New research from Flinders University shows how changes in diatoms (microalgae) could further undermine the foundation of aquatic life’s food webs—as well as vital deep-sea carbon capture or sequestration.
A new study published in Marine Ecology used high-tech methods to test common microalgal species to assess how various stressors, including acidification from excessive carbon dioxide (CO2) levels, affect absorption of trace metals and therefore undermine their overall health and role in Earth’s carbon cycling.
Although microscopic, the single-celled algae diatoms that live in oceans, lakes, rivers, and even damp soil are among the most important organisms on Earth, as they produce a significant portion of oxygen in the atmosphere.
Diatoms account for 40%–50% of primary production in oceans, and they contribute to organic carbon being exported to the deep ocean by fixing CO2 from near-surface waters, says senior author Professor Sophie Leterme, director of the ARC Industry Transformation Training Centre for Biofilm Research and Innovation at Flinders University’s College of Science and Engineering.
“We showed that changes in the ocean pH can affect the growth, abundance and elemental composition of these diatoms,” said Professor Leterme. “We need to investigate how these changes interplay between various trace elements and can lead to broader ecological impacts, such as disruption to marine food webs, reduced carbon and silicon export, and increased microbial and nutrient activity.”
Rising carbon emissions affect pH levels in seawater, which can alter planktonic algae’s absorption of trace elements including iron, zinc, and cadmium, which are essential for inorganic carbon acquisition.
The dissolution of CO2 into the ocean has already induced a global drop in pH of 0.1 units since the end of the Industrial Revolution, and values are expected to drop another 0.3–0.6 units by the end of this century.
Diatom species are great bio-indicators, often used to assess water quality and boost understanding of how ongoing ocean acidification and rising water temperatures downgrade their physiology and functioning—which have important consequences for the future of oceans.
The Flinders researchers say a better understanding of how these complex processes work in seawater will help find solutions, including the development of novel biofilms to reduce shipping pollution in harbors.
Using seawater samples collected in South Australia’s Gulf St Vincent and from the CSIRO algae collection, the researchers’ highly sensitive neutron activation analysis was used in experimental setups on the species Thalassiosira pseudonana and Nitzschia navis-varingica.
The experiments, supported by ANSTO expertise, showed how trace metal uptake by marine diatoms could be applied to other marine organisms’ absorption of a wide range of other elements in the environment.
“While a higher abundance and growth of diatoms might be beneficial to reduce carbon dioxide levels, the impact of lower concentrations of major and trace elements in the environment is not well understood.”
The research article—’The impact of ocean acidification on the sorption of trace metals by diatoms‘ (2026) by Sophie C Leterme, Tamar Jamieson, Alessandra Mazzoli, Angus Hambrook, Rachel S Popelka-Filcoff, John Bennett, and Attila Stopic—has been published in Marine Ecology (Wiley). DOI: 10.1111/maec.70112.
Seven breached Planetary Boundaries continue to worsen as record ocean heat, droughts, floods, wildfires and extreme heat reveal an Earth system under strain, according to the latest Planetary Health Check. The annual update is authored by more than 60 scientists, and produced by the Planetary Boundaries Science Lab at the Potsdam Institute for Climate Impact Research (PIK).
The Planetary Boundaries describe the interconnected Earth-system processes that must remain within safe limits to preserve the planet’s stability and resilience. Seven of the nine Planetary Boundaries are now transgressed, with ocean acidification the latest to breach its boundary in 2025. All seven are now at their highest recorded levels of transgression.
The seven transgressed boundaries are: climate change, change in biosphere integrity, land system change, freshwater change, modification of biogeochemical flows, introduction of novel entities and ocean acidification. Only the stratospheric ozone depletion and atmospheric aerosol loading boundaries have shown improvement over the last decade. However, the authors caution that global progress may mask unsafe aerosol levels persisting in some regions.
“The diagnosis is unambiguous. Pressure is rising across every Planetary Boundary already outside the safe operating space. It means that the risk of large-scale, persistent and potentially irreversible change is increasing, while our margin for error in tackling these problems is shrinking,” commented Boris Sakschewski, PIK scientist and lead author of the report.
“We do not have the luxury of time, but we do have the knowledge, capacity and solutions to change course. Accelerating action to return to the safe operating space across all Planetary Boundaries is essential to protect lives and livelihoods, and to deliver on the promise of shared future prosperity,” said Johan Rockström, PIK Director and co-author of the report.
A year of extreme events highlights escalating risks
The report comes after 12 months marked by extremes across land and oceans. Human-caused warming intensified several major weather extremes, while degraded ecosystems, water stress, land-use change, exposure and social vulnerability often magnified their impacts.
Pakistan’s 2025 monsoon floods affected more than 6.9 million people. Global ocean heat content reached a new record in 2025, with Hurricane Melissa rapidly ramping up to a Category 5 Hurricane and striking Jamaica after passing over exceptionally warm seas. January 2023 to September 2025 saw bleaching-level heat stress impacting approximately 84.4 percent of the world’s coral reef area, making it the largest global coral-bleaching event observed to date.
In 2026, Western Europe experienced its hottest June-July period on record, accompanied by drought across France, Spain, Germany and the United Kingdom, with major wildfires across Europe and Canada. Record-breaking heat was also recorded in Japan, South Korea and parts of the Middle East.
Hindou Oumarou Ibrahim, Chair of the Planetary Guardians said, “Read that list again: Pakistan, the Caribbean, Europe, the reefs beneath our oceans. These are not separate emergencies; the planet is telling us, in every region at once, that it is out of balance. As Chair of Planetary Guardians, I hear this same story wherever I go, whether from a pastoralist watching the rains fail season after season or a coastal community watching the sea rise. The 2026 Planetary Health Check puts data behind what communities on the frontlines already know from living it. We do not have the luxury of treating these as separate crises any longer.”
“Any kind of movement requires patience, trust, and the will to keep going, even when it may be easier to stop. The 2026 Planetary Health Check tells us we need that same collective resolve now, applied to the whole planet. Seven of nine boundaries are broken, and no single nation can restore them alone; this is a peace process the entire world must commit to, together, starting now,” said Juan Manuel Santos, former President of Colombia and Co-Vice Chair of the Planetary Guardians.
Natural carbon sinks under pressure
Vegetation and soils absorb a substantial share of human carbon dioxide emissions, but repeated heat, drought, fire and ecosystem degradation can reduce carbon uptake and, in some regions, turn ecosystems from sinks into carbon sources.
This year’s report discusses whether the models that we use to calculate the land carbon sink may overestimate its resilience.
“Our path to net zero emissions relies on functioning carbon sinks. Current observations raise the alarm that our planet may be losing its buffering capacity against the increasing pressures we’re putting on it,” Sakschewski said.
Planetary Boundaries Science (PBScience), 2026: Planetary Health Check 2026. Potsdam Institute for Climate Impact Research, Potsdam, Germany.
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Woods Hole, Mass. (September 16, 2026) — Eastern oyster larvae are only 100–300 micrometers long, but their dense calcium carbonate shells make them substantially heavier than the surrounding seawater. A new study led by the Woods Hole Oceanographic Institution (WHOI) shows that this excess weight allows gravity to drive the feeding currents the larvae use to bring food to their mouths, a finding that reveals a critical role for gravity in how these tiny animals feed and survive.
The study, published in Physical Review Fluids, challenges the long-standing assumption that larvae this small rely primarily on the drag produced by swimming to generate the feeding currents that carry food toward their mouths. While it may be true in the case of many small plankton, oyster larvae prove to be an exception, placing them in the same gravity-dominated feeding regime as much larger copepods and revealing an unexpected role for their shells in helping them feed. The key difference is that drag depends primarily on the larva’s movement through the water, but gravity depends on the difference in density between the larva and the surrounding seawater.
