Category Archives: Oceanography

Ship of legendary explorer Shackleton found in Antarctica 107 years after it sank

The Endurance was finally uncovered, over a century after it sank in the Weddell Sea in Antarctica. The ship was part of a famous expedition led by Sir Ernest Shackleton but got trapped in pack ice, forcing the expedition members to camp for months in the Antarctic and make a heroic escape.

Despite laying under 3km (10,000 feet) of frigid water for over a century, the ship seems to be in impeccable shape, almost frozen in time. The ship was discovered just several kilometers from where it was abandoned after a search mounted by the Falklands Maritime Heritage Trust (FMHT) investigated the area for two weeks.

Using a South African icebreaker, Agulhas II, the search team deployed submersible units to comb the area. After coming across various interesting targets, they finally uncovered the wreck site on Saturday, spending the next few days documenting and photographing the site.

In a blog post announcing the find, Director of Exploration Mensun Bound couldn’t contain his excitement:

“Ladies and Gentlemen,

I don’t know how else to say this, so I am going to come straight to the point.

We have found the wreck of the Endurance!”

“In a long career of surveying and excavating historic shipwrecks, I have never seen one as bold and beautiful as this.”

The mission’s leader, the veteran polar geographer Dr. John Shears also told the BBC that this is an incredible achievement, describing the moment when they saw the ship as “jaw-dropping”. Shears also emphasized that this was “the world’s most difficult shipwreck search”, battling blizzards, bitterly cold temperatures, and constantly shifting sea-ice. “We have achieved what many people said was impossible,” Shears said.

Pristine shape

The ship looks much like it did when it was last photographed by Shackleton’s filmmaker, Frank Hurley, in 1915. While some things have obviously broken down, you can still see the hull, the deck, and the porthole window from Shackleton’s cabin. The anchors are still around, as are some of the boots and crockery the crew abandoned with the ship.

“Most remarkable of all was her name – E N D U R A N C E – which arcs across her stern with perfect clarity. And below is the 5-pointed Polaris star. Just as in Hurley’s famous photographs,” Bound adds.

Some sea creatures (such as filter feeders) have colonized the wreck but there don’t seem to be any wood-eating worms that would degrade the ship structurally.

The wreck itself cannot be moved or disturbed in any way, as it is a designated monument under the international Antarctic Treaty. Therefore, researchers can’t bring anything to the surface, and all they’ve done now was to document the position and situation for the ship.

A legendary expedition

Sir Ernest Henry Shackleton led three expeditions into the Antarctic. The one that employed the Endurance was launched in 1914, and Endurance departed from South Georgia, British Overseas Territory in the southern Atlantic Ocean, for the Weddell Sea on 5 December. But the situation quickly took a turn for the worse, as the ship became trapped in an ice floe. The crew waited until February and then realized that the ship would be trapped until spring (in the southern hemisphere, spring starts in September).

Shackleton ordered the conversion of the ship to a winter station, and the crew managed to tough it out until September. But when the ice started to release, the crew’s hopes that the ship would be freed safely were destroyed. The ice put extreme pressure on the ship’s hull, damaging it, and the ship was taking water. In November, the crew abandoned the ship.

The next two months, Shackleton and his crew camped on a large, flat ice floe (basically an ice island), hoping that it would drift towards Paulet Islands 250 miles (402 km) away, where some stores were cached. This too failed. Shackleton decided to set up a more permanent camp on a different flow, hoping to drift to a safe island. This too did not happen. The floe broke in two, and Shackleton’s crew was forced into lifeboats, heading towards the nearest island.

The exhausted men managed to end up their three lifeboats at Elephant Island, 346 miles (557 km) from where the Endurance sank, after being adrift on ice for almost 500 days. Shackleton gave his mittens to photographer Frank Hurley (who had lost his) and suffered severe frostbites as a result. In a desperate last-ditch attempt, Shackleton decided to take one of the three lifeboats and head for whaling stations 720 nautical miles (1,334 km) away.

Launching the lifeboat from the shore of Elephant Island, 24 April 1916.

Shackleton packed minimal supplies and head out with a handful of people, only to be met by a hurricane. They landed on an island and Shackleton and two members braced a yet-untried land route over dangerous, uncharted mountainous terrain. Ultimately, they were able to reach a whaling station and after several tries, rescue the surviving members of the expedition.

The fact that researchers now have such a connection to this expedition is a spectacular achievement. “We will pay our respects to ‘The Boss’,” said Dr. Shears, using the nickname the Endurance crew had for their leader.

Still, the current expedition hopes they can uncover even more from the ship and will now embark on thorough scientific research of the vessel.

“You can even see the holes that Shackleton’s men cut in the decks to get through to the ‘tween decks to salvage supplies, etc, using boat hooks. In particular, there was the hole they cut through the deck in order to get into “The Billabong”, the cabin in “The Ritz” that had been used by Hurley, Leonard Hussey (meteorologist), James McIlroy (surgeon) and Alexander Macklin (surgeon), but which was used to store food supplies at the time the ship went down,” Bound concluded in an article for the BBC.

Sea sponges survive in the Arctic by feasting on extinct creatures

The bottom of the Arctic Ocean is not the easiest of places to live in. Nutrients and vegetation are very scarce, it’s cold, it’s dark, the elements are pretty much against you. That’s why researchers were very surprised to find a dense population of sponges alive and kicking in the volcanic seamounts of the ocean. As it turns out, they were feeding off fossilized remains of extinct animals and fauna.

Image credit: The researchers.

Researchers from Germany’s Alfred Wegener Institute were around 200 miles from the North Pole on board their research vessel when a submarine camera they were towing caught sight of fuzzy sponges on top of the extinct volcanoes. They just couldn’t believe it. Some of the sponges even stretched over three feet (one meter) across — very big for sponge standards. 

Sponges don’t have a digestive tract, so they rely on passive filter feeding to collect nutrients from water passing through them. Ocean currents in the Arctic Ocean are slow, with not many particles swirling in the water. This made the sighting even more unusual, especially considering tests showed the average sponge was 300 years old. How were they surviving there, for centuries, in what was basically an ocean wasteland?

Studying the sponges

The researchers collected samples of the organisms and the sediment around them and sent the samples to the lab for examination. The analysis showed the seafloor wasn’t as desolate as thought. In fact, the sediment samples were full of fossils. 

The fossils were the empty shells of large deep-sea worms. While they don’t live there anymore, the researchers weren’t surprised to find the shells. Many years ago, gases leaked from the vents of the submerged volcanoes, creating a perfect habitat for the worms. That dynamic ecosystem from a long time ago is still influencing the area. 

The samples collected suggest the sponges are packed with microbial bacteria, with which they form a symbiotic relationship. The bacteria break down the ancient leftovers that then the sponges use to obtain nutrients from. The researchers spotted different sizes of sponges, with the average measuring 30 centimeters or 12 inches.

“This allows them to feed on the remnants of former, now extinct inhabitants of the seamounts, such as the tubes of worms composed of protein and chitin and other trapped detritus,” said first study author Teresa Morganti, a sponge expert from the Max Planck Institute for Marine Microbiology in Bremen, Germany, in a statement.

The researchers believe that there could be more sponge grounds similar to this one along the volcanic ridge of the Arctic Ocean. This would be good news for many other creatures that live there because sponges are natural ecosystem engineers. As they grow, they create places for other animals to live in, depositing a sticky surface for bacteria to settle on. 

A better understanding these ecosystems is essential to protect and manage the diversity of the Arctic Sea, which is currently under serious pressure, the researchers stress. With the sea ice retreating at record rates, the researchers want that the web of life in the Arctic Sea is under pressure. Both the sea ice and its thickness have shown a big decline, affecting the oceanic environment. 

Last year, another group of researchers found sponges below the Antarctic ice shelves while drilling in the Filchner-Ronne Ice Shelf neat the southeastern Weddell Sea. It was an accidental discovery that left the researchers perplexed, calling for further studies (like this one) to better understand what’s actually going on below the Arctic Sea. 

The study was published in the journal Nature

Atomic isotopes solve mystery about jellyfish diet

Jellyfish aren’t exactly picky eaters — it’s hard to be picky when you’re not really in control of where you’re going and what you’re doing. They munch on most things they come across, and this “whatever” approach to eating has shrouded our understanding of their eating habits. Now, researchers from the Institute for the Oceans and Fisheries (IOF) in Canada used biochemical tools, stable isotopes, and fatty acids, to unravel the mystery of jellyfish feeding.

Image credits: Cody Chan.

Jellyfish evolved more than 500 million years ago and they’re still around, so they must be doing something right — which seems weird at first glance. After all, they just drift along with the oceans, swaying at the mercy of currents. But if there’s one thing that jellyfish do right, it’s eating.

Most of them are carnivorous or parasitic, feeding on plankton, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and eliminating undigested waste through the mouth. They don’t spend much energy hunting, either — they passively hunt, leaving their tentacles as drifting lines that stun or kill the prey.

But these habits are hard to track, and researchers aren’t sure exactly where jellyfish fit in the oceanic food chain.

“Jellyfish have long been ignored in research, often considered more of a nuisance than an organism of interest,” said Dr. Brian Hunt, IOF professor and study co-author. “However, there is a growing awareness that they can play a key role as both predators and prey.”

To get to the bottom of this, researchers tracked biomarkers: natural isotopes of elements like carbon and nitrogen (which exist in certain ratios in tissues), and fatty acids, which are produced in unique compositions by plants at the base of the food web. As these biomarkers get passed on along the food chain, they develop specific signatures.

Based on these signatures, researchers can figure out an animal’s position on the food chain, but they first need some calibration values — this study developed the first such calibration values for jellyfish.

“Until now, jellyfish ecologists were using a generalized calibration value for these biomarkers because they didn’t have jellyfish-specific ones,” said Jessica Schaub, the study’s lead author and recent M.Sc. graduate at the IOF. “This study tested how much the concentrations of isotopes and fatty acids changed, and how quickly they were absorbed when jellyfish digested their prey and incorporated prey signatures into their bodies.”

