Archive for the 'Press releases' Category

Decline of diatoms due to ocean acidification

Study shows unexpected negative impact by CO2 on important plankton group

Diatoms are an important plankton group in the ocean. Photo: Annegret Stuhr / Jan Taucher / GEOMAR

Diatoms are the most important producers of plant biomass in the ocean and help to transport carbon dioxide (CO2) from the atmosphere into the deep ocean and thus regulate our climate. Because diatoms rely on silica rather than calcium carbonate to build their shells, they were previously thought to benefit from ocean acidification – a chemical change in seawater triggered by the increasing uptake of CO2 that makes calcification more difficult. In a study published today in Nature, scientists at GEOMAR Helmholtz Centre for Ocean Research Kiel show that diatoms, which are a type of plankton, are also affected. Analyses of data from field experiments and model simulations suggest that ocean acidification could drastically reduce diatom populations.

While calcifying organisms like oysters and corals have difficulty forming their shells and skeletons in more acidic seawater, diatoms have been considered less susceptible to the effects of ocean acidification – a chemical change triggered by the uptake of carbon dioxide (CO2). The globally widespread tiny diatoms use silica, a compound of silicon, oxygen and hydrogen, as a building material for their shells. That diatoms are nevertheless under threat has now been demonstrated for the first time by researchers from GEOMAR Helmholtz Centre for Ocean Research Kiel, the Institute of Geological and Nuclear Sciences Limited New Zealand and the University of Tasmania in a study published in Nature. For the study, researchers linked an overarching analysis of various data sources with Earth system modeling. The findings provide a new assessment of the global impact of ocean acidification.

Dr. Jan Taucher, marine biologist at GEOMAR and first author of the study says: “With an overarching analysis of field experiments and observational data, we wanted to find out how ocean acidification affects diatoms on a global scale. Our current understanding of ecological effects of ocean change is largely based on small-scale experiments, that is, from a particular place at a particular time. These findings can be deceptive if the complexity of the Earth system is not taken into account. Our study uses diatoms as an example to show how small-scale effects can lead to ocean-wide changes with unforeseen and far-reaching consequences for marine ecosystems and matter cycles. Since diatoms are one of the most important plankton groups in the ocean, their decline could lead to a significant shift in the marine food web or even a change for the ocean as a carbon sink.”
The meta-analysis examined data from five mesocosm studies from 2010 to 2014, from different ocean regions ranging from Arctic to subtropical waters. Mesocosms are a type of large-volume, oversized test tube in the ocean with a capacity of tens of thousands of liters, in which changes in environmental conditions can be studied in a closed but otherwise natural ecosystem. For this purpose, the water enclosed in the mesocosms was enriched in carbon dioxide to correspond to future scenarios with moderate to high increases in atmospheric CO2 levels. For the present study, the chemical composition of organic material from sediment traps was evaluated as it sank through the water contained in the experimental containers over the course of several weeks of experiments. Combined with measurements from the water column, an accurate picture of biogeochemical processes within the ecosystem emerged.
The findings obtained from the mesocosm studies could be confirmed using global observational data from the open ocean. They show – in line with the results of the meta-analysis – a lower dissolution of the silicon shells at higher seawater acidity. With the resulting data sets, simulations were performed in an Earth system model to assess the ocean-wide consequences of the observed trends.

“Already by the end of this century, we expect a loss of up to ten percent of diatoms. That’s immense when you consider how important they are to life in the ocean and to the climate system,” Dr. Taucher continued. “However, it is important to think beyond 2100. Climate change will not stop abruptly, and global effects in particular take some time to become clearly visible. Depending on the amount of emissions, our model in the study predicts a loss of up to 27 percent silica in surface waters and an ocean-wide decline in diatoms of up to 26 percent by the year 2200 – more than a quarter of the current population.”

Taucher, J., Bach, L.T., J.A., Prowe, A.E.F., Boxhammer, T., Kvale, K., Riebesell, U. (2022):
Enhanced silica export in a future ocean triggers global diatom decline. Nature, doi:

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California shellfish farmers adapt to climate change

San Diego State University and Oregon State University researchers probe growers’ strategies for keeping the sustainable industry resilient as oceans turn more acidic

Shellfish growers at Hog Island Oyster Farm in Tomales Bay, Northern California. Courtesy of Remy Hale/Hog Island Oyster Co.

Because of their proximity to the ocean, Californians get to enjoy locally-sourced oysters, mussels, abalone and clams. Most of the shellfish consumed here come from aquaculture farms along the coast — from San Diego to Humboldt County. And because the animals are filter feeders that siphon tiny plankton out of seawater, growing them is environmentally sustainable. 

But due to rising greenhouse gas emissions, the ocean has become more acidic, conditions hostile to shellfish growth.

In a new study, SDSU and Oregon State University researchers interviewed California shellfish growers to find out how they perceive ocean acidification, and to learn what strategies they think will help their operations adapt to changing environmental conditions. 

“This study is fairly unique in that we’re getting information directly from the people who are being affected by change and learning directly from their experiences,” said geographer Arielle Levine, director of the sustainability program in SDSU’s College of Arts and Letters.. 

Ward added: “They’re on the front lines of observing climate change and they also are going to be most well-suited to describe what they think they need to adapt to those changes.”