“This tells us that the shell is doing more than just protecting the animal,” explained Houshuo Jiang, a senior scientist at WHOI and sole author of the study. “It is actually helping the larva feed. That means anything that changes the shell could also change how the larva gets its food.”
Jiang captured the larvae’s feeding behavior using a high-speed microscale imaging system (HSMIS) developed in his laboratory. Rather than observing larvae under a conventional microscope, the system uses long-working-distance optics and a high-speed camera to record animals swimming freely in a larger volume of seawater. He also added tiny tracer particles to the seawater and used a technique called micro-particle image velocimetry to track how those particles moved around the larvae, allowing him to measure the invisible currents generated as the larvae feed.
“Usually, when you use a microscope, you need a lot of light, and if you put a lot of light on these tiny animals, you can heat the water and change their behavior,” Jiang said. “And conventional cameras are not fast enough to capture these very rapid movements. So we developed a system that uses a low-heat red LED and a high-speed camera that can record 2,000 frames per second. That lets us watch the larva in a larger volume of water without disturbing it and actually see how the water moves as it feeds.”
These findings offer a possible explanation for results from earlier experiments that raised bivalve larvae in space. In a 1999 study, scientists raised bivalves in microgravity and found that larvae reared without normal gravity tended to have lower feeding and growth rates and were in poorer condition than larvae kept under normal gravity. At the time, the physical reason for those differences was not clear.
“Thanks to high-speed imaging, we now see that gravity is essential for their feeding,” Jiang said. “If a larva is dealing with a stressor that affects its ability to build a dense shell, that could also affect the physical force that helps it feed. Understanding that connection gives us a better way to think about how environmental stressors can affect larvae at one of the most vulnerable stages of their lives.”
Oysters are particularly vulnerable to ocean acidification, which changes seawater chemistry and makes it harder to build calcium carbonate shells. This study’s findings suggest that if acidification alters shell formation enough to reduce a larva’s density relative to seawater, it could also weaken the gravity-driven feeding current it relies on to bring food to its mouth, potentially affecting young oysters.
Eastern oysters also face other challenges including pollution, disease, and overfishing. According to NOAA Fisheries’ Commercial Fishing Landings database, the commercial harvest of eastern oysters in the United States fell by about $15.2 million, or 7.2%, from 2023 to 2024.
“Ultimately, this could help us better understand what determines whether oyster larvae survive and become part of the adult population,” Jiang said. “That matters for fisheries and aquaculture because the number of larvae that survive each year helps determine the oysters available to harvest in the future. If environmental stressors affect both shell formation and feeding, we need to understand those effects to better predict how oyster populations will respond to a changing ocean.”
Global analysis finds rising ocean temperatures could reduce omega-3 fatty acids across marine food webs, with implications for seafood nutrition.
A global study has found that ocean warming could reduce levels of omega-3 fatty acids in fish and other marine organisms, potentially affecting the nutritional value of seafood. Photo by Damon Hall.
Ocean warming could reduce levels of omega-3 fatty acids in fish and other marine organisms, potentially affecting the nutritional value of seafood, according to a global study.
Researchers analyzed 489 experiments from 143 published studies involving 132 marine species, including algae, invertebrates and fish. The study, published in Global Change Biology, examined how warming and ocean acidification affect fatty acids throughout marine food webs. The researchers found that warming generally reduced omega-3 fatty acids, with larger declines occurring as temperatures increased.
“Our new study shows many fish and other seafood will become less rich in omega-3s over time, due to rising ocean temperatures as the climate changes,” the researchers wrote in an article for The Conversation. “In fact, we found omega-3 could drop by 50 percent under very high warming scenarios. This is very bad news for human health but also for the health of other animals in the food web.”
Marine algae produce EPA and DHA, two important omega-3 fatty acids, and sit at the base of marine food webs. Those nutrients move through the food chain as algae are eaten by other organisms, which in turn are consumed by fish and larger animals.
“If EPA and DHA levels get disrupted along the food chain, less of those crucial fatty acids are available for animals higher up – including humans,” the researchers wrote.
The effects varied among species and experiments, but the overall analysis found warming had a stronger effect on fatty acids than ocean acidification. “We found ocean acidification had less impact on fatty acids than warming, suggesting rising temperature is the dominant driver of this problem,” the researchers wrote.
The results should not be read as a prediction that omega-3 levels in seafood will fall by 50 percent across the board. The study combined results from controlled experiments, and responses varied among species and experimental conditions. The researchers called for more long-term studies under realistic environmental conditions to improve predictions of how climate change will affect the nutritional quality of marine organisms.
The findings could have implications for fisheries and aquaculture because omega-3 availability is important to both the nutritional value of seafood and the health of marine organisms. The study’s authors said anticipating climate-driven nutritional declines will be important for fisheries management, aquaculture and food security.
The researchers also pointed to better use of fish processing byproducts as one way to make more of existing sources of omega-3. With up to 80 percent of fish parts discarded during food processing, they suggested those parts could be used to produce omega-3-rich fish oil or as nutritional ingredients in aquaculture feed.
“Given the projected declines in nutrition into the future, these wasted fish parts could be better utilized,” the researchers said. “This might, for instance, include making fish oil products rich in omega-3 and other nutrients, or using these fish parts as nutritional aquaculture feed.
Our oceans are in trouble and new research from Flinders University shows how changes in diatoms (microalgae) could further undermine the foundation of aquatic life’s food webs – as well as vital deep-sea carbon capture or sequestration.
A new study published in Marine Ecology used high-tech methods to test common microalgal species to assess how various stressors, including acidification from excessive carbon dioxide (CO₂) levels, affect absorption of trace metals and therefore undermine their overall health and role in Earth’s carbon cycling.
Although microscopic, the single-celled algae diatoms that live in oceans, lakes, rivers and even damp soil are among the most important organisms on Earth as they produce a significant portion of oxygen in the atmosphere.
Diatoms account for 40%-50% of primary production in oceans, and they contribute to organic carbon being exported to the deep ocean by fixing CO₂ from near-surface waters, says senior author Professor Sophie Leterme, director of the ARC Industry Transformation Training Centre for Biofilm Research and Innovation at Flinders University’s College of Science and Engineering.
“We showed that changes in the ocean pH can affect the growth, abundance and elemental composition of these diatoms,” says Professor Leterme. “We need to investigate how these changes interplay between various trace elements and can lead to broader ecological impacts, such as disruption to marine food webs, reduced carbon and silicon export, and increased microbial and nutrient activity.”
Rising carbon emissions affect pH levels in seawater, which can alter planktonic algae’s absorption of trace elements including iron, zinc and cadmium, which are essential for inorganic carbon acquisition.
The dissolution of CO₂ into the ocean has already induced a global drop in pH of 0.1 units since the end of the Industrial Revolution, and values are expected to drop another 0.3–to-0.6 units by the end of this century.
Diatom species are great bio-indicators, often used to assess water quality and boost understanding of how ongoing ocean acidification and rising water temperatures downgrade their physiology and functioning – which have important consequences for the future of oceans.
The Flinders researchers say a better understanding how these complex processes work in seawater will help find solutions, including the development of novel biofilms to reduce shipping pollution in harbours.
Using seawater samples collected in South Australia’s Gulf St Vincent and from the CSIRO algae collection, the researchers’ highly sensitive neutron activation analysis was used in experimental setups on the species Thalassiosira pseudonana and Nitzschia navis-varingica.
The experiments, supported by ANSTO expertise, showed how trace metal uptake by marine diatoms could be applied to other marine organisms’ absorption to a wide range of a wide range of other elements in the environment.
“While a higher abundance and growth of diatoms might be beneficial to reduce carbon dioxide levels, the impact of lower concentrations of major and trace elements in the environment is not well understood.
The research article – ‘The impact of ocean acidification on the sorption of trace metals by diatoms’ (2026) by Sophie C Leterme, Tamar Jamieson, Alessandra Mazzoli, Angus Hambrook, Rachel S Popelka-Filcoff, John Bennett and Attila Stopic – has been published in Marine Ecology (Wiley). DOI: 10.1111/maec.70112.
