Revealing critical insights into air-sea carbon dioxide exchanges, pH trends in the North Atlantic, and detailed observations in UK shelf seas, the study also details how ocean acidification impacts marine species through both direct physiological effects from changing pH and CO2 levels and indirect effects via food web disruption.
While some organisms like certain phytoplankton and seaweeds may show positive or neutral responses to elevated CO2, many marine invertebrates and fish species experience neutral or negative effects. Species that build calcium carbonate structures, including corals, shellfish, and important plankton groups, face particularly high risk. Even more developed organisms like fish, though less susceptible to direct impacts, could suffer from the loss of key prey species. The research highlights the need for better integrated approaches that scale from experiments to biogeochemical models. It also emphasizes the urgent need for enhanced observational capacity and improved model accuracy to better understand and address ocean acidification.
Atmospheric CO2 surpassed 420 ppm in 2024, continuing to rise by approximately 2.5 ppm annually over the past decade
The global ocean absorbs roughly 25% of anthropogenic carbon dioxide emissions each year
The North Atlantic Ocean, containing the highest levels of anthropogenic CO2 among ocean basins, is experiencing ongoing surface water acidification
Bottom waters in some locations are acidifying faster than surface waters
Certain marine species already show effects from ocean acidification during short-term fluctuations, potentially serving as indicators for long-term ecosystem impacts
Models project that continental shelf seawater pH will continue to decline through 2050, with rates increasing in the second half of the century depending on emissions scenarios
Coastal pH decline is projected to be faster in areas like the Bristol Channel compared to the Celtic Sea
Under high-emission scenarios, bottom waters on the North-West European Shelf seas could become corrosive to aragonite as soon as 2030
A fishing tender with 65,000 pounds of Bristol Bay red king crab arrives at Peter Pan in King Cove for processing in 2011. Photo by Margaret Bauman for The Cordova Times.
Ocean acidification appears to be a driver in the decline of Bristol Bay red king crab, a highly value wild Alaska seafood that has for years been threatened by climate change.
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A new report published on Feb. 7 in the Canadian Journal of Fisheries and Aquatic Science said that negative effects of acidification explained 21% of recruitment variability of Bristol Bay red king crab between 1980 and 2023, and 45% since 2000.
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“Anthropogenic emissions of carbon dioxide into the atmosphere have generated a substantial increase in ocean carbon uptake and a shift in the marine carbonate system to a state of higher acidity and lower carbonate saturation states in a process referred to as ocean acidification,” the report said. “Carbon dioxide is more soluble in cold water, and high-latitude waters that are naturally cold and carbon-rich, such as the Bering Sea, are particularly vulnerable to acidification.”
According to Darcy Dugan, director of the Alaska Ocean Acidification Network, these findings mark a shift in messaging from the research community.
“Prior to the study researchers believed species in Alaska were likely being impacted but we didn’t have the data or analysis to back it up,” she said. “Red king crab is the first species where we can see a correlation between acidity and the decline of a wild stock.”
Recent research reveals how fluctuations in storm season intensity can significantly influence ocean acidification (OA) conditions in the northern Strait of Georgia, located on the northeast Pacific coast. This area, characterized by weakly-buffered seawater, faced extreme OA characterized by multiple stressors, including calcite undersaturation, low pH, and elevated partial pressure of CO2 (pCO2) over three years.
The study, which utilized data from eight years of high-resolution monitoring at the long-term oceanographic station QU39, indicates stark shifts between storm seasons are pivotal for OA forecasting. The research highlights years characterized by weak storm activity, where OA conditions intensified, contrasting sharply with years of strong storms which led to healthier sea chemistry.
Researchers examined the interplay of factors leading to extreme OA, where variability in storm seasons plays a decisive role. During years with weaker storms, there was reduced conservative mixing and biogeochemical feedbacks, directly correlatively resulting in severe OA impacts. This correlation could provide predictive capacity for the coming years, illustrating the direct influence of environmental conditions on marine life vulnerability.
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Lead researcher Will Evans stated, “The emergence and abatement of corrosive conditions for calcite occurred not over extended chronologies, but rather during specific storm seasons, fundamentally reshaping the physical and biological underwater environments.” The conclusions drawn from this research underline the precarious state of the Strait of Georgia’s ecology as it grapples with anthropogenic changes.
Exploring the biogeochemical indicators, the research pointed to significant increases of total dissolved inorganic carbon (TCO2), impacting the seawater’s ability to buffer pH changes, highlighting how weakly-buffered settings are less resilient to both gradual and sudden changes.
Overall, this study not only documents the vulnerability of the northern Strait of Georgia but also emphasizes the immediate need for thorough monitoring and evaluation of coastal ecosystems as they adjust to changing climate conditions.
Dr. Emily Hall researching ocean acidification and climate change conditions on corals using a sea anemone as the model organism in the OASys lab on Tuesday, March 21st, 2017.
A pioneering study led by Mote Marine Laboratory, in collaboration with the Florida Fish and Wildlife Conservation Commission-Fish and Wildlife Research Institute (FWC-FWRI) and the U.S. Geological Survey (USGS), has uncovered a potential critical link between harmful algal blooms (HABs) and acidification in Florida’s estuaries.
