Category Archives: Oceanography

Why is the ocean salty?

Every time you bathe in the sea, you have geology to thank for the extra buoyancy that salty water provides. Large-scale geological processes bring salt into the oceans and then recycle it deep into the planet. The short answer to ‘why is the ocean salty’ sounds something like this:

Salts eroded from rocks and soil are carried by rivers into the oceans, where salt accumulates. Another source of salts comes from hydrothermal vents, deep down on the surface of the ocean floor. We say “salts” — because the oceans carry several types of salts, not just what we call table salt.

But the longer answer (that follows below) is so much more interesting.

Image credits: Olia Nayda.

In the beginning there was saltiness

As it is so often the case in geology, our story begins with rocks and dirt, and we have to go back in time — a lot. Billions of years ago, during a period called the Archean, our planet was a very different environment than it is today. The atmosphere was different, the landscape was different, but as far as ocean saltiness goes, there may have been more similarities than differences.

Geologists look at ancient rocks that preserved ancient water (and therefore, its ancient salinity); one such study found that Earth’s Archean oceans may have been ~1.2 times saltier than they are today.

At first glance, this sounds pretty weird. Since salt in the seas and oceans is brought in by river runoff and erosion, the salts hadn’t yet had time to accumulate in Earth’s earliest days. So what’s going on?

It is believed that while the very first primeval oceans were less salty than they are today, our oceans have had a significant salinity for billions of years. Although rivers hadn’t had sufficient time to dissolve salts and carry them to oceans, this salinity was driven by the oceanic melting of briny rocks called evaporites, and potentially volcanic activity. It is in this water that the first life forms on Earth emerged and started evolving.

“The ions that were put there long ago have managed to stick around,” says Galen McKinley, a UW-Madison professor of atmospheric and oceanic sciences. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years.”

The ancient salinity of oceans is still an area of active research with many unknowns. But while we don’t fully understand what’s going on with the ancient oceans, we have a much better understanding of what drives salinity today.

So how do the oceans get salty today?

Salinity map of the world’s oceans. Scale is in parts per thousand. Image credits: NASA.

Oceans today have an average of 3.5% salinity. In other words, 3.5% of the ocean’s weight is made of dissolved salts. Most, but not all of that is sodium chloride (what we call ‘salt‘ in day to day life). Around 10% of the salt ions come from different minerals.

At first glance, 3.5% may not seem that much, but we forget that around 70% of our planet is covered in oceans. If we took all the salt in the ocean and spread it evenly over the land surface, it would form a layer over 500 feet (166 meters) thick — a whopping 40-story building’s height of salt covering the entire planet’s landmass. That’s how much 3.5% means in this particular case.

All these salts come from rocks. Rocks are laden with ionic elements such as sodium, chlorine, and potassium. Much of this material was spewed as magma by massive volcanic eruptions and can form salts under the right conditions.

Because it is slightly acidic, rainwater can slowly dissolve, erode rocks. As it does so, it gathers ions that make up salts and transfers them to streams and rivers. We consider rivers to be “freshwater”, but that’s not technically true: all rivers have some salt dissolved in them, but because they flow, they don’t really accumulate it. Rivers are agents for carrying salts, but they don’t store salts themselves.

The main culprit for why oceans are salty: rivers. Image credits: Jon Flobrant.

Rivers constantly gather more salts, but they constantly push it downstream. Influx from precipitation also ensures that the salt concentration doesn’t increase over time.

Meanwhile, the oceans have no outlet, and while they also have currents and are still dynamic, they have nowhere to send the salts to, so they just accumulate more and more salt. Which leads us to an interesting question.

So, are the oceans getting saltier?

Bodies of water can be classified by their salt content.

No, not really. Although it’s hard to say whether oceans will get saltier in geologic time (ie millions of years), ocean salinity remains generally constant, despite the constant influx of salt.

“Ions aren’t being removed or supplied in an appreciable amount,” says McKinley. “The removal and sources that do exist are so small and the reservoir is so large that those ions just stay in the water.” For example, she says, “Each year, runoff from the land adds only 0.00005 percent of total ocean salts.”

A part of the minerals is used by animals and plants in the water and another part of salts becomes sediment on the ocean floor and is not dissolved. However, the main reason why oceans aren’t getting saltier is once more geological.

The surface of our planet is in a constant state of movement — we call this plate tectonics. Essentially, the Earth’s crust is split into rigid plates that move around at a speed of a few centimeters per year. Some are buried through the process of subduction, taking with them the minerals and salts into the mantle, where they are recycled. The movement of tectonic plates constantly recirculates material from and into the mantle.

Schematic of subduction (and some other associated processes). Image credits: K. D. Schroeder.

With these processes, along with the flow of freshwater, precipitation, and a number of other processes, the salinity of the Earth’s oceans remains relatively stable — the oceans have a stable input and output of salts.

But isolated bodies of water, however, can become extra salty.

Why some lakes are freshwater, and some are *very* salty

Lakes are temporary storage areas for water, and most lakes tend to be freshwater. Rivers and streams bring water to lakes just like they do to oceans, so then why don’t lakes get salty?

Well, lakes are usually only wide depressions in a river channel — there is a water input and a water output, water flows in and it flows out. This is called an open lake, and open lakes are essentially a buffer for rivers, where water accumulates, but it still flows in and out, without salts accumulating. Many lakes are also the result of chaotic drainage patterns left over from the last Ice Age, which makes them very recent in geologic time and salts have not had the time to accumulate.

Beautiful glacial lakes such as this one are the remains of Ice Age melting. Image credits: K. D. Schroeder.

But when a lake has no water output and it has had enough time to accumulate salts, it can become very salty. This is called a closed lake, and closed lakes (and seas) can be very salty, much more so than the planetary oceans. They accumulate salts and lose water through evaporation, which increases the concentration of salts. Closed lakes are pretty much always saline.

We mentioned that world oceans are 3.5% salt on average. The Mediterranean Sea has a salinity of 3.8%. The Red Sea has some areas with salinity over 4%, and Mono Lake in California can have a salinity of 8.8%. But even that isn’t close to the saltiest lakes on Earth. Great Salt Lake in Utah has a whopping salinity of 31.7%, and the pink lake Retba in Senegal, where people have mined salt for centuries, has a salinity that reaches 40% in some points. The saltiest lake we know of is called Gaet’ale Pond — a small, hot pond with a salinity of 43% — a testament to just how saline these isolated bodies of water can get.

Worker digging the salt in Lake Retba. Image in public domain.

It’s important to note that lakes are not stable geologically, and many tend to not last in geologic time. Some of the world’s biggest lakes are drying up, both as a natural process and due to rising temperatures, drought, and agricultural irrigation.

Salt can also come from below

Hydrothermal vent. Image credits: NOAA.

We’ve mentioned that rock weathering and dissolving makes oceans salty, but there is another process: hydrothermal vents.

A part of the ocean water seeps deeper into the crust, becomes hotter, dissolves some minerals, and then flows back into the ocean through these vents. The hot water brings large amounts of minerals and salts. It’s not a one-way process — some of the salts react with the rocks and are removed from seawater, but this process also contributes to salinization.

Lastly, underwater volcanic eruptions can also bring salts from the deeper parts to the surface, affecting the salt content of oceans.

This is what ocean acidification is doing to creatures in the Arctic

As we emit more and more carbon dioxide, the effects are being felt not just above ground, but also underwater.

 A marine snail shows damage to its shell (jagged line radiating from center) due to acidic ocean waters. Image credits: National Oceanic and Atmospheric Administration NOAA

Ocean acidification is often regarded as the unseen twin of climate warming. It’s unseen because we humans don’t spend much of our time underwater, but for the creatures that do, it’s a catastrophe.

When carbon is emitted into the atmosphere, a part of it gets absorbed by the oceans, producing carbonic acid. This acid essentially dissolves the shell of marine creatures such as mollusks, sea urchins, starfish, and corals, making it difficult or impossible for them to survive. Researchers have already identified this process, as well as the way ripples it down the entire oceanic food chain.

But according to a new study, it’s even worse than we thought. The study results show that the Arctic Ocean, the smallest of the seven seas will take up 20% more CO2 over the 21st century than previously expected.