New mechanistic review shows warming, pollution, and pH compete for same ATP pool powering every shell
Photo: Dave Meckler/unsplash.com
A review published Monday in Frontiers in Marine Science is the first to map exactly which molecular components inside a shellfish shell each ocean stressor attacks — and to show why combining them produces damage no single-stressor model can predict. Ocean acidification suppresses one set of enzymes. Warming shunts cellular energy toward heat-shock proteins. Heavy metal contamination poisons crystal-growth sites through a different mechanism entirely. A common anti-inflammatory drug, at concentrations already detectable in urban coastal waters, destroys 99 percent of shellfish larvae in 96 hours when paired with even moderately acidified seawater. And all five stressors draw from the same limited pool of ATP — the cellular energy currency that powers shell construction. When they hit simultaneously, as they do in every real coastal environment, the damage can tip past any threshold the animal can compensate for.
The paper — authored by Wenxiao Guo, Hao Li, Dongfang Li, Peiyao Sun, and Ran Zhao of Shenzhen MSU-BIT University — synthesizes research covering literature through May 2026 across bivalves (oysters, mussels, clams, scallops) and gastropods (snails, abalone), the groups that form the commercial and ecological backbone of global shellfish aquaculture. Its central contribution is a conditional hierarchical response framework: a model linking ionoregulatory and acid-base disruptions at the molecular level to defects in crystal microstructure to compromised shell physical properties — while explicitly accounting for compensatory mechanisms, nonlinear thresholds, species-specific strategies, and life-stage-specific outcomes. For the aquaculture industry, the framework offers something more immediately actionable: a map of why current adaptation strategies, almost all oriented around single-stressor OA response, may be systematically underestimating the combined burden their animals are already carrying.
Shell Construction Is Precision Molecular Clockwork
To understand what each stressor breaks, it helps to understand what has to work.
Molluscan shells are built from calcium carbonate, which makes up more than 95 percent of their dry mass, plus a small but critical fraction of organic matrix — proteins, polysaccharides, and lipids that orchestrate how crystals form, stack, and align. At the center of the process is carbonic anhydrase (CA), an enzyme that converts carbon dioxide and water into bicarbonate ions — the raw material for calcium carbonate deposition. Another key protein, nacrein, simultaneously catalyzes bicarbonate availability and inhibits crystal overgrowth through a specialized repeat domain, giving the organism fine control over shell architecture. The shell matrix proteins Aspein and N16 govern crystal nucleation and orientation in the prismatic and nacreous layers respectively. A structural polysaccharide, chitin, provides the scaffold on which crystals nucleate and grow. Calcium ions reach the crystallization site via Ca²⁺-ATPase, an active transporter that requires ATP to run.
This is not a passive chemical precipitation process. It is a biologically orchestrated system with multiple interdependent molecular actors. When any one of them is disrupted, the effects propagate upward — from abnormal gene expression to defects in crystal microstructure to shells that are measurably softer, more porous, or structurally misshapen. The phylum Mollusca encompasses more than 70,000 species; the review focuses on bivalves and gastropods, which together form the commercial and ecological centerpiece of global shellfish systems.
What Makes Ocean Acidification Different From — and Worse With — Every Other Stressor
Ocean acidification (OA) operates through three simultaneous routes: it lowers the carbonate saturation of seawater, making it thermodynamically harder to deposit calcium carbonate; it acidifies body fluids, forcing animals to spend metabolic energy on acid-base regulation that would otherwise fund shell construction; and it directly suppresses the genes and enzymes that build shells.
The ocean has already absorbed enough anthropogenic CO₂ to lower average ocean pH by approximately 0.11 units from a preindustrial baseline of roughly 8.20. Model projections indicate a further drop of 0.3–0.4 pH units by 2100, with declines of up to 0.7 units possible by 2300. These global averages substantially understate regional variability in coastal and estuarine zones — precisely where most shellfish aquaculture occurs.
In the blue mussel Mytilus edulis, carbonic anhydrase activity remained stable at 550 µatm CO₂ but dropped significantly at 750 µatm. In the pearl oyster Pinctada fucata, shell hardness, calcium content, and total weight were unchanged at pH 8.10 and 7.70 but collapsed at pH 7.40, suggesting OA damage can arrive not as a gradual slide but as an abrupt deterioration once a critical saturation threshold is crossed. Some species show mechanical weakening even before carbonate saturation falls below the dissolution threshold: in the thick-shelled mussel Mytilus coruscus, both whole-shell compressive strength and shell closure force fell significantly at pH 7.80 — well above the level at which aragonite becomes thermodynamically unstable — apparently because physiological acid-base disorder drives the damage before the chemistry does.
Shell architecture also shapes vulnerability. Under identical acidification stress, a gastropod (Tegula funebralis) whose outer layer consists of a fibrous prismatic calcite structure exposing many crystal edges to seawater lost 14–25% of its shell density. A gastropod (Nucella ostrina) armored with a dense homogeneous calcite layer lost only 8–11%. The geometry of crystals, not just their chemistry, determines how quickly an acidified ocean erodes them.
Larvae face the sharpest risks. In larval bay scallops (Argopecten irradians), shell length was reduced by 11.5% at pH 7.39, detectable within just 12 hours of exposure. Larvae that experienced early growth deficits did not subsequently catch up, suggesting that OA imposes a lasting developmental penalty rather than a temporary one. It was the early-stage death toll — larval mortality reaching 80 percent in Pacific Northwest hatcheries between 2005 and 2009 — that first brought OA’s shellfish consequences into sharp commercial focus, and led to the development of real-time aragonite saturation monitoring systems now standard in the industry.
Similar to weather forecasts for the atmosphere, numerical models can also be used to forecast ocean conditions. Since the ocean changes more slowly, particularly below the surface, forecasts of ocean conditions can be made for multiple months out. These forecasts can be helpful for marine resource managers by providing early warning of anomalous events, such as marine heatwaves or more acidic ocean conditions.
A new study, focused on the Bering Sea, tested an ocean model to see if it was capable of forecasting acidified bottom water conditions several months in advance. The cold and carbon rich waters of the Bering Sea make the region vulnerable to ocean acidification (OA) due to the naturally low carbonate saturation states. Scientists assessed the ocean model by running a suite of reforecasts (retroactively forecasting previous years) and comparing to the conditions that did occur.
They found that the ocean forecasting model was skilled at predicting anomalies in bottom water pH on lead times up to nine months owing primarily to strong persistence. However, predictive skill for finer scale spatial anomalies was more limited and variable. They found that the model can be an effective tool to notify marine resource managers several months in advance of the expected development of relatively more acidic water conditions. This early warning can enable managers to make tactical decisions regarding upcoming fisheries quotas and assist rebuilding plans following fishery closures, such as the red king crab fishery that has faced recent closures and is threatened by OA.
Learn how NOAA Pacific Marine Environmental Laboratory studies the ecosystems of the North Pacific Ocean, Bering Sea and U.S. Arctic to improve understanding of ecosystem dynamics and applies that understanding to the management of living marine resources by clicking here.
Disaster declarations have been declared for both the Bering Sea snow crab and Bristol Bay red king crab fisheries in recent years. Corey Arnold/Alaska Bering Sea Crabbers
Crab populations in the Bering Sea are struggling. And researchers say climate change is a big cause. A new tool described in a study published Aug. 3 in the Journal of Geophysical Research Oceans will help researchers predict one of climate change’s biggest threats to crabs: ocean acidity. The study’s authors hope their work can help crabbers and fishery managers.
“I’m excited with this new model and study,” said Jamie Goen, the executive director of the nonprofit trade association Alaska Bering Sea Crabbers. “It will help us better understand what could be happening and how that might impact fisheries.”
Darren Pilcher, the study’s lead author and an oceanographer at the University of Washington, said he started the study because of requests from fisheries stakeholders.