“The numbers we found were different enough that it’s worth going back to previous jellyfish studies that applied the general values—they will likely get different results if they applied our values,” Schaub said.

The results were quite surprising. The study found that jellyfish seem able to “elongate” fatty acids — in other words, they create their own omega-3 and omega-6 fatty acids. These acids are important for many organisms, but most creatures are unable to produce them, so instead, they get them from their diet. This phenomenon has only been observed in a few other organisms, and it’s the first time it’s ever been observed in jellyfish.

Jellyfish also don’t seem to be as indifferent to what they eat as we thought.

“It seems straightforward, but it’s never that easy—you get the data and you’re like, ‘what’s happening here?'” Schaub said. “We were surprised about the moon jellyfish. We fed them two crustaceans, krill and artemia, but they didn’t really incorporate the krill. We think of jellyfish as not being picky eaters, but in this case, it seemed that they didn’t like feeding on a single diet. Either it didn’t meet their nutritional needs, or they preferred the live artemia over the dead, frozen krill. The aquarium has been feeding them these krill for a long time, so it’s good to be able to tell the aquarium that it’s maybe not worth investing in the krill any longer.”

All in all, it seems like we’re just starting to unravel the secret lives of jellyfish — and there may be more lurking beneath the surface.

Journal Reference: Jessica Schaub et al, Experimentally derived estimates of turnover and modification for stable isotopes and fatty acids in scyphozoan jellyfish, Journal of Experimental Marine Biology and Ecology (2021). DOI: 10.1016/j.jembe.2021.151631

Whales eat much more than we assumed, and it has huge ecological implications

Baleen whales eat a lot more food than previously assumed: three times as much, to be exact, according to new research. The findings are not meant to shame these animals into going on a diet. Rather, they shed light on the key ecological role whales play in the ocean.

Image via Pixabay.

The sheer size and appetite of whales make them important players in the ocean. In particular, they serve as key drivers of nutrient recycling in the ocean. They consume vast amounts of food, releasing important nutrients back into the water following digestion. A new paper refines our understanding of just how much food whales as a group can consume, and take a look at the ecological implications of the decline in whale numbers since the onset of the 20th century.

Big eaters

“While it may just seem like a fun trivia fact, knowing how much whales eat is an important aspect of ecosystem function and management,” Matthew Scott Savoca, a Postdoctoral Research Fellow at Stanford University and corresponding author of the paper, told ZME Science. “If we want to protect whales and make sure they are thriving in modern oceans, then knowing how much food they need to survive and reproduce is critical.”

“There are implicit benefits of having whales on the planet — isn’t it cool to think that we live at a time when we’re alongside the largest animal in the history of life on Earth? Beyond that, whales have direct value as carbon sinks (e.g., sequestering carbon in their bodies and exporting it to the deep sea when they die and sink – which we did not discuss in this study). In addition, whale watching is a multi-billion dollar per year global business that is expanding as whales are recovering.”

Previous estimates of just how much whales eat were built upon data obtained from metabolic models or direct analysis of the stomach contents of whale carcasses. Such data can give us a ballpark figure but, according to the new paper, they are quite inaccurate.

Savoca and his colleagues directly measured the feeding rates of 321 baleen whales across seven species in the Atlantic, Pacific, and Southern oceans. They tracked foraging behavior and estimated prey consumption by tracking the whales using GPS tags. Location data was then combined with sonar measurements of prey density, of the quantity of prey consumed per feeding, and current estimates of how much each species typically eats per feeding event.

Overall, the results suggest that we’ve underestimated how much food baleen whales ingest by a factor of three. On average, these animals consume between 5% and 30% of their body weight per day, depending on species, across all the investigated regions. In total, blue, fin, and humpback whales in the California Current Ecosystem consume over two million tonnes of krill every year per species.

The study also puts into perspective just how massive an impact whaling and other stressors have placed on whales and, by extension, on the ecosystems they inhabit. Prior to the 20th century, the team estimates, whales in the Southern Ocean were consuming around 430 million tonnes of Antarctic krill per year. This figure is twice the total estimated biomass of Antarctic krill today.

Whales, the paper explains, serve an important ecological role as nutrient recyclers, tying into that last tidbit of information. Prior to the 20th century, before whales were hunted in meaningful numbers, these animals consumed a massive amount of biomass, releasing much of the nutrients in their food back into the ocean as waste. This, in turn, allowed for much greater productivity in the ocean (as they made large quantities of nutrients freely-available for krill and other phytoplankton to consume).

“In brief, if whales eat more than we thought, then they also recycle more nutrients (i.e., poop) than we thought. If that is the case then limiting nutrients may have been used more effectively and efficiently in a system that had many more whales,” Savoca said for ZME Science. “It’s not that these whales add more iron (or other nutrients) to the system, they just [move] it from within the bodies of their prey, to in the seawater itself where it could, in theory, fertilize phytoplankton — the base of all open ocean food webs.”

To put things into perspective, the authors estimate that today, baleen whales in the Southern Ocean recycle around 1,200 tons of iron per year; prior to the 20th century, this figure was likely around 12,000 tons of iron per year. In essence, whaling has led to a 90% decrease in the amount of essential nutrients whales can recycle in their ecosystems.

I asked Savoca whether there is any overlap between the decline in baleen whale populations and the detrimental effects of industrial fishing on today’s ocean ecosystems. Should we expect trouble ahead as we’re removing key nutrient recyclers from one side of the equation, and taking more fish out of the sea on the other?

“You are hitting on a major issue,” he admitted. “We have noticed that oceans have become less productive after removing millions of large whales in the 19th and 20th centuries. The same is true of ongoing industrial fishing. The collapse of predatory fish communities have the same detrimental impacts on marine communities as the wholesale decimation of the whales did.”

“I am not against fishing, but we have to do so as sustainably as possible if we want to maintain essential ocean productivity into the future.”

Whales and their extended family — cetaceans — have been experiencing immense pressures ever since the onset of industrial-scale whaling in the early 20th century. Commercial whaling only slowed down in the 1970s, which is a very, very short time ago from an ecological perspective. This has allowed whales and other cetaceans some much-needed respite, but they are still struggling. Over half of all known cetacean species today are inching towards extinction, 13 of which are listed as “Near Threatened”, “Vulnerable”, “Endangered”, or “Critically Endangered” on the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species. Besides the lingering effects of whaling, this family is still struggling under the combined effects of (chemical and noise) pollution, loss of habitat, loss of prey, climate change, and direct collisions with ships.

Research such as this study and many others before it can raise an alarm that not all is well with the whales. But actually doing something about it hinges on us and governments the world over taking the initiative to protect them. Understanding just how important whales are for the health of our oceans and, through that, for our own well-being and prosperity definitely goes a long way towards spurring us into action.

But Savoca’s conclusion to our email discussion left an impression on me. There is great beauty in natural ecosystems that we’re destroying, oftentimes unaware. Beyond the practical implications of conserving whale species, we have a chance to conserve these for our children and all future generations.

“I remember one day in Monterey Bay when we were surrounded by blue whales (likely over a dozen), each about twice the size of the boat we were on. I will also never forget the sound and scale of the ice in Antarctica,” Savoca wrote for ZME Science.

“My life’s work is devoted to making sure people and animals have these (and ideally ever better) ecosystems of awe and plenty well into the future.”

The paper “Baleen whale prey consumption based on high-resolution foraging measurements” has been published in the journal Nature.

Could we use plastic to end the ocean’s plastic problem? A new paper says: “Yes!”

The world’s oceans have a plastic problem. However, a bold new approach from researchers at several institutions says that the same plastic could also be the solution.

Image via Pixabay.

The team, with members from Worcester Polytechnic Institute, Woods Hole Oceanographic Institution, and Harvard University, believes that the plastic clogging up our oceans can be used as fuel for ships that work to clean the oceans of plastic. In a new study, they describe the process through which plastic can be converted to ship fuel in order to support such a scheme.

If applied, this approach would allow ships to operate continuously to clean the oceans.

Putting it to good use

“Plastic waste accumulating in the world’s oceans forms massive ‘plastic islands’ in the oceanic gyres. Removing [it] offers an opportunity to restore our oceans to a more pristine state,” the authors explain. “To clean the gyres, ships must collect and store the plastic before transporting it to port, often thousands of kilometers away. Instead, ocean plastic waste can be converted into fuel shipboard, for example, using hydrothermal liquefaction”.

Millions of tons of plastic find their way into the ocean year after year. The smaller fragments disperse, while larger pieces of plastic clump together forming plastic ‘islands’. These tend to end up in ocean gyres, large systems of ocean currents generated by winds and the rotation of the planet that ‘spin’ in place.

Plastic waste poses a very real threat to marine life. As such, efforts to clean up the seas have been repeatedly attempted over time. Ships are sent out to garbage patches where they collect as much plastic as they can hold and bring it back to port for processing. Although this approach works, it’s by no means ideal. Going back and forth between these patches and port areas takes time, fuel, and slows down the efforts overall.

The authors of this study propose using the plastic itself as fuel for the ships and machines used to process the waste. This could have a powerful dual benefit. It would dramatically improve the efficiency of clean-up efforts by slashing downtime, while also being a greener option overall, as it would reduce emissions associated with fuel use (and ships can be very polluting).

Plastic waste can be converted to a type of oil via a process known as hydrothermal liquefaction (HTL), the authors explain. During HTL, plastic is heated to around 300–550 degrees Celsius (572-1022 Fahrenheit) at high pressure — 250 to 300 times the standard atmospheric pressure.

According to their estimates, one ship equipped with an HTL converter could produce enough oil to be self-sustainable (i.e. to keep both the ship and the converter operational). They envision a system where permanent collection booms would be stationed at multiple sites around a large garbage patch and maintain a steady supply of plastic for the ships to convert.

