tag:theconversation.com,2011:/nz/topics/hadal-zone-25397/articles
Hadal zone – The Conversation
2021-06-01T11:28:50Z
tag:theconversation.com,2011:article/161214
2021-06-01T11:28:50Z
2021-06-01T11:28:50Z
How we discovered a giant new crustacean scavenging on the deepest depths of the ocean floor
<figure><img src="https://images.theconversation.com/files/401617/original/file-20210519-13-168up36.JPG?ixlib=rb-1.1.0&rect=121%2C675%2C4039%2C2032&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">_Eurythenes atacamensis_, a giant scavenging amphipod from hadal depths of the Peru-Chile Trench.</span> <span class="attribution"><a class="source" href="https://doi.org/10.1007/s12526-021-01182-z">Alan Jamieson</a>, <span class="license">Author provided</span></span></figcaption></figure><p>Discovering a new species and placing it on the tree of life is a big responsibility. I have been fortunate to name four species from some of the <a href="https://doi.org/10.11646/zootaxa.4748.1.9">deepest</a>, most remote and <a href="https://doi.org/10.1080/14772000.2020.1729891">least sampled</a> parts of the ocean. Each new species helps us uncover how life thrives in the <a href="https://books.google.co.uk/books?hl=en&lr=&id=hqsPBgAAQBAJ&oi=fnd&pg=PR1&dq=jamieson+hadal+zone&ots=mwSGRXURPG&sig=UknVAyND0muPevPRqfvTtWB3BQs#v=onepage&q=jamieson%20hadal%20zone&f=false">hadal zone</a> (anywhere deeper than 6,000 metres or 3.7 miles). Now, let me introduce you to <a href="https://doi.org/10.1007/s12526-021-01182-z"><em>Eurythenes atacamensis</em></a>.</p>
<p><em>Eurythenes atacamensis</em> is an amphipod, a type of crustacean closely related to a shrimp, endemic to the <a href="https://www.britannica.com/place/Peru-Chile-Trench">Peru-Chile Trench</a> (also known as the Atacama Trench). Measuring more than 8cm in length, it is nearly twice the size of its nearest relative, making it a giant. Spanning an extensive vertical range, juveniles and adults can be found in the trench between 4,974 to 8,081 metres. This includes the deepest point, known as Richard’s Deep. </p>
<p>It is one of the most abundant members of the trench community, joining a <a href="https://theconversation.com/snailfish-how-we-found-a-new-species-in-one-of-the-oceans-deepest-places-103003">trio of snailfish</a> and long-legged, spider-like <a href="https://www.youtube.com/watch?v=txSOP_9yLCI">isopods</a>. As a <a href="https://doi.org/10.4319/lo.2007.52.4.1685">scavenger</a>, this amphipod plays a critical role within the food web by intercepting and redistributing food sinking down from above. They quickly detect and consume new carrion, like the mackerel bait we used to coax individuals into the trap. Unfortunately, they can accidentally ingest <a href="https://doi.org/10.1098/rsos.180667">microplastics</a> too.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/bFqluXB9HcE?wmode=transparent&start=10" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Timelapse of <em>Eurythenes atacamensis</em> feasting on the baited scientific lander at 6,980 metres deep in the Atacama Trench.</span></figcaption>
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<p>Their home is one of <a href="https://doi.org/10.1016/j.pocean.2018.01.007">35 trenches</a> that reach hadal depths. These trenches are formed by a geologic process called subduction (where one tectonic plate is forced under another causing the ocean floor to quickly plunge). The volume of the Atacama Trench is almost the same as the neighbouring Andes mountain range, also created by the tectonic subduction zone. </p>
<figure class="align-right ">
<img alt="Colour map of Atacama Trench." src="https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1184&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1184&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1184&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1488&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1488&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402227/original/file-20210523-17-1agzf2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1488&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Atacama Trench in dark blue running along the spine of Peru to Chile.</span>
<span class="attribution"><span class="source">NOAA/Wikipedia</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Compared to the conditions at the surface, the <a href="https://doi.org/10.1016/j.tree.2009.09.009">hadal (or deep-sea) environment</a> seems extreme. It is pitch black with water temperatures varying between 1°C and 4°C at the deepest points. The hydrostatic pressure at hadal depths ranges from 600 to 1,100 atmospheres – equivalent to placing one-tonne on the end of your finger.</p>
<p>But this environment is entirely normal to the organisms that live there. Hadal inhabitants have a suite of biochemical, morphological and behavioural <a href="http://digital.ecomagazine.com/publication/?i=562381&article_id=3286789&view=articleBrowser&ver=html5">adaptions</a> that allow them to thrive in the trenches. Studying these ecosystems is not an easy task – which is why the hadal zone has been understudied compared to shallower parts of the ocean. </p>