The ocean absorbs a quarter of our carbon emissions, which make the water more acidic when the two mix. Acidic conditions are harmful for many different animals. This is especially true for shellfish, like crabs.
“They can eat more, and that helps a little bit, only to a certain point,” Pilcher said. “In fact, in some of the previous experiments with red king crab, if you lower the pH to a value of 7.5, the crab just die.”
Scientists have pointed to factors from climate change, like ocean acidification, as the reason the number of Bristol Bay red king crabs has plummeted in recent years. Goen said that other species, like snow crab, have also tanked.
“When I started this job eight years ago, we had 60 vessels in the fleet,” she said. “But obviously with the collapse of snow crab and the closure of red king crab, we’re down to 40 active vessels right now.”
Pilcher and his team wanted to help the fishery by creating a tool that could forecast acidity in the Bering Sea. Ocean acidity doesn’t exist in a vacuum, so the first step was to make a computer model of the entire Bering Sea, recreating the water conditions at any given time. They put a lot of existing data into their model on ocean conditions over time, measuring things like temperature, currents, and distribution of phytoplankton.
Then they added in ocean acidity data collected from the region, and tested their new tool by having it forecast the acidity of the Bering Sea over a roughly 40 year period. They compared that forecast to what actually happened each year.
Pilcher said they also compared their new tool to a simple baseline model, which predicts that conditions at the beginning of the year will stay the same throughout the year.
“It’s actually a really good forecast for the ocean because the ocean doesn’t really change that quickly,” he said.
They tested both models for both the bottom and surface of the ocean. Pilcher found that they were both equally good at predicting acidity at the bottom of the ocean. But he said their new model did a lot better at predicting surface temperatures than the baseline model.
“It kind of makes sense because the bottom waters, especially during the summer, are more cut off from the atmosphere,” he said. “Whereas of course the surface is still very connected to the atmosphere and is responding to it on a quicker time frame.”
Pilcher hopes the information from their experiment, and his new model, can inform future management.
“We could say, ‘Hey, this is what we’re predicting for the upcoming summer,’ so that we can give everybody a little bit advance notice if there are, say, worse acidification conditions,” he said.
He said they’ve also discussed partnering with a new king crab mariculture project happening on St. Paul Island. The plan is to raise larval Bristol Bay red king crabs in a lab, and release them back into Bristol Bay when they reach a certain size. But because juvenile crabs are more vulnerable to ocean acidity than adults, Goen said Pilcher’s model could provide important data.
“Where I could see an immediate benefit is knowing if those waters are going to be unusually acidic or higher in temperature in a given year,” she said. “Then maybe that’s not the best year to put some brood stock back into Bristol Bay.”
Goen said she hopes for more research on the changing ocean chemistry in the Bering Sea, so fishermen can make informed decisions. But for now, she said Pilcher’s results are very promising.
A chemistry tug-of-war between ocean acidity and carbon in warming oceans determines when and where these damaging events strike.
This data visualization shows an intense marine heat wave in the Atlantic Ocean and Mediterranean Sea on 13 August 2026. New research examines the relationship between marine heat waves and ocean acidification. Credit: European Union, Copernicus Marine Service Data
Marine heat waves and extreme ocean acidification events are each damaging on their own. But when both stressors hit simultaneously, their individual effects can be exacerbated.
That threat may be best exemplified by “the Blob” of 2013–2015, during which both a marine heat wave and an ocean acidification extreme event hit the northeastern Pacific. Fisheries were closed, marine mammals were stranded, seabirds died, and sea creatures either changed their distribution or perished.
But our understanding of these compound heat-acidity ocean extreme events is limited, with more research focused on the marine heat wave component than on the acidification aspect.
Gregor and Gruber used 43 years of monthly data (1982–2024) on surface ocean temperatures and acidity to determine when, where, and why compound heat-acidity extreme events have occurred. They defined extreme events as those situations when detrended acidity and temperature exceed their 95th percentiles.
Compound ocean heat-acidity events happen more often than would be expected by chance, the authors found. In the low to midlatitudes, they occur roughly 4 times more often than compared to chance, mostly in places with permanent stratification. In these places, heat waves drive waters to be more acidic. The compound events were least common in the eastern equatorial Pacific and around the poles, where deep waters upwell to the surface. When marine heat waves strike in these upwelling regions, a warm lens (top layer of water) prevents the surfacing of the deep acidic waters, leading to unusually low acidity for the region.
A majority (73%) of compound heat-acidity extreme events in the study period were smaller than 500,000 square kilometers (193,000 square miles, roughly the size of Spain) and lasted for about a month. But a few events, like the Blob in 2015, lasted for more than a year, sometimes with long-lasting consequences.
El Niño and La Niña events are important drivers of these compound events, but the events seldom happen at the weather events’ epicenter in the equatorial Pacific. During El Niño, warmer waters create a lens that prevents upwelling, thus reducing the typical acidity of the region. And during La Niña, cold, deep waters with higher acidity upwell, resulting in only an acidification extreme. However, it is in the neighboring regions where the knock-on effect of this warming or acidity causes compound extremes to occur.
Ancient ocean acidification triggered one of the ocean’s most severe extinctions
New research examining hundreds of microscope fossils offers one of the clearest examples yet of how rising CO2 can alter ocean chemistry and harm marine life. Above, Jonathan Chen, the study’s lead author, uses a fine-tipped brush to separate tiny fossils from surrounding sediment.
A 113-million-year-old marine murder mystery may finally be solved.
Using chemical clues locked inside microscopic fossils, Northwestern University scientists found evidence that ocean acidification drove one of the largest extinction events in the history of planktic foraminifera — tiny shell-building organisms that help regulate Earth’s carbon cycle.
The scientists attribute the acidification to the eruption of the Kerguelen Plateau, a massive volcanic province in the southern Indian Ocean. During the Early Cretaceous period, the volcanic province spewed vast quantities of carbon dioxide (CO2) into the atmosphere. As the oceans absorbed that CO2, seawater became more acidic, making it more difficult for marine organisms to build and maintain their shells.
The new study, published in Science, marks the fifth Northwestern-led investigation to link widespread volcanic eruptions to ocean acidification and extinction, strengthening evidence for a recurring pattern that played out across more than 60 million years.
The findings also provide one of the clearest examples yet of how rising CO2 can alter ocean chemistry and harm marine life. As current-day oceans absorb human-generated CO2, the ancient events offer a natural experiment for understanding how modern ocean acidification might affect shell-building organisms and the ecosystems that depend on them.
“By examining fossils, scientists already knew surface plankton were getting smaller and building thinner shells, which suggested they were under stress,” said Northwestern’s Jonathan Chen, who led the study. “But we didn’t know that ocean acidification was responsible. By measuring the fossils’ calcium isotopes, we finally provided that missing evidence. We found a giant increase in calcium isotope ratios right as the extinction unfolded, indicating the organisms’ shells were calcifying at a much slower rate. That was the smoking gun linking ocean acidification to the severe biocalcification stress that ultimately led to their extinction.”
Genome-wide data revealed a mahimahi evolutionary history shaped by vicariance, ocean currents and local environments, needing models, functional genomics and selection tests for climate adaptation
This study examined the worldwide population structure of the cosmopolitan pelagic fish Coryphaena hippurus using a dataset of 8.7 million SNPs and complete mitochondrial genomes. The analyses reveal, for the first time, four genetically distinct populations corresponding to the major oceanic basins: the Atlantic, Pacific, Indian Ocean and Mediterranean Sea. Photo of Atlantic mahimahi by NOAA Fisheries.
The processes that generate and sustain marine biodiversity are still incompletely understood, especially in open-ocean systems where high dispersal potential is expected to prevent strong population differentiation. Understanding how evolutionary forces shape divergence or speciation in such environments requires detailed knowledge of a species’ life history and its interactions with key environmental variables.