“This leads to substantially enhanced ocean acidification, particularly between 200 and 1000 meters” — a crucial depth where many marine organisms live, explains Jens Terhaar, member of the group for ocean modeling at the Oeschger-Center for Climate Change Research at the University of Bern.

The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales. This pterapod shell dissolved over the course of 45 days in seawater adjusted to an ocean chemistry projected for the year 2100. Image Credits: National Oceanic and Atmospheric Administration NOAA, David Liittschwager

The problem with ocean acidification is you can’t really do anything about it other than try to reduce carbon emissions — and once a certain level is reached, the shells of marine creatures become unstable and start to dissolve.

By 2100, the study found, Arctic waters may be too acidic for many shelled creatures, and according to the model produced by the researchers, if greenhouse gases continue to develop according to existing projections, it’s bad news for the marine environment.

“Our results suggest that it will be more difficult for Arctic organisms to adapt to ocean acidification than previously expected,” says co-author Lester Kwiatkowski.

Limiting global warming to below 2 °C, as mandated by the Paris Agreement, would significantly help reduce the acidification pressure on marine creatures.

The study has been published in Nature.

Great white sharks hunt for meals in unexpected places

We tend to picture them as majestic hunters hunting unsuspecting prey near the surface, but great white sharks might be spending more time foraging on the ocean floor for small morsels, according to a new study.

Credit: Flickr.

Great whites are the largest predatory fish on Earth, capable of growing to an average of 15 feet (4.5 meters) in length. They are usually found in cool, coastal waters throughout the world and their numbers are decreasing due to overfishing and accidental catching. Great white sharks are currently considered a vulnerable species, although population estimates are often unreliable.

Between 2008 and 2009, Australian researchers analyzed the stomach contents of 40 juvenile great white sharks captured off the coast of eastern Australia. That information plus data from studies from other parts of the world helped to get a better picture of the diets of these young sharks.

“Within the sharks’ stomachs we found remains from a variety of fish species that typically live on the seafloor or buried in the sand. This indicates the sharks must spend a good portion of their time foraging just above the seabed,” said lead author Richard Grainger. “The stereotype of a shark’s dorsal fin above the surface as it hunts is probably not a very accurate picture.”

The study showed that, on average, the shark diets consisted of 32% mid-water ocean swimming fish such as Australian salmon, 17.4% bottom-dwelling fish such as stargazers, 14.9% batoid fish that lurk on the seafloor such as stingrays, and 5% reef fish such as eastern blue gropers.

Meanwhile, the rest of the stomach contents was made up of unidentified or less abundant groups of fish. The findings show that marine mammals, cuttlefish and squids also are part of the diet of the juvenile great white shark, but only occasionally and far from being the main element of the diet.

“We discovered that although mid-water fish, especially eastern Australian salmon, were the predominant prey for juvenile white sharks in NSW, stomach contents highlighted that these sharks also feed at or near the seabed,” said in a statement Dr Vic Peddemors, co-author of the study.

As they get older, sharks tend to move around more and take on board more fat in their diet to help power longer journeys. The study showed that they are unlikely to begin hunting larger prey such as dolphins or other sharks until they reach around 2.2 m in length (7.2 feet).

While the study covered only a small sample, it is consistent with tagging programs that show white sharks spend much of their time swimming far beneath the surface. In Australia, tracking data showed sharks migrate from Queensland to Tasmania and that the range of movement expands as they get older.

Looking ahead, the researchers called for more work to be done to analyze the exact nutritional composition of shark diets — not just the calorific content — in order to understand the relationship between their physiology, behavior, and ecology.

“This will give insights into what drives human-shark conflict and how we can best protect this species,” said co-author Gabriel Machovsky-Capuska.

The study was published in the journal Frontiers in Marine Science.

The iconic ‘Dumbo’ octopus stars in the deepest-ever octopus sighting

The adorable cephalopod has been photographed on the bottom of the Indian Ocean in the Java Trench, at around 7,000 meters of depth.

Image credits amieson, A.J., Vecchione, (2020), Mar Biol.

This is roughly 2 kilometres deeper than any previous reliable sighting of a cephalopod, the family that includes octopus and squids. Given that we now know how deep these animals can live — seemingly very comfortably, too — the findings “increase the potential benthic (ocean floor) habitat available to cephalopods from 75 to 99% of the global seafloor”.

The deep end

The researchers who spotted the boneless animal say it’s a species of “Dumbo” octopus, so named due to its distinctive side fins. Due to their size and shape, they’re very reminiscent of an elephant’s ears, most notably to those of Disney’s 1940s’ animated elephant Dumbo.

Still, spotting the octopus at this depth was no mean feat. Lead author Dr Alan Jamieson from the School of Natural and Environmental Sciences, Newcastle University is a pioneer of the use of “landers” for deep-sea exploration. These landers are crew-less craft, in essence large metal frames outfitted with various instruments that are dropped overboard and land on the seafloor. Once there, they observe their surroundings and record any passers-by.

And record they did. The lander picked up two octopuses, a 43-cm-long one at a depth of 5,760m and the other (35 cm) at 6,957m. Based on their physionomy, Dr. Jamieson and his co-author Michael Vecchione from the NOAA National Systematics Laboratory are confident that they belong to the Grimpoteuthis family, the group commonly known as the Dumbo octopuses.

God, it’s so cute.
Image credits amieson, A.J., Vecchione, (2020), Mar Biol.

Further down, the landers also spotted octopus fragments and eggs. The study provides the deepest-ever sightings of cephalopods. Previously, the deepest reliable sighting was a 50-year-old black-and-white photograph of one such animal taken at a depth of 5,145m.

For starters, it’s impressive that anything can live at such depths, where pressure is literally crushing.

“They’d have to do something clever inside their cells. If you imagine a cell is like a balloon — it’s going to want to collapse under pressure. So, it will need some smart biochemistry to make sure it retains that sphere,” Dr. Jamieson explained.

“All the adaptations you need to live at pressure are at the cellular level.”

Furthermore, it helps fill out our understanding of hoe octopuses live. The authors explain that the study shows that such animals can (potentially) live across 99% of the global seafloor, as the Java Trench is one of the deepest points on Earth.

The paper “First in situ observation of Cephalopoda at hadal depths (Octopoda: Opisthoteuthidae: Grimpoteuthis sp.)” has been published in the journal Marine Biology.

Iceland won’t be whaling this year

You can add Icelandic whaling to the increasingly long list of industries disrupted by the coronavirus pandemic.

Image credits: Hard to Port.

Coronavirus distancing requirements have made the processing of whale meat in Iceland “almost impossible,” said Kristjan Loftsson, chief executive of Hvalur, the largest whaling company in the country. Loftsson said that it’s impossible to maintain a distance at whaling stations, and workers need to work “very closely together” — and if one is tested positive for COVID-19, the entire station would need to be quarantined.

This would be the second year in a row that Hvalur, which hunts fin and minke whales for export to Japan, will not hunt or process whale meat. Fin whales (Balaenoptera physalus) are considered threatened but are still being hunted in Iceland and Japan.

In addition, Hvalur added that it cannot compete with Japan’s own whale meat products, which are heavily subsidized by the Japanese government.

Another Icelandic whaling company, IP-Utgerd — which mainly targeted minke whales (Balaenoptera acutorostrata) — cited financial difficulties after no-fishing zones were established around Iceland’s coast. This forces whaling ships to go farther offshore, which is more costly.

Whaling vessels in Reykjavik harbor. Image credits: Wurzeller.

The interruption has been hailed by conservationists, though it’s important to note that this isn’t the first time the Icelandic whaling industry has been halted, only to be resumed later.

“This is indeed terrific news that for a second straight year, vulnerable fin whales will get a reprieve from Hvalur hf.’s harpoons, the sole fin whaling company,” Fabienne McLellan, co-director of international relations at Ocean Care, told Mongabay. “This said, fin whaling has been suspended in Iceland in the past, only to resume. While it looks promising that whaling in Iceland might stop for good, the temporary cessation of fin whaling must become permanent.”

Whaling in Iceland began as soon as Iceland was colonized. Early hunters in the 12th century used spear-drift hunting and this vestigial hunting continued until the late 19th century when other countries brought modern ships to Iceland and changed the whaling industry.

