders to continue to provide critical data for managing the krill fishery.</p>
<p>This is a profound accomplishment for us and for NOAA, and it also has far-reaching promise for the future of fisheries research globally. The cost of science keeps going up, and autonomous instruments offer an affordable way to collect critical data for effectively managing ocean resources and conserving fragile marine ecosystems worldwide. </p>
<p>Our gliders are like toddlers in one final way: They’re advanced technology, yet they’re still in their infancy. Their ongoing usefulness to understand our changing planet in real time will depend on new sensors and instruments yet to be developed. What we accomplished is only the the tip of Yacu compared to what the future of autonomous oceanographic research holds.</p><img src="https://counter.theconversation.com/content/119499/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Walsh is employed and funded by the U.S. National Oceanic and Atmospheric Administration. The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect the views of NOAA or the Department of Commerce.</span></em></p>Sending autonomous vehicles to the Southern Ocean can be fraught with anxiety, especially if one of them doesn’t make radio contact when it’s supposed to.Jennifer Walsh, Research Biologist, National Oceanic and Atmospheric AdministrationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/173832013-08-23T04:29:26Z2013-08-23T04:29:26ZA view to a krill: warming seas may leave predators hungry<figure><img src="https://images.theconversation.com/files/29762/original/kc8kpqfv-1377188615.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Best served chilled: Antarctic krill (Euphausia superba)</span> <span class="attribution"><span class="source">Uwe Kils/BAS</span></span></figcaption></figure><p>Although it is far from the power stations, roads and flight paths of the populated world, the Southern Ocean is already responding to climate change. Average sea temperatures in some parts have risen by about 1°C in 50 years.</p>
<p>This is a significant change for creatures such as <a href="http://www.coolantarctica.com/Antarctica%20fact%20file/wildlife/krill.htm">Antarctic krill</a> that live within a narrow range of temperatures spanning no more than 6°C. These tiny but abundant crustaceans are perhaps best known as the reason why half a dozen whale species migrate to the cold waters of the Southern Ocean each summer to feed. They are also familiar from their appearance in animated form on the big screen and as krill oil, a health supplement, on supermarket shelves. </p>
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<figcaption><span class="caption">From Happy Feet 2 (Warner Bros 2011)</span></figcaption>
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<p>A critical part of the Southern Ocean food web, the total biomass (weight) of Antarctic krill is <a href="http://www.iced.ac.uk/documents/Atkinson%20et%20al,%20Deep%20Sea%20Research%20I,%202009.pdf">roughly equivalent</a> to that of every adult human on Earth, and every year they produce a similar amount of new material through growth and reproduction. </p>
<p>This incredible production sustains the diverse array of charismatic marine predators that people commonly associate with the Antarctic: whales, seals, penguins and albatrosses, for example. None of these species feeds exclusively on Antarctic krill but it is often their main prey, and an important food source for many less well known species of fish and sea-bed invertebrates.</p>
<p>The current generation of <a href="http://www.whoi.edu/fileserver.do?id=50024&pt=2&p=56967">climate projections</a> suggest that Southern Ocean warming will continue throughout the 21st Century under all but the most optimistic scenarios. How will this warming affect Antarctic krill and the important food web that it supports? In a <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0072246">recent paper</a> published in the journal PLoS One, my co-authors and I have begun to answer this question by focusing on the potential consequences for Antarctic krill growth. Growth is a useful indicator of habitat quality: when small animals can no longer grow, something must be wrong.</p>
<p>Marine ecologists collected Antarctic krill from different parts of the Southern Ocean and observed their growth rates aboard a research ship. They derived an equation that described the relationship between these observed growth rates and the temperature and food availability in the waters that the krill were taken from. We applied this equation to the current generation of sea temperature projections to assess how Antarctic krill growth rates might change between now and the final decades of the 21st century. Our study focused on the area between the Greenwich Meridian and 90°W, historically known as the Weddell Quadrant, and centred around the <a href="http://www.britannica.com/EBchecked/topic/529436/Scotia-Sea">Scotia Sea</a>. This is where the highest concentrations of Antarctic krill and its predators occur.</p>
<p>Our results suggest that the effects of warming could reduce growth habitat, the area that supports Antarctic krill growth, by a fifth. That is, by about 1.2 million km<sup>2,</sup> an equivalent area to France and Spain. Antarctic krill growth rates in the remaining habitat could also be reduced by a fifth. These effects are unlikely to be evenly spread out, and results suggest that the most serious habitat loss will be concentrated in the northern half of the Southern Ocean, where temperatures are warmest.</p>
<p>This includes the waters around the island of South Georgia, home to 95% of the world’s Antarctic fur seals, 30% of its Macaroni penguins, and substantial populations of other penguins and seabirds. These species are busy rearing offspring during the few summer months when krill can grow. The penguins and seals forage close to the island and return regularly to the shore to feed their young. A reduction in the available supply of Antarctic krill could have particularly severe consequences for the wildlife of South Georgia.</p>
<p>This type of study is a form of risk assessment. It uses available knowledge to produce a best estimate of potential outcomes. Change in the Southern Ocean is driven by the naturally extreme climate, the repercussions of the <a href="http://rstb.royalsocietypublishing.org/content/279/963/81.short">massive removal of whales during the 20th century</a>, and the effects of human-induced climate change.</p>
<p>It is difficult to definitively attribute any observed change to a particular cause and it is impossible to predict the future with certainty. Nonetheless our study follows others which suggest that human-induced acidification and sea-ice loss could also affect Antarctic krill populations. This mounting evidence suggests that the Southern Ocean, far from being a haven from climate change, is likely to be severely affected.</p><img src="https://counter.theconversation.com/content/17383/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simeon Hill receives funding from the Natural Environment Research Council.</span></em></p>Although it is far from the power stations, roads and flight paths of the populated world, the Southern Ocean is already responding to climate change. Average sea temperatures in some parts have risen…Simeon Hill, Marine Biologist, British Antarctic SurveyLicensed as Creative Commons – attribution, no derivatives.