The study reveals that distinct acidification events occurred following red tide blooms, and the growth of Karenia brevis (commonly referred to as Florida red tide) may contribute to ocean acidification and significant changes in water chemistry. This finding underscores the need for continuous monitoring to better understand and manage the interaction between HABs and acidification in coastal ecosystems.
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By analyzing the growth and decomposition of algal cell communities during blooms, the study revealed that biological processes play a significant role in altering water chemistry. These processes can sometimes intensify water acidity, a phenomenon closely tied to harmful algal blooms.
“This study highlights the importance of understanding how elevated CO2 affects red tide growth in natural ecosystems,” said Dr. Emily Hall, Senior Scientist and Manager of Mote’s Ocean Acidification Research Program. “By doing so, we can better anticipate and mitigate the impacts of harmful algal blooms on coastal communities.”
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By analyzing how red tide affects water chemistry, researchers have provided valuable insights into the biological and chemical processes driving acidification. Seasonal changes, such as increased carbon and alkalinity during dry periods, further emphasize the complexity of these interactions.
“Our study clearly highlights the important link between red tide and ocean acidification, but also indicates a need for much more clarity on the impacts of this connection,” said Dr. Michael P. Crosby, President and CEO of Mote Marine Laboratory. “Continuous sampling and sensor deployment are essential to understanding the relationship between K. brevis and acidification.”
The findings highlight the critical need for adaptive management strategies to protect Florida’s estuaries from the dual threats of harmful algal blooms and acidification.
Scientists at Yale and in Singapore have devised what may be the ultimate acid test — a comprehensive model for estimating the origins of Earth’s habitability, based in part on ocean acidity.
The new theoretical model applies previously published, Yale-led research to a wide range of interconnected geological and atmospheric processes. It may provide the clearest picture yet of how Earth evolved to a point where life was able to flourish.
“This is a tour-de-force theoretical endeavor, bridging a longstanding gap between surface processes and processes deep in the Earth,” said Jun Korenaga, a professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences, and co-author of a new study in the journal Nature Geoscience. “This work presents by far the most comprehensive whole-Earth system model to estimate how ocean pH likely evolved during Earth’s history.”
The term pH (“potential of hydrogen”) is a measure of the concentration of hydrogen ions in an aqueous — watery — solution. A lower pH level equals higher acidity. A solution with a pH lower than 7 is considered acidic; modern-day seawater has a pH of about 8.
But it is widely believed that Earth’s ancient ocean was much more acidic, making it harder to sustain life. Many scientists have found that the synthesis of organic molecules is extremely difficult in environments with a pH level lower than 7.
El Cambio Global ha generado múltiples impactos en los ecosistemas marinos, desde la elevación del nivel del mar, hasta el aumento en la frecuencia de eventos climáticos extremos. Sin embargo, entre ellos la acidificación del océano (AO) sigue siendo un fenómeno poco comprendido a pesar de sus graves consecuencias para los ecosistemas y recursos marinos. Producida por la absorción de dióxido de carbono generado por actividades humanas, la AO altera la química del agua, dificultando la formación de conchas y estructuras calcáreas en muchas especies marinas, afectando directamente la acuicultura. En particular a bivalvos como choritos y ostiones, que podrían ver comprometida su calidad comercial debido a cambios en su color, tamaño, textura y valor nutricional, entre otros atributos.
Frente a esta problemática, un equipo de investigadores del Instituto Milenio en Socio-Ecología Costera (SECOS), la U. Católica de la Santísima Concepción, la Universidad del Desarrollo, y el Centro de Ecología Aplicada y Sustentabilidad (CAPES), entre otras instituciones, llevó a cabo un estudio publicado en la revista Future Foods. Utilizando técnicas de Preferencias Declaradas, los investigadores diseñaron un experimento para evaluar cómo la entrega de información sobre la AO podría influir en las decisiones de compra de los consumidores.
El estudio reveló que los consumidores prefieren productos con una “buena apariencia”, caracterizada por un color uniforme, ausencia de epibiontes [ciertos organismos pegados a la concha] y sin quiebres en la concha. Además, valoran la composición nutricional al momento de tomar una decisión de compra. “Justamente este es un atributo que será modificado por el cambio global, donde hemos observado una disminución en ácidos grasos, minerales, proteínas y vitaminas”, señala Valeska San Martín, investigadora del Centro de Investigaciones Costeras de la U. de Atacama y también del SECOS. La investigación además indicó que, cuando los consumidores reciben información sobre la AO, tienden a elegir el “mejor producto” disponible en el mercado, influenciados por factores como calidad, conveniencia personal y valor.
Unlike many vertebrates, oysters do not possess fixed sex chromosomes that dictate whether they develop as male or female at the moment of fertilization. Instead, they utilize a sophisticated biological mechanism known as environmental sex determination, where the surrounding environmental conditions influence their sexual development. Previous investigations have largely concentrated on factors such as temperature and food availability as drivers of sex ratios within aquatic populations; however, the role of fluctuating pH levels remained largely unexamined until now. The recent study led by researchers Xin Dang and Vengatesen Thiyagarajan breaks new ground in understanding how ocean acidification might modify the sex ratio of oysters across multiple generations, both in controlled hatchery environments and in natural habitats.