In recent decades, environmental pressure has been mounting against the whaling industry, culminating with a global moratorium by the International Whaling Commission in 1986. Iceland is one of only a handful of countries that object to the moratorium and maintain a whaling fleet.

Arne Feuerhahn, founder of Hard to Port, a German organization working to end whaling in Iceland, believes Hvalur may yet resume whaling in 2021.

Feuerhahn hopes that Hvalur’s whaling facility can be converted into an educational center where children could learn about whaling history without killing any more whales.

In 2018, Hvalur killed 146 fin whales, many of which were pregnant females. Hvalur was also the center of controversy when it was revealed that two of the whales were hybrids between fin whales and blue whales

Microbes discovered in the ocean’s crust rely on recycling to survive

Extreme and remote conditions don’t seem to be an impediment for microbe communities, according to a new study, which found some of them living in the crust of the ocean far beneath the seafloor and relying on recycling to survive.

A detailed look at the rocks. Credit Woods Hole Oceanographic Institution

Researchers found bacteria, fungi, and archaea (single-celled organisms) in rocks at about 700 meters below the bottom of the Indian Ocean. The finding was possible by looking at rock samples from the Atlantis Bank, a part of the seafloor where rock is exposed close to the surface.

The microbe communities were living in the cracks and fissures of the rock, according to researchers at the Woods Hole Oceanographic Institute. The rock samples had biosignatures of life such as DNA and lipid biomarkers, while messenger RNA extractions showed some cells were still active.

The fact that there’s life in seafloor sediments isn’t new, but only one study in 2010 had looked at the oceanic crust in the Atlantic Ocean for signs of life. Ocean crust covers nearly 70% of the earth’s surface and is made up mainly by the gabbroic layer. Gabbro is intrusive igneous rock.

“These [communities] can basically be hanging out for millions of years in a very quiescent state,” study author and associate scientist Virginia Edgcomb said in a statement. “I’m sure even the active microbes are carrying on at a very slow rate relative to those near the surface, but nevertheless, they’re buzzing along.”

The study claimed that the survival of the bacteria, fungi, and archaea relied on underground fluid flow. Seawater travels through the cracks in the rock, carrying organic matter down from the ocean. The researchers found signs of life in those currents of seawater.

At the same time, the study found a set of survival strategies used by the microorganisms. Some showed the ability to store carbon in their cells, while others were able to process nitrogen and sulfur to generate energy, recycle amino acids, and produce vitamins.

Steven D’Hondt, a professor at the University of Rhode Island who was not involved with the research, told EOS that this “runs counter to standard assumptions about subseafloor crustal life” and that “the readiness of that community to consume organic matter suggests that it is metabolically linked to the broader world.”

Whether the results can be applied to other areas of the ocean’s lower crust is still an open question. The study focused on the Atlantis Bank, where the lower crust is exposed at the ocean bottom, an unusual phenomenon. Future research will have to confirm whether life is possible with the upper crust and bottom sediments still intact.

The study was published in the journal Nature.

Australia’s deep-sea canyons feature coral gardens

The deep-sea isn’t the barren, bizarre environment we once thought it to be. It can be brimming with life, often in unexpected shapes.

Image credits: Schmidt Ocean Institute.

Coral gardens

Bremer Canyon Marine Park is already well-known as a biodiversity hotspot. All sorts of whales and dolphins, fish and seabirds, call it home. Marine scientists have been conducting research on megafauna in the area for over a decade, but there’s still much more to discover.

In the most recent survey, researchers at the University of Western Australia teamed up with the philanthropic Schmidt Ocean Institute to explore the deeper parts of the sea — specifically, the canyon itself.

Using the deep-sea remotely operated vehicle, SuBastian, which is capable of sampling depths to 4,500 meters, they set out to explore the depths of Bremer Canyon.

Image credits: Schmidt Ocean Institute.

The canyon starts to descend from the continental shelf (at about 200 meters deep) to abyssal depths (around 4,000 meters deep).

The team wasn’t entirely sure what to expect from the canyon floor, although previous surveys suggested that the canyon is teeming with wildlife. They strategically collected deep-sea coral and fauna samples, as well as water and geological samples.

“We have already made a number of remarkable discoveries from the Bremer Canyon,” said Dr. Julie Trotter, the Chief Scientist from UWA who led the expedition. “The vertical cliffs and ridges support a stunning array of deep-sea corals that often host a range of organisms and form numerous mini-ecosystems”.

In particular, the ‘coral gardens’ inside the canyon are stunning hotspots of biodiversity.

Benthic animals on substrate. Image credits: Schmidt Ocean Institute.

The new discoveries are enabling researchers to understand the canyon environment in a new light. For all the studies of Australia’s corals, the deep-sea environment remains largely unexplored. This does not only help biologists understand these understudied ecosystems, but also help conservationists devise strategies to protect this vulnerable life. It’s an important contribution to the broader topic of oceanic life conservation.

Australia is surrounded by three oceans, and all of them have submarine canyons, some of which run several kilometers deep. In addition to living corals, these canyons also have extensive fossil coral deposits — they’re a pedestal-like coral graveyard, which researchers can also study to better understand this environment and how it evolved in both historic and geological time.

Australia has only one oceanographic vessel available for scientific research and no supporting deep-sea underwater robots, which makes this expedition so important and rare.

Image credits: Schmidt Ocean Institute.

The waters in Bremer Canyon come from Antarctica, which means the canyon can also harbor important information about processes that regulate our planet’s climate

“This has global implications given these waters originate from around Antarctica which feed all of the major oceans and regulate our climate system” said Professor Malcolm McCulloch from UWA.

Corals are also important in climate studies, as they require specific conditions to survive.

Understanding coral thermal susceptibility has been a central focus of coral studies, especially as climate change and ocean acidification are threatening all the planet’s reefs — including the Great Barrier Reef.

Image credits: Schmidt Ocean Institute.

“A particular species of solitary cup coral was found during the expedition. This is significant because we are working on the same coral in the Ross Sea on the Antarctic shelf, in much colder waters”, said collaborator and co-Chief Scientist Dr. Paolo Montagna from the Institute of Polar Sciences in Italy, who was a part of the study. “This is an important connection between disparate sites across the Southern Ocean, which helps us trace changes in water masses forming around Antarctica and dispersing northward into the Indian and other oceans”.

At least 26% of the ocean needs to be relegated to conservation to prevent marine collapse

A new study reports that the oceans need “urgent conservation” in order to avoid massive biodiversity loss. According to the team’s estimates, between 26% and 41% of the ocean’s total surface needs to be designated as conservation areas and safeguarded to act as habitats for wildlife.

Image via Pixabay.

Key regions include the Northern Pacific Ocean near China and Japan, and the Atlantic between West Africa and the Americas, the team explains.

An oceanful of problems

“Preserving a portion of habitat for all marine species would require 8.5 million square kilometres of new conservation areas,” said Dr. Kendall Jones, lead author of the study and a PhD student at the University of Queensland’s School of Biological Sciences. “Currently one-third of all marine species have less than 10 percent of their range covered by protected areas.”

“We found that a minimum of 8.5 million km2 (2.5% of the ocean) of new conservation areas are required, and show that, in total, at least 26% of the ocean needs effective conservation to preserve marine biodiversity,” the paper reads.

“[This percentage] should be regarded as a bare minimum.”

The team determined which areas of the global ocean would need to be turned into conservation sites in order to maintain adequate (or at least, the bare minimum of) marine biodiversity. Oceans cover around 70% of the Earth’s surface and harbor between 50% and 80% of life on Earth. Marine ecosystems underpin all life on Earth at large by providing food, oxygen, by scrubbing atmospheric CO2 and through the recycling of other essential nutrients such as phosphorus and nitrogen.

For the study, the team mapped the habitats of over 22,000 marine species and used a mathematical model to estimate the minimum area required to capture a portion of each species’ ranges. The team also included areas of importance for global biodiversity (Key Biodiversity Areas) and those where human impact is very low (known as marine wildernesses).

In essence, the team determined the smallest area that would give all of these species some space free from human activity to live in. Dr. Jones says that a coordinated international effort is needed, and needed fast, to step up marine conservation efforts in time to preserve the health of the global ocean.