Such an approach is not without its problems. The HTL process itself, as well as the burning of the oil it produces, would obviously release carbon dioxide. That being said, the authors explain that it would still be a lower quantity than what a ship burning conventional fuel would emit during a clean-up mission. There would still be practical constraints on how long a mission could carry on for; the HTL process would produce a relatively small quantity of solid waste that would eventually need to be returned to port, and there’s only so much time a crew’s supplies and sanity can last for on the open seas. However, it would reduce the need for round trips down to once every few months or so, which would also be fueled by the oil produced by the converters.

I personally like the idea of such an approach. It makes practical sense, and I’m sold on the idea of turning a problem into an opportunity or solution. So far the idea is still in its theoretical stage, but it definitely has promise. Fingers crossed that we’ll see it implemented in the not-so-distant future.

The paper “Thermodynamic feasibility of shipboard conversion of marine plastics to blue diesel for self-powered ocean cleanup” has been published in the journal PNAS.

Climate change is choking the oxygen out of deep water, and it’s putting fish in a double bind

Being a fish was never easy, but a new paper reports that it’s been getting harder over the last 15 years or so. According to the findings, oxygen levels are dropping in the depths of the oceans, forcing fish to move ever closer to the surface.

Image via Pixabay.

New research from the University of California – Santa Barbara and the University of South Carolina is warning us that fish are slowly drowning. Changes in ecology, as well as the effects of climate change on seasonal patterns, water temperature, and its gradient over different depths, have been causing deeper layers of the ocean to lose their dissolved oxygen content. This, in turn, is forcing fish to either move closer to the surface, or asphyxiate.

It may seem like a trivial matter, but this shift is causing wide-scale changes in marine ecosystems and could have a very real impact on the health of the ocean as a whole. It also raises important questions for fishery management and conservation efforts, with the authors underscoring the importance of accounting for this shift with policy to avoid further damaging marine ecosystems.

Swimming out of breath

“This study finds that oxygen is declining at all the depths we surveyed: from 50 meters to 350 meters,” said lead author Erin Meyer-Gutbrod, assistant professor at the University of South Carolina, “and so fish seem to be moving up to shallower regions to get to an area where the oxygen is relatively higher.”

The findings are based on 15 years’ worth of recordings, surveys, and measurements. These included measurements of dissolved oxygen in samples of water taken at varying depths, of temperature, salinity, and surveys of the average depth at which certain fish species tend to congregate. A total of 60 different species of fish were encountered often enough during these 15 years to be statistically relevant and included in the study.

Data was collected on a yearly basis, every fall, from 1995 through to 2009. The team focused on three reef features between the Anacapa and Santa Cruz islands in Southern California. These were the Anacapa Passage area, with an average depth of 50m, a seamount known as the “Footprint”, at around 150m, and the “Piggy Bank”, with an average depth of around 300m. During the surveys, the team identified all fish species that came within two meters of the submarine or were visible and within two meters of the seafloor. They also estimated the length of each individual fish.

During this time, they saw depth changes in 23 species. Four of these shifted towards deeper waters, while the other 19 moved towards the surface in response to low oxygen conditions (as shown by analysis of water samples).

The team explains that surface waters tend to be better oxygenated (have higher levels of dissolved oxygen) due to surface motions such as waves continuously mixing gases into the top layer of bodies of water. Over time, as waters mix, this oxygen also finds its way lower along the column of water. However, the team explains that warming climates make for warmer surface waters, which increases the buoyancy of these layers compared to those deeper down, reducing their ability to mix. This process is known as ocean stratification.

In addition to this, warmer water has a lower ability to dissolve and hold oxygen compared to colder water, so there’s less of this gas being mixed into the ocean to begin with.

In the end, this means less oxygen makes it to the bottom layers of water. Although salinity and temperature gradients along the column of water also influence the extent of vertical mixing, the team reports that both remained relatively constant over the study period. In other words, the trend towards lower oxygen levels seen at the study site is primarily driven by climate-associated changes in surface water temperatures. That being said, the other factors can’t be discounted completely either.

“A third of [the 60 fish species’] distributions moved shallower over time,” Meyer-Gutbrod said. “I personally think that’s a remarkable result over such a short time period.”

The team acknowledges that their study only included a relatively small area, but it did include a wide range of depths, which was the ultimate objective of the research. This narrower area actually helps reduce confounding factors, they explain, since it allowed for most conditions (apart from depth) to be constant across all the survey areas.

“Other scientists have used lab experiments to show that fish don’t like low oxygen water,” Meyer-Gutbrod said, “but what nobody’s ever done is just return to the same location year after year to see if there’s actually a change in the distribution of fish stemming from a change in oxygen over time.”

In closing, the authors explain that this trend can have quite severe negative impacts on marine ecosystems, and indirectly, on all life on Earth. Fish are simply forced to move away from their optimal depths, which will eventually result in them being pushed out entirely out of several ecosystems. According to co-author Milton Love, a researcher at UC Santa Barbara’s Marine Science Institute, we could even see a point in which species are forced into depth ranges that they simply cannot survive in.

They also cite previous research showing that many fish species also cannot tolerate high water temperatures, and are migrating towards lower depths. In the end, these factors can leave many species in an impossible situation — where they cannot breathe if too low, and can’t bear the heat if too close to the surface.

In the end, even if we start working to redress climate change right now, meaningful progress will take quite a lot of time. Until then, policymakers need to recognize and react to the pressures faced by fish species and issue regulation that protects them as best as possible, or risk wide-ranging ecological collapse in the world’s oceans.

“If you throw your net in the water and you get a ton of fish — more than you’re used to getting — you may think, ‘Oh, it’s a good year for the fish. Maybe the population is recovering,'” Meyer-Gutbrod said. “But instead, it could be that all the fish are just squished into a tighter area. So you could have fishery regulations changing to increase fish allowances because of this increase in landings.”

The paper “Moving on up: Vertical distribution shifts in rocky reef fish species during climate‐driven decline in dissolved oxygen from 1995 to 2009” has been published in the journal Global Change Biology.

Submersible robots help us better understand ocean health and carbon flows

Floating robots could become indispensable in helping us monitor the health of ocean ecosystems and the flow of carbon between the atmosphere and oceans, according to a new study.

Although the microscopic marine plants and animals which make up plankton are the bedrock of ocean ecosystems. While they’re essential for the well-being of everything that swims, they’re also very important for our comfort and well-being, too. Plankton is one of the largest single sources of oxygen on the planet, and it consumes a lot of CO2 to do it. This process is known as marine primary productivity.

Knowing how they’re faring, then, would be a great help. Floating robots can help us out in that regard, according to a new paper.

Floats my boats

“Based on imperfect computer models, we’ve predicted primary production by marine phytoplankton will decrease in a warmer ocean, but we didn’t have a way to make global-scale measurements to verify models. Now we do,” said Monterey Bay Aquarium Research Institute (MBARI) Senior Scientist Ken Johnson, first author of the paper.

Together with former MBARI postdoctoral fellow Mariana Bif, Johnson shows how a fleet of marine robots could completely change our understanding of primary productivity on a global scale. Data from these crafts would allow researchers to more accurately model the flow of carbon between the atmosphere and the ocean, thus improving our understanding of the global carbon cycle.

Furthermore, the duo explains, shifts in phytoplankton productivity can have significant effects on all life on Earth by changing how much carbon oceans absorb, and by altering oceanic food webs. The latter can easily impact human food security, as the oceans are a prime source of food for communities all over the world. In the context of our changing climate, it’s especially important to know with accuracy how much carbon plankton can scrub out of the atmosphere, and what factors influence this quantity.

Part of what makes the ocean such a good carbon sink is that dead organic matter sinks to the bottom. Plankton grows by consuming atmospheric oxygen, and is in turn consumed by other organisms, such as fish. As these eventually die, they sink to the bottom of the sea, where they’re decomposed by bacteria, releasing carbon in the process. However, because this happens at great depths, the carbon is effectively prevented from returning to the atmosphere for very long periods of time. Generally, it seeps into deep-water sediments and stays there for millions of years or more.

That being said, this process is very sensitive to environmental factors such as changes in climate. While we understand that this happens, we’ve not been able to actually monitor how primary productivity is responding to climate change on a global scale, as most of it happens in the depths of the oceans.

“We might expect global primary productivity to change with a warming climate,” explained Johnson. “It might go up in some places, down in others, but we don’t have a good grip on how those will balance.”

“Satellites can be used to make global maps of primary productivity, but the values are based on models and aren’t direct measurements,”

Autonomous robots could help us get the data we need, the study argues. For starters, it’s much easier to build robots that can withstand the humongous pressures of the deep ocean than it is to build equivalent manned submarines. Secondly, robots are mass-producible for relatively little cost. Human crews are expensive and slow to train — they’re also quite limited in availability. Finally, robots can operate for much longer periods of time than human crews, and nobody needs to risk their life in the process.

The authors point to the deployment of Biogeochemical-Argo (BGC-Argo) floats across the globe as a great example of how robots can help monitor primary productivity. These automated floats can measure temperature, salinity, oxygen, pH, chlorophyll, and nutrient content in marine environments, at depths of up to 2,000 meters (6,600 ft). A float can perform its monitoring tasks autonomously, shifting between different depths and supplying live data to researchers onshore. These robots have been deployed in increasing numbers over the past decade, providing reliable — but as of yet, still sparse — measurements of oxygen production across the globe.

Although the data they’ve been feeding us didn’t tell us anything new, it is the first time we’ve been able to quantitatively measure primary productivity directly.

“Oxygen goes up in the day due to photosynthesis, down at night due to respiration—if you can get the daily cycle of oxygen, you have a measurement of primary productivity,” explained Johnson.

In order to confirm that these robots were actually performing their job reliably, the team compared primary productivity estimates computed from the BGC-Argo floats to ship-based sampling data in two regions: the Hawaii Ocean Time-series (HOT) Station and the Bermuda Atlantic Time-series Station (BATS). The data from these two sources matched over several years, proving the reliability of the system.