In their experiment, the researchers began with a collection of wild oysters to serve as the foundational population for their study. These oysters were divided into two groups, one maintained in water with a neutral pH and the other introduced to conditions simulating ocean acidification, characterized by a slightly more acidic pH. The results of this initial phase were revealing. The offspring of oysters that were spawned in the acidic environment exhibited a significantly higher ratio of females to males compared to the offspring of those raised in a neutral pH tank. This implies that the acidification of ocean waters could skew reproductive outputs towards female progeny, potentially altering population structures over time.
The follow-up experiments were equally illuminating. The second-generation oysters from the acidic environment were transplanted into two contrasting natural settings: one with a neutral pH and another with an acidic pH. Remarkably, regardless of whether these third-generation oysters were placed in an acidic or neutral pH habitat, they still exhibited an increased female-to-male ratio. This observation strongly suggests that the effects of ocean acidity on sex determination are not merely a transient phenomenon; rather, they can persist across generations. Such findings provide deeper insights into the transgenerational impacts of environmental stressors on marine life.
Recent research indicates a delayed onset of ocean acidification in the Gulf of Maine due to complex water mass interactions and temperature variations. The Gulf of Maine, significant for its ecological and economic value, particularly for fisheries, has become the focus of increasing scrutiny due to concerns about rising atmospheric CO2 levels affecting marine life。
The study reveals a surprising trend: seawater pH levels were low (~7.9) for much of the last century, but increased by +0.2 pH units over the past 40 years, contradicting the rising levels of atmospheric CO2. This unexpected increase raises questions about the factors influencing coastal water chemistry and the potential impacts on marine species.
Conducted by researchers including J.A. Stewart, B. Williams, and M. LaVigne, the study spans pH records from 1920 to 2018 CE, primarily focusing on changes noted from 1980 to 2000 CE. The researchers employed boron isotope measurements from long-lived coralline algae to create proxy records indicating seawater pH trends.
Significantly, the researchers highlight the remarkable interplay between different water masses within the Gulf of Maine. The influx of warmer, higher alkalinity waters derived from the Gulf Stream contributed to the increased pH, acting as a buffer against ocean acidification’s effects.
Coastlines face growing threats as climate change accelerates. Research from the University of Prince Edward Island warns that warming waters, ocean acidification, sea-level rise, and erratic rainfall are driving coastal ecosystems toward irreversible changes.
Critical habitats like mangroves, coral reefs, and wetlands, which protect against storms and support fisheries, are at risk of steep decline.
Global data reveals that heatwaves, shifting storm patterns, and disrupted river flows are pushing these ecosystems to the brink, threatening their stability and identity.
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Ocean acidification and brittle defenses
Oceans absorb carbon dioxide, becoming more acidic and making it harder for shellfish, corals, and some plankton to grow. Weakening these creatures means less food for predators and fewer stable habitats.
Laboratory work and field studies show that corals already struggle with bleaching and diseases when seas heat. Acidified waters add another layer of stress by reducing their ability to build and maintain reef structures.
According to the Pew Charitable Trusts, “unless global climate change is curbed, some of the world’s most productive coastal habitats could be irreversibly transformed.”
This spells trouble for communities relying on reefs for coastal protection, tourism, and sustenance.
Climate shift and coastal currents
With more intense hurricanes and unexpected winds, coastal habitats must work harder to recover from pounding waves and scoured seabeds.
Extreme storms can break coral skeletons, uproot mangroves, and bury seagrasses under sediment.
NOAA notes that “coastal ecosystems are on the frontline of climate change, with rising seas, warming waters, and coastal acidification already impacting fisheries, wetlands, and coral reefs.”
If protective habitats vanish, shorelines will feel the full brunt of storms. Altered ocean currents and changed upwelling patterns can also redirect nutrient flows, starve certain zones of essential ingredients, and shift fish stocks away from regions that depend on them.
Adding local fuel to the fire
Coastal development, runoff, and unsustainable fishing make climate problems worse. By degrading water quality, removing natural buffers, and altering sediment flows, human actions reduce the resilience of coastal habitats.
WWF’s Living Blue Planet report states that “climate change is affecting coastal systems at all levels — from coral reefs to Arctic ice-edge zones — and urgent action is needed to preserve these essential ecosystems.”
When layered on top of warming, acidification, and sea-level rise, these local pressures lock ecosystems into downward spirals.
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A call for climate coastal action
Halting greenhouse gas emissions is a big step. Reducing local stress — like runoff and destructive construction — helps too.
Many places already experiment with restoring marshes, planting mangroves, or opening fish passages in tidal zones. These steps buy time and boost resilience, but they are not a substitute for cutting emissions.
To keep vital resources intact, global and local efforts must move together. The sooner we make changes, the better our odds of passing on healthy coastal ecosystems to future generations.