<p>In 2018 two international research expeditions focused on the southern portion of the Atacama Trench. Scientists first set off on the Chilean vessel, RV Cabo de Hornos, to study the deepest part of the trench, Richard’s Deep, as part of the <a href="https://en.imo-chile.cl/post/2018-02-10-un-viaje-a-nuestro-mar-inescrutable-la-fosa-de-atacama.html">Atacamex expedition</a>. A month later, scientists on the German vessel, RV Sonne, <a href="https://epic.awi.de/id/eprint/49388/1/BzPM_0729_2019.pdf">studied</a> the wider trench ecosystem, sampling from 2,500 metres to Richard’s Deep.</p>
<p>During the expeditions, unmanned submersibles called <a href="https://www.sdu.dk/en/forskning/hadal/research/lander+work">landers</a> were deployed. Landers were equipped with robust deep-sea imaging equipment and baited traps to bring animals up for closer inspection. Both expeditions were a success and collected hundreds of hours of footage and thousands of amphipods – including <em>Eurythenes atacamensis</em> – as well as a <a href="https://theconversation.com/snailfish-how-we-found-a-new-species-in-one-of-the-oceans-deepest-places-103003">new species of snailfish</a>, affectionately nicknamed the “Little Purple Lovely” until its official scientific name is decided. </p>
<figure class="align-center ">
<img alt="A drawing of an deep-sea creature." src="https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=297&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=297&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=297&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=374&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=374&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402228/original/file-20210523-13-1hlljwb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=374&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Scientific illustration of the <em>Eurythenes atacamensis</em> holotype, a female from 8052 metres in the Atacama Trench.</span>
<span class="attribution"><span class="source">Johanna Weston/Marine Biodiversity</span>, <span class="license">Author provided</span></span>
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</figure>
<p>Once the specimens were back on land, the detailed work to sort, measure, identify and describe new species commenced. <em>Eurythenes atacamensis</em> is a member of a well-studied deep-sea genus (<em>Eurythenes</em>), which is notorious for what is known as <a href="https://doi.org/10.11646/zootaxa.3971.1.1">cryptic speciation</a>. In other words, when it is hard to visually tell one species from another. The fantastic photographs of <em>Eurythenes atacamensis</em> were actually taken back in a <a href="https://doi.org/10.3354/meps10489">2009 expedition</a> to the trench. </p>
<p>At the time, it was first identified as <em>Eurythenes gryllus</em>. With the new 2018 specimens, we accounted for cryptic speciation by applying an <a href="https://doi.org/10.1186/1742-9994-7-16">integrative taxonomy approach</a> – pairing traditional morphology (the detailed study of an organism’s shape) with <a href="https://theconversation.com/dna-barcoding-a-better-way-to-discover-species-4933">DNA barcoding</a>. This latest research showed it was actually a different and undescribed species. </p>
<p>This taxonomic process helped us categorise organisms so we could more easily communicate the biological information. Together, the detailed visual assessment and genetics gave us a clear result that <em>Eurythenes atacamensis</em> was a new species. Once confident in the data, we selected several individuals to be described and illustrated. These individuals are called type specimens – the most important of which is the <a href="https://ecologyforthemasses.com/2019/09/12/preserving-biological-heritage-the-importance-of-type-specimens/">holotype</a> or the “name-bearing” specimen. We chose the name <em>atacamensis</em> in tribute to its home.</p>
<p>This discovery is another piece in the puzzle of understanding the world that we live in and the subtle interactions between organisms and their environment. It helps us understand how life thrives in the deepest parts of the ocean, under conditions that seem impossible to terrestrial mammals like us. It also gives us a glimpse into the hadal zone – not an extreme habitat bereft of life, but one filled with extraordinary biodiversity.</p><img src="https://counter.theconversation.com/content/161214/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The RV Sonne SO261 Expedition was funded by the HADES–ERC Advanced Grant “Benthic diagenesis and microbiology of hadal trenches” (Grant Agreement Number 669947) and the German Federal Ministry of Education and Research. The Atacamex Expedition was funded by the National Agency for Research and Development of Chile (ANID; Grant AUB 150006/12806). Additional support came from the Danish National Research Foundation, HADAL, (Grant number DNRF145), ANID through the Millennium Science Initiative Program (Grant ICN 12_019-IMO), and internal funding from Newcastle University</span></em></p>
Deep ocean trenches are home to extraordinary biodiversity waiting to be discovered.