Growing threat

Burning coal, oil and natural gas emits carbon dioxide and other greenhouse gases into the atmosphere. About a third of that CO2 is absorbed by the ocean, reducing pH levels. 

As the water becomes more acidic, the calcium carbonate shellfish need for their shells is less abundant.

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‘Ghost’ fossils reveal how oceans could be affected by climate change

Coccolithophores produce individual coccolith plates using calcium carbonate, taking carbon dioxide out of the atmosphere. Image © Nannotax

Plankton which help feed the ocean, lock away carbon dioxide and even influence the weather may not be as vulnerable to climate change as feared.

Despite their fossils having been dissolved away by acidic sediment waters, new research has found that the organisms themselves were thriving during the Jurassic, providing hope that they can still act as a carbon sink in modern global warming. 

Though measuring smaller than the width of a human hair, the ‘ghost’ fossils of Jurassic plankton can help us understand how their modern relatives will respond to an increasingly acidic ocean.

Coccolithophores are a group of phytoplankton which form microscopic scales made of calcite, a type of calcium carbonate, in a case around themselves. With rising carbon dioxide levels making seawater more acidic, there were concerns coccolithophores may be left unable to form their exoskeleton.

This was supported by evidence from past warming events, where plankton body fossils are scarce in the record.

Prof Richard Twitchett, a Research Leader at the Museum and co-author of the paper, says, ‘The “ghost” fossils show that nannoplankton were abundant, diverse and thriving during past warming events in the Jurassic and Cretaceous, where previous records have assumed that plankton collapsed due to ocean acidification.

The findings of the study, conducted by an international group of researchers, were published in the journal Science.

How does calcium carbonate influence climate change?

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Unmixing deep sea sedimentary records identifies sensitivity of marine calcifying zooplankton to abrupt warming and ocean acidification in the past

Ocean acidification and rising temperatures have led to concerns about how calcifying organisms foundational to marine ecosystems, will be affected in the near future. We often look to analogous abrupt climate change events in Earth’s geologic past to inform our predictions of these future communities. The Paleocene-Eocene thermal maximum (PETM) is an apt analog for modern climate change. The PETM was a global warming and ocean acidification event driven by geologically abrupt changes to the global carbon cycle approximately 56 million years ago. Much of what we know about the PETM is from the study of deep sea sedimentary records and the microfossils within them. However, these records can experience intense sediment mixing—from bottom water currents and burrowing by organisms living along the seafloor—which can blur or distort the primary climate and ecological signals in these paleorecords.

Figure 1. A) Frequency distribution of single-shell stable carbon isotope (δ13C) values for planktic foraminiferal shells from a deep sea sedimentary PETM record from the equatorial Pacific (n = 548). Note that 50% of shells measured record distinctly PETM values, while 49.5% record distinctly pre-PETM values. B) Comparison of diversity metric (Shannon-H) between the isotopically filtered (i.e., unmixed) and unfiltered (i.e., mixed) planktic foraminiferal assemblages.

A recent study in the Proceedings of the National Academy of Sciences used geochemical signatures measured from individual microfossil shells of planktic foraminifera (surface-dwelling marine calcareous zooplankton) to deconvolve the effects of sediment mixing on a deep sea PETM record from the equatorial Pacific. Use of this “isotopic filtering” (unmixing) method revealed that nearly 50% of shells in the PETM interval were reworked contaminants that lived before the global warming event (Figure 1A). The identification and removal of these older shells from fossil census counts drastically changed interpretations of how these organisms responded to the PETM. Prior interpretations assumed that planktic foraminiferal communities living near the equator diversified during the PETM. However, by deconvolving the effects of sediment mixing on the same equatorial deep sea record, researchers found that these communities actually suffered an abrupt decrease in diversity at the onset of the PETM (Figure 1B). This decrease is likely due to several taxa migrating towards the poles to escape the extreme heat of the tropics and lower oxygen conditions found at deeper water depths (i.e., thermocline) during the PETM. Additionally, some taxa may have undergone morphological changes, signaling reduced calcification, in response to extreme acidifying conditions. Today, anthropogenic carbon emission rates are ~10 times faster than the carbon cycling perturbation that triggered the PETM. Although planktic foraminifera and other key zooplankton survived the PETM, these communities suffered at the hands of extreme sea surface temperatures and acidifying waters, and may not be able to cope the rate of environmental changes in our ocean over the coming centuries.

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Under ocean acidification, embryos of a key forage fish struggle to hatch

A potential ripple effect from carbon in the atmosphere could have severe impacts throughout the ocean ecosystem

This photo shows sand lance embryos that have and have not hatched. Sand lance have trouble hatching at future ocean CO2 levels (photo courtesy of Emma Cross).

When carbon is emitted into the atmosphere, about a quarter of it is absorbed by the earth’s oceans. As the oceans serve as a massive ‘sink’ for carbon, there are changes to the water’s pH – a measure of how acidic or basic water is. As oceans absorb carbon, their water becomes more acidic, a process called ocean acidification (OA). For years, researchers have worked to understand what effect this could have on marine life.

While most research so far shows that fish are fairly resilient to OA, new research from UConn, the University of Washington, the National Oceanic and Atmospheric Administration (NOAA), and Southern Connecticut State University, shows that an important forage fish for the Northwest Atlantic called sand lance is very sensitive to OA, and that this could have considerable ecosystem impacts by 2100. The team’s findings have just been published in Marine Ecology Progress Series.