The eastern Bering Sea is a highly productive marine ecosystem, supporting more than 40 percent of the annual commercial fisheries landings by volume in the United States. Scientists have developed new models that predict more extreme changes in this ecosystem by the end of the century. They anticipate larger summer northward shifts and changes (both increases and decreases) in the area occupied by important commercial crab and fish species.
Specifically, the majority of models estimate changes in the center of distribution for several commercially important species. They predict that most species’ summer distributions will shift north by between 50 and 200 kilometers by 2080-2089. Scientists also project:
Large declines in the amount of area occupied by red king crab and snow crab and potentially northern rock sole in the summer months.
A substantial increase in the area occupied by arrowtooth flounder, a key predator of walleye pollock.
Declines in probability of occurrence for most species in areas with low pH and oxygen concentration.
These changes are altogether more extreme than previous species distribution model projections, which accounted for fewer climate effects.
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Maps of two metrics of environmental novelty in the Bering Sea survey region for average temperature, pH, and oxygen conditions during 2040-2059 and 2080-2099, under each climate scenario (SSP 1-2.6 & SSP 5-8.5) and ESM (CESM, GFDL, & MIROC). Areas in gray are those for which temperature, pH, and oxygen are within the range of the average hindcasted conditions between 1995 and 2015. Areas in red / orange are those for which temperature, pH, and/or oxygen lie completely outside of the set of average conditions observed between 1995 and 2015. Areas in blue / green are those for which temperature, pH, and oxygen lie inside the range of hindcasted conditions, but represent novel combinations of these covariates. For both metrics, brighter colors indicate more novel conditions.
New and Better Models to Anticipate Ocean Changes
Scientists built species distribution models for eight common and/or commercially important species of groundfish and crabs in the eastern Bering Sea (adults and juveniles). These include walleye pollock, Pacific halibut, Pacific cod, arrowtooth flounder, northern rock sole, yellowfin sole, snow crab, and red king crab.
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To date, most studies projecting marine species distributions rely principally on temperature and static habitat characteristics such as depth. This can potentially lead to significant underestimation of species vulnerability to climate change.
However, for this study, ecologists combined 40 years of scientific surveys with a high-resolution oceanographic model. This model was adapted to the eastern Bering Sea by scientists at NOAA’s Alaska Fisheries Science Center as part of the Alaska Climate Integrated Modeling project. They examined the effects of bottom temperature. But they also incorporated information on oxygen, pH, and a regional climate index (the extent of the eastern Bering Sea “cold pool”). They considered all of these factors to produce a range of different climate projections through the end of the century. Model projections also anticipated warming under both low and high greenhouse gas emission scenarios.
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Oxygen and pH
The oceans absorb about 30 percent of global carbon dioxide emissions, and warmer water holds less oxygen. Climate change is also leading to the acidification of deoxygenation of much of the global ocean. All animals need oxygen to survive, and many species are expected to shift towards deeper, cooler waters to keep up with climate change. Lower dissolved oxygen content at depth may constrain their ability to do so. Reduced pH in water has the potential to impair organisms by changing their metabolism and physiological function. For crabs and other calcifying organisms, it can decrease calcification and shell formation rates.
Yet, few studies projecting future changes in species distributions integrate the effects of oxygen and pH. In many cases, these variables are not available to modelers, but recent advances in oceanographic modeling have made it possible to include their effects.
The authors found that the estimated effects of oxygen and pH were largely consistent among species. Where environmental oxygen and pH levels were lower, groundfish and crabs were less likely to be observed in scientific surveys. However, they also found the effects of oxygen and pH were difficult to disentangle using survey data, so they modeled their effects using separate models. In projecting future climate-driven changes in species distributions, they gave more say to models that did a better job reproducing past trends.
Where Scientists Hope to Go Next with this Research
These results build on—and in many cases agree with—previous distribution modeling efforts in the Bering Sea. However, they demonstrate that models that account for factors beyond temperature can result in more pronounced range shift projections.
“What’s really exciting about this research is we are now able to construct long-term species range forecasts, which incorporate a wider array of climate impacts,” said Kirstin Holsman, co-author and research fishery biologist, Alaska Fisheries Science Center.
In future work, species distribution models may be used to improve the representation of species interactions in multispecies stock assessment models. Scientists also hope to be able to produce short-term forecasts and long-term projections that incorporate a better understanding of predator-prey overlap.
Antarctica is approaching a series of cascading tipping points that could reshape ecosystems and intensify global climate disruptions, according to a new study by an international team of scientists, including researchers from the University of Tasmania.
The study identifies eight potential tipping points spanning physical, biological, chemical, and governance systems. The research is published in the journal Ambio.
These include collapsing ice sheets, invasive species, ocean acidification, and pressures on the Antarctic Treaty System (ATS), which oversees human activity in the region.
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The study warns that these tipping points are interconnected, creating a risk of cascading effects.
Melting ice sheets, for example, not only contribute to sea-level rise but also disrupt ocean circulation, which is crucial for transporting heat, carbon, and nutrients around the globe. Such disruptions threaten marine ecosystems, global fisheries, and food security.