Johanna Weston, PhD Marine Science candidate, School of Natural and Environmental Sciences, Newcastle University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/88991
2018-02-01T11:39:17Z
2018-02-01T11:39:17Z
The deepest-dwelling fish in the sea is small, pink and delicate
<figure><img src="https://images.theconversation.com/files/203477/original/file-20180125-100902-h0oik.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Image from video of Mariana snailfish. </span> <span class="attribution"><span class="source">SOI/HADES/University of Aberdeen (Dr. Alan Jamieson) </span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Thanks to movies and nature videos, many people know that bizarre creatures live in the ocean’s deepest, darkest regions. They include <a href="http://ocean.si.edu/ocean-photos/midnight-hunter">viperfish</a> with huge mouths and big teeth, and <a href="http://ocean.si.edu/ocean-news/meet-tiny-bacteria-give-anglerfishes-their-spooky-glow">anglerfish</a>, which have bioluminescent lures that make their own light in a dark world. </p>
<p>However, the world’s deepest-dwelling fish – known as a hadal snailfish – is small, pink and completely scaleless. Its skin is so transparent that you can see right through to its liver. Nonetheless, hadal snailfish are some of the most successful animals found in the ocean’s deepest places. </p>
<p>Our research team, which includes scientists from the United States, United Kingdom and New Zealand, found a new species of hadal snailfish in 2014 in the Mariana Trench. It has been seen living <a href="https://www.jamstec.go.jp/e/about/press_release/20170824/">at depths of almost 27,000 feet</a> (8,200 meters). We recently published its <a href="https://biotaxa.org/Zootaxa/article/view/zootaxa.4358.1.7">scientific description</a> and officially christened it <em>Pseudoliparis swirei</em>. Studying its adaptations for living at such great depths has provided new insights about what kinds of life can survive in the deep ocean.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/EuaAMHuAfuA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Mariana snailfish, <em>Pseudoliparis swirei</em>, the deepest-living fish. Video by Alan Jamieson and Thomas Linley, University of Aberdeen. Schmidt Ocean Institute.</span></figcaption>
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<h2>Exploring the hadal zone</h2>
<p>We discovered this fish during a survey of the Mariana Trench in the western Pacific Ocean. Deep-sea trenches form at subduction zones, where one of the tectonic plates that form the Earth’s crust slides beneath another plate. They extend 20,000 to 36,000 feet deep below the ocean’s surface. The Mariana Trench is deeper than Mount Everest is tall. </p>
<p>Ocean waters in these trenches are known as the hadal zone. Our team set out to explore the Mariana Trench from top to bottom in an effort to understand what lives in the hadal zone; how organisms there interact; how they survive under enormous pressure created by six to seven miles of water above them; and what role hadal trenches play in the global ocean ecosystem. </p>
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<a href="https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202888/original/file-20180122-182948-y5fckv.jpg?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"></a>
<figcaption>
<span class="caption">Mariana Trench location.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mariana_trench_location.jpg">Dcfleck</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
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<h2>Getting to the bottom</h2>
<p>Sending instruments to the ocean floor is pretty straightforward. Bringing them back up is not. Researchers studying the deep sea often use nets, cameras or robots connected to ships by cables. But a 7-mile-long cable, even if it is very strong, can break under its own weight. </p>
<p>We used <a href="https://schmidtocean.org/11000-meters-under-the-sea-meet-schmidt-ocean-institutes-new-landers-part-one/">free-falling landers</a> – mechanical platforms that carry instruments and steel weights and are not connected to the ship. When we deploy landers, it takes about four hours for them to sink to the bottom. To call them back, we use an acoustic signal that causes them to release their ballast and float to the surface. Then we search for them in the water (each carries an orange flag), retrieve them and collect their data. </p>
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<a href="https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202497/original/file-20180118-158525-pekw6t.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">Deploying the fish trap in the Mariana Trench from the R/V Falkor. © Schmidt Ocean Institute.</span>