“We can’t yet say if there is change in ocean primary productivity because our time series is too short,” cautioned Bif. “But it establishes a current baseline from which we might detect future change. We hope that our estimates will be incorporated into models, including those used for satellites, to improve their performance.”

Seeing as we have drones flying about the atmosphere taking pictures of everything and anything, it only makes sense that we’d eventually have some doing the same underwater. I am personally very thrilled to see robots taking on the deepest depths. The ocean is a fascinating place, but I’m also terrified of drowning, so I’ll probably never work up the courage to actually explore it. Hopefully, our automated friends will do the work for us and help us understand what is still a very much unexplored frontier of Earth.

The paper “Constraint on net primary productivity of the global ocean by Argo oxygen measurements” has been published in the journal Nature.

We can now track ocean microplastics from space, by looking at how winds and water interact

Researchers at the University of Michigan (U-M) have developed a new approach to tracking microplastics in ocean waters, anywhere in the world, on a daily basis. This relies on satellites from the Cyclone Global Navigation Satellite System (CYGNSS), which can provide a global view of the seas or zoom in on particular areas for a high-resolution look.

Image via Pixabay.

The team says this approach is a major improvement over current options, as most tracking methods today rely on field reports from plankton trawlers — which are unreliable. While there are still unknowns, the technique seems reliable so far.

Plastic and small

“We’re still early in the research process, but I hope this can be part of a fundamental change in how we track and manage microplastic pollution,” said Chris Ruf, the Frederick Bartman Collegiate Professor of Climate and Space Science at U-M, principal investigator of CYGNSS and senior author on a newly published paper on the work.

Microplastics, as the name suggests, are very small pieces of plastic. They’re either produced like this for use in products like exfoliants, or result from the breakdown of larger plastics. An estimated eight million tons of plastic enter the ocean every year, and, eventually, they all degrade into microplastics. Since they’re hard to biodegrade, these particles can travel hundreds of thousands of miles on ocean currents, harming sea life and marine ecosystems as they go.

Accurately tracking microplastic movements is quite difficult, mostly due to how small they are. The new approach developed at U-M draws on CYGNSS, a constellation of satellites launched in 2016 to monitor weather patterns at the heart of large storms (and thus better predict their severity).

In order to track the microplastics in the sea, the team looks at local ocean surface roughness — a characteristic that CYGNSS was already designed to measure, using on-board radars. These are meant to allow researchers to calculate wind speeds inside hurricanes, but the team adapted the method to help them estimate microplastic content in the water.

“We’d been taking these radar measurements of surface roughness and using them to measure wind speed, and we knew that the presence of stuff in the water alters its responsiveness to the environment,” Ruf said. “So I got the idea of doing the whole thing backward, using changes in responsiveness to predict the presence of stuff in the water.”

Using independent wind speed measurements (supplied by NOAA — the US National Oceanic and Atmospheric Administration), the authors searched for stretches of the ocean that seemed less rough than they should be, considering local wind speeds. Then, they drew on field reports  from plankton trawlers to estimate local microplastic content, and then ocean current models in order to estimate which direction these would flow towards.

All in all, they report that there’s a strong correlation between areas that are ‘too smooth’ and those that have higher levels of microplastics. These changes in surface texture are likely not caused by the microplastics themselves, but by the surfactants they contain. Surfactants are a chemical family which includes several oily and soapy compounds, which got their name because they lower the surface tension of liquids they’re mixed into. The two are often released together or accumulate as they have similar behaviors in the ocean, so they travel and collect in similar ways.

“Areas of high microplastic concentration, like the Great Pacific Garbage Patch, exist because they’re located in convergence zones of ocean currents and eddies. The microplastics get transported by the motion of the water and end up collecting in one place,” Ruf said. “Surfactants behave in a similar way, and it’s very likely that they’re acting as sort of a tracer for the microplastics.”

The authors are now working on proving their approach, collaborating with their colleagues at the  Aaron Friedman Marine Hydrodynamics Lab to better understand the relationship between water surface roughness and the levels of microplastics / surfactants it contains.

“We can see the relationship between surface roughness and the presence of microplastics and surfactants, so the goal now is to understand the precise relationship between the three variables, as well as the reasons behind them,” Pan said. “The wave tank and its ultrasonic sensors enable us to focus on those relationships by taking measurements under very precisely monitored wave, surfactant and microplastic conditions.”

As for the results we have available so far, the team reports that microplastic levels in the ocean seem to vary by season. In the Northern Hemisphere, they peak during June and July, while in the Southern Hemisphere they peak between January and February. Levels were generally lower during the summer months for both hemispheres, likely due to the influence of stronger water currents driving some of them to greater depths.

The paper “Toward the Detection and Imaging of Ocean Microplastics With a Spaceborne Radar” has been published in the journal IEEE Transactions of Geoscience and Remote Sensing.

Swallowed whole: lobster diver swallowed and spat out by humpback whale

Humpback whales are gentle giants who don’t enjoy interacting with humans — but it’s still advisable to keep a distance from them. Image credits: Flicker Photos.

Michael Packard has been a lobster diver out of Provincetown for 40 years, but he wasn’t prepared for what was about to happen.

“All of a sudden, I felt this huge shove and the next thing I knew it was completely black,” Packard recalled Friday afternoon following his release from Cape Cod Hospital in Hyannis. “I could sense I was moving, and I could feel the whale squeezing with the muscles in his mouth.”

Packard’s vessel, the “Ja’n J,” was surrounded by a fleet of boats catching striped bass. He went diving when, without warning, he felt scooped up. Although he didn’t feel any injuries or teeth, he realized he had been swallowed and things were pretty bad.

“Then I felt around, and I realized there was no teeth and I had felt, really, no great pain,” he said. “And then I realized, ‘Oh my God, I’m in a whale’s mouth. I’m in a whale’s mouth, and he’s trying to swallow me.’ “

“I was completely inside; it was completely black,” Packard said. “I thought to myself, ‘there’s no way I’m getting out of here. I’m done, I’m dead.’ All I could think of was my boys — they’re 12 and 15 years old.”

Still in his scuba gear, Packard started moving and struggling, until the whale began shaking its head. Packard felt the whale didn’t like, and after 30 seconds that seemed like an eternity, the whale finally surfaced and spat him out.

“I saw Mike come flying out of the water, feet first with his flippers on, and land back in the water,” Joe Francis, a charter boat captain who happened to be nearby, told WBZ-TV. “I jumped aboard the boat. We got him up, got his tank off. Got him on the deck and calmed him down and he goes, ‘Joe, I was in the mouth of a whale.’ “

“Then all of a sudden he went up to the surface and just erupted and started shaking his head. I just got thrown in the air and landed in the water,” Packard recalled. “I was free and I just floated there. I couldn’t believe. . . I’m here to tell it.”

Packard’s story was corroborated by his own crew, as well as Francis, and experts say that while extremely rare, this type of accident can happen. The whale doesn’t want to swallow people, but it can do so out of carelessness — much like a cyclist swallowing a fly. When a humpback whale opens its mouth to feed, it billows out and blocks its forward vision. This helps the whale scoop up more prey, but also makes it unable to distinguish what it’s scooping up.

Unlike toothed whales such as orcas, baleen whales such as the humpbacks cannot injure humans with their teeth; their esophagus is also too small to actually swallow a human. But whales can still cause a lot of damage to the unfortunate creatures they swallow. “He’s damn lucky to be alive,” Captain Joe Francis added.

Even so, what Packard went through is extremely rare. Whales don’t generally want to interact with humans, and it’s not uncommon for divers in the tropics to swim alongside them, enjoying a lovely experience. Experts generally advise keeping a distance of around 100 meters to avoid any potential accident.

Packard was released from Cape Cod Hospital Friday afternoon. He described his injuries as “a lot of soft tissue damage” but no broken bones. He said he’d return to diving as soon as he was healed.

New “Genomic Microscope” for the Microbiome Discovers Carbon Dioxide-Eating Microbes Living in Superheated Seafloor Hydrothermal Vents

Earth is our hearty oasis in the cosmos. Yet our planet also harbors some environments so harsh and hostile that they could easily be mistaken for another planet.

Image credits: NOAA.

Few spots on Earth appear less Earth-like than deep-sea hydrothermal vents. Along these swathes of the seafloor, the forces of plate tectonics have ripped our planet open, unleashing jets of superheated water that strip chemicals rich in sulfur, iron and other elements from surrounding rock and release them into the ocean.

Yet even these extreme, seemingly inhospitable environments can be teeming with life. Hydrothermal vents host rich ecosystems anchored by microbial communities with exotic metabolic talents. For example, with photosynthesis impossible at those dark depths, many bacteria in and around hydrothermal plumes utilize compounds stripped from rock and mineral as energy sources.

Scientists understand precious little about these plume microbes — their number, variety and how they fit in to wider ocean food webs. Phase Genomics brought its expertise in microbial metagenomics down to these depths, working with scientists who are upending old theories about plume ecosystems and how they interact with the rest of the ocean.

The team, led by research associate Ben Tully at the University of Southern California, used Phase Genomics’ Hi-C proximity ligation and metagenome reconstruction for a sample of plume water from one major hydrothermal vent complex — the East Pacific Rise.

“This approach is so valuable because of how Hi-C linkage works,” said Tully. “We can link different DNA sequences to the same cell of origin: chromosomal sequences, plasmids, viruses. This tells us about host metabolism, active host-virus interactions and so much more.”

Tully’s group — which includes researchers at USC, Caltech, the University of Rhode Island, the Bigelow Laboratory for Ocean Sciences, Stanford University and the University of Alaska — seeks to understand not just the microbial communities around hydrothermal vents, but also how microbial residents change as water moves away from these unique environments.