Sand lance spawn in the winter months in offshore environments that tend to have stable, low levels of CO2, explains UConn Department of Marine Sciences researcher and lead author Hannes Baumann.

“Marine organisms are not living in a uniform ocean,” Baumann says. “In near shore environments, large CO2 fluctuations between day and night and between seasons are the norm, and the fish and other organisms are adapted to this variability. When we stumbled upon sand lances we suspected they are different. We thought that a fish that lives in a more open-ocean offshore environment might be more sensitive than the near-shore fish because there’s just much less variability.”

The project was a collaboration with physical oceanographers, including Assistant Professor of Marine Sciences Samantha Siedlecki and Michael Alexander from NOAA’s Physical Sciences Laboratory in Boulder, Colorado, who modeled CO2 levels in 2050 and 2100 for a specific part of the Gulf of Maine where sand lance spawn. Then Baumann and his team reared sand lance embryos in the lab under experimentally higher CO2 levels matching the projected levels.

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Effects of ancient carbon releases suggest possible scenarios for future climate

New findings reveal a precursor event before the Paleocene-Eocene Thermal Maximum, giving scientists a fresh perspective on future global climate scenarios

A massive release of greenhouse gases, likely triggered by volcanic activity, caused a period of extreme global warming known as the Paleocene-Eocene Thermal Maximum (PETM) about 56 million years ago. A new study now confirms that the PETM was preceded by a smaller episode of warming and ocean acidification caused by a shorter burst of carbon emissions.

Marine sediments contain the microscopic shells of organisms called foraminifera that lived in the surface waters. The chemical composition of these shells records the environmental conditions in which they formed. (Photo credit: Marci Robinson/USGS)

The new findings, published March 16 in Science Advances, indicate that the amount of carbon released into the atmosphere during this precursor event was about the same as the current cumulative carbon emissions from the burning of fossil fuels and other human activities. As a result, the short-lived precursor event represents what might happen if current emissions can be shut down quickly, while the much more extreme global warming of the PETM shows the consequences of continuing to release carbon into the atmosphere at the current rate.

“It was a short-lived burp of carbon equivalent to what we’ve already released from anthropogenic emissions,” said coauthor James Zachos, professor of Earth and planetary sciences and Ida Benson Lynn Chair of Ocean Health at UC Santa Cruz. “If we turned off emissions today, that carbon would eventually get mixed into the deep sea and its signal would disappear, because the deep-sea reservoir is so huge.”

This process would take hundreds of years—a long time by human standards, but short compared to the tens of thousands of years it took for Earth’s climate system to recover from the more extreme PETM.

Jim Zachos holds a sediment core from the seafloor showing the red clay layer that marks the Paleocene-Eocene Thermal Maximum (PETM), a period of extreme global warming and ocean acidification around 56 million years ago. (Photo by Ira Block/National Geographic)

The new findings are based on an analysis of marine sediments that were deposited in shallow waters along the U.S. Atlantic coast and are now part of the Atlantic Coastal Plain. At the time of the PETM, sea levels were higher, and much of Maryland, Delaware, and New Jersey were under water. The U.S. Geological Survey (USGS) has drilled sediment cores from this region which the researchers used for the study.

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Pacific herring, an important food source for salmon, show sensitivity to marine heatwaves

Pacific herring are known as one of the ‘great fishes of the North Pacific Ocean’ as they are inextricably connected via complex food webs and overlapping habitats with Pacific salmon species, such as Chinook and Coho, sea lions and orcas. 

Despite the importance of Pacific herring, the consequences of climate change and ocean acidification on this species remain poorly understood. The Washington Ocean Acidification Center (WOAC) would like to change that. WOAC postdoctoral researcher Chris Murray is the lead author on a new paper, which investigated how Pacific herring respond to the co-occurring stressors of high temperatures and increased levels of CO2. The paper was published in the Journal of Experimental Biology on March 10, 2022.

“In the past decade, the North Pacific Ocean has experienced two significant heatwave events, including the event known as ‘the blob’ between 2014-2016. We also know that ocean acidification, which is linked to increased carbon dioxide levels in the ocean, doesn’t exist in a vacuum,” said Murray. “We wanted to better understand the implications of heat stress on this important fish while incorporating ocean acidification into the framework.” 

The research team designed an experiment to mimic environmental fluctuations predicted over the next 100 years in Padilla Bay, a Puget Sound estuary that is broadly representative of Pacific herring spawning habitat. The researchers tested the upper limit of projected carbon dioxide in combination with a simulated heatwave event to determine how herring embryos reacted to rapid warming, increased carbon dioxide and to a combination of the two stressors.

They measured oxygen consumption, developmental rates and energy efficiency– typical measures for basic survival and growth–under these conditions. In general, the results showed that Pacific herring embryos are largely tolerant of increased CO2, both as a single stressor and as a compound stressor. This may be due to the fact that Pacific herring populations have over time adapted to life in the Salish Sea, which is relatively acidified from natural processes. 

However, the authors found that the heat wave on its own did produce a number of adverse effects. The heat wave caused a sharp increase in metabolic rate and caused embryos to expend a greater amount of their fixed energetic reserves provisioned in their yolk sacs to maintain homeostasis. This resulted in smaller larvae at hatch with less remaining yolk, which could yield a higher mortality rate for larvae in the wild.