In a study by Píndaro Díaz Jaimes and coworkers – at the Universidad Nacional Autónoma de México, the Tecnológico de Monterrey, and the Instituto Politécnico Nacional in Mexico; Universitat Pompeu Fabra in Spain, and the University of Palermo in Italy – the authors applied a genome-wide approach to examine the global population structure of the cosmopolitan pelagic dolphinfish or mahimahi (Coryphaena hippurus), an important commercial species. A comprehensive dataset comprising 8.7 million single-nucleotide polymorphisms together with complete mitochondrial genomes was generated during this research.
The analyses reveal, for the first time, four genetically distinct populations that correspond to the major oceanic basins: the Atlantic, Pacific, Indian Ocean and Mediterranean Sea. The Mediterranean population carries a unique genomic signature, most probably reflecting historical isolation and limited contemporary gene flow through the Strait of Gibraltar.
Despite this clear inter-basin structure, genome-wide data also retain extensive signals of historical connectivity. Results of various tests show significant excess allele sharing (meaning that two groups of individuals carry the same version or allele of a particular gene or DNA segment), particularly between the Indo-Pacific and Atlantic groups. In addition, phylogenetic network analyses (drawing evolutionary relationships that allows for mixing between groups, not just simple branching) show multiple migration events. These results underline the lasting influence of ancestral gene flow on present-day genetic patterns.
At finer geographic scales, modest but statistically significant structure was detected within both the Atlantic and Pacific basins. Seascape genomic analyses (how genetic differences in marine species are linked to the environment around them) further demonstrate that environmental gradients – including salinity, phosphate concentration, pH and others – are significantly associated with genomic variation, indicating that ecological factors play a role in shaping population differentiation across heterogeneous marine habitats.
Fig. 1: Graphical summary of the study. Adapted from the original.
Relevance of research findings to the industry
For fisheries managers and the fishing sectors, the discovery of four basin-scale genetic populations is important. Stocks that look continuous on a map may in fact be demographically independent. Management plans that treat all dolphinfish as a single global unit risk over-harvesting one basin while under-utilizing another.
Knowing that Mediterranean fish are particularly distinct and that Atlantic and Pacific populations also show internal structure gives managers a clearer basis for setting regional catch limits, seasonal closures or size regulations. The environmental associations also hint that climate-driven changes in salinity or nutrient levels could alter population boundaries in the future, which both industry and regulators should monitor.
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Perspectives
This research demonstrates that even highly dispersive oceanic species can maintain meaningful genetic structure. Future studies should combine these genomic results with ocean-circulation models to assess how currents move larvae and adults between basins. Functional genomic approaches and tests for loci under selection would help identify which genes allow each population to cope with local conditions and with rapid environmental change.
Expanding sample sizes, especially from under-represented regions of the Indian Ocean and southern Pacific, would refine the picture further. Overall, the four genetic groups identified in this study provide a solid starting point for designing management units that better match the true biology of the species.
Modeling ocean acidification and warming effects on Atlantic Sea scallop growth for adaptive management
Results of this study show that warming stress is stronger than previously recognized, especially in the southern Mid-Atlantic, while ocean acidification appears first in the north. Together these stressors shrink the optimal growth range of sea scallops, showing the value of the spatially coupled DEB model for adaptive fisheries management. Photo of a sea scallop (Placopecten magellanicus) – which has over 100 blue eyes along the edge of its mantle to sense light intensity – by Dann Blackwood, USGS (Public domain, via Wikimedia Commons).
Effective climate-ready fisheries management depends on robust predictions of how species will respond to environmental change across broad spatial scales. Bioenergetic approaches such as Dynamic Energy Budget (DEB) models link physiological processes to environmental conditions and can therefore forecast organismal growth under future climate scenarios.
In a recent study by Halle M. Berger and colleagues (University of Connecticut and NOAA Northeast Fisheries Science Center and Océanopolis in France) the scientists presented the first large-scale integration of a DEB model with downscaled regional oceanographic simulations. This coupling allows resolving spatiotemporal patterns and examine how climate stressors appear at biogeographic, economic and oceanographic scales that matter for management.
The researchers calibrated a DEB model for the Atlantic Sea scallop (Placopecten magellanicus) using output from a realistic oceanographic–biogeochemical model of the Northeast U.S. continental shelf. The model was used to project the combined effects of ocean acidification (OA) and warming on individual growth both historically and through the coming century. It successfully reproduced observed historical patterns in age at harvest size and maximum attainable size.
At mid-century (2035–2050), scallop growth was projected to increase across most of the region, with the exception of the southern Mid-Atlantic; OA effects remained confined to the deep Gulf of Maine. By the end of the century (2080–2095) under a high-emissions scenario, scallops were expected to grow more rapidly yet reach smaller maximum sizes. The results indicate that warming stress is more severe than previously recognized, especially in the southern Mid-Atlantic. Warming impacts appear first in the south, whereas OA stress precedes warming in the north.
Overall, together these stressors progressively shrink the geographic area that supports optimal growth, and the results of this study demonstrate the value of a spatially explicit, climate-forced DEB model as a practical tool for guiding adaptive fisheries management.
Fig. 5: Mean (± SD) dry flesh mass (top row) and shell height (bottom) of experimental juvenile scallops exposed to low (503 microatm – the microatmosphere is a unit of pressure equal to one-millionth of an atmosphere – black symbols), moderate (805 microatm, yellow symbols), or high (1168 microatm; red symbols) pCO2 (data from Pousse et al. 2023) used to calibrate the model. In ocean science (especially ocean acidification studies), a microatm is the standard unit used to express the partial pressure of carbon dioxide (pCO₂) in seawater. Typical surface ocean values today are around 400–450 microatm. Adapted from, and with additional information in the original publication.
Relevance of research findings to the industry
For the scallop fisheries industry, the most immediate value of the work is its ability to flag which fishing grounds are likely to become less productive and which may temporarily improve. Southern mid-Atlantic beds face the earliest risk of slower growth and smaller maximum size, while some northern areas may see short-term gains before acidification becomes limiting. Processors, vessel operators and managers can use these regional signals when planning long-term investments, lease decisions or rotational closures.
The finding that animals may grow faster yet end up smaller also has direct economic consequences: smaller scallops command lower prices and may require changes in gear or processing methods. Because the model is spatially explicit, it can be updated as new climate projections or survey data become available, giving the industry a living tool rather than a one-time snapshot.
Perspectives
Results of this study demonstrate that linking bioenergetic models to regional ocean forecasts is both feasible and useful for climate-ready management. Future work could refine the food-supply component of the model, incorporate density-dependent effects, and assess additional emission scenarios. Expanding the approach to other shellfish or finfish would allow multi-species comparisons and more integrated ecosystem planning.
Managers should consider that waiting until declines appear in the catch is no longer necessary. The spatial patterns of stress are already projected; adaptive measures – such as shifting effort northward, adjusting size limits, or protecting residual high-growth habitats – can be designed now. Overall, the model developed provides a practical bridge between climate science and the day-to-day decisions that will hopefully keep the Atlantic Sea scallop fishery viable through the coming decades.
Spatial distribution of global surface ocean pH trends from 1985 to 2024 Credit: Earth-Science Reviews (2026). DOI: 10.1016/j.earscirev.2026.105623
When most people hear the phrase “ocean acidification,” they think of coral reefs, shellfish or declining fisheries. Those concerns are real. But while working on our recent research, I found myself asking a different question: What if ocean acidification is telling us something much bigger than the health of marine ecosystems?
The more we examined geological records, marine chemistry and Earth-system feedbacks, the more one idea became impossible to ignore. Ocean acidification is not simply a modern environmental problem. It is becoming a planetary-scale signal that records how human activities are altering Earth’s long-term carbon cycle.