<span class="attribution"><span class="source">Paul Yancey, Whitman College.</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
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<h2>Life in the trenches</h2>
<p>Hadal trenches are named after Hades, the Greek god of the underworld. To humans, they are harsh, extreme environments. Pressure is as high as 15,000 pounds per square inch – equivalent to a large elephant standing on your thumb, and 1,100 times greater than atmospheric pressure at sea level. Water temperatures are as low as 33 degrees Fahrenheit (1 degree Celsius). Yet, a host of animals thrive under these conditions.</p>
<p>Our team put down cameras baited with mackerel to attract mobile animals in the trench. At shallower depths, from approximately 16,000 to 21,000 feet (5,000-6,500 meters) on the abyssal plain, we saw large fish such as rattails, cusk eels and eel pouts. At the upper edges of the trench, below 21,000 feet, we found decapod shrimp, supergiant amphipods (swimming crustaceans), and small pink snailfish. This newly discovered species of snailfish that lives to near 27,000 feet (8,200 meters), is now the world’s deepest living fish. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/6N4xmNGeCVU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video footage captured from the University of Aberdeen’s Hadal-Lander in the Mariana Trench from 16,000 to 35,000 feet deep. Video by Alan Jamieson and Thomas Linley.</span></figcaption>
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<p>At the trench’s greatest depths, near 36,000 feet (11,000 meters), we saw only large swarms of small scavenging amphipods, which are somewhat similar to garden pill bugs. Amphipods live all over the ocean but are highly abundant in trenches. The Mariana snailfish that we filmed were eating these amphipods, which make up most of their <a href="https://www.sciencedirect.com/science/article/pii/S0967063716302540">diet</a>.</p>
<p>The Mariana Trench houses the ocean’s deepest point, at Challenger Deep, named for the <a href="http://www.divediscover.whoi.edu/history-ocean/challenger.html">HMS Challenger expedition</a>, which discovered the trench in 1875. Their deepest sounding, at nearly 27,000 feet (8,184 meters), was the greatest known ocean depth at that time. The site was named Swire Deep, after Herbert Swire, an officer on the voyage. We named the Mariana snailfish <em>Pseudoliparis swirei</em> in his honor, to acknowledge and thank crew members who have supported oceanographic research throughout history. </p>
<h2>Life under pressure</h2>
<p>Hadal snailfish have several adaptations to help them live under high pressure. Their bodies do not contain any air spaces, such as the swim bladders that bony fish use to ascend and descend in the water. Instead, hadal snailfish have a layer of <a href="http://dx.doi.org/10.1098/rsos.171063">gelatinous goo</a> under their skins that aids buoyancy and also makes them more streamlined.</p>
<p>Hadal animals have also adapted to pressure on a molecular level. We’ve even found that some enzymes in the muscles of hadal fish are <a href="https://doi.org/10.1016/j.dsr.2017.05.010">adapted to function better under high pressure</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=150&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=150&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=150&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=188&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=188&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203582/original/file-20180126-100926-5f86t5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=188&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scientific drawing of <em>Pseudoliparis swirei</em>, the Mariana snailfish.</span>
<span class="attribution"><span class="source">Thomas Linley/Zootaxa</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Whitman College biologist <a href="http://people.whitman.edu/%7Eyancey/">Paul Yancey</a>, a member of our team, has found that deep-sea fish use a molecule called trimethyl-amine oxide (TMAO) to help stabilize their proteins under pressure.</p>
<p>However, to survive at the highest water pressures in the ocean, fish would need so much TMAO in their systems that their cells would reach higher concentrations than seawater. At that high concentration, water would tend to flow into the cells due to a process called osmosis, in which water flows from areas of high concentration to low concentration to equalize. To keep these highly concentrated cells from rupturing, fish would have to continually pump water out of their cells to survive. </p>