“While the herring embryos have a wider thermal tolerance than expected, this experiment showed that there may be a limit to what the species can withstand,” said Murray. “This has opened the door to other research that is necessary in order to better understand the Pacific herring.”

Murray noted that this experiment didn’t test what is potentially the most sensitive developmental stage, which occurs shortly after fertilization before the embryo develops functioning organ systems. Additionally, there are multiple environmental factors that are difficult to replicate in a lab, such as high-frequency fluctuations of temperature, pH, and dissolved oxygen and intense solar radiation during low tide, as environmental conditions in shallow seagrass meadows may fluctuate widely over a single tidal or day/night cycle.  

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Hawaiian corals show surprising resilience to warming oceans

A long-term study of Hawaiian coral species provides a surprisingly optimistic view of how they might survive warmer and more acidic oceans resulting from climate change.

Researchers found that the three coral species studied did experience significant mortality under conditions simulated to approximate ocean temperatures and acidity expected in the future — up to about half of some of the species died.

But the fact that none of them completely died off — and some actually were thriving by the end of the study — provides hope for the future of corals, said Rowan McLachlan, who led the study as a doctoral student in earth sciences at The Ohio State University.

“We found surprisingly positive outcomes in our study. We don’t get a lot of that in the coral research field when it comes to the effects of warming oceans,” said McLachlan, who is now a postdoctoral researcher at Oregon State University.

The study lasted 22 months, which is much longer than most similar research, which often spans days to up to five months, Grottoli said.

Rising levels of carbon dioxide in the atmosphere have led to warmer oceans and about a quarter of the carbon dioxide in the air dissolves into the ocean, causing it to become more acidic. Both rising acidity and temperatures threaten coral, Grottoli said.

In this study, the researchers collected samples of the three most common coral species in Hawaii: Montipora capitataPorites compressa and Porites lobata.

The samples were placed in tanks with four different conditions: a control tank with current ocean conditions; an ocean acidification condition (-0.2 pH units); an ocean warming condition (+2 degrees Celsius); and a condition that combined warming and acidification.

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Ancient example of modern global warming was too hot for tiny, important ocean creatures

The carbon composition of sand grain-sized shells left behind 56 million years ago by single-cell ocean organisms called foraminifera—like this one from foram species Morozovella allisonensis—helped UW-Madison researchers describe a likely catastrophic collapse of the marine food web during a global warming very similar to the one we are embarking on now. Credit: Brittany Hupp

During another time in which Earth warmed rapidly in conjunction with a spike in atmospheric carbon similar to our modern climate, seawater temperature and chemical changes decimated an important piece of the food web in the tropical Pacific Ocean, according to new research from the University of Wisconsin-Madison.

Planktonic foraminifera are single-celled ocean organisms known for making intricate shells that aren’t just the size of a grain of sand, they often are grains of sand on ocean floors and beaches. Planktonic foraminifera evolved approximately 180 million years ago, and they’ve spent all that time evolving further, while dying off and sinking to the bottom of the ocean, where their distinctive shells pile up to form layer after layer of sediment.

Foraminifera were around 56 million years ago during an event called the Paleocene-Eocene Thermal Maximum (the PETM), when atmospheric chemistry and carbon dioxide levels changed abruptly—as they are doing today—and global temperatures warmed rapidly by 4 to 5 degrees Celsius.

“Foraminifera are pretty sensitive environmental indicators. I think of them as canaries in the coal mine,” says Clay Kelly, a UW-Madison geosciences professor and one author of a new study of the PETM published recently in Proceedings of the National Academy of Sciences. He also notes that “the PETM is arguably our best ancient analog for future climate change.”

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Regional policies a critical linchpin for marine protection – new report

Nairobi, 03 March 2022 – A series of regional conventions and policies are playing an essential role in monitoring climate change and preparing for extreme weather events, preventing oil spills, reducing plastic and other waste, saving coral reefs, and providing overall ocean protection and restoration of marine ecosystems. These are the key findings of a UN Environment Programme (UNEP) report, whose authors calls for expanding the scope of collaboration on regional seas in the coming decade.

The report, Contributions of Regional Seas Conventions and Action Plans to a Healthy Ocean, draws on a series of case studies which examine the cumulative impact of these conventions and policies over the past 45 years. Through a robust body of evidence, the UN-led Regional Seas Programme – which produced the report – convenes and coordinates countries and institutions, and undertakes ecosystem-based planning and management to progress towards a healthy ocean and healthy people

The Regional Seas Programme aims to bring all relevant stakeholders together to address the accelerating degradation of the world’s oceans and coastal areas through a “shared seas” approach; since its establishment in 1974, 146 countries have joined 18 Regional Seas. Through cultivating joint scientific research, policy development and implementation, this network of regional policies has become one of the cornerstones of protection, conservation, and restoration of marine and coastal environments.

Susan Gardner, Director of UNEP’s Ecosystems Division, said: “Marine pollution, invasive species and natural habitat loss, excessive extraction, and ocean acidification all share one common trait: they do not respect national borders. Regional Seas demonstrate what can be achieved by working together for common goals at a regional scale. To secure the livelihoods of over three billion people, Regional Seas must not only be recognised, but their mandate ought to be expanded.”

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Reef-building corals at risk from ocean warming, acidification

Physiological limitations on regulating internal chemistry restricts corals’ ability to deal with ocean acidification and warming, thereby reducing resilience to continued environmental change.