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At the same time, the Southern Ocean’s ability to absorb carbon dioxide—a crucial buffer against global warming—is diminishing.
“The interconnected nature of these systems means small failures can quickly escalate,” Professor King said. “Without decisive action, we risk triggering a chain reaction with far-reaching and irreversible consequences.”
The researchers call for stronger international cooperation, urgent climate policies, and greater investment in Antarctic science. Their findings frame Antarctica not as a remote and isolated region, but as a critical player in the Earth’s environmental systems.
The rise in carbon dioxide (CO2) levels in our world’s atmosphere is fueling an environmental threat to marine life. Ocean acidification is growing in magnitude as it moves into deeper waters.
Jens Müller and Nicolas Grube are environmental physicists in the Institute of Biogeochemistry and Pollutant Dynamics at ETH Zurich. They set out to investigate the consequences of acidification by developing a 3D model of our oceans.
The research, recently published in the journal Science Advances, sheds light on how ocean acidification has intensified since the industrial revolution kicked off.
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Mapping ocean acidification depths
Müller and Grube carefully designed an experiment to untangle the spread of ocean acidification.
Their focus: How deep down has acidification seeped into our oceans over time? To answer this, they developed an ocean model simulating the effects of rising atmospheric CO2 levels.
The model was based on historical data spanning over two centuries, with CO2 estimates for the years 1800, 1994, 2004, and 2014. This gave the researchers a timeline to monitor how acidification spread through the ocean layers.
Constructing the ocean model
Creating a model of this scale required careful planning. Starting with a standard ocean model that simulates water movement and chemistry, the researchers then added data points on CO2 levels and acidification indicators like proton concentrations, pH levels, and aragonite saturation states.
This comprehensive approach enabled the experts to accurately map acidification trends.
Acidification reaches new ocean depths
Ocean acidification is moving deeper into the ocean, with the average depth impacted by acidification measuring around 1,000 meters by 2014.
In regions influenced by the Atlantic meridional overturning current, acidification reached depths of up to 1,500 meters.
But this spread isn’t uniform; different ocean regions face varying levels of change due to factors like water circulation patterns and temperature.
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Future implications of deeper acidification
Müller and Grube’s findings emphasize the urgent need to address carbon emissions. As CO2 levels rise, ocean acidification will only get worse.
The deeper it goes, the harder it is to reverse the impacts. The long-term consequences for marine biodiversity and human communities relying on ocean resources are unclear.
Reducing carbon emissions will help slow acidification. Initiatives to shift to renewable energy, enhance energy efficiency, and promote conservation could also contribute.
New research out of the School of Public Policy shows how policymakers can help shellfisheries in Northern California and Oregon adapt to ocean acidification caused by climate change
Average ocean pH has declined by 30 percent since the industrial revolution, a process termed Ocean Acidification (OA), which has direct, negative impacts on coastal communities reliant on ocean industries such as fishing and shellfish-specific aquaculture.
New research by Erika Allen Wolters, assistant professor of political science, and Ana Spalding, associate professor of marine and coastal policy (currently based at the Smithsonian Tropical Research Institute in Panama), examines how existing U.S. State and Federal policies impact the ability of shellfish growers in California and Oregon to adapt to OA. The paper, published in Marine Policy and supported by the National Oceanic and Atmospheric Administration, also identifies areas of opportunity for policymakers to better support shellfish growers.
This research builds on previous studies by Wolters and Spalding on the adaptive capacity of shellfish growers in both California and Oregon; both of which were published in Ocean and Coastal Management.
Coastal communities in California, Oregon, and Washington, are uniquely vulnerable to OA. This is due to both socioeconomic reliance on marine resources, like shellfish farming, and, in many cases, their geographic positioning along OA “hot spots” where a confluence of global and local variables such as runoff, pollutants, and coastal upwelling push pH levels to relatively extreme lows compared to other regions.
OA directly affects oysters during their seedling stage. The ocean is absorbing more carbon dioxide than ever before, however a lower pH means there’s less calcium carbonate in the water, which shellfish rely on to build their essential shells. As acidity increases, shells become thinner and growth slows.
Paleo-locations of SST proxies and CaCO3 datasets for the PETM. Credit: Nature Geoscience (2024). DOI: 10.1038/s41561-024-01579-y
A research team led by Prof. Li Mingsong at Peking University has provided new insights into the Paleocene-Eocene Thermal Maximum (PETM) and its effects on ocean chemistry.
The study, titled “Coupled decline in ocean pH and carbonate saturation during the Palaeocene–Eocene Thermal Maximum,” published in Nature Geoscience reconstructs ocean acidification during this ancient climate event, offering parallels with current trends linked to human-driven CO2 emissions.
The Paleocene-Eocene Thermal Maximum (PETM), 56 million years ago, was a major carbon release event that resulted in rapid global warming and significant ocean acidification. This study highlights parallels with current climate change, emphasizing the need to understand past events to predict future impacts. The findings stress the urgency of addressing human-driven CO2 emissions to protect marine ecosystems, particularly in vulnerable regions like the Arctic.