<p>The evidence suggests that fish don’t actually live all the way to the deepest ocean depths because they are not able to keep enough TMAO in their cells to combat the high pressure at that depth. This means that around 27,000 feet (8,200 meters) may be <a href="http://dx.doi.org/10.1073/pnas.1322003111">a physiological depth limit for fish.</a></p>
<p>There may be fish that live at levels as deep, or even slightly deeper, than the Mariana snailfish. Different species of hadal snailfish are <a href="https://doi.org/10.1016/j.dsr.2016.05.003">found in trenches worldwide</a>, including the <a href="https://www.britannica.com/place/Kermadec-Trench">Kermadec Trench</a> off New Zealand, the <a href="https://www.britannica.com/place/Japan-Trench">Japan</a> and <a href="https://www.britannica.com/place/Kuril-Trench">Kurile-Kamchatka trenches</a> in the northwestern Pacific, and the <a href="https://www.britannica.com/place/Peru-Chile-Trench">Peru-Chile Trench</a>. As a group, hadal snailfish seem to have found an unlikely haven in a place named for the proverbial hell.</p><img src="https://counter.theconversation.com/content/88991/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mackenzie Gerringer 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>
The Mariana snailfish lives nearly 27,000 feet underwater, but has features that help it adapt to intense water pressure and cold. Physiological limits may prevent fish from surviving in deeper water.
Mackenzie Gerringer, Postdoctoral Researcher, University of Washington
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/55172
2016-03-01T16:21:59Z
2016-03-01T16:21:59Z
Ten things you never knew about the ocean’s deepest places
<figure><img src="https://images.theconversation.com/files/113207/original/image-20160229-4080-15cdkcf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An Amphipod at 8,000 metres.</span> <span class="attribution"><span class="source">Alan Jamieson</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The ocean is deep. In fact, most of it is deep. Officially anything deeper than just 200 metres is considered the “deep sea”, but the average depth of the entire ocean is about 3.5km and the deepest point – <a href="http://www.tandfonline.com/doi/abs/10.1080/01490419.2013.837849">the Challenger Deep</a> in the Mariana Trench, in the western Pacific – is a little short of 11km down. That means that most of the living space on Earth is in the deep sea.</p>
<p>We scientists like to categorise things and the ocean depths are no exception. Depths from the surface to 0.2km is known as the “littoral zone”, from 0.2km to 3km, the “bathyal zone”, and from 3km to 6km, the “abyssal zone”. Anything deeper than that is the <a href="https://books.google.co.uk/books?hl=en&lr=&id=hqsPBgAAQBAJ&oi=fnd&pg=PR1&dq=jamieson+hadal+zone&ots=mwSGRXURPG&sig=UknVAyND0muPevPRqfvTtWB3BQs#v=onepage&q=jamieson%20hadal%20zone&f=false">“hadal zone”</a>. </p>
<p>The hadal zone is largely comprised of deep trenches caused by tectonic plate subduction that drive the vast abyssal plains steeply down to depths of 11,000 metres in places. But even here, animals thrive, blissfully unaware of how little attention they receive. Here’s an insight into their incredible world.</p>
<h2>1. The kingdom of Hades</h2>
<p>The term “hadal” comes from “Hades,” which refers both to the Greek kingdom of the Underworld and the god of the Underworld himself, <a href="http://www.greekmythology.com/Olympians/Hades/hades.html">Hades</a> (brother of Zeus and Poseidon). The term can also mean the “abode of the dead”. In modern times, Hades is seen as evil, but in mythology he was often portrayed as unreasonably “stringent” rather than actively malicious. Interestingly, he strictly prohibited the inhabitants of his dominion to leave, which is a rather apt analogy for hadal fauna, as these species are often confined to trenches and are rarely capable of going elsewhere. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=459&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=459&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=459&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=577&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=577&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113208/original/image-20160229-4080-1n5ald3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=577&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cusk eel at 6,500 metres.</span>