Schematic of seawater and physiological controls for cold and warm seasons on calcifying fluid and skeletal geochemistry for 18th century fossil (pre-industrial) corals and modern corals. The reduction in active transport (red arrows, with thickness indicating relative magnitude) in modern corals, critical for regulating the geochemistry of the calcifying fluid, is enhanced by thermal stress such as occurs during El Niño conditions. Credit: Thompson et al., 2022, Figure 3

Environmental stress imposed by ocean warming and acidification has important implications for organism growth, especially those with carbonate skeletons, such as reef-building corals. Thompson et al. [2022] use coral geochemistry and results from Earth system modeling to examine the effects of these stressors on calcification and resiliency in Galápagos corals. Their analysis of calcifying fluid geochemistry in pre-industrial and modern corals suggests that there are physiological limits to coral buffering capacity that affect growth. The implication is that the capacity of corals to buffer against ocean acidification may be more limited than indicated by previous experimental studies. The reduced buffering capacity has consequences for calcification, which affects reef structure, function, and resilience, especially in marginal environments, such as the Galápagos.  

Citation: Thompson, D., McCulloch, M., Cole, J., Reed, E., D’Olivo, J., Dyez, K., et al. [2022]. Marginal reefs under stress: physiological limits render Galapagos corals susceptible to ocean acidification and thermal stress. AGU Advances, 3, e2021AV000509.

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Rapid evolution fuels transcriptional plasticity in fish species to cope with ocean acidification

A research team led by Dr Celia Schunter at School of Biological Sciences (area of Ecology and Biodiversity) & The Swire Institute of Marine Science, The University of Hong Kong (HKU), in collaboration with researchers from The University of Adelaide, James Cook University in Australia, IRD Institute in New Caledonia, and Okinawa Institute of Science and Technology Graduate University in Japan, revealed the basis to variability across different fish species and uncovered that some species evolve more rapidly, providing them with evolved molecular toolkits and allowing them able to cope with future ocean acidification. The journal paper was recently published in Global Change Biology.

Global ocean surface pH is projected to decline with the ongoing uptake of anthropogenic atmospheric CO2 by the oceans, a process termed ocean acidification (OA). A decade of laboratory experiments indicate that predicted OA conditions affect some marine fishes’ physiological performance, growth, survival, and crucial behaviours for the survival of the fish.

To test how marine life will respond and whether adaptation to this rapid acidification is possible, researchers went to a remote place on this planet to study in situ exposure to elevated partial pressure of carbon dioxide (pCO2, the amount of carbon dioxide dissolved in water) and be able to predict how in the wild fish can cope with these environmental conditions predicted to exist across the globe by the end of this century. With rapidly changing environments due to human activities, it is crucial to be able to predict what will happen to marine organisms and in particular fish populations to optimise our conservation and management efforts.

The study here indicated some fish species that evolve more rapidly may have a flexible way to cope with OA, which should be helpful for these species to maintain their population size and biodiversity. However, for some other species evolving slowly, OA will be difficult for them once the OA level is beyond their tolerance levels.

Natural laboratories with elevated pCO2

Volcanic CO2 seeps can be used as natural laboratories where CO2 rises from the substratum and acidifies the surrounding seawater to levels similar to, or sometimes beyond, the projections for ocean acidification by the end of this century. Six adult coral reef fish species including damselfishes and a cardinalfish species from a reef within the Upa-Upasina CO2 seep in Papua New Guinea (pH 7.77, pCO2 846 µatm) and an adjacent reef (500 m distance) with ambient pCO2 (pH 8.01, pCO2 443 µatm) were sampled, tissues were extracted, analysed and sequenced for their cellular response to elevated CO2 in their brains. The six fish species in this study are common coral reef fish but exhibit slightly different ecologies including differences in parental care and being active during the day or night, and therefore we can, to a certain extent, extrapolate the found patterns also to other fishes.

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Three critical factors in the end-Permian mass extinction

Blueprint for today’s climate change?

The end of the Permian was characterized by the greatest mass extinction event in Earth’s history. 252 million years ago, a series of volcanic eruptions in Siberia led to a massive release of greenhouse gases. In the course of the next several millennia, the climate ultimately warmed by ten degrees. As a consequence, on land, roughly 75 percent of all organisms went extinct; in the oceans, the number was roughly 90 percent.

By analyzing how the now-extinct marine organisms once lived, Dr. Foster and his team were able to directly link their extinction to the following climate changes: declining oxygen levels in the water, rising water temperatures, and most likely also ocean acidification.

Fossils that be became extinct millions of years ago can reveal various aspects of how they lived. Credit: W.J.Foster
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Sediment cores from ocean floor could contain 23-million-year-old climate change clues

Texas A&M oceanographers are examining ancient methane gas ocean cores that reveal clues about global and environmental changes.

Methane gas bubbles rising from the ocean floor. Justin Kim

Sediment cores taken from the Southern Ocean dating back 23 million years are providing insight into how ancient methane escaping from the seafloor could have led to regional or global climate and environmental changes, according to a study from two Texas A&M University researchers.

Yige Zhang, assistant professor in the Department of Oceanography at Texas A&M, and doctoral student Bumsoo Kim have had their work published in the current issue of Nature Geoscience.