Once we began viewing it from this perspective, the ocean no longer appeared as a passive victim of climate change. Instead, it emerged as an active archive that stores information about our civilization for thousands—perhaps even hundreds of thousands—of years. “That realization completely changed how we think about the future of our planet,” Dr. Das says. The research is published in the journal Earth-Science Reviews.
Most discussions focus on what happens near the ocean surface. Carbon dioxide released from burning fossil fuels dissolves into seawater, forming carbonic acid. Since the Industrial Revolution, average surface ocean pH has declined by about 0.1 units, representing roughly a 30% increase in hydrogen ion concentration. Although that numerical change seems small, it fundamentally alters marine carbonate chemistry and reduces the availability of carbonate ions needed by countless marine organisms to build shells and skeletons.
Ocean acidification as a planetary signal, showing how rapid atmospheric CO₂ forcing cascades through ocean chemistry, deep-ocean circulation, sedimentary buffering, and lithospheric feedbacks, imprinting long-lived Earth system memory far beyond human timescales. Credit: Earth-Science Reviews (2026). DOI: 10.1016/j.earscirev.2026.105623
Das says, “These biological consequences have been studied extensively. Yet they represent only the beginning of a much larger story.”
The ocean is not an isolated body of water. It is tightly connected to the atmosphere, deep-sea sediments and Earth’s crust through an intricate network of chemical exchanges that operates over vastly different timescales. Surface waters communicate with the deep ocean through global circulation. Sediments continuously exchange minerals with seawater. Continental rocks slowly weather and eventually replenish the ocean’s alkalinity. Together, these processes regulate Earth’s carbon cycle over thousands to millions of years.
“Our study argues that ocean acidification should be viewed within this entire Earth-system framework rather than solely as a biological stressor.”
One concept became particularly important throughout this work: Earth system memory. Unlike human memory, which exists in our brains, Earth stores information inside rocks, sediments, ice and chemical signatures. Every major disruption of the carbon cycle leaves traces that future geologists can detect long after the original event has disappeared.
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Marine sediments are among the most remarkable examples of this planetary memory.
As acidic waters penetrate deeper into the ocean, calcium carbonate begins dissolving from seafloor sediments. The boundary separating carbonate preservation from dissolution, known as the carbonate compensation depth, gradually shifts upward. Over time, this movement leaves behind distinctive layers that permanently record changes in ocean chemistry.
These sedimentary archives preserve evidence of carbon-cycle disturbances for tens of thousands—or even millions—of years.
In other words, today’s emissions are already beginning to write a geological chapter that future civilizations, if they exist, could eventually read.
This long-term perspective naturally led us to Earth’s geological past.
The Paleocene–Eocene Thermal Maximum, which occurred approximately 56 million years ago, is often regarded as one of the closest natural analogs to modern carbon release. During that event, thousands of petagrams of carbon entered the atmosphere and oceans, triggering global warming, widespread ocean acidification and extensive dissolution of deep-sea carbonates.
An ongoing research project exploring the effects of rising levels of oceanic CO2 on squid neurology reveals that exposure to future levels of ocean acidification could shrink their brain volume by around 50%. This severe brain shrinkage appears to be most pronounced in the areas that interpret visual information, correlating with significant reductions in normal feeding behaviours and suggesting serious consequences for the future of squid and other cephalopods.
“Cephalopods are widely regarded as being one of the most intelligent groups of animals living in the ocean,” says Dr Garett Allen, an assistant professor at Acadia University, Canada. The Coleoidea subclass of cephalopods that includes squid, cuttlefish and octopuses are believed to be the most intelligent invertebrates on Earth, possessing a similar number of neurons to dogs.
Bigfin reef squid in the research tank. Credit: Su Huai
Ocean acidification caused by elevated levels of atmospheric CO2 is known to be pose a serious threat to many marine species, but this project, presented at the Society for Experimental Biology conference in Florence, Italy, reveals a previously unknown impact of ocean acidification on cephalopod neural anatomy.
Preliminary data from this study suggests that bigfin reef squid, Sepioteuthis lessoniana, reared from hatching within elevated levels of dissolved CO2 exhibited significant changes in brain physiology – the most surprising being an average 49% reduction in brain volume compared to a control group.
To investigate the effects of future ocean acidification on the squid neurology, collaborations between Dr Allen and project lead Dr Yung-Che Tseng whose his team is located at Academia Sinica’s Marine Research Station reared the squid in one of two parallel water tanks: one representing the modern oceans (pH 8.2) and one representing the oceans in the year 2100 under a predicted climate change scenario (pH 7.8). After 90 days, the squid were removed and their heads were preserved for visual analysis with diffusion magnetic resonance imaging (dMRI).
Once the images were visualized and the brain morphometrics could be assessed, Dr Allen discovered that the brains from the ocean acidification tank squid were substantially smaller than the control tank squid. “I immediately saw that their brains were half the size and had to check the diagnostic output of the software,” says Dr Allen. “It was a real surprise – I wasn’t expecting that at all.”
The study found no effect of CO2 on whole body size, so the brain volume was normalised to mantle length to account for variation in body size. This volume reduction was observed across the whole of the brain, but the greatest reductions were found in regions identified as the optic lobes and optic tracts, which were 52% and 62% less voluminous than squid reared under modern ocean conditions, respectively.
These new findings follow on from an earlier study that linked rising CO2 levels to reductions in hunting behaviours in bigfin reef squid, finding that an acute 7-day exposure to high CO2 levels resulted in a 65% reduction in hunting behaviours, and squid exposed to a full 90 days exposure from hatching showed a 42% reduction in hunting behaviours compared to controls.
The ability to rapidly capture and interpret visual information is vitally important for bigfin reef squid, as they rely on their eyesight for tracking and catching their prey. “We think that the reduced willingness to feed may be linked to a decline in visual acuity,” says Dr Allen. “Not because of the retina itself, which looks to stay the same, but perhaps because the optic lobe is shrinking.”
The factors causing this brain volume shrinkage are still being investigated, but Dr Allen believes that they may be likely due to energetic constraints within the brain or oxidative damage, which could mean that the brain is unable to relay information correctly and lead to the abnormal feeding behaviour that the team have observed.
Dr Allen and Dr Tseng are currently carrying out further studies on the brains of squid reared in the same future conditions at 30 and 60 days to further validate these findings and examine how this neural shrinkage manifests as the squid grows and matures.
Published in the prestigious journal Environmental Pollution and co-authored by ISPRA researchers, the study “Climate Change and Ocean Acidification Outweigh Local Stressors in Mediterranean Mussels: A Multi-Method Convergence Analysis” presents the results of a ten-year biomonitoring programme (2014–2023) carried out in the Ligurian Sea.
The research focused on the Mediterranean mussel (Mytilus galloprovincialis) at Gorgona Island (used as the reference site) and near an offshore regasification terminal. By integrating biomarker data, tissue metal concentrations, and high-resolution oceanographic variables, the study quantified the relative contribution of different environmental stressors affecting mussel health using five complementary statistical approaches.
The study’s main finding is that climate change—particularly ocean acidification—emerged as the primary driver of biological stress, accounting for approximately 40% of the observed variance. This significantly exceeded the contribution of metal contamination (around 30%) and the local influence of the offshore regasification terminal (approximately 13%). Notably, about 64% of the climate-related impact was found to operate indirectly by enhancing the bioaccumulation of metals.
International institutions managing fisheries and climate change operate in silos, leaving a critical gap in protection for communities dependent on blue foods.
London, 18th June 2026 – A new study, launched during Our Oceans Conference being held in Mombasa, finds that international governance frameworks are poorly equipped to address the combined threat of ocean acidification (OA) and blue food insecurity — despite both issues becoming increasingly urgent for global sustainability. The research, published in Environmental Research: Food Systems, maps the international governance landscape for both issues and finds that, while the two policy domains overlap significantly, they are rarely addressed together.
Annika Frosch, lead author and Research Fellow at the UCL Energy Institute Shipping and Oceans Research Group, said: “Without coordinated action across climate and food systems, the growing impacts of ocean acidification will continue to undermine fisheries and aquaculture that underpin global nutrition and livelihoods.”