“Conserving the areas we’ve identified in our study would give all marine species a reasonable amount of space to live free from human impacts like fishing, commercial shipping or pesticide runoff,” he explains.

All in all, they report that between 26% and 41% of the total ocean surface needs to be relegated to conservation, depending on how much of each species’ range we decide to protect.

James Watson, a Professor at the University of Queensland, Director of Science at the Wildlife Conservation Society, and the study’s corresponding author says that the findings should help inform world leaders who will be meeting in Rome later this year “to sign an agreement that will guide global conservation for the next ten years”. The meeting was originally planned to take place in Kunming, China, but the location was moved following the COVID-19 outbreak. Professor Watson explains that the success of such conservation programs hinge on taking rapid action to protect endangered species and ecosystems while also implementing long-term strategies to manage the global ocean more sustainably.

“This science shows that governments must act boldly, as they did for the Paris Agreement on climate change, if we are to stop the extinction crisis facing many marine species,” he says.

“This isn’t just about strict marine protected areas. We need to use a broad range of strategies such as no-fishing zones, community marine reserves, and broad-scale policies to put an end to illegal and unsustainable commercial fishing operations.”

As millions of people all around the world directly rely on the ocean (and its biodiversity) for food and income, politicians should have ample incentive to design and ratify measures like as the ones proposed by this study. If not, they’ll have quite a bit of civil unrest on their hands in the future — but all of us, everywhere, will have to contend with a much more barren ocean and Earth.

The paper “Area Requirements to Safeguard Earth’s Marine Species” has been published in the journal One Earth.

Oceans could be unviable for coral reefs by 2100 due to warmer, more acidic waters

Warmer and more acidic oceans could destroy nearly all of today’s coral reefs by the end of the century.

Image credits Marcelo Kato.

New research presented Monday at the Ocean Sciences Meeting 2020 paints a dire picture for the Earth’s reefs. According to the team, between 70% and 90% of coral reefs will disappear in the next 20 years due to a combination of climate change and pollution. By 2100, they add, very few habitats suitable for corals will remain on Earth — if any.

Reefless

“Trying to clean up the beaches is great and trying to combat pollution is fantastic. We need to continue those efforts,” said Renee Setter, a biogeographer at the University of Hawaii Manoa who presented the findings.

“But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors.”

The issues identified by the team will likely pose major challenges for ongoing reef conservation programs. For example, the researchers cite efforts to grow corals in laboratories and later transplant them back into wild reefs in an attempt to boost their health and resilience. While there is value to such an approach, Setter cautions that few to no habitats will remain suitable for reefs by 2100, rendering the lab-grown corals powerless.

What we need to do, she argues, is to focus on the issues of rising sea surface temperatures and acidity, as these are the two most pressing environmental factors plaguing reefs today. While pollution also poses a very real threat to marine life in general, the team adds, corals in particular are most at risk from environmental changes associated with human CO2 emissions.

Corals are very sensitive to increased temperatures. They can bear them for a short while but will expel their symbiotic algae if exposure continues for longer periods of time in a process known as ‘bleaching’ (these algae live inside the mineralized structures of the coral, giving them their color, and helping feed the polyps). Bleached corals aren’t necessarily dead, but they’re far less resilient to further shocks and stressors. Bleaching events have greatly increased in frequency in the last few years due to climate change.

A bleached coral reef.
Image via Wikimedia.

Setter and co-author Camilo Mora, also at the University of Hawaii Manoa, mapped the areas of the world that would be suitable for coral reefs over the coming decades. They based this on modeling of future environmental conditions that accounted for factors such as sea surface temperature, wave energy, water acidity levels, pollution, and overfishing in areas currently inhabited by corals. They also factored in human population densities and land cover use as proxies for how much pollution and waste would be present at different sites.

They found that most areas that harbor coral reefs today wouldn’t be able to sustain them by 2045; the situation would only worsen by 2100. Small portions of Baja California and the Red Sea would still be viable, but they’re not ideal locations for coral reefs because of their proximity to rivers, the team explains.

“By 2100, it’s looking quite grim,” said Setter. “Honestly, most sites are out [by this time].”

One of the more encouraging findings is that projected increases in human populations (and an associated increase in pollution) pose a limited threat to reef habitats in the future. On the flip side, the team explains that this is because human activity has already caused significant damage to coral reefs — meaning that there are only so many locations left to impact. Still, the authors underline that CO2 emissions and their associated effect on the climate and water acidity need to be addressed if the corals are to stand a chance in the future.

The poster “Impacts of climate change on site selection for coral restoration” has been presented on Monday, February 17 at the Ocean Sciences Meeting 2020 in San Diego (poster number PC14A-1691).

Global warming is literally dissolving the ocean’s plankton

Ocean acidification is wreaking havoc on the ocean’s tiniest inhabitants, and the entire ocean is likely feeling the effects.

The color scale shows shell thickness. Old plankton had thicker, healthier shells than modern samples. Image from Fox et al / Scientific Reports (2020).

As a geology student, many things can be unusual. You start to think about time in millions of years, which is completely counterintuitive. You start to realize just how intricate (and beautiful) the processes that shape our planet are, and you also start to understand that there are firm physical laws governing how our planet looks like. There’s a reason why mountains on Earth don’t grow forever and why the continents move about the way they do — the laws of physics constrain geology, and they constrain nature.

What does this have to do with plankton, one might ask, and the oceans in general?

Well, many of the ocean’s inhabitants have soft bodies protected by hard shells. Clams, oysters, and sea snails have them, as do multiple other types of mollusks and plankton. These seashells are almost always made of calcium carbonate — which, under most conditions, is fine. The ocean water is well-suited to support calcium carbonate under normal conditions. But here, too, there is a physical rule that allows this.

Seawater is slightly basic (meaning pH > 7). When we increase the amount of carbon dioxide (CO2) we emit, not all of it goes into the atmosphere. Much of it, in fact, is absorbed by the oceans. As oceans absorb CO2, their chemistry starts to change, and they become more acidic.

When there is too much carbon dioxide in the oceans, it makes for acidic waters that don’t support seashells. If current emission trends continue, it might spell disaster for many of the ocean’s inhabitants. Image credits: Elisajans / Wikipedia.

When the acidity reaches a certain threshold, animals can no longer build and maintain seashells, and they can’t survive anymore.

This is already happening, a new study shows.

Plankton old, plankton new

The new study started in a museum.

When it comes to comparing our current environment with that of the past, museums can provide a trove of information. The museum is not just what you see when you visit it — museums have additional storage rooms, where they sometimes keep thousands upon thousands of samples gathered by researchers. In this case, Lyndsey Fox, a researcher from Kingston University in London, analyzed plankton fossils gathered by the 1872–76 expedition of the HMS Challenger.

Studying micro-fossils is never an easy task. Analyzing how thick their shells are and then using a tomography scanner to create 3D models of their shells (which are less than 1 millimeter in diameter) is an even trickier job. But Fox and colleagues succeeded, and built stunning reconstructions of this century-old plankton. They then did the same thing for plankton gathered from a 2011 expedition to the eastern equatorial Pacific Ocean called Tara.

The results were striking.

All modern plankton had much thinner shells — up to 76% thinner. In some cases, the shells were so thin that the team wasn’t even able to image them.

No matter where researchers looked, modern plankton had thinner, more vulnerable shells. Image credits: Fox et al / Scientific Reports (2020).

It’s a shocking result. Researchers were well aware that ocean acidification was taking a toll, but the extent to which this was observed is concerning.

Stress on all sides

Some species seem to handle it better than others, presumably due to biological differences among species (though researchers did not attempt to explain this).

“Whilst all specimens analyzed showed some reduction in shell thickness, the degree to which different species responded varied greatly,” the authors of the study write.

There are plenty of old samples in museums, and researchers want to look at more species from different areas of the ocean and study the differences and peculiarities — but the elephant in the room is clear. As we pump more and more carbon dioxide, much of it will end up in our oceans, with long-lasting consequences for the entire ecosystem. We are reaching a point where some organisms are already struggling to maintain their shells, the study highlights.