<span class="attribution"><span class="source">Alan Jamieson</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>2. Exactly how deep is the ocean?</h2>
<p>The extreme depths of the hadal trenches were discovered using “bomb sounding”, whereby someone threw a half-pound block of TNT off a ship and the echo was recorded on board the ship. This method was used to sound the depths of many trenches, but the exact depth of the deepest point, currently in the Mariana Trench, is still difficult to compute. <a href="http://www.sciencedirect.com/science/article/pii/S0169534709002997">Four other trenches, all in the Western Pacific, also exceed 10km</a>: the Tonga, Kuril-Kamchatka, Philippine, and Kermadec trenches. </p>
<h2>3. Who has explored it?</h2>
<p>The <a href="http://oceanexplorer.noaa.gov/explorations/03mountains/background/challenger/challenger.html">HMS Challenger expedition</a> (1873 to 1876) was the first to sample hadal depths – having collected sediment from about 8km – although it could not confirm whether or not the sediment was merely the remnants of shallower animals. The 1901 <a href="https://books.google.co.uk/books?id=hqsPBgAAQBAJ&pg=PA11&lpg=PA11&dq=princess+alice+expedition+1901&source=bl&ots=mwSGSUPMNC&sig=vVfhNdc_blRymkYaIBxab5E4dvs&hl=en&sa=X&ved=0ahUKEwiezu6Y2J_LAhVHQhQKHfFAAH8Q6AEIMjAE#v=onepage&q=princess%20alice%20expedition%201901&f=false">Princess Alice expedition</a> successfully trawled specimens from over 6km. However, it was a 1948 <a href="http://onlinelibrary.wiley.com/doi/10.1002/iroh.19700550413/abstract">Swedish expedition</a>, which successfully trawled a variety of species from 7km to 8km in the Puerto Rico Trench, that finally proved that life existed at depths greater than 6km. In 1956, the first photographs of the hadal zone were taken by none other than <a href="http://www.cousteau.org">Jacques Cousteau</a> in the Romanche Trough in the Atlantic.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wfsXgcAfzvU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Exploring the depths.</span></figcaption>
</figure>
<h2>4. How big is the hadal zone?</h2>
<p>The hadal zone comprises a series of disjointed trenches and other deep spots. <a href="https://books.google.co.uk/books?hl=en&lr=&id=hqsPBgAAQBAJ&oi=fnd&pg=PR1&dq=jamieson+hadal+zone&ots=mwSGRXURPG&sig=UknVAyND0muPevPRqfvTtWB3BQs#v=onepage&q=jamieson%20hadal%20zone&f=false">There are 33 trenches and 13 troughs around the world</a> – 46 individual hadal habitats in total. The mean depth of the trenches is 8.216km. The total area of the hadal zone is less than 0.2% of the entire seafloor but accounts for 45% of the total depth range. It is therefore surprising that the deepest 45% of the sea is rarely mentioned in deep sea literature.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=477&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=477&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=477&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=600&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=600&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113209/original/image-20160229-4066-f4fb0s.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=600&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A large prawn, 7,000 metres down in the Kermadec Trench.</span>
<span class="attribution"><span class="source">Alan Jamieson</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Of the 33 hadal trenches, 26 (84%) are located in the Pacific, three are found in the Atlantic (8%), two (4%) in the Indian Ocean, and two (4%) in the Southern Ocean. The majority run up the western Pacific. Most of the hadal trenches in their modern form are believed to have formed 65.5m years ago <a href="http://www.sciencedirect.com/science/article/pii/0146631359900632">during the Cenozoic</a> period.</p>
<h2>5. The secret behind our existence</h2>
<p>Earth appears to be the only terrestrial planet with <a href="http://www.livescience.com/43220-subduction-zone-definition.html">subduction</a> zones and plate tectonics. Both Mercury and the Earth’s moon are tectonically dead. Mars appears to have tectonically ceased, and Venus is dominated by thick lithosphere with mantle plumes. On Earth, subduction zones produce continental crust, which can protrude from the ocean (the continents). It has been <a href="http://www.nbcnews.com/science/science-news/plate-tectonics-bring-us-earthquakes-volcanoes-life-earth-n228516">speculated</a> that without subduction, the land would still be underwater and terrestrial life, including humans, would never have evolved.</p>
<h2>6. What’s it like down there?</h2>