The thematic nodes represent issue areas related to blue food security (blue) and ocean acidification (green). The nodes in the centre are those that apply to both blue food security and ocean acidification, and issues that were identified as critical governance areas at the OA-blue food nexus. The fisheries, aquaculture, and climate change nodes represented in red are discussed further in the paper.
Blue foods — fish, shellfish, and algae sourced from marine and freshwater environments — provide essential nutrients to millions of people worldwide, and global consumption has grown more than fivefold over the past 60 years. At the same time, ocean acidification, driven primarily by rising CO₂ emissions, is already harming shellfish aquaculture and fisheries, degrading coral reef ecosystems, and altering the nutritional quality and safety of seafood. Communities in the Global South, which rely most heavily on blue foods for daily protein, face the greatest risks — yet also receive the least research attention and policy support.
Using a structured review of international governance literature and a thematic mapping exercise, the researchers identified thirteen policy domains relevant to blue food security and ten relevant to ocean acidification, seven of which overlap — including fisheries and aquaculture, biodiversity, climate change, and land-based pollution.
Despite this overlap, the study finds that most international actors and instruments treat the two issues in isolation. A detailed examination of two central institutions — the Food and Agriculture Organization (FAO) and the UN Framework Convention on Climate Change (UNFCCC) — illustrates the problem clearly:
The FAO lacks an explicit mandate to govern ocean acidification. When OA is mentioned in FAO instruments, it typically appears as one item in a longer list of climate stressors, rather than being treated as a distinct and direct threat to food security.
The UNFCCC addresses ocean acidification only indirectly, through its broader CO₂ mitigation goals. Neither the UNFCCC nor the Paris Agreement explicitly names OA, and it does not feature as a core governance priority. Food security is referenced in UNFCCC objectives but is not linked to OA even in documents that mention both.
The study also highlights a troubling asymmetry: blue food security tends to receive legal and political recognition, while ocean acidification remains largely confined to scientific discussion — making coordinated policy action harder to achieve.
Keiko Nomura, co-author and Postdoctoral Researcher at the University of Colorado Boulder, said “Our findings suggest that ocean acidification remains more visible in scientific discussions than in international policy frameworks. Bridging this science-policy divide could help improve governance of climate risks to blue food systems.”
The paper makes recommendations for policy makers to bridge these governance gaps, including:
Strengthening FAO instruments to treat OA as a distinct climate-related stressor to fisheries and aquaculture, including through binding policies, vulnerability thresholds for key species, and the promotion of socioeconomic strategies.
Developing a dedicated OA workstream or technical body under the UNFCCC
Incentivising countries to include OA monitoring and adaptation measures in their Nationally Determined Contributions (NDCs)
Creating formal institutional links and coordination between climate bodies and marine science and fisheries organisations modelled on the Joint Capacity-building Programme of the three ‘Rio Conventions’, adapted for the OA–blue food security nexus
Inken Dressler, co-author and European Programme Lead at the International Alliance to Combat Ocean Acidification (OA Alliance): “The siloed recognition and approach to ocean acidification and blue food security hinders effective governance of both issues. To bridge this gap, closer cooperation between existing frameworks such as the UNFCCC and FAO must be achieved.”
The researchers note that some Pacific Island nations — including Fiji and the Solomon Islands — are already leading the way by integrating ocean acidification into their national climate strategies and fisheries management plans, demonstrating what more coherent governance could look like.
The study accompanies Dr Frosch’s new book ‘Navigating the Souring Seas: The Global Experimentalist Governance of Ocean Acidification’ which explores how OA is being addressed at the global stage. Bridging science, law, and international policy, this interdisciplinary book provides a clear overview of the scientific background of OA and maps the international governance landscape, identifying it as a regime complex. Through detailed interview-based case studies of the Ocean Acidification Alliance and the International Maritime Organization, the book evaluates real-world efforts to govern OA and highlights how flexibility, learning, and multilevel collaboration, can enhance their effectiveness.
CO2 hydrates releasing droplets of liquid CO2, filmed in 2021 at a depth of 1,367 meters by the Victor 6000 ROV in the Fer à Cheval area during the Geoflamme campaign aboard the Pourquoi Pas. (Image credit: Ifremer)
More than 120 CO2 hydrate deposits were discovered at the Fer à Cheval site, located 10 km east of Petite-Terre (Mayotte), during the Geoflamme expedition co-led by Ifremer and the Paris Institute of Earth Physics (IPGP) in 2021. No comparable site had ever been documented before. Published in Nature Geoscience, the study shows that this site is unique worldwide for investigating the mechanisms of transient CO2 sequestration in the ocean and the impacts of ocean acidification on biodiversity.
The data collected on these CO2 hydrates discovered in the Indian Ocean were analyzed by an international team from Ifremer, IPGP, the French Alternative Energies and Atomic Energy Commission (CEA), the French National Center for Scientific Research (CNRS), the National Oceanic and Atmospheric Administration (NOAA), and the University of Milan.
Solid CO2 Deposits at the Bottom of the Ocean
Hydrates are solid compounds similar to ice, consisting of water and gas molecules. In nature, hydrates are usually composed of methane, and it is extremely rare to find carbon dioxide hydrates on the ocean floor.
Cécile Cathalot, marine geochemistry researcher at Ifremer and the study’s lead author, said: “This is the first time we have observed clusters of CO2 hydrates that remain stable for several years on the ocean floor, of this size and in such quantities. Composed of agglomerated CO2 droplets, these domes range in height from a few centimeters to 2 meters. This discovery raises new questions about the natural mechanisms of temporary CO2 storage in the ocean. It could also fuel discussions on certain geoengineering approaches aimed at limiting climate change.”
These hydrates were observed within the active Fer à Cheval volcanic structure, located 10 km east of the island of Mayotte. Surrounded by cliffs reaching 250 meters in height, this 6 km² underwater feature is one of many structures in the underwater volcanic chain that extends east of Mayotte to the Fani Maore underwater volcano. It forms a semi-enclosed space within which CO2 released onto the seafloor accumulates periodically with the tides.
Furthermore, this site offers the conditions necessary for the formation of hydrates: the combination of cold water—here at 4 degrees Celsius—and sufficient pressure exerted by the water column at a depth of 1,400 meters.
Olivia Fandino, a specialized physical chemistry of gas hydrates researcher at Ifremer, said: “At the Fer à Cheval site, CO2 hydrates form when droplets of liquid CO2 come into contact with cold water under high pressure. A solid film then develops on their surface, the growth of which depends closely on temperature, salinity, and emission rate. What is remarkable here is that, despite the ocean currents, these hydrates were able to grow and form large, relatively stable structures.”
Structures Associated with the Fani Maore Volcano
It is likely that the emergence of these magmatic sources of liquid CO2 in the Fer à Cheval area is linked to the seismic-volcanic crisis affecting the island of Mayotte, which was notably marked by the formation of the new Fani Maoré volcano discovered in 2019. This activity likely destabilized the volcanic structure of the Fer à Cheval, which formed long before the eruption of Fani Maoré.
Unlike Fani Maoré, which has shown no activity since 2021, the Fer à Cheval site remains highly active in terms of seismicity and fluid emissions, particularly CO2.
A joint campaign conducted by Ifremer and OceanX made it possible to revisit this site of interest four years later.
Carla Scalabrin, a specialized water-column acoustics researcher at Ifremer, said: “Using the ROV Argus, deployed from the OceanXplorer vessel, we observed that the field of hydrate mounds appeared to have remained stable since 2021. The formation of these hydrates depends on the balance between incoming and outgoing carbon dioxide fluxes over time. This provides a first indication of the ability of hydrate mounds to store carbon dioxide over periods of several years.”