Ocean acidification
The team used paleoclimate data assimilation (DA), integrating proxy data and Earth system model simulations to reconstruct ocean carbonate chemistry. Atmospheric CO2 rose dramatically from 890 ppm to 1980 ppm during the PETM. Acidification was most severe in high-latitude regions, similar to current trends in the Arctic, where aragonite saturation is declining.
The PETM was triggered by a massive carbon release, causing rapid warming and disrupting ecosystems. Ocean pH declined by 0.46 units, from 7.91 to 7.45, causing widespread disruptions to marine life. The ocean acidification led to the extinction of 30%–50% of benthic foraminifera and significant marine biodiversity loss.
Current CO2 emissions are rising faster than during the PETM, threatening marine ecosystems and emphasizing the need for urgent climate action.
More information: Mingsong Li et al, Coupled decline in ocean pH and carbonate saturation during the Palaeocene–Eocene Thermal Maximum, Nature Geoscience (2024). DOI: 10.1038/s41561-024-01579-y
Planktonic foraminifera are tiny marine organisms important for the ecosystem. In response to increasing ocean warming and acidification, they are migrating deeper in an effort to survive. Sonia Chaabane, Julien Sulpis
Planktonic foraminifera — single-celled organisms who live in seawater — are under threat from warming oceans, a press release from the Max Planck Society said. In tropical regions, the unprecedented conditions could lead to more extinctions.
“Our data shows that planktonic foraminifera, which play a crucial role in the ocean’s carbon cycle, are struggling to survive in a rapidly changing climate. These organisms are like sentinels, warning us of the drastic effects that warming and acidification have on marine ecosystems,” said lead author of the study Sonia Chaabane, a researcher at the Max Planck Institute for Chemistry and the European Centre for Research and Teaching in Environmental Geosciences (CEREGE), in the press release.
The international team of researchers from Germany, France, Japan, Spain and the Netherlands analyzed almost 200,000 datasets going back to 1910 to find out how planktic foraminifers responded to climate change.
The researchers found that many species of foraminifera are migrating toward the poles at rates as high as 10 kilometers a year to escape rising sea surface temperatures. The data also showed that some species are migrating deeper into the ocean in search of cooler waters.
Even with these adjustments, foraminifera populations have shrunk by a quarter in the past eight decades. Tropical species have been the most impacted due to their reproductive cycles being disrupted by the extreme warming in these regions.
Rising carbon dioxide levels in the ocean, coupled with ocean acidification, lower calcium carbonate formation. Foraminifera use calcium carbonate to build their shells. When plankton die, their empty shells sink to the seafloor, so less shell production means less carbon storage.
“Rising carbon dioxide emissions are provoking ocean warming and acidification, altering plankton habitats and threatening calcifying organisms, such as the planktonic foraminifera (PF). Whether the PF can cope with these unprecedented rates of environmental change, through lateral migrations and vertical displacements, is unresolved,” the authors of the study wrote.
Bioindicators such as foraminifera, rather than individual measurements, are likely to provide a better understanding of the complex interactions between ecosystems and climate, the press release said.
“In view of advancing climate change, researchers are faced with the question of adaptation strategies individual species of planktonic foraminifera will develop in the near future,” said Ralf Schiebel, head of micropaleontology group at the Max Planck Institute for Chemistry, in the press release.
The study, “Migrating is not enough for modern planktonic foraminifera in a changing ocean,” was published in the journal Nature.
“Our insights into the adaptation of foraminifera during the Anthropocene suggest that migration will not be enough to ensure survival. This underscores the urgent need for us to understand how the interplay of climate change, ocean acidification and other stressors will impact the survivability of large parts of the marine realm,” the scientists wrote in the study.
Measurements were taken in various different sea states during two trips on royal research ships. Daniel Ford, CC BY-NC-ND
The oceans play a pivotal role in drawing down atmospheric carbon dioxide (CO₂) and have so far acted as a brake on the full impact of climate change. Current estimates of the CO₂ from the atmosphere that disappears in the ocean, commonly referred to as the ocean CO₂ sink, suggests that around 25% of all human CO₂ emissions have been taken up by the oceans.
In our recent journal paper in Nature Geoscience, we show that a thin layer at the ocean surface called the “ocean skin,” a layer thinner than a human hair, increases this ocean CO₂ uptake by about 7%. That sounds like a small difference, but this additional uptake is equivalent to the CO₂ absorbed by the entire Amazon rainforest each year.
This long-term uptake of carbon into the ocean has negative implications for ocean health. It is slowly causing the acidification of the oceans—as sea water takes up more CO₂ it is altering the ocean chemistry and lowering its pH, and this cannot easily be reversed.
Since the 1990s, scientists have suggested that a cooler skin would enhance CO₂ uptake by the oceans. As such, estimates of CO₂ absorption that ignore this effect would be inaccurate.
Since then, the sea surface temperature researchers have shown that the ocean skin is slightly cooler than the waters just below. This surface skin is, on average, ~0.17°C cooler. A temperature change like this increases the concentration of CO₂ in this tiny sliver of water. This matters because it’s this water that is in direct contact with the atmosphere.