<p>Bottom water temperatures are cold and vary between 1°C and 4°C. However, hydrostatic pressure increases linearly by 1 atmosphere (atm) for every ten metres of depth. The pressure at hadal depths therefore ranges from 600 to 1,100 atmospheres. The pressure at the deepest point is, therefore, equal to a one tonne weight being placed on the end of your finger.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113210/original/image-20160229-4087-ux7d1x.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A snailfish swims 7,400 metres below the surface.</span>
<span class="attribution"><span class="source">Alan Jamieson</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>7. What lives there?</h2>
<p>Many marine organisms are found at hadal depths and the most common groups are the <a href="http://www.sciencedirect.com/science/article/pii/0146631359900632">polychaetes, bivalves, gastropods, amphipods and holothurians</a>. All of these groups are found at full-ocean depth and often in large aggregations. Contrary to popular media, the hadal zone is not a mysterious realm inhabited by aliens or “monsters of the deep”. Instead, it is a poorly understood region largely inhabited by <a href="http://www.sciencedirect.com/science/article/pii/S0169534709002997">hoppers, snails, worms, and sea cucumbers</a>. In fact, the upper trenches are inhabited by <a href="http://www.sciencedirect.com/science/article/pii/S0967063708002264">little pink fish and bright red prawns</a>.</p>
<h2>8. But there are some horrors …</h2>
<p>In the 1970s, the Puerto Rico Trench was a <a href="http://link.springer.com/article/10.1007/BF02340472#page-1">pharmaceutical waste</a> disposal site. The figures are astonishing: in just five years, more than 387,000 tons of waste material was discarded in the trench, an amount equivalent to <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0022588">880 Boeing 747s</a>. In addition, the ill-fated Apollo 13 mission to the moon in 1970 carried a <a href="http://www3.ans.org/pubs/magazines/nn/pdfs/1999-4-2.pdf">radioisotope thermoelectric generator (RTG)</a> that was supposed to remain on the moon with the lunar lander. The RTG contained 3.9kg of plutonium-238, and in the end was jettisoned over the south-west Pacific, where it reportedly survived re-entry and settled in the Tonga Trench at a depth of 6km to 9km where it should now remain radioactive for several thousand years.</p>
<h2>9. Time-shifting earthquakes</h2>
<p>The 2011 magnitude 9.0 <a href="http://www.livescience.com/39110-japan-2011-earthquake-tsunami-facts.html">Tōhoku-Oki earthquake</a> off Japan was caused by a fault rupture in the Japan Trench. The event and subsequent tsunami left about 20,000 dead or missing and affected more than 35 coastal cities. The quake was followed by <a href="http://www.nature.com/articles/srep01915?WT.ec_id=SREP-704-20130603">666 aftershocks</a> that exceeded magnitude 5.0. The energy involved in high-magnitude earthquakes originating in trenches is immense. The 2004 Sumatra-Andaman earthquake in the Java Trench caused a sufficiently massive release of energy to alter the Earth’s rotation, shortening the day by 2.68 microseconds. Similarly, the Tōhoku-Oki earthquake shifted the Earth’s axis by between 10cm and 25cm, shortening the day by another 1.8 microseconds.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/HXrMnR00FHU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">James Cameron in the Challenger Deep.</span></figcaption>
</figure>
<h2>10. How deep is deep?</h2>
<p>One of the most common analogies used in trench science is “Mount Everest would fit into the Mariana Trench with a mile or so to spare”. This is true, and from an evolution and physiology perspective it is immense. Likewise, exploring these extreme depths is highly problematic.</p>
<p>But how far is 11km really? The Mississippi River is 11km at its widest point, Manhattan Island is twice as long as the Mariana Trench is deep, and assuming the average running speed of Mo Farah at the 2012 Olympics, he could run 11km in 30 minutes. Given how easily we can affect our planet over far larger distances, our effective proximity to these “extreme” locations means even the deepest places on Earth are no longer pristine – and remain hugely vulnerable.</p><img src="https://counter.theconversation.com/content/55172/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Jamieson receives funding from NERC (UK), EU FP7 and the Total Foundation (France)</span></em></p>
From time-shifting earthquakes to bizarre creatures, the crushing depths of the hadal zone are another world.
Alan Jamieson, Senior Lecturer, Oceanlab, University of Aberdeen
Licensed as Creative Commons – attribution, no derivatives.