Past research shows that plume water doesn’t just diffuse into the rest of the ocean. Plume-enriched water can travel in “pockets” up to thousands of kilometers along the ocean floor, according to Tully. By sequencing bacteria in water samples near hydrothermal plumes and at fixed distances away from them, the team wants to capture snapshots of how microbial communities in those packets shift on their journey.

“We could see many types of changes — like some species leaving and others coming in as the plume water travels, and changes in chemical composition due to the metabolic activity of other microbes,” said Tully.

In sequencing this first sample, the team is getting its foot in the door. The sample came from a depth of 2,400 meters, just 300 meters above the seafloor and about a kilometer from the East Pacific Rise. Hi-C found some expected microbes — like Marinobacter hydrocarbonclasticus, which can remove nitrogen from food webs by stripping it from organic compounds and converting it into nitrogen gas.

The plume water also held some surprises, such as a previously unknown member of the Chromatiales clade of bacteria. Based on its genome, this unexpected resident may be able to utilize hydrogen sulfide — a compound toxic to us — as an energy source. A new Plantomycetes microbe can extract carbon dioxide from water to build its biomass, similar to how plants at the surface pull carbon dioxide out of the air. And those are just the initial surprises.

This isn’t just deep thoughts on deep places. Since plume water travels far, its microbes make waves far from their source. Tully and his colleagues want to use the Hi-C data to examine other community qualities, such as the prevalence of viruses and plasmids. These are increasingly important data for understanding overall microbial health and even issues like antibiotic resistance. These metagenomes will serve as a baseline to compare samples from other locations.

“These are whole ecosystems that we knew almost nothing about,” said Tully. “But now we’re starting to learn.”

Plume life may even help in the search for life elsewhere. Scientists use hydrothermal vent communities to predict how life might look on alien worlds. Since these plumes seem full of surprises, they’re not a bad place to start.

This is an article by Dr. Kayla Young. Young received her Ph.D. in Molecular Physiology and Biophysics from Vanderbilt University in 2016. Kayla is currently Chief Operations Officer of Seattle-based genomics startup Phase Genomics.

Study finds Greenland ice-sheet has already melted before – and it could again

It seems like a Hollywood blockbuster but it’s actually a real and concerning story: catastrophic sea level rise could be on the way. Researchers analyzed ice core samples taken in the 1960s from a secret Arctic military base and found that the Greenland ice sheet – which has enough water to raise sea levels by 20 feet worldwide – could melt much faster than previously thought.

Image credit: Flickr / Ting Chen

More than 60 years ago, US Army scientists dug up the ice core in northwestern Greenland as part of the Iceworm project – a mission to build a subsurface base to hide hundreds of nuclear warheads. The army created a research base called Camp Century as a cover story, but the base was eventually abandoned and the ice core lay forgotten in a freezer.

Researchers rediscovered the ice samples in 2017 and started investigating them in 2019. They found fragments of fossilized plants that could have bloomed a million years ago, which implies there was once vegetation in a spot now buried with ice. Greenland’s current ice cover was thought to be three million years old, but these fragments say otherwise.

Most of Greenland is now covered by the Greenland Ice Sheet, which spans 656,000 square miles (1.7 million square kilometers) – three times the size of Texas, according to the National Snow and Ice Data Center (NSIDC). If the new research is right and most of Greenland’s ice vanished relatively recently, this isn’t good news for the stability of the current ice sheet.

If all of Greenland’s ice were to melt, the seas would rise by about 24 feet (seven meters), according to a 2019 report by the National Oceanic and Atmospheric Administration. This would be enough to flood most coastal cities around the world. While this won’t happen tomorrow, Greenland’s ice sheet is already melting now six times faster than it was in the 1980s and if things don’t change soon, we could face a worst-case scenario.

“Before humans added hundreds of parts per million of fossil fuels to the atmosphere, our climate was able to melt away the ice sheet. In the future as we continue to warm the planet at an uncontrollable rate, we could force the Greenland ice sheet past some threshold and melt it and raise sea levels,” Drew Christ, the study’s lead author, told Gizmodo.

The US Army started building Camp Century in 1959, followed by the extraction of an ice core measuring 11 feet (3.4 meters) from a depth of 4,488 feet (1,368 m) below the ice. The core went to storage after the army finished the project, first in New York and then in Copenhagen. Following an inventory of materials in 2017, researchers were called on to examine the core.

Christ and the group of researchers noticed “little black things” floating in the water. They placed them under a microscope and discovered fossil twigs and leaves in the frozen sediment. Such plants, probably from a boreal forest, could have only grown if Greenland’s ice sheet was mostly gone. So now the next step will be to figure out how recently that happened.

To date the plants, the researchers looked at isotopes of aluminum and beryllium, which accumulate in minerals when exposed to radiation that filters through the atmosphere. They determined that the soil and the plants last saw sunlight between a few hundred thousand and about a million years ago. The traces of leaf waxes resembled those now found on tundra ecosystems.

The researchers estimated that the present ice sheet persisted at more or less the same size for about 2.6 million years, using geological records and ocean geochemistry. However, the findings showed that ice vanished almost entirely from Greenland during at least one period in the island’s most recent deep freeze – a previously unknown threshold for ice sheet stability.

“This is important as we move forward into a warmer future,” Christ told Gizmodo. “Our climate system has a delicate balance to it. If it changes enough, you can melt away large portions of these ice sheets and raise sea levels — and that would inundate and flood large portions of the most densely populated areas on Earth.”

The study was published in the journal PNAS.

Otters maintain patches of healthy kelp forests even when surrounded by “urchin barrens”

Kelp forests around the California coast have declined dramatically in recent years. Attacked by urchins, heat, and left without the defense of sea stars, kelp has fallen by up to 95% in some areas, leaving large swaths of “urchin barrens” behind. Even in these conditions, researchers have found, otters can help ensure that the remaining patches of kelp stay healthy.

Kelp forests in California. Image credits: UCSD.

It all starts with kelp. Kelp is an umbrella term for a group of large brown algae that grow in “underwater forests” (kelp forests) in shallow oceans. They harbor rich ecosystems and can grow quite fast and reach impressive heights. Up to a few years ago, this is exactly what was seen off the coast of California.

“I’ve been diving here in this ecosystem since 2012 and back then, things looked very different,” UC Santa Cruz graduate student Joshua Smith, lead author of the study, explains in an interview. “We had these kelp forests that were so dense that being underwater was like walking through a redwood forest. Back then, I remember some times when the kelp canopy — the top part of the kelp that’s made its way all the way to the surface of the ocean — was so dense, that we couldn’t even get a boat into the place where we needed to do our science. There were just hundreds of meters of kelp extending offshore.”

But then, in 2013, things started to change. Despite its ability to grow, kelp is vulnerable to overgrazing by sea urchins. Normally, sea urchins are themselves kept in check by sea stars, but around 2013, a mysterious disease called sea star wasting syndrome started to decimate the starfish population.

“Around 2013, I was diving in this area and I started to notice that the sea stars had these lesions,” Smith continues. “And before we even knew what was going on, these sea stars dissolved, they were being hit by this wasting syndrome.”

It didn’t take long for the sea urchins to figure out what was going on. Normally, they spend their time in crevices where they’re hiding from predators and eating drift kelp, kind of like leaves falling from a tree. But after the sea star wasting event, the urchins were emboldened. They started going out and actively grazing on the remaining kelp until they ate it all.

That’s when the otters came in.

“Sea otters haven’t been seen on the North Coast since the 1800s,” said Meredith McPherson, a graduate student in ocean science at UC Santa Cruz, and author of a separate study on California kelp forests. “From what we observed in the satellite data from the last 35 years, the kelp had been doing well without sea otters as long as we still had sunflower stars. Once they were gone, there were no urchin predators left in the system.”

Empty boxes of pizza

A snapshot of a sea urchin barren. Image credits: Ed Bierman.

Climate dealt the finishing blow to kelp. The 2014 marine heatwave called “the blob” made the underwater forests more vulnerable and hampered their growth.

“And so as a diver, I remember seeing all of these events unfold,” Smith recalls. “Then finally, in 2017, when we spun up this study, the region had already kind of shifted from that really dense, lush kelp forests to this patchy mosaic of kelp forests interspersed with sea urchin barrens.”

“It happened so fast, before we knew it we had lost over 80 percent of the historic kelp forest cover in Northern California,” Smith said. “We also had an urchin outbreak on the Central Coast, but not to the same extent as in the areas north of San Francisco.”

By then, otters had already become very active in the area. Smith and colleagues had been keeping an eye on otters, who also like to munch on sea urchins. They found that after 2014, otters were eating three times more urchins than they had before — but not from the barrens. Otters were careful and focusing on urchins within remaining kelp forests, skipping those in the barrens.

A close-up of a sea otter, taken in Morro Bay, California in 2016. Image credits: Marshall Hedin.

Eager to understand why this is, divers surveyed those places not targeted by otters and collected urchins to examine in the lab. They found that urchins in the barrens have far fewer nutrients than those in healthy kelp forests. For the otter, the barren urchins are just not worth it.

“The sea otters prefer to eat those healthy, nutritionally valuable sea urchins that are in patches of kelp forests and they mostly ignore those that are in the barrens that are completely starved out,” says Smith.

It’s a bit like buying a pizza from a nearby shop, Smith explains, and getting an empty box. At first, you’d be confused, and perhaps get another pizza. But if the second one also comes up empty, you’d probably opt for a different pizza shop, even if it’s farther away — this is what’s happening to the otters. They quickly realized that barren urchins are no good for them and so they opt for the healthier urchins, even if it means traveling a greater distance.

Sea deserts

This is good on one hand because it means that it’s helping remaining forests stay healthy and not become barrens. But on the other hand, this means that urchin barrens will continue to remain barren.