The oceanographers examined cores – sediment samples from deep parts of the ocean floor – from the Oligocene-Miocene era, roughly 23 million years ago, from areas near Tasmania and Antarctica in the Pacific sector of the Southern Ocean. There are billions of tons of carbon stored beneath the ocean floor as gas hydrates – ice-like crystals composed of water and natural gas. Past releases of methane are believed to be related to huge earth events, such as global warming and subsequent climate shifts.

“For a long time, people thought that methane released from the ocean floor could go into the atmosphere and directly contribute to the greenhouse effect, leading to rapid warming and even mass extinctions,” Zhang said. “But this idea is no longer popular in the last decade or so because we lack direct evidence of methane release in Earth’s history. Also, modern observations show that even when methane gases are released, they rarely make it to the atmosphere.”

However, Kim and Zhang are now able to document past methane release by using markers that consume methane. These “methane-eating” substances are preserved in sediments for tens of millions of years, the researchers said. They could provide direct evidence of methane release from different places in the Southern Ocean.

“We saw that a methane release occurred during a peak glaciation about 23 million years ago,” Zhang said.

Glaciation is the formation, movement and recession of glaciers, and the process mostly commonly occurs in Antarctica and Greenland. When large ice sheets form, they draw in a tremendous amount of water that could lower the sea-level by tens to hundreds of feet.

Zhang added that the methane gas release and its after-effects led to ocean acidification and hypoxia (a lack of oxygen in the water), something that has been observed after the Deepwater Horizon incident in 2010, when large amounts of methane were released in the Gulf of Mexico.

“One implication of our study is that if gas hydrates start to decompose in the future due to ocean warming, places like the Gulf of Mexico could suffer severely from ocean acidification and expansion of the low oxygen ‘dead zones’,” Kim said.

The project was funded by Texas A&M’s T3 grants and Texas Sea Grant.

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Jiang leads international effort to create new data standard for oceanographic research

Figure: A rosette of Niskin (seawater sampling) bottles used to collect discrete water samples at specific, predetermined depths. Instruments for measuring depth, temperature, and conductivity (which helps determine salinity) are inside of the ring near the bottom (not visible). (Photo provided to Jiang et al. by Sabine Mecking of the University of Washington for the publication).

ESSIC/CISESS Scientist Li-Qing Jiang, who works on the Ocean Carbon Acidification Data System (OCADS) project at the National Center for Environmental Information (NCEI), coordinated a massive effort by the international community to develop a best practice data standard for discrete bottle-based chemical oceanographic data. The study, co-authored by ESSIC/CISESS Scientist Alex Kozyr and esteemed scientists at over 30 institutions in 10 countries, was published on January 21st in Frontiers in Marine Science

Effective data management is paramount in oceanographic research because investigations of regional and global oceanographic processes often involve compiling cruise-based data from different laboratories and expeditions, such as the seawater collection depicted in the image below. The creation of the international data standard was motivated by feedback from OCADS users and covers column header abbreviations, quality control flags, missing value indicators, and standardized calculation of numerous parameters. This project represents a major step forward in terms of (a) bringing the subject matter expertise from the research community to the data management world, and (b) creating common data standards for the international ocean acidification (OA) research community, so as to streamline data management, quality control, and data product developments. It creates the potential for future data management automation, and the creation of a unified data access interface for OA data residing at international locations. In turn, this effort will promote the advancement of ocean biogeochemistry research on regional to global scales. 

Jiang is a chemical oceanographer specializing in the study of inorganic carbon cycling and ocean acidification in coastal and global oceans. He received his Ph.D in Oceanography from the University of Georgia in 2009 and did his postdoctoral research at Yale University. Dr. Jiang has been working at NOAA’s National Centers for Environmental Information (NCEI) since 2011. He is currently the lead principal investigator of the Ocean Carbon and Acidification Data System (OCADS) project, which is partially funded by NOAA’s Ocean Acidification Program (OAP). In addition to data management, Dr. Jiang has been leading the North American coastal synthesis project.

To access the paper, click here: “Best Practice Data Standards for Discrete Chemical Oceanographic Observations”.

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River runoff creates a buffer zone for ocean acidification in the Gulf of Mexico

Feature image photo credit: NASA’s Moderate Resolution Imaging Spectroradiometer

A new study by scientists at NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) and Northern Gulf Institute (NGI) has revealed the alkalinity of river runoff to be a crucial factor for slowing the pace of ocean acidification along the Gulf of Mexico’s northern coast. This valuable, first-time finding may be indicative of ocean carbon chemistry patterns for other U.S. coastal areas significantly connected to rivers.

The research, published in Geophysical Research Letters, used models to identify the main drivers of ocean acidification for different regions of the gulf. They provide evidence that river alkalinity has counteracted the progression of ocean acidification for coastal areas along the gulf.

Ocean acidification refers to a reduction in seawater pH over time, mainly caused by increased levels of carbon dioxide in the atmosphere being absorbed into the ocean. Seawater chemically reacts with carbon dioxide to form carbonic acid, causing the ocean to become more acidic. 

The pH scale indicates the concentration of hydrogen ions in a solution. It works in an inverse way such that the higher the concentration of hydrogen ions, the more acidic and the lower the pH value will be. The lower end of the scale is acidic and the higher end of the scale is basic or alkaline. Image Credit: NOAA Pacific Marine Environmental Laboratory (PMEL), available at

These changes in ocean chemistry negatively impact marine species such as corals and shellfish by impairing their ability to grow and survive. As the ocean’s pH level decreases, there is also a reduction in the aragonite saturation statei.e., the water conditions that will more likely dissolve calcium carbonate, one of the materials used by shells and coral skeletons to form their structure. 