“Oceanic carbonate ion concentrations decrease as a consequence of increased atmospheric CO2 levels, which, in turn, has a negative effect on the capacity for calcifying organisms (such as molluscs, crustaceans, corals, and foraminifera) to form their essential skeletal or shell material out of calcium carbonate,” the study continues.

It’s not just microscopic creatures, either. A recent study found that ocean acidification is also destroying the shells of crabs, and while some creatures might take it better than others, no creature is spared from its effects. When the plankton suffers, the entire food chain on Earth suffers.

The evil twin of global warming, as ocean acidification is often referred to, is even more insidious than its sibling. We don’t see when plankton is being dissolved in the ocean. We hardly know how many creatures are unable to maintain their shells due to it. We may not know the full scale of the problem, but we know the cause, and we know that if we want to address it, reducing our emissions is key.

To make matters even worse, ocean acidification doesn’t act in a vacuum. The oceans are getting warmer, and as the oceans gather more carbon, they have less available oxygen — which creatures also need. This is a one-two punch which, many creatures are struggling to withstand.

“Ocean acidification is not the only stressor faced by the world’s oceans in the coming decades and over the time period studied here. Rising temperatures and deoxygenation are also likely to have a substantial impact on marine ecosystems, and eastern boundary upwelling systems are likely to be strongly affected by all three stressors,” the study concludes.

We might not see it, but it just goes to show how insidious the effects of global warming really are.

The study was published in Scientific Reports.

How albatrosses could help fight illegal fishing

The magnificent birds could help researchers pinpoint the location of illegal fishing vessels.

The majestic albatross could help fight illegal fishing.

The world is not fishing sustainably. Across the oceans, fish stocks have shrunk and collapsed, and a recent study found that if fishing rates continue unchanged, all the world’s fisheries will collapse by the year 2048.

Illegal fishing makes up a large part of that problem. It is believed illegal and unregulated fishing account for up to 30% of total catches. The problem is, enforcing regulations is difficult. The oceans are vast and policing them has proven a gargantuan task.

The first difficult step is detecting illegal vessels. There’s just no easy way to see which vessels go where — and this is where lazy albatrosses can help.

Albatrosses are majestic birds, having the largest wingspan of any living bird: up to 3.7 m (12 ft). They scour the seas searching for fish, squid, and krill, flying up to 16,000 kilometres (9,900 mi) without landing. They’re also opportunistic, not only hunting but also scavenging when they can.

We’ve known for quite a while that albatrosses also like to follow fishing vessels around. They see this as a “free lunch” — a way to eat something without going through the effort of hunting.

This makes them ideal ocean sentinels.

In a new study, researchers show how albatrosses can be used to help monitor illegal fishing vessels. The idea is pretty simple: tag some birds with GPS trackers and radar loggers. When the loggers receive a radar signal (coming from a boat), you can see if the boat is legally registered, and if not — boom, you’ve found an illegal fishing boat. It’s a simple but very efficient idea, and the loggers are small enough that they don’t cause any real discomfort to the birds.

This was put to the test by researchers from France and New Zealand, as a part of the Ocean Sentinel program.

The researchers equipped almost 170 albatrosses with GPS loggers for 6 months, monitoring more than 47 million square kilometers of the Southern Ocean. When they looked at the data, researchers found that more than a third of the fishing vessels operating in international waters were illegal.

The method is remarkably cheap and efficient and can cover fast swaths of the ocean almost free of cost. As an added bonus, the data could also be used independently for animal conservation.

Already, similar equipment is being tested in New Zealand and Hawaii for other marine species, like sharks and sea turtles. If this technology could also be easily adapted to avoid any discomfort for the animals, this could mark a very important step in monitoring and combating illegal fishing.

Tropical sharks are using their fins to walk

Four tropical shark species have been caught in the act: using their fins not to swim, but to walk.

Hemiscyllium halmahera, one of the walking sharks, chilling on a rock. Image credits: Mark Erdmann.

As if sharks weren’t amazing enough, some of them have apparently started walking. Four species of sharks living in coastal waters around Australia and New Guinea have been spotted using their fins to walk on rocks and in very shallow water.

The walking sharks were discovered during a 12-year study with Conservation International, a joint effort involving researchers from the CSIRO, Florida Museum of Natural History, the Indonesian Institute of Sciences and Indonesian Ministry of Marine Affairs and Fisheries.

The sharks reportedly use this technique to hunt. According to Dr. Christine Dudgeon, from University of Queensland, ornate sharks are already on top of the food chain. Now, they are using their fins during low tides, walk-crawling in shallow water to get an extra edge.

“At less than a metre long on average, walking sharks present no threat to people but their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and molluscs,” Dr Dudgeon said.

“These unique features are not shared with their closest relatives the bamboo sharks or more distant relatives in the carpet shark order including wobbegongs and whale sharks.”

We don’t really know when this started. It may be a novel process, but it may have also started a long time ago.

However, researchers do suggest that the evolution of these sharks was influenced by tectonic movement in the area — particularly the tectonic plate movement approximately 20 to 5 million years ago that completed Australia’s break-up from the supercontinent Gondwana.

This movement triggered a series of fluctuations in the area and produced a unique environment where a number of species thrived. This created not only new possibilities for species, but also barriers and isolation — and this isolation tends to lead to the development of new, unique species.

It may very well be that this tectonic movement millions of years ago is responsible for walking sharks today.

“Data suggests the new species evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species,” Dudgeon said in a statement.

“They may have moved by swimming or walking on their fins, but it’s also possible they ‘hitched’ a ride on reefs moving westward across the top of New Guinea, about two million years ago.

However, these aren’t the first sharks to exhibit this type of behavior. Four new species have been observed now, raising the total number to nine — in a remarkable example of convergent evolution.

They are also probably not the last we find, Dudgeon notes.

“We believe there are more walking shark species still waiting to be discovered,” she concludes.

The study has been published in Marine and Freshwater Research.

Martian water was mineral-rich and salty — good hints of habitability

Curiosity has found new hints of the Red Planet’s past — and they look intriguing.

So far, we’ve only ever found life on Earth. Until very recently, we didn’t even know of other Earth-like planets — but that all changed, fast. We’ve since found thousands of exoplanets, some of which are very promising in terms of habitability.

But for now, at least, we can only explore the planets inside our own solar system. Mars was always a candidate for extraterrestrial life. It’s comparable in size to our planet, lies at a good distance for the Sun, and it seemed to have a decent atmosphere at some point. More recent investigations have found strong evidence for ancient systems of water. Other exotic places, like Europa or Enceladus may also harbor (or have harbored) life, but Mars will always be a promising candidate.

Very promising, as recent evidence shows.

Curiosity has drilled two small cores into what researchers believe to be lake sediments. Using the scientific instruments at its disposal, the rover analyzed the sediments, tracing their chemical makeup.

This makeup suggests that, in addition to Mars’ wet past, we can also infer that the lakes (or seas) may have been very rich in minerals, and were also salty.

In other words, Mars’ oceans bared striking similarities to those on Earth.

It’s become increasingly clear that Mars used to have an active water system — both from topographical imagery (such as the one above) and mineralogic studies.

It gets even better. Not only was the chemical make-up similar to that of Earth, but the acidity (pH) was also close to that of Earth’s modern oceans.

We know that life can emerge in Earth’s oceans, so if water on Mars looked a lot like that on our planet, there’s a good chance life might have emerged there as well.

However, this would have been the case billions of years ago. Nowadays, Mars is a pretty barren wasteland, and it’s not clear if any life can exist there at all — even microbial life.

But even if life on Mars doesn’t exist now, it might have been there at some point in the past, which begs the question: how likely are we to find traces of it, such as fossils or more likely, chemical traces of living creatures?

That’s not exactly clear, and it’s not something that Curiosity is well-equipped to do.

NASA’s 2020 rover, on the other hand, will do just that: look for signs of life (especially microbial life) and habitable conditions on Mars — and we can’t wait for the results.

The study has been published in Nature Communications.

This algorithm lets you delete water from underwater photos

Image credits: Derya Akkaynak.