It’s different than in other ecosystems. If overgrazing were to happen on land, say if deer were to overgraze grasslands or shrublands, they would starve. But in the case of the urchins, that doesn’t really happen. Urchins can survive for years even being starved out. They can eat microorganisms living on the reef, or even scrape the reef itself for other types of algae. Even once all these food sources are depleted, they can still survive for a long time by slowing down their metabolism to a state of dormancy.

Satellite images show the dramatic reduction from 2008 to 2019 in the area covered by kelp forests (gold) off the coast of Mendocino and Sonoma Counties in Northern California. Images by Meredith McPherson.

“Urchins can persist and survive and a starved state for a really long time. We’re talking several years. So when urchins overgraze kelp forests and transform for us to these underwater deserts that we call sea urchin barrens there’s no more food available for them or, or very little food,” Smith adds.

This is also why they’re so unappealing to otters: the urchins are starving themselves and have little that’s of interest to a predator.

That’s part of what makes these sea urchin barrens so tricky. They’re like environmental deserts, and the only way to change that is by bringing kelp back into the mix. But the moment kelp comes back in, the urchins will just devour it down to nothing — and predators like otters have little interest in these urchins.

But there are ways to get rid of an urchin barren.

A healthy kelp forest. Photo by Steve Lonhart/NOAA, MBNMS.

While it hasn’t happened in the California area, urchins can contract devastating diseases that could quickly wipe out large parts of their population. Wind is another mechanism to dislodge urchins: large waves could physically swipe urchins off the reef. The third mechanism is predation.

“It’s clear that the otters are not foraging on urchins in the barrens, however, there could be other animals that would target urchin barrens. It’s possible that if and when the sunflower stars recover, they may be able to reduce the number of urchins in these barrens,” Smith adds.

In addition to those things, Smith notes, there are a number of pilot studies looking to see how effective urchin cleaning is. In some areas, especially in northern California, the state has approved divers to go out and remove the urchins themselves. There’s also one organization called California Reef Check which mobilizes members of the community to engage in science and survey these areas.

“The purpose of those pilot studies is twofold. Number one is to see if this is something that could actually be done by the local community. Can humans go in the water and remove enough urchins to make a difference? And then the second part of it is the science side, which is being charged by California Reef Check. And so they are going out and doing the monitoring of those locations where the urchins are being eliminated to see what happens once their numbers are reduced. Does that help the kelp come back? They’re the ones who are actually tracking all of those things.”

The study has been published in Proceedings of the National Academy of Sciences.

One of the largest ecosystems on Earth lives beneath the seafloor and eats radiation byproducts

Researchers at the University of Rhode Island’s (URI) Graduate School of Oceanography report that a whole ecosystem of microbes below the sea dines not on sunlight, but on chemicals produced by the natural irradiation of water molecules.

Image credits Ely Penner.

Whole bacterial communities living beneath the sea floor rely on a very curious food source: hydrogen released by irradiated water. This process takes place due to water molecules being exposed to natural radiation, and feeds microbes living just a few meters below the bottom of the open ocean. Far from being a niche feeding strategy, however, the team notes that this radiation-fueled feeding supports one of our planet’s largest ecosystems by volume.

Cooking with radiation

“This work provides an important new perspective on the availability of resources that subsurface microbial communities can use to sustain themselves. This is fundamental to understand life on Earth and to constrain the habitability of other planetary bodies, such as Mars,” said Justine Sauvage, the study’s lead author and a postdoctoral fellow at the University of Gothenburg who conducted the research as a doctoral student at URI.

The process through which ionizing radiation (as opposed to say, visible light) splits the water molecule is known as radiolysis. It’s quite natural and takes place wherever there is water and enough radiation. The authors explain that the seafloor is a particular hotbed of radiolysis, most likely due to minerals in marine sediment acting as catalysts for the process.

Much like radiation in the form of sunlight helps feed plants, and through them most other life on Earth, ionizing radiation also helps feed a lot of mouths. Radiolysis produces elemental hydrogen and oxygen-compounds (oxidants), which serve as food for microbial communities living in the sediment. A few feet below the bottom of the ocean, the team adds, it becomes the primary source of food and energy for these bacteria according to Steven D’Hondt, URI professor of oceanography and a co-author of the study.

“The marine sediment actually amplifies the production of these usable chemicals,” he said. “If you have the same amount of irradiation in pure water and in wet sediment, you get a lot more hydrogen from wet sediment. The sediment makes the production of hydrogen much more effective.”

Exactly why this process seems to be more intense in wet sediment, we don’t yet know. It’s likely the case that some minerals in these deposits can act as semiconductors, “making the process more efficient,” according to D’Hondt.

The discovery was made after a series of experiments carried out at the Rhode Island Nuclear Science Center. The team worked with samples of wet sediment collected from various points in the Pacific and Atlantic Oceans by the Integrated Ocean Drilling Program and other U.S. research vessels. Sauvage put some in vials and then blasted these with radiation. In the end, she compared how much hydrogen was produced in vials with wet sediment to controls (irradiated vials of seawater and distilled water). The presence of sediment increased hydrogen production by as much as 30-fold, the paper explains.

“This study is a unique combination of sophisticated laboratory experiments integrated into a global biological context,” said co-author Arthur Spivack, URI professor of oceanography.

The implications of these findings are applicable both to Earth and other planets. For starters, it gives us a better understanding of where life can thrive and how — even without sunlight and in the presence of radiation. This not only helps us better understand the depths of the oceans, but also gives clues as to where alien life could be found hiding. For example, many of the minerals found on Earth are also present on Mars, so there’s a very high chance that radiolysis could occur on the red planet in areas where liquid water is present. If it takes place at the same rates it does on Earth’s seafloor, it “could potentially sustain life at the same levels that it’s sustained in marine sediment.”

With the Perseverance rover having just landed on Mars on a mission to retrieve samples of rocks and to keep an eye out for potentially-habitable environments, we may not have to wait long before we can check.

At the same time, the authors explain that their findings also have value for the nuclear industry, most notably in the storage of nuclear waste and the management of nuclear accidents.

“If you store nuclear waste in sediment or rock, it may generate hydrogen and oxidants faster than in pure water. That natural catalysis may make those storage systems more corrosive than is generally realized,” D’Hondt says.

Going forward, the team plans to examine how the process takes place in other environments, both on Earth and beyond, with oceanic crust, continental crust, and subsurface Mars being of particular interest to them. In addition to this, they also want to delve deeper into how the subsurface communities that rely on radiolysis for food live, interact, and evolve.

The paper “The contribution of water radiolysis to marine sedimentary life” has been published in the journal Nature Communications.

Sawfish could soon become completely extinct if we don’t stop overfishing, says a study

A new study from the Simon Fraser University (SFU) warns that one of the most distinctive marine species — sawfish — are at real risk of extinction due to overfishing.

Image via Pixabay.

Sawfishes have already disappeared from roughly half of their known range, the authors report, as overfishing is driving their numbers into the ground. The species used to be quite a common sight for around 90 coastal countries around the globe, but are now one of the most threatened family of ocean fish and presumed extinct in 46 of those nations. A further 18 countries presume at least one species of sawfish to be locally extinct, while 28 others presume at least two.

A fish in need

“Through the plight of sawfish, we are documenting the first cases of a wide-ranging marine fish being driven to local extinction by overfishing,” says Nick Dulvy, one of the two authors of the paper.

“We’ve known for a while that the dramatic expansion of fishing is the primary threat to ocean biodiversity, but robust population assessment is difficult for low priority fishes whose catches have been poorly monitored over time. With this study, we tackle a fundamental challenge for tracking biodiversity change: discerning severe population declines from local extinction.”

Sawfishes get their name from the highly distinctive rostra they sport. These are long and narrow noses lined by teeth, making them very similar to sawblades. According to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, three of the five species of sawfish alive today are critically endangered, with the other two being endangered.

According to the authors of this study, overfishing is to blame. The animals’ long rostra and the teeth they sport can easily become entangled in fishing nets. They can fetch a high price on the market as their fins are among the most pricy shark fins. Rostra can also be sold for a variety of reasons, from folk medicine and novelty to spurs used in cockfighting.

Although we have no reliable global account of sawfish numbers, Dulvy says that the data we do have paints a very bleak picture. Unless an effort is made to stop overfishing and protect the habitats these species live in, there’s a very real risk of them going completely extinct.

In regards to solutions, the team recommends a concerted international conservation project focusing on Cuba, Tanzania, Columbia, Madagascar, Panama, Brazil, Mexico, and Sri Lanka, where such efforts are likely to see the greatest payoff. Fishing restrictions in these countries could also help. Australia and the United States both have solid protections already in place and retain populations of sawfish — they should act as “lifeboat” nations to ensure the species doesn’t go the way of the dodo.

“While the situation is dire, we hope to offset the bad news by highlighting our informed identification of these priority nations with hope for saving sawfish in their waters,” says Helen Yan, the paper’s other co-author.

“We also underscore our finding that it’s actually still possible to restore sawfish to more than 70 percent of their historical range if we act now.”

The paper “Overfishing and habitat loss drive range contraction of iconic marine fishes to near extinction” has been published in the journal Science Advances.

Living fossil fish has 62 copies of a “parasite gene” humans share too — we have no idea how they got there

The capture of a ‘living fossil’ fish off the coast of South Africa in the 1930s is now helping us understand one of the more exotic ways evolution can happen — interspecies genetic hijacking.

A model of Latimeria chalumnae, one of two known species of coelacanths. Image via Wikipedia.

Coelacanths are one of the oldest lineages of fish in existence today. They’re so old, in fact, that they’re more closely related to the ancestors of reptiles and amphibians than modern-day fish. We first encountered them as fossils from the Late Cretaceous (some 66 million years old), and naturally assumed they must’ve died off by now. However, the capture of a live African Coelacanth (Latimeria chalumnae) fish in 1938 showed that it was actually still living in the deep oceans, and had hardly changed compared to its fossilized relatives.