Corals and shellfish need a higher aragonite saturation state and less acidic waters, i.e., higher on the pH scale, to thrive. If waters become too acidic, less coral reef habitat will be available for fish and other reef dwelling animals, diminishing biodiversity and marine ecosystem health. 

The Mississippi River has a relatively high level of alkalinity for a freshwater body. Over recent decades, agricultural practices such as liming (adding neutralizing materials to lower soil acidity) and water quality improvements have contributed to the increased water alkalinity in the Mississippi River system. Alkalinity acts as a neutralizing factor to make a solution less acidic and more basic or alkaline. 

“Our study showed that river alkalinity inputs from the Mississippi River can offset the progression of ocean acidification in northern coastal areas of the Gulf of Mexico. We can expect river alkalinity to have a similar counteracting effect on ocean acidification in other US coastal regions, since the dominant pattern for US rivers is alkalinization,” said Fabian Gomez, a research scientist at AOML and NGI.

Average surface aragonite saturation state (ΩAr ), an indicator for ocean acidification (left), and its long-term trend (right) showing less acidic waters (with a higher aragonite saturation state) around the northern inner-shelf of the Gulf of Mexico. This ocean acidification buffer was caused by the Mississippi-Atchafalaya River’s alkaline water mixing and neutralizing the seawater in that area.

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Marine science during Covid-19

A large-scale ocean acidification capacity building program for developing countries led by the IAEA learns from the COVID-19 crisis to develop a new strategy

Developing countries are among the most sensitive to climate and other environmental changes. Efforts to reverse the cycle of decline in environmental health is highly dependent on local science. However, developing countries are also facing tremendous practical challenges and scientists often have limited access to laboratories and equipment.

This is particularly true in the field of ocean acidification. Ocean acidification is the ongoing increase in ocean acidity resulting from the anthropogenic carbon dioxide (CO2) emissions since the beginning of the industrial era. The potential impacts to marine ecosystems and associated services have resulted in ocean acidification becoming one of the targets for the United Nations Sustainable Development Goals (SDGs). SDG target 14.3 aims at “Minimizing and addressing the impacts of ocean acidification, including through enhanced scientific cooperation at all levels”.

The International Atomic Energy Agency (IAEA) Ocean Acidification International Coordination Centre (OA-ICC) is working with international partners to promote the development and implementation of best practices for ocean acidification research. Since 2012, the OA-ICC has supported and organized 29 training courses and workshops on ocean acidification with more than 460 participants from around the world. The OA-ICC works to raise awareness around ocean acidification among stakeholders and inform the global community about the role that nuclear and isotopic techniques can play in assessing its impacts.

We quickly realized the challenge of training scientists in developing countries as complex techniques and methodologies are often required in ocean acidification science. Our evaluation showed that many institutions are lacking the most basic laboratory infrastructure”, explained Ashley Bantelman, lead project officer for the OA-ICC.

The COVID-19 pandemic has limited the ability of researchers to generate new science, particularly in the field of ocean acidification, which put many marine scientists in industrialized countries in situations similar to those of colleagues in developing countries.

Sam Dupont, Senior Lecturer at the University of Gothenburg and IAEA expert, explains “in 2020, with colleagues from all around the world, we had planned a joint experiment to test a theoretical idea we had published in 2017 in Nature Ecology and Evolution. But without being able to travel, we had no way to conduct those experiments, so we decided to test our idea using existing data in the literature”.

This exercise led to a new article published in Nature Climate Change and has provided new ways to understand the sensitivities of marine species to ocean acidification. The article highlights the importance of combining field chemical monitoring and biological studies. It also demonstrates that it is possible to create new knowledge from the resources already available.

At the IAEA OA-ICC, we have created an ocean acidification bibliographic database as well as a data compilation on the biological response to ocean acidification that can be used by scientists lacking experimental facilities to test their ideas and hypotheses”, says Florence Descroix-Comanducci, Director of the IAEA Environment Laboratories.

A new generation of training focusing on this approach will be organized by the IAEA OA-ICC in 2022.

Reference: Vargas C. A., Cuevas L. A., Broitman B. R., San Martin V. A., Lagos N. A., Gaitán-Espitia J. D. & Dupont S., in press. Upper environmental pCO2 drives sensitivity to ocean acidification in marine invertebratesNature Climate Change.

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L’impact réel de l’acidification des océans sur le comportement des poissons n’a rien à voir avec ce qu’on en a longtemps dit (in French)

Alors que le One Ocean Summit (sommet international sur l’océan) débute mercredi 9 février à Brest, une méta-analyse des chercheurs de l’université norvégienne des sciences et technologies de Trondheim apporte un nouvel éclairage sur cet enjeu.

Photo sous-marine d'un banc de poissons prise au large de l'île de Saint-Barthélémy.
Photo sous-marine d’un banc de poissons prise au large de l’île de Saint-Barthélémy.