Studying the Adaptation of Biodiversity to Environmental Acidification
Marjolaine Matabos, benthic ecology researcher at Ifremer, said: “The dynamics of these domes, which sequester liquid CO2 and then release it as they dissolve, will be monitored over the long term to better understand the mechanisms involved and assess their viability in the medium to long term. This monitoring, conducted during the MAYOBS missions (IPGP, IPGS, BRGM, IFREMER) and as part of the Mayotte Volcanological and Seismological Monitoring Network (REVOSIMA, IPGP), could also help determine the consequences of ocean acidification for biodiversity.”
This discovery will allow researchers to study the ability of the surrounding biodiversity to thrive and adapt to changes in the acidity of their environment.
Scientists have shown conclusively for the first time that tiny marine organisms in polar oceans survived the mass extinction event that wiped out prehistoric dinosaurs because they needed less energy and were more tolerant to darkness.
The study, led by the University of Bristol and published in the journal Nature, sought to solve a longstanding evolutionary enigma: what factors determined whether marine species would survive a mass extinction event known as the Cretaceous-Paleogene (K-Pg) boundary some 66 million years ago? Findings revealed that being small and accustomed to darkness proved to be the vital attributes.
Image shows microscopic marine plankton, which are larger in size and went extinct. Credit: Brian Huber Smithsonian
Study lead author Dr Rui Ying said: “It’s an exciting breakthrough. For so many years scientists have been unable to test what actually decided whether a species prevailed or perished because the extinction event involves multiple environmental changes like ocean acidification and darkness.”
“It is difficult to understand the causality because of the lack of fossil data and environmental proxy data, especially at century timescale. Using a numerical model, I looked at the base of the food chain – plankton – which helped us to identify the most likely cause and the best survival strategies for plankton.”
The Cretaceous–Paleogene (K–Pg) boundary is an ancient and much-studied geological signature marking the mass extinction that wiped out non-avian dinosaurs, separating the Mesozoic Era (the age of reptiles) from the Cenozoic Era (the age of mammals). It is thought that the impact of an asteroid, called Chicxulub, caused the extinction of around 75% of species in the fossil record by triggering catastrophic environmental changes.
Despite decades of research, the mechanisms linking the environmental changes to the selective extinction patterns observed in the fossil record have until now been unresolved. But by creating and deploying a unique model which maps ecosystem traits globally, the scientists have been able to establish what attributes resulted in the marine plankton community’s survival.
Dr Ying, who is now a Senior Research Associate at the University of East Anglia, said: “The model is based on trades and the trade-off of how often they are eaten by predators and what they can eat against specific attributes, such as temperature, light level and body size.”
Study co-author Dr Fanny Monteiro, Associate Professor in Ocean Sciences at the University of Bristol, explained: “The body size and abundance of small plankton mean the organisms rely on less energy, increasing their likelihood of survival. An ability to deal with lower light and darkness and turbulent waters in higher latitudes also makes them more adaptable to polar regions. In contrast, species adapted to higher light and warmer waters were more vulnerable to this type of mass extinction.”
The model allowed the traits of millions of organisms to be analysed and quantified with unprecedented accuracy, providing important insights into the physical and chemical changes linked to diversity. Besides shining a light on the distant past of marine life, the research can also help inform forecasts of how ecosystems might respond in future.
Study co-author Professor Daniela Schmidt, Professor of Earth Sciences at the University of Bristol, said: “This study not only demonstrates how trait-based models can help us better understand biodiversity crises in ancient history, but it also has potential to indicate how less light and hotter environments, as a result of global warming, might impact current and future ecosystems.”
For years, scientists have known that the ocean does a huge amount of the planet’s climate work for us.
The ocean absorbs a large share of the carbon dioxide, taking in roughly 20 to 30 percent of human-caused CO2 emissions since the industrial era. At the same time, tropical cyclones are among the most violent things that happen on Earth’s surface. They churn the upper ocean, stir up deep water, cool the sea surface, and leave behind lingering physical changes that can last for weeks. What has been much less clear is how those storms affect the ocean’s role in the carbon cycle. Do tropical cyclones help the ocean absorb carbon, or do they cause it to release more back into the atmosphere?
A new study suggests the answer is not simple, and it may also be changing.
A role reversal for tropical cyclones
The study was led by experts at the National University of Defense Technology (NUDT), Chinese Academy of Sciences, the NSF National Center for Atmospheric Research, and the GEOMAR Helmholtz Centre for Ocean Research Kiel.
The team pulled together a large set of observations to build a globally available daily dataset of air-sea CO2 flux. Using that, they were able to track how tropical cyclones have influenced the exchange of carbon between the ocean and the atmosphere over time. Their conclusion is that tropical cyclones have tended to push carbon out of the ocean and into the air. But that effect has been weakening in recent decades, and if warming continues under high emissions, the role of these storms may eventually flip.
A messy carbon signal
At first, the result sounds a little counterintuitive. The researchers found that tropical cyclones generally cause net ocean carbon outgassing. The main reason is that the intense winds of a cyclone greatly strengthen the transfer of CO2 from sea to air. But there is another process happening at the same time. After a tropical cyclone passes, it often leaves behind a cold wake, a patch of sea surface that has cooled because the storm mixed the upper ocean so strongly. That cooling can increase the ocean’s ability to take up carbon dioxide from the atmosphere, partly offsetting the carbon being released. Tropical cyclones are doing two things at once: they are helping CO2 escape because of their winds, while also setting up conditions that can later encourage carbon uptake.
The new study suggests that, historically, the first effect has usually won out. Even so, that balance has not stayed fixed.
As ocean temperatures rise and marine ecosystems change, scientists are working to understand how valuable species like the American lobster will respond. New research from William & Mary’s Batten School of Coastal & Marine Sciences & VIMS suggests one source of resilience may come from the microscopic bacterial communities living on lobster embryos.
The study, published in Scientific Reports, found that lobster eggs host surprisingly diverse microbiomes that change as the embryos develop but otherwise remain remarkably stable even under conditions simulating future environmental conditions. The findings challenge decades of assumptions that lobster eggs contained only a few key bacterial species and could help scientists better understand disease risks in one of North America’s most valuable fisheries.
“We were hoping to discover one dominant microbe early on,” said study coauthor Jeffrey Shields, a professor at the Batten School & VIMS who collaborated with several of his students on the research, including lead author Sarah Koshak. “Instead, it was a mishmash, a rich community of different bacteria whose roles we don’t yet fully understand.”
The exterior surface of a late-stage lobster embryo covered by filamentous bacteria at 400x magnification.Credit: Jeffrey Shields.
A hidden ecosystem on lobster eggs
Using advanced genetic sequencing techniques, researchers analyzed microbial communities on lobster embryos and newly hatched larvae raised under varying temperatures and pH conditions designed to mimic present-day and future ocean conditions in the Gulf of Maine.
Climate change is endangering the health of Europe’s oceans, and it’s not just marine life that is affected.
A new study warns that precious underwater cultural heritage is being threatened by ocean acidification.
The research found that materials that make up many archaeological treasures are at risk of deterioration when water pH levels drop.
The research, coordinated by the University of Padua in Italy, examined how ocean acidification, a direct consequence of climate change, can accelerate the decay of submerged archaeological sites.
The scientists studied how quickly historical materials deteriorate through dissolution and biological decay in marine environments, and then integrated these findings with large-scale climate models, lead researcher Luigi Germinario explains.
The results were concerning. While stone degradation was minimal in pre-industrial times and remains relatively limited today, rising emissions could trigger an exponential increase in deterioration rates.
These changes would be “irreversible over the coming decades and centuries, influenced by the materials’ properties and shifting dynamics of biocolonisation” – the growth of microorganisms on the surfaces of submerged structures – Germinario told Italian national newspaper La Repubblica.
The study, published in Communications Earth & Environment, warned that “ocean acidification will pose a severe challenge to protecting underwater cultural heritage, making conservation and adaptation policies more urgent than ever.”