But we should never judge a fish by its scales, as new research explains that the species did in fact gain 62 new genes around 10 million years ago. The most interesting part is how — these didn’t appear spontaneously in their genomes but are ‘parasitic’ DNA gained through encounters with other species.

Genetic stowaways

“Our findings provide a rather striking example of this phenomenon of transposons contributing to the host genome,” says Tim Hughes, senior study author and a professor of molecular genetics in the Donnelly Centre for Cellular and Biomolecular Research at the University of Toronto.

“We don’t know what these 62 genes are doing, but many of them encode DNA binding proteins and probably have a role in gene regulation, where even subtle changes are important in evolution.”

Coelacanths have earned the moniker of “living fossils” because they share so much of their anatomy with the fossilized specimens — in fact, they’re pretty much identical from a physical point of view. But the current findings showcase how gene transfer between species (through elements known as transposons or “jumping genes”) can shape evolution and, perhaps, even alter the genetic trajectory of entire species or lineages.

Transposons are genes that use a self-encoded enzyme to recognize themselves. This enzyme can then cut them out of the genetic strand and paste them in somewhere else. Sometimes, this process can interact with the cell division process and generate new copies of the transposon.

Still, nothing lasts forever, and eventually, the information describing the enzyme degrades. At this point, the transposon can no longer move throughout the code, but it’s still there and acts like any other gene. If it confers some kind of advantage to the host organism, it can be selected for over time through evolutionary processes and become part of their genetic lineage. Coelacanths aren’t by any means the only animals we’ve seen such ‘parasite’ genes in, but they do have a very high number of such genes.

“It was surprising to see coelacanths pop out among vertebrates as having a really large number of these transposon-derived genes because they have an undeserved reputation of being a living fossil,” says graduate student Isaac Yellan who spearheaded the study.

“The Coelacanth may have evolved a bit more slowly but it is certainly not a fossil.”

The team was actually studying counterparts of a human gene, CGGBP1, in other species. We knew that this was a legacy of a particular transposon in the common ancestor of mammals, birds, and reptiles. During their work, the team found CGGBP-like genes in some but not all fish species they studied, and one type of fungus. Worms, molluscs, and most insects had none. But the Coelacanth (whose genome was sequenced in 2013) had 62.

As a common ancestry was out of the question, the team concluded that these transposons entered various lineages at various times in history through horizontal gene transfer. We don’t exactly know where they came from, but one known documented source of such transfers are parasites. This would also explain why the gene was introduced in the fish’s genome several times.

We still don’t know what these genes do. Lab experiments showed that the protein they encode binds to unique sequences of DNA, so they could be involved in gene regulation, like their human counterpart. Their origin however is still a mystery.

Given the extreme rarity of living specimens — the only other living species ever found, Latimeria menadoensis, was discovered in 1998 after being pulled by a fishing boat and winding its way into an Indonesian market. These two species split before the genes were introduced.

The paper “Diverse Eukaryotic CGG Binding Proteins Produced by Independent Domestications of hAT Transposons” has been published in the journal Molecular Biology and Evolution.

Researchers develop a new tool to identify at-risk corals

One of the first signs that climate change is already upon us came from heat-stressed corals. Now, new research aims to help us understand which species need protection the most.

Image via Pixabay.

Corals form sprawling reefs below the ocean’s surface, which provide food and shelter for a myriad of species. They are a very important link in marine ecosystems and a very useful indicator for their health. But they’re also being slowly killed by the heat. When corals experience an environment that is too hot for too long they ‘evict’ bacteria they share their chalky bodies with. They can recover from such bleaching events if they’re not too frequent. Sadly, however, climate change is making multiple bleaching events take place in quick succession, pushing corals way beyond their breaking point.

New research aims to address the issue by allowing us to tell which coral reefs are at risk of bleaching before such events take place — an ounce of prevention is worth a pound of cure, after all.

Deadly hot

“This is similar to a blood test to assess human health,” said senior author Debashish Bhattacharya, a distinguished professor in the Department of Biochemistry and Microbiology in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. “We can assess coral health by measuring the metabolites (chemical byproducts) they produce and, ultimately, identify the best interventions to ensure reef health.”

“Coral bleaching from warming waters is an ongoing worldwide ecological disaster. Therefore, we need to develop sensitive diagnostic indicators that can be used to monitor reef health before the visible onset of bleaching to allow time for preemptive conservation efforts.”

The new approach could help us tell exactly which species of coral need special care and protection from climate change, the authors explain. Around 500 million people depend on reefs or reef-supported ecosystems around the world, so such a tool would be no mean feat.

Apart from higher average water temperatures (which lead to bleaching but also higher water acidity), corals and coral reefs need to contend with rising sea levels (which threaten their access to sunlight), unsustainable fishing (which can physically damage the reefs and damages the ecosystem’s balance), invasive species, impacts from crafts or marine debris, and natural events such as cyclones.

The study looked at how Hawaiian stony corals respond to heat stress to identify the metabolites that indicate the organisms are under stress. They used the heat-resistant Montipora capitata and heat-sensitive Pocillopora acuta corals, which were placed in seawater tanks at the Hawai’i Institute of Marine Biology for several weeks under warm conditions. The chemicals they produced were then compared to those of other corals not subjected to heat stress.

“Our work, for the first time, identified a variety of novel and known metabolites that may be used as diagnostic indicators for heat stress in wild coral before or in the early stages of bleaching,” Bhattacharya said.

The team is hard at work replicating their findings in a larger-scale experiment — so far, they say, the results are quite promising. Their end goal is to create a “coral hospital” featuring a new lab-on-a-chip device, which can monitor the organisms’ health in real time.

The paper “Metabolomic shifts associated with heat stress in coral holobionts” has been published in the journal Science Advances.

Ocean warming is a wrecking ball for coral reef systems. This researcher wants to understand it all

Year in and year out, scientist Thomas DeCarlo saw the writing on the wall — the wall of coral reefs, that is — and his findings are sounding the alarm: ocean warming and acidification could spell doom for coral reef ecosystems.

Coral reefs are vital for the health of the oceans. Image credits: Olga Tsai.

Billion-dollar buffers

“Ocean temperatures are now approaching one degree above what they were in industrial times, with a projected increase of two to four degrees, which could have terrible consequences for corals,” DeCarlo says.

DeCarlo has studied the history of monsoon upwelling, wind patterns, and other weather factors affecting coral reef ecosystems in the Red Sea. His research shows that reefs are essential not just to the corals themselves, but to the entire surrounding ecosystems, and human society as well.

If reefs collapse, so too do biodiverse life systems that rely on them to survive — and the damage will continue to cascade. Coral reefs are a nursery to different marine species, they provide fish for humans, and they buffer shores from storms.

That storm-buffer feature is apparently quite significant in dollars. In a US Geological Survey report, coral reef barriers as a force in flood protection protect $1.8 billion worth of coastal infrastructure and economic activity in the US and trust territories alone. Reefs reduce the energy of the waves as they wash ashore, which prevents or limits coastal erosion, flooding, and water surges.

DeCarlo’s detailed explorations use microsope, climate models, coral cores, and computerized tomography (CT) analysis, to study the relationship between climate stressors, bleaching, and calcification. He’s not the first scientist to study the environmental impact of coral reefs but he has taken a special look at instances where the upwelling of nutrient levels can be toxic to corals.

Composite photo shows samples of coral cores alongside CT scans of coral skeletal cores showing annual pairs of light and dark bands of high and low density. Photo: Thomas DeCarlo.

His plan, he says, is to build a global database of the history of coral bleaching events, helping to fill the gaps in our knowledge of coral resilience and vulnerability. But to do that, we first need to understand how the climate is affecting corals.

High, hot, and deadly

Winds blowing across the ocean surface push water away. Water then rises up from beneath the surface to replace the water that was pushed away, a process known as “upwelling,” explains the National Ocean Service (NOS). The water that rises to the surface is typically colder and is rich in nutrients, which “fertilize” surface waters, and have high biological productivity.

For corals, upwelling can be a blessing or a curse. According to DeCarlo knows, nutrient-dense waters can spell good news or bad news. It depends.

“Summer monsoons circulate nutrient-dense waters from the Gulf of Aden to the Red Sea. The symbiotic algae that live in corals thrive on these nutrients. In return, they provide food and energy for the corals to grow,” said DeCarlo. “But warmer waters create more nutrients, which create more algae, which create more oxygen and waste build-up in corals. When high waste conditions combine with high heat, this situation causes bleaching, which could turn deadly.”

According to the NOS, bleaching events might or might not be a dire threat for coral. If stress caused bleaching is not severe, the coral may recover. But if (1) there is prolonged algae loss and (2) continued stress, coral eventually dies.

There’s much work to be done, and DeCarlo has no intentions of stopping anytime soon. From King Abdullah University of Science and Technology (KAUST) and now on to Hawaii, at Hawaii Pacific University, his work offered valuable insight into the life of corals, but there’s much more research to be done, especially in regards to global warming. DeCarlo’s website states that “global warming is driving an increase in the frequency of mass coral bleaching events worldwide.”

Healthy coral reef and marine life in the central Red Sea of Saudi Arabia. Photo: KAUST.

It took the researcher 4 years to finish his PhD studying corals, an accomplishment he says he is “especially proud of,” since it was a first of its kind comprehensive study.

One important takeaway from this research is that coral reef environments are not a cookie-cutter affair. One-sized conclusions and conservation measures cannot address and fix everything. One must recognize the complexities due to what are the oceanographic settings of any individual coral reef.

Disentangling these oceanographic processes will help us predict when and where we may find coral reefs that are relatively resistant to rising temperatures, and this information will be critical to informing local management decisions.”

Nanocrystals allow dragonfish to camouflage their teeth

The deep ocean are a cold and unforgiving environment — the stuff of nightmares, some would say. Its inhabitants have developed remarkable adaptations to survive, from decoy lights to large, detached mouths capable of swallowing big prey; one creature, the dragonfish, has a more inconspicuous, but just as deadly adaptation: transparent teeth.