Vous avez récemment publié une étude intitulée “Une méta-analyse révèle un “effet de déclin” extrême des impacts de l’acidification des océans sur le comportement des poissons” (“Meta-analysis reveals an extreme “decline effect” in the impacts of ocean acidification on fish behavior“). Comme son nom l’indique, vous avez observé un “effet de déclin”. Pour les personnes qui ne sauraient pas de quoi il s’agit, comment définiriez-vous cet “effet de déclin” ?

Jeff C. Clements, Josefin Sundin, Timothy D. Clark, Fredrik Jutfelt : L’effet de déclin décrit la tendance de la force des effets, ou de la force des preuves, d’une affirmation scientifique à diminuer avec le temps.

Par exemple, lorsque les scientifiques mesurent l’effet d’un élément sur un aspect de la biologie – qu’il s’agisse de l’effet du café sur votre rythme cardiaque ou, dans le cas présent, de l’effet de l’acidification des océans sur le comportement des poissons – les effets peuvent aller de très forts à nuls.

Lorsque de nouvelles découvertes scientifiques sont faites et publiées, les effets sont généralement assez forts. Mais dans certains cas, alors que de plus en plus d’études tentent de reproduire ces effets, leur intensité diminue pour diverses raisons.

Dans le cas de l’impact de l’acidification des océans sur le comportement des poissons, comment se manifeste-t-il ? Quelle est son importance ?

Nous avons constaté que si les études initiales testant les effets de l’acidification des océans sur le comportement des poissons ont rapporté des effets très forts, la force de ces effets a diminué de telle sorte que les études des cinq dernières années ont rapporté des effets négligeables depuis 2015.

Cette constatation est importante car elle suggère que, si d’autres aspects du changement climatique auront des effets négatifs sur les espèces marines, l’acidification des océans pourrait ne pas avoir d’effets graves sur le comportement des poissons comme on le pensait auparavant.

Cela signifie-t-il que les nouvelles inquiétantes que nous avons entendues ces dernières années concernant les effets de l’acidification des océans sur le comportement des poissons sont totalement inexactes ?

Nous pensons que les résultats des premières expériences ont fortement surestimé le véritable effet de l’acidification des océans sur le comportement des poissons. Si des conditions de CO2 élevées peuvent affecter certaines espèces dans des circonstances spécifiques, nos résultats suggèrent que l’acidification des océans n’a pas d’effets généraux sur le comportement des poissons.

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Ocean acidification, global warming affecting supply of seafoods

A school of Japanese amberjack at the north-east coast of Taiwan. A new report warns that ocean warming and acidification are affecting the behaviour of fish. Copyright: Vincent C. Chen(CC BY SA 4.0). This image has been cropped.

Seafood supplies risk been affected if ocean acidification and global warming continue to interfere with the group interaction of fishes. This is according to a study.

Ocean acidification and global warming are interfering with the way fish interact in groups, posing a threat to their survival which could affect seafood supplies, researchers say.

Marine ecosystems worldwide have shown an increased dominance of warm water species following seawater temperature rise, with parallel changes in the species composition of fish catches since the 1970s, according to a report by the Intergovernmental Panel on Climate Change (IPCC).

Global fish catches

Fisheries from marine ecosystems provide foodnutrition, income and livelihoods for many millions of people around the world, the IPCC, said. Globally, total fish catches amount to 80—105 million tonnes annually, generating over US$80 billion in revenue, the report said.

“Fish show gregarious behaviour and cluster in shoals which helps them to acquire food and protects them against predators,” says Ivan Nagelkerken, professor at the University of Adelaide’s Environment Institute and Southern Seas Ecology Laboratories and author of a study on the effect, published in Global Change Biology.

Warming, acidification, marine ecosystems

Under controlled laboratory conditions, the researchers observed how species interacted and behaved in new ways with changing temperature and acidification. While warming and acidification are different phenomena, they interact to the detriment of marine ecosystems.

According to Nagelkerken, mixed shoals of tropical and temperate species became less cohesive under future climate conditions and showed slower escape responses from potential threats. Strong shoal cohesion and coordinated movement, whether to acquire food or evade predators, are important for fish survival.

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Study examines the effects of ocean acidification on phytoplankton’s energy stores

Credit: Pixabay/CC0 Public Domain

Ocean acidification—which is mainly caused by carbon dioxide gas in the atmosphere dissolving into the ocean—is a significant threat to the structure and function of marine life. In a study published in the New Phytologist, investigators have uncovered the different effects that ocean acidification has on the energy stores of phytoplankton (single-celled plants that are critical to the aquatic food chain) called diatoms.

The work focused on diatoms from a natural Antarctic phytoplankton community exposed to a gradient of carbon dioxide levels. Certain diatoms showed preferences towards proteins at high carbon dioxide levels, while others increased both lipid and protein stores.

Studying these adaptations to carbon dioxide levels may reveal how phytoplankton responses to climate change could have cascading effects on food web dynamics in the world’s oceans.

“To date, we know little about how ocean acidification will affect the nutritional value of phytoplankton. Our study showed that diatom species exposed to acidified conditions change the way they store excess energy in unique ways,” said senior author Katherina Petrou, Ph.D., Associate Professor at the University of Technology Sydney. “Our work suggests that ocean acidification will influence the type of energy available at the base of the food web, which ultimately could affect the productivity of our marine ecosystems.”

More information: Rebecca J. Duncan et al, Ocean acidification alters the nutritional value of Antarctic diatoms, New Phytologist (2022). DOI: 10.1111/nph.17868

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