Because the exchange of CO₂ between the ocean and atmosphere is controlled by the concentration difference between the surface and the layer of water below, this cooler skin increases the absorption of CO₂ into the ocean.
European researchers confirmed these concentration-driven processes in 2007. They used equipment similar to a powerful microscope with a camera to visualize oxygen gas concentrations within these tiny layers in a laboratory. In recent years, the impact of the surface layer on global ocean carbon has been evaluated using theory, modeling and satellite-based observations, but until now, nobody had actually measured this effect in the sea.
To carry out our research, the European Space Agency helped us put specialist measurements on board two research ships taking part in the annual Atlantic Meridional Transect scientific cruises that each year hosts UK and international scientists.
The Triassic-Jurassic extinction was a very sudden event, researchers assert
Summary: The Triassic-Jurassic Extinction, 201.6 million years ago, has been considered by some to have been a fairly slow-burn event, driven by rising temperatures and ocean acidification. A new study says it was kicked off for the most part by volcanic winter.
201.6 million years ago, one of the Earth’s five great mass extinctions took place, when three-quarters of all living species suddenly disappeared. The wipeout coincided with massive volcanic eruptions that split apart Pangaea, a giant continent then comprising almost all the planet’s land. Millions of cubic miles of lava erupted over some 600,000 years, separating what are now the Americas, Europe and North Africa. It marked the end of the Triassic period and the beginning of the Jurassic, the period when dinosaurs arose to take the place of Triassic creatures and dominate the planet.
The exact mechanisms of the End Triassic Extinction have long been debated, but most prominent: Carbon dioxide surfaced by the eruptions built up over many millennia, raising temperatures to unsustainable levels for many creatures, and acidifying the oceans. But a new study says the opposite: cold, not warmth was the main culprit. The study presents evidence that instead of stretching over hundreds of thousands of years, the first pulses of lava that ended the Triassic were stupendous events lasting less than a century each. In this condensed time frame, sunlight-reflecting sulfate particles were spewed into the atmosphere, cooling the planet and freezing many of its inhabitants. Gradually rising temperatures in an environment that was hot to begin with — atmospheric carbon dioxide in the late Triassic was already three times today’s level — may have finished the job later on, but it was volcanic winters that did the most damage, say the researchers.
“Carbon dioxide and sulfates act not just in opposite ways, but opposite time frames,” said lead author Dennis Kent of the Columbia Climate School’s Lamont-Doherty Earth Observatory. “It takes a long time for carbon dioxide to build up and heat things, but the effect of sulfates is pretty much instant. It brings us into the realm of what humans can grasp. These events happened in the span of a lifetime.”
In the new study, Kent and colleagues correlated data from CAMP deposits in the mountains of Morocco, along Nova Scotia’s Bay of Fundy, and New Jersey’s Newark Basin. Their key evidence: the alignments of magnetic particles in the rocks that recorded the past drifting of Earth’s magnetic pole at the time of the eruptions. Due to a complex set of processes, this pole is offset from the planet’s unchanging axis of rotation — true north — and to boot, changes position by a few tenths of a degree each year. (The reason that compasses do not point exactly north.) Because of this phenomenon, magnetic particles in lavas that were emplaced within a few decades of each other will all point in the same direction, while ones emplaced, say, thousands of years later will point 20 or 30 degrees in a different direction.
What the researchers found was five successive initial CAMP lava pulses spread over about 40,000 years — each with the magnetic particles aligned in a single direction, indicating the lava pulse had emerged in less than 100 years, before drift of the magnetic pole could manifest itself. They say that these huge eruptions released so many sulfates so quickly that the sun was largely blocked out, causing temperatures to plunge. Unlike carbon dioxide, which hangs around for centuries, volcanic sulfate aerosols tend to rain out of the atmosphere within years, so resulting cold spells don’t last very long. But due to the rapidity and size of the eruptions, these volcanic winters were devastating. The researchers compared the CAMP series to sulfates from the 1783 eruption of Iceland’s Laki volcano, which caused widespread crop failures; just the initial CAMP pulses were hundreds of times greater, they say.
How climate change impacts contaminants in the sea
The ocean is warming, becoming more acidic, and losing oxygen – these are well-known effects of climate change. What has been less studied is how these changes are affecting contaminants in the seas. A new study titled “Impacts of Climate Change on the Transport, Fate, and Biogeochemistry of Contaminants in Coastal Marine Ecosystems” has investigated the interaction of trace elements with climate change. The findings have been published in the Nature journal Communications Earth & Environment.
Climate Events are Releasing More Contaminants
“We wanted to understand how trace elements are being affected by climate change – an area that has seen very little research so far,” explains Dr Rebecca Zitoun, marine chemist at GEOMAR Helmholtz Centre for Ocean Research Kiel and co-lead author of the study alongside her Croatian colleague Dr Saša Marcinek from the Ruđer Bošković Institute in Zagreb. “We examined both human-induced and natural sources.” Metals such as lead, mercury, and cadmium enter the oceans not only through human activities such as industry or fossil fuel burning. Natural sources are also changing due to climate change: rising sea levels, rivers overflowing or drying up, melting sea ice and glaciers – all these processes mobilise and increase contaminant flows.