Underwater photography is not just for Instagram feeds — they are very important for biologists who monitor underwater ecosystem such as coral reefs. Coral reefs are some of the most colorful and vibrant environments on Earth, but like all underwater photos, photos of coral reefs tend to come out tainted by hues of blue and green. This makes it more difficult for researchers to identify species and traits of species from images, and makes monitoring considerably more difficult.

Now, there’s a solution for that: it’s called Sea-Thru.

Engineer and oceanographer Derya Akkaynak and her postdoctoral adviser, engineer Tali Treibitz, spent four years working to develop and improve an algorithm that would essentially “remove” the water from underwater photography.

The way the light is absorbed and scattered in water causes photos to be dim and overtaken by blue tones. Sea-thru removes the color cast and backscatter, leaving behind a crisp and clear image.

Image credits: Derya Akkaynak.

The method relies on taking multiple images of the same thing, from slightly different angles factoring in the physics of light absorption. Then, the algorithm produces a model of the photo, reversing the effects caused by the scattering and absorption.

“The Sea-thru method estimates backscatter using the dark pixels and their known range information,” the researchers describe the method in a working paper. “Then, it uses an estimate of the spatially varying illuminant to obtain the range-dependent attenuation coefficient. Using more than 1,100 images from two optically different water bodies, which we make available, we show that our method with the revised model outperforms those using the atmospheric model. “

The downside of this is that it requires quite a lot of images, and therefore, large datasets. Thankfully, many scientists are already capturing images this way using a process called photogrammetry (a technique that uses photographs to make certain measurements). Sea-Thru will readily work with photogrammetry images, Akkaynak says, which already raises intriguing prospects.

Results on different processing methods. Image credits: Derya Akkaynak.

This method is not akin to image manipulation — it’s not photoshopping or image manipulation. The colors are not enhanced or modified, it’s a physical correction rather than a visually pleasing modification, says Akkaynak.

Although the algorithm was only recently announced, it’s already causing quite a stir due to its potential. Any tool that can help scientists better understand the oceans, particularly at this extremely delicate time, can’t come sooner enough.

“Sea-thru is a significant step towards opening up large underwater datasets to powerful computer vision and machine learning algorithms, and will help boost underwater research at a time when our oceans are increasing stress from pollution, overfishing, and climate change,” the researchers conclude.

Food availability acts as a cap for whales’s maximum size

Whale size may be held in check by the availability of prey, a new study reports. While baleen whales have evolved to leverage size as an advantage while feeding — which put them on an “energetic knife’s edge” — toothed whales instead stand to benefit from being less massive.

Humpback whale and her calf.
Image credits National Marine Sanctuaries.

Growing to more than 100 tons, blue whales are considered to be the largest creatures to have ever roamed the Earth. Seeking to understand why baleen (filter-feeding) whales and toothed whales are so different in body size — and what factors limit their growth — a new study is looking into how much energy the two groups spend when feeding.

Large-scale nomming

“Blue whales and sperm whales are not just kind of big,” said Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian’s National Museum of Natural History and the corresponding author of this study. “They are among the biggest animals ever to have evolved.”

“They rival and, in some cases, exceed the heaviest dinosaurs. That’s pretty spectacular. But why aren’t they bigger?”

Since whales spend most of their time deep underwater, it’s very hard for researchers to actually monitor what they’re doing. The current study, written by an international team of researchers led by Pyenson and Stanford University biologist Jeremy Goldbogen stuck multi-sensor arrays onto the backs of whales, porpoises, and dolphins of various sizes using suction cups.

The sensor arrays were used to track the animals’ underwater activities using accelerometers, pressure sensors, cameras, and hydrophones. Sonar sweeps in the surrounding waters, alongside older records of prey in whale stomachs, were used to estimate the density of prey in the vicinity of each tagged animal. Over 10,000 distinct feeding events were analyzed as part of the study, with the team calculating the energy cost and payoff for each.

“Energy is a key currency for all life, and we wanted to know how energy gain compares to energy use in foraging whales with different body sizes and feeding strategies,” Goldbogen said.

“The ratio of energy gain relative to energy use reveals a whale’s foraging efficiency and that provides clues as to why different whales are big and why they aren’t bigger.”

The net energy return on feeding, they found, largely depended on how each whale fed — i.e. by hunting individual prey (toothed whales) or by filter-feeding (baleen whales). Body size in all whales is limited by this net return of energy.

Less bang for your kill, more bang for your krill

Killer whale.
Image credits Ed Schipul / Flickr.

Filter-feeding whales are the only ones to have evolved a feeding strategy that favors larger body sizes — which turned them into the largest animals to have ever evolved on Earth. Size, they explain, plays right into the feeding style of baleen whales. They feed by straining patches of krill from ocean water — which aren’t particularly smart or able to move out of the way, so catching them is like shooting fish in a barrel. Having a larger body (and mouth) therefore means the whales can generate more calories for the same effort. In other words, their net energy return from feeding increases with the size of the whale.

Toothed whales, in contrast, need to hunt down individual prey, like a cheetah would on land. The whales use echolocation to spot a target and then hunt it down — so they are, in essence, limited to feeding on one target at a time. This hunting process requires a lot of energy, as the prey obviously would rather not be eaten, and does its best to escape. The larger a toothed whale becomes, the more energy it needs to give chase and catch prey. In other words, their feeding strategy favors smaller body sizes.

In some cases, the team reports, larger toothed specimens like sperm whales actually lost energy on some food dives; it simply takes more calories to dive and eat than they get out of what they ate. In effect, energy expenditure related to hunting acts as the hard cap for the size of toothed-whales. There aren’t enough large animals in the ocean for them to grow larger.

“They literally can’t eat enough to achieve a higher energetic payoff before they have to return to the surface and breathe,” Pyenson said.

“Being a sperm whale today is really pushing a serious biological limit.”

Filter-feeding whales, on the other hand, only seek out the densest patches of krill and almost always, the data showed, consume significantly more calories than they expend. The largest whales in this category saw the best energy return rates in the whole study. But they’re also limited in size by prey availability.

Krill population numbers explode but only for short periods of time every year in specific areas of the globe. This seasonal variation is what keeps baleen whale size in check.

Are whales the limit?

“The largest baleen whale species must reap the energy gains of krill patches in only a few of the most productive summer months at high latitudes,” Goldbogen said.

“Highly efficient filter-feeding strategies mean that these whales can build up fat stores that can then power their migrations across ocean basins to breeding grounds at lower latitudes that are leaner and provide much less food.”

While it may seem that filter-feeding whales have it nailed down, Pyenson explains that they’re actually playing a dangerous game here. They’re superbly adapted to take advantage of one resource. It’s an abundant resource, for sure, but if anything were to happen to the supplies of krill, filter-feeding whales have nothing to fall back on. Given their huge bulk, it’s hard to imagine any source of food in the ocean that could serve as a fall-back.

“You have to wonder just how perilous it is for whales living on an energetic knife’s edge,” Pyenson said, noting that climate change, overfishing, and other threats to the oceans are rapidly impacting their food suply.

“If you’re a blue whale and your only prey item is krill, and something causes krill populations to go into decline, then you are at an evolutionary dead end because you would not be able to eat enough to sustain yourself,” he said. “It’s a good reason for us to try to better understand these predator-prey relationships.”

This study identifies food sources as a limiting factor in whale size, but previous research has suggested that it may be biologically impossible for blue whales to grow any larger anyway due to mechanical constraints on their cardiocirculatory systems.

Beyond the immediate value of the findings, the team says it helps us better understand the dynamics between other huge beasts — particularly dinosaurs — and their food source, and how this limited their growth. “We don’t know how badly a herd of sauropod dinosaurs would chomp down on a forest in the Cretaceous period,” Pyenson adds, “but they probably did a number on it.”

The paper “Why whales are big but not bigger: Physiological drivers and ecological limits in the age of ocean giants” has been published in the journal Science.

There’s a million times more microplastic in the ocean than we thought

Microplastics come from household items all around us. Here’s a kitchen sponge with small pieces breaking away. Image credits: Hungchaka / Wikipedia.

If you took 1,000 liters (264 gallons) of ocean water, how many pieces of plastic do you think you’d end up with: a hundred? A thousand? A hundred thousand?