With its dark body and transparent teeth, the deep-sea dragonfish (Aristostomias scintillans) is essentially invisible in the low-light deepths. Having white teeth would harm its ability to sneak by unsuspecting prey, but the dragonfish has translucent teeth that don’t reflect light — and how it evolved this way remains a mystery.

“It’s an adaptation that, to our knowledge, has not yet been explored in detail,” said Audrey Velasco-Hogan, a materials science Ph.D. student at the UC San Diego Jacobs School of Engineering and first author of the study. “By studying why these teeth are transparent, we can better understand deep-sea organisms like the dragonfish and the adaptations they evolved to live in their environments.”

Deep-sea dragonfish with transparent teeth. Credit: David Baillot/UC San Diego Jacobs School of Engineering.

They’re unusual predators by any standards. Relatively small, at about 15 cm (6 in), they’re also pretty slow. Instead, they’re ambush predators, spending most of their time wandering about with their mouth wide open, hoping for some unfortunate prey to swim right in (or sufficiently closeby). Since their teeth are almost always exposed, having them camouflaged is important — and surprisingly enough, its teeth really are perfectly camouflaged. You wouldn’t think the dragonfish has too much success with this simple approach, but it’s close to the top of the food chain, despite its shortcomings.

Researchers were interested in the structure of the teeth, to see what makes them transparent and well-suited for this type of predatory behavior. In order to uncover its secrets, they imaged and analyzed the nanostructure of the teeth using a combination of electron microscopy, focused ion beam and nanoindentation tests. They discovered a series of unique characterstics both in the outer enamel layer and in the inner dentin layer.

For starters, the enamel (or rather, the enamel-like structure) of the teeth seems to consist of hydroxyapatite nanocrystals. Apatite is a fairly common phosphate mineral, and hydroxyapatite is merely its hydrated form. It’s not the minerals themselves that were surprising to researchers, but rather their distribution.

“Typically, teeth are not nanostructured. And they tend to have microscale features such as dentin tubules. From a materials perspective, it’s really interesting to see that dragonfish teeth have architectures that we do not see in others,” Velasco-Hogan said.

“I also find it fascinating how there are fundamental similarities between materials in the lab and in nature,” she added. “Experimentally, we know that the way to make a material transparent is by reducing its grain size to make it nanostructured. So to see that is also how nature is accomplishing transparency is an interesting parallel.”

Marc Meyers, UC San Diego professor in the Departments of NanoEngineering and Mechanical and Aerospace Engineering, and Audrey Velasco-Hogan, a materials science Ph.D. student at UC San Diego. Credit: David Baillot/UC San Diego Jacobs School of Engineering.

When the team carried out optical spectroscopy on the enamel structure, they found that these nanocrystals sharply reduce the scattering of light, essentially making them less reflecting and camouflaging them in the dark waters. The teeth aren’t just transparent, they’re also very strong — stronger than that of piranha.

The team that worked on the project was an interdisciplinary one. The study was carried out on a biological structure, but the research group was actually looking for interesting materials that can be applied in human society.

“My group is always looking for new materials in nature to study,” said Marc Meyers who supervised the research and whose work focuses on biomimicry. “And interdisciplinary collaborations are a key part of our work. When we bring scientists from different backgrounds together, we can advance the knowledge in our fields in ways that a single lab could not do alone.”

The team also worked with a few other labs, including Dimitri Deheyn, a marine biologist at the Scripps Institution of Oceanography at UC San Diego who researches bioluminescence and biomimicry. By gathering researchers from multiple areas, the team was able to put together such an intriguing find about the materials inside a deep-sea creature, and pave the way for novel technologies based on this.

“Taking advantage of the ultimate adaptation organisms show to specific environments has always been a driver for technological innovation, and the dragonfish is no exception to this,” said Deheyn. “There is clearly still broad inspiration to gather from the dragonfish and nature in general, and this intercept between biology and engineering through biomimicry is clearly a lucrative path for sustainable innovations.”

Journal Reference: Matter, Velasco-Hogan et al.: “On the nature of the transparent teeth of the deep-sea dragonfish (Aristostomias scintillans)” , DOI: 10.1016/j.matt.2019.05.010

We can now see ancient carbon dioxide levels with coral time machines

Corals are wonderful little things. They offer habitats for the ocean’s inhabitants, they protect the coastline from storms and erosion, and are hotspots of biodiversity and tourism. They’ve also been around for a very, very long time.

Corals are thought to have evolved some 500 million years ago, during a period called the Cambrian, and they’ve changed remarkably little in the passing time. In fact, corals are well known from the fossil record — geologists already use them as indicators for environmental conditions.

But we can now use them for something else. According to a new study, they can serve as ‘time machines’ that reveal the carbon dioxide evolution at the end of the last age.

Image credits: Dann Blackwood, USGS.

The current global heating event is unprecedented in several ways. It’s happening extremely quickly, for starters, and it’s caused by a species, instead of being a natural process. But in our planet’s geological history, climate change is a common process.

The last ice age, for instance, was ended by a familiar culprit: rising CO2 emissions. But geologists aren’t exactly sure what caused this rise in carbon dioxide. Using geochemical analysis of fossil corals, an international team of scientists found that changing ocean circulation might be to blame, and showed how corals can be used to derive even more environmental information.

The team started by collecting fossil remains of deep-sea corals that lived thousands of meters beneath the waves. They then dated them using radioactive decay, selecting only the ones that grew at the end of the ice age 15,000 years ago. Further geochemical fingerprinting (including radiocarbon measurements) allowed researchers to reconstruct changes in ocean circulation. The corals suggest a link between these changes and the rising CO2 levels, says study author Dr. James Rae, of the University of St Andrews:

“The corals act as a time machine, allowing us to see changes in ocean circulation that happened thousands of years ago. They show that the ocean round Antarctica can suddenly switch its circulation to deliver burps of CO2 to the atmosphere.”

Image credits: Dann Blackwood, USGS.

It’s not the first time something like this has been suggested. Deep ocean circulation can change rapidly, and this can release a lot of CO2 into the atmosphere, says Professor Laura Robinson, co-author of the new study.

In a separate study published in Nature Geoscience this week, the same team used coral data to refute the idea that the global increase of CO2 at the end of the ice age was owed to carbon from deep-sea sediments.

“There have been some suggestions that reservoirs of carbon deep in marine mud might bubble up and add CO2 to the ocean and the atmosphere, but we found no evidence of this in our coral samples”, said Andrea Burke, of the School of Earth and Environmental Sciences at the University of St Andrews.

The study has been published in  Nature Geoscience (2020). DOI: 10.1038/s41561-020-0638-6

Climate change is destabilizing marine food webs

Climate change could starve out the oceans, finds a new study from the University of Adelaide.

Image credits Susanne Pälmer.

Man-made climate change is a threat to all life on the planet whether it flies, walks, swims, or crawls. That being said, individual types of ecosystems will feel the heat at different times, and in different ways.

Sadly for us, marine ecosystems will be among the first. The oceans have always had a special connection to life — this is where it spawned. Even today, ocean ecosystems are the linchpin of life, supplying food, oxygen, and recycling essential nutrients for us landlubbers.

Marine ecosystems, the new paper reports, are in for a rough time. Increased average temperatures and higher CO2 atmospheric content threaten to push the food webs maintaining marine ecosystems beyond their breaking point.

Storms a-brewing

“Healthy food webs are critical for ecosystems so that the world’s oceans can continue to provide an important source of food for humans,” says lead author Professor Ivan Nagelkerken, from the University of Adelaide’s Environment Institute.

“Greenhouse gas emissions are affecting the health and persistence of many marine species because of increasing seawater temperatures and CO2 levels. Our research shows that ocean warming reshuffles species communities; the abundance of weedy plant species increases but the abundance of other species, especially invertebrates, collapses.”

The researchers modeled a coastal ecosystem consisting of three habitats that are predominant in the Gulf St. Vincent, Adelaide, where the South Australian Research and Development Institute (SARDI) maintains a site. They then observed how higher temperatures and ocean acidification would impact these areas.

All in all, the ‘trophic pyramid’, which is a schematic of who eats who in an ecosystem, would grow at the base and the top, but contract in its middle layers. This “unusual profile” most likely describes a “transitory state” before a collapse, Nagelkerken explains. After this collapse, marine food webs will be “shortened, bottom-heavy”, meaning they will house much fewer species, and most of them will be plants or plant-eaters. In marine food webs, fish are generally the top predators (and, as such, the highest on the pyramid).

Trophic pyramids show how energy and nutrients flow in an ecosystem; to be sustainable, they need to be triangular in shape, with many species at the bottom (thereby concentrating energy on this level). As each species feeds on the level below, this energy is moved up the pyramid. If the lower levels aren’t abundant enough, everything above them falls apart (goes extinct, or close to).

“Where food web architecture lacks adjustability, ecosystems lack the capacity to adapt to global change and ecosystem degradation is likely,” says collaborator and co-author Professor Sean Connell from the University of Adelaide’s Environment Institute.

“Marine food webs that are not able to adapt to global change show all the signs of being transformed into a food web dominated by weedy algae. Even though there were more plants at the bottom of the food web, this increased energy does not flow upwards towards the top of the food web.”

While things don’t look encouraging now, the team says that future emissions of carbon dioxide are only going to make the problem worse.

Unless some species quickly adapt to the new conditions, ocean ecosystems are likely to become much less abundant in the future. The species we most rely on economically and for food are exactly the ones that are at risk of collapse.

“An ecological tipping point may be passed beyond which the top of the food web can no longer be supported, with an ensuing collapse into shorter, bottom-heavy trophic pyramids,” says Professor Nagelkerken.

“This will weaken the health and sustainability of ocean ecosystems unless species are capable of genetic adaptation to climate stressors in the near future.”

The paper “Trophic pyramids reorganize when food web architecture fails to adjust to ocean change” has been published in the journal Science.