According to a new study, the answer is 8.3 million. That’s 8,300 for every liter of water, or 31,439 per gallon.

That’s also a million times more than previous estimates.

A big tiny problem

The problem with plastic is that it never really goes away — well, it does go away, but it takes centuries or millennia. Instead, what plastic usually does is break down into smaller and smaller pieces, until you can’t really see it; but it’s still there.

Microplastics are pieces of plastic smaller than 5 millimeters. They come from a variety of sources, either from products that contain microplastics themselves (like some cosmetics or cleaning products) or from larger pieces of plastic that break down.

Plastic is everywhere, and it usually makes its way into the oceans. It doesn’t just stay in the water. It’s absorbed by creatures and accumulates higher up the food chain, even ending up inside humans.

It’s not exactly clear how microplastics are affecting wildlife and human health, but establishing just how much of it is around is a good step.

Biological oceanographer Jennifer Brandon had an unsettling idea: what if we’ve been counting microplastics wrong? She suspected that the current counting methods miss the smallest plastic pieces.

“For years we’ve been doing microplastics studies the same way (by) using a net to collect samples,” said Brandon in a press release. “But anything smaller than that net mesh has been escaping.” She suspected that existing papers are missing some of the plastics.

“I saw these published size ranges and thought, we are under-sampling this smaller range. There’s a big knowledge gap,” Brandon said.

So instead, Brandon and colleagues used a different method, gathering samples from both water and salps, gelatinous filter-feeding invertebrates that suck in water both to eat and propel themselves around the upper 2,000 meters (6,500 feet) of the ocean. Salps suck in and expel the water. They presumably also expel the microplastics, but it takes them a few hours to do so, so you’d be able to see if their last meal included any microplastics.

Salps are barrel-shaped gelatinous invertebrates that feed on plankton. They have one of the most efficient examples of jet propulsion in the animal kingdom, and efficient internal feeding filters. Image credits: Peter Southwood / Wikipedia.

The researchers gathered 100 salps and sent them to the Scripps Oceanography, where co-authors Alexandra Freibott and Michael Landry searched for plastic in salp guts. They used a fluorescent microscope because conveniently, plastic lights up when exposed to multiple wavelengths of light — which means it’s easy to detect with this type of method. But the results were not so convenient.

Out of the 100 analyzed salps, 100 contained microplastics. There is good reason to believe that close to 100% of all the ocean’s salps are infested with microplastics. This was even surprising to the researchers.

“I definitely thought some of them would be clean because they have a relatively quick gut clearance time,” Brandon said. The time it takes a salp to consume and defecate is two to seven hours. As filter feeders, salps are almost always eating.

From land to sea

Surprisingly, the concentration of microplastic wasn’t higher around the great garbage patch in the ocean. Instead, there seemed to be more pieces in surface waters closest to the shore. The most likely cause for this is runoff pollution from the land.

Other than that, the plastic distribution seemed to be quite uniform, which is quite concerning. This suggests that the plastic is spread throughout entire ecosystems. Since most plastics are too strong to be broken by bacteria and digestive systems, they are simply passed along the food chain. Humans don’t eat salps, but other things do — and other things eat those other things… and after a few connections, you end up in the range of fish that humans do eat.

“No one eats salps but it’s not far away on the food chain from the things you do eat,” Brandon said.

Some microplastics can also be small enough to enter the human bloodstream. While the consequences of this ingestion are not fully understood, there are valid concerns about potential health impacts.

Microbeads are not a recent problem. We’ve recently started to properly acknowledge it, but according to the United Nations Environment Programme, plastic microbeads appeared when the firs plastics appeared, more than 50 years ago. As the world is producing more and more plastic, the number of microplastics continues to grow dramatically. Researchers from several countries are working to understand their distribution and impacts. Studies such as this one fill an important knowledge gap in this direction.

You can read the full study here.

Stop climate change or the Emperor penguins die, a new paper warns

Unless we get a grip on climate heating, the emperor penguin is going the way of the dodo — extinct.

Image credits Christopher Michel / Flickr.

An international study led by researchers at the Woods Hole Oceanographic Institution (WHOI) reports that warming climate conditions might cause emperor penguins (Aptenodytes forsteri) to become extinct by the end of the century.

The Emperor’s new environment

“If global climate keeps warming at the current rate, we expect emperor penguins in Antarctica to experience an 86% decline by the year 2100,” says Stephanie Jenouvrier, a seabird ecologist at WHOI and lead author on the paper.

“At that point, it is very unlikely for them to bounce back.”

Emperor penguins live and die by sea ice, which is where they breed and molt. The animals build their colonies on spans of ice that satisfy very specific conditions: it must be locked to the Antarctic shoreline but close to open seawater (giving the birds access to food). Climate heating is melting sea ice, however, which effectively destroys the birds’ habitat, food access, and ability to reproduce.

For their study, the team combined a global climate model (created by the National Center for Atmospheric Research, NCAR) and a model of the penguin populations themselves. The first gave the team a rough idea of how sea ice will evolve in the future, especially in terms of where and when it will form or melt in the future. The second one worked to predict how colonies might react to the changes in their environment.

“We’ve been developing that penguin model for 10 years,” says Jenouvrier. “It can give a very detailed account of how sea ice affects the life cycle of emperor penguins, their reproduction, and their mortality. When we feed the results of the NCAR climate model into it, we can start to see how different global temperature targets may affect the emperor penguin population as a whole.”

The compound model was then used to examine three different scenarios. The first assumes an increase in global average temperatures of only 1.5 degrees Celsius (the goal set out by the Paris climate accord). The second involves a temperature increase of 2 degrees Celsius. The final scenario assumes no action was taken against climate change, leading to temperature increases of 5 to 6 degrees Celsius.

The first one led to a loss of around 5% of sea ice by 2100, causing a roughly 20% drop in the penguin population. The 2-degree warming scenario led to around 15% ice loss and a 30% drop in penguin numbers. The business as usual scenario was by far the most damaging, leading to almost complete loss of the penguin colonies.

“Under that scenario, the penguins will effectively be marching towards extinction over the next century,” she says.

The paper “The Paris Agreement objectives will likely halt future declines of emperor penguins” has been published in the journal Global Change Biology.

Roughly 98% of plastic waste in the ocean dissolves due to sunlight

Around 98% of all the plastic waste going into the ocean is unaccounted for. A new paper looks into where it winds up, and its effect on marine life.

It’s hard to overstate just how much plastic humanity has dumped into the ocean. Trillions of bits of plastic float into massive “garbage patches” along the subtropical gyres (rotating ocean currents). These patches have a dramatic impact on ocean life, ranging from the largest mammals to the humble bacteria.

And yet, these immense plastic patches only account for 1% to 2% of all the plastic going into the ocean. Which is quite a scary thought. One promising theory is that sunlight-driven chemical reactions break the materials down until they lose buoyancy, or become too small to be captured by researchers. However, direct, experimental evidence for the photochemical degradation of marine plastics remains rare.

Where’s the plastic?

“For the most photoreactive microplastics such as expanded polystyrene and polypropylene, sunlight may rapidly remove these polymers from ocean waters. Other, less photodegradable microplastics such as polyethylene, may take decades to centuries to degrade even if they remain at the sea surface,” said Shiye Zhao, Ph.D., senior author of the paper.

“In addition, as these plastics dissolve at sea, they release biologically active organic compounds, which are measured as total dissolved organic carbon, a major byproduct of sunlight-driven plastic photodegradation.”

The team, which included members from Florida Atlantic University’s Harbor Branch Oceanographic Institute, East China Normal University, and Northeastern University wanted to verify the theory. They selected polymers that are often seen in the garbage patches, and plastic-fragments collected from the surface waters of the North Pacific Gyre, and irradiated them for approximately two months using a solar simulator.

During this time, the team captured the kinetics of plastic degradation. To assess degradation levels, they used optical microscopy, electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy.

All in all, the team reports, plastic dissolution led to an increase in carbon levels in their surrounding water and reduced particle size of the plastic samples. The irradiated plastics fragmented, oxidized, and changed in color. Recycled plastics, overall, degraded more rapidly than polymers such as polypropylene (e.g. consumer packaging) and polyethylene (e.g. plastic bags, plastic films, and containers including bottles), which were the most photo-resistant polymers studied.

Based on the findings, the team estimates that recycled plastics tended to degrade completely in 2.7 years and that plastics in the North Pacific Gyre degrade in 2.8 years. Polypropylene, polyethylene, and standard polyethylene (which see ample use in food packaging) degrade completely in 4.3, 33, and a whopping 49 years, respectively, the team estimates.

The compounds leaching out of the plastic as it degrades seem to be broadly biodegradeable, the team reports. While levels of plastic-sourced carbon in ocean water pale in comparison to natural marine-dissolved organic carbon, the team found that it can inhibit microbial activity. The carbon from degraded plastics was readily used by marine bacteria, the team adds.

“The potential that plastics are releasing bio-inhibitory compounds during photodegradation in the ocean could impact microbial community productivity and structure, with unknown consequences for the biogeochemistry and ecology of the ocean,” said Zhao.

“One of four polymers in our study had a negative effect on bacteria. More work is needed to determine whether the release of bioinhibitory compounds from photodegrading plastics is a common or rare phenomenon.”

Samples in the study included post-consumer microplastics from recycled plastics like a shampoo bottle and a disposable lunch box (polyethylene, polypropylene, and expanded polystyrene), as well as standard polyethylene.

The paper “Photochemical dissolution of buoyant microplastics to dissolved organic carbon: Rates and microbial impacts” has been published in the Journal of Hazardous Materials.

3D-printed coral can help save reefs and the fish that live there

New research is looking into 3D-printed corals as a possible cure for the world’s ailing reefs and the animals that call them home.

Close-up of a brain coral.
Image via Pixabay.

Coral reefs aren’t faring very well anywhere on Earth right now. Environmental shocks such as climate shifts, more acidic waters, and pollution are pushing corals — often beyond their limit. As the reefs wither and die, the animals that live there find themselves essentially homeless.

New research at the University of Delaware (UD) is looking into the use of 3D-printed corals as a potential fix.

Hit print

“If the fish on a reef won’t use the 3D-printed coral models as a habitat in the wild, it could place them at greater risk for predation by other larger species,” said Danielle Dixson, an associate professor in UD’s College of Earth, Ocean and Environment’s School of Marine Science and Policy and the paper’s second author.

“If coral larvae won’t settle on 3D-printed materials, they can’t help to rebuild the reef.”

The team has shown that 3D-printed objects don’t impact the behavior of damselfish (a species closely associated with coral reefs) or the survival of a settling stony coral. Fish showed no preference for any of the materials used to print the corals, which suggests that biodegradable materials (such as cornstarch) could successfully be employed in lieu of plastics. This latter finding is particularly relevant in the context of today’s discussion on the role of plastic pollution in the ocean.

The team worked with damselfish and mustard hill coral larvae, which they presented with a coral skeleton and four 3D-printed corals (made from different materials). These artificial corals were replicas of an actual coral skeleton (that the team took around 50 images of using a smartphone). All four filaments used were low-cost, the researchers explain, and widely available; they included polyester and two biodegradable materials, one made from cornstarch and the other from cornstarch and stainless steel powder.

Blue-green damselfish (Chromis viridis) are a common coral-associated fish found in the Indian and Pacific Oceans, while mustard hill corals (Porites astreoides) are a stony coral found in the Caribbean Sea, the team explains. They placed the fish into a tank alongside the corals in a ‘cafeteria-style’ choice experiment — basically, they sat around to see if the fishes preferred one habitat/coral over another. Behavioral analysis showed that the fishes didn’t have a preference between the native coral skeleton and the 3D-printed ones. The fishes’ activity levels (such as frequency of movement and the total distance they swam in the tank) also stayed constant regardless of the habitat they were provided with.

UD alumnus Emily Ruhl, the study’s first author, says that it was surprising to see the fishes behaving the same near a natural or artificial coral skeleton. Furthermore, mustard hill coral larvae settled more readily on 3D-printed coral surfaces than on no settlement surface (as would be the case in a reef destroyed by a storm, for example).

“I thought the natural skeleton would elicit more docile behavior compared to 3D-printed objects,” said Ruhl, who earned her master’s degree in marine biosciences at UD in 2018. “But then we realized the small reef fish didn’t care if the habitat was artificial or calcium carbonate, they just wanted protection.”

When coral reefs degrade, they often lose structural complexity. Reef-associated fish, which tend to spend all of their lives in the reef, rely on this complexity for food and shelter — simpler reefs just don’t give them enough opportunities. Without the proper habitat, they don’t grow to their full size. This mechanism leaves the reef open to an overgrowth of algae (on which larger fish feed) that can destroy the whole reef.

“Offering 3D-printed habitats is a way to provide reef organisms a structural starter kit that can become part of the landscape as fish and coral build their homes around the artificial coral,” Dixson said. “And since the materials we selected are biodegradable, the artificial coral would naturally degrade over time as the live coral overgrows it.”

In addition, 3D-printed coral models can be useful as a control for fish-related laboratory studies, enabling researchers to provide each fish an identical habitat, something that is currently not possible with the use of coral skeletons.

The paper “3D printed objects do not impact the behavior of a coral-associated damselfish or survival of a settling stony coral” has been published in the journal PLOS ONE.

Whales blow bubbly nets to help them fish — and we have it on camera

New research at the University of Hawaiʻi at Mānoa is shedding light on whales’ bubble-net fishing.

Cetaceans, the group that whales and dolphins are part of, are pretty smart creatures. We’ve known that they can use ‘nets’ to catch food — the animals dive deep and swim in a circle around their prey, blowing out bubbles as they do. The rising body of air traps fish in the middle. Other whales then simply have to swim up with their mouths open and cash in on the food with virtually zero effort.

Now, new research is showing what this process looks like from the perspective of the whales.

Like shooting fish in a barrel

“We have two angles. The drone’s perspective is showing us these bubble nets and how the bubbles are starting to come to the surface and how the animals come up through the bubble net as they surface, while the cameras on the whales are showing us the animal’s perspective,” said marine biologist Lars Bejder of the university’s Marine Mammal Research Program.

The study included members from the Alaska Whale Foundation, members of Stanford University’s Goldbogen Lab, and from the Bio-telemetry and Behavioral Ecology Lab at the University of California, Santa Cruz. Together with Bejder and colleagues at UH Mānoa, they stuck cameras and accelerometers on whales using suction cups. The material was supplemented by drone footage of the behavior from above to create an “exciting” set of data, Bejder explains.

Migratory humpback whales spend their summer along Alaska’s coast before heading down to Hawaii for winter — where they’ll raise a new generation of whales. However, all that romance leaves little time for feeding (the humpbacks eat very little during their breeding period), so fat reserves need to be plumped up before the journey.

That’s where the bubble nets come into play. Whales could just swim around and filter krill the old fashioned way, but time is of the essence during winter. The bubble-fishing technique allows groups of whales to invest as little time and energy as possible while maximizing their caloric intake. It’s a win-win approach.

The team notes that the behavior is learned — the whales don’t instinctively engage in bubble fishing. Not all humpbacks hunt this way, they add, and there is a pretty wide range of variations in technique among those who do. However, it’s always a cooperative process, requiring groups of whales to work together to ensure that everyone has a chance at the buffet.

The team reports that the behavior has also been observed Bryde’s whales (Balaenoptera edeni) and bottlenose dolphins (genus Tursiops) off the coast of Florida. Instead of using bubbles, however, these groups of cetaceans engage in mud-ring feeding: this involves stirring up a ring of sediment in shallow waters to trap schools of fish.

This study was done in an effort to understand just what is going on with humpback whales. A ban on commercial whaling in 1985 saved the species from almost assured extinction and, while they have recovered somewhat, there has been a substantial decline in humpback whale sightings over the last five years, the researchers report. Some of the factors they are considering include changes to food populations, anthropogenic impacts on their habitat, and climate breakdown.

But, while the researchers ply their trade, we’re left with some awesome shots of whales doing whale things — of course no one’s complaining.

“The footage is rather groundbreaking,” Bejder said. “We’re observing how these animals are manipulating their prey and preparing the prey for capture. It is allowing us to gain new insights that we really haven’t been able to do before.”