The study summarises the findings of a working group of the UN Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) focusing on metal contaminants in the ocean. The working group was initiated by Dr Sylvia Sander, Professor of Marine Mineral Resources at GEOMAR and former head of the Marine Environmental Studies Laboratories at the International Atomic Energy Agency (IAEA) in Monaco. Christoph Völker from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) is also contributing from Germany.
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Trace Elements in Seawater are Sensitive to Climate Change
Climate changes, such as rising sea temperatures, ocean acidification, and oxygen depletion, impact trace elements in various ways.
Higher water temperatures increase the bioavailability and uptake of trace elements such as mercury by marine organisms. This happens because higher temperatures boost metabolism, reduce oxygen solubility, and increase gill ventilation, leading to more metals entering organisms and accumulating in their bodies.
As the ocean absorbs most of the carbon dioxide (CO2) released by humans, it becomes more acidic – the pH level drops. This increases the solubility and bioavailability of metals such as copper, zinc, or iron. The effect is particularly pronounced with copper, which is highly toxic to many marine organisms at higher concentrations.
Furthermore, the growing depletion of oxygen, especially in coastal zones and on the seabed, enhances the toxic effects of trace elements. This stresses organisms that live directly in or on the seabed, such as mussels, crabs, and other crustaceans.
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Helmholtz Centre For Ocean Research Kiel (GEOMAR) (via EurekAlert!), 9 October 2024. Press release.
Eelgrass and oysters are ecosystem building species that both have economic, ecological, and cultural importance in Maine. Eelgrass populates much of the soft-sediment coastal subtidal in the Northern Hemisphere, which is also where most of the world’s oysters are farmed. Eelgrass and oysters can co-occur in Casco Bay, for example.
When grown in co-culture, oysters and seagrass have may offset the negative effects of climate related stressors on one another. This phenomenon, known as phytoremediation, has been seen in other parings of mollusks and marine plants as well. This is likely because mollusks need calcium carbonate to build their shells, and marine plants can remove carbon dioxide from the water column. Because large amounts of carbon dioxide can inhibit the production of calcium carbonate, marine plants can, in theory and in practice, increase shell growth in mollusks and other calcifying organisms.
Global ocean change, including rising sea temperatures and decreasing pH, will likely impact the interactions between eelgrass and oysters. As ocean temperatures increase, coastal waters are becoming simultaneously more favorable for raising oysters and less favorable for the health and survival of eelgrass meadows. The effects of the decline of eelgrass meadows and the benefits they provide to oysters and other organisms are currently unknown.
In this study, we sought to explore the impact of ocean change on this interesting relationship.
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The How:
We grew Eastern oysters (Crassostrea virginica) and eelgrass (Zostera marina) together or independently in a manipulated system. We raised our subjects in seawater-filled bucket-based mesocosms. We simulated ocean conditions in coastal Maine in the year 2100 by heating or bubbling CO2 into the seawater. We spent our summer monitoring the mesocosms, cleaning the buckets, and taking weekly pH and temperature measurements. At the end of the summer, we collected various eelgrass and oyster growth metrics including shoot length, shoot density, belowground biomass, and condition index.
Researchers maintaining outdoor seawater experimental tanks, growing seagrass and oysters under different ocean warming and acidification scenarios. Left to Right: David Carlon, Justin Baumann, Eban Charles, and Fiona Ralph. Photo by K. Dubois.
Close up of juvenile oysters growing attached to tiles and embedded within seagrass planted in an experimental bucket. Photo by K. DuBois.
The What:
The facilitative relationship between oysters and eelgrass that exists under ambient (current) conditions became muddled under future conditions (higher temperature and lower pH). We saw that in ambient conditions both partners benefitted from co-culture, but when any future ocean stressor was added, that positive interaction was lost or possibly even reversed.
Under ambient conditions, oyster presence increased eelgrass leaf growth by 35% and clonal reproduction (a way of measuring changes in meadow density) by 38%. Oysters exposed to eelgrass in ambient conditions saw decreases in the Oyster Condition Index: they were devoting more energy to shell growth than tissue growth.
Under future ocean conditions with higher temperatures and lower pH, oysters’ positive impact on eelgrass growth disappeared. In these same conditions, oysters saw an increase in Oyster Condition Index by 36%, meaning they spent more energy building up their tissue.
These findings illustrate how susceptible species interactions are to global environmental change. In many cases such as this one, the impacts of warming and acidification can compound on one another to alter these relationships.
Coral reefs are expected to continue facing severe heat stress as rising temperatures cause the oceans to warm excessively. However, new research suggests that modifying coral feeding habits could help local populations avoid complete extinction.
A study focusing on two coral species native to Hawaii revealed that warmer waters, a result of climate change, are a major factor in coral bleaching – a process that leads to a loss of color in coral, significantly harming their health and growth.
The researchers also examined the effects of ocean acidification on heat-stressed corals. Ocean acidification occurs when seawater absorbs excess carbon dioxide and becomes more acidic.
Coral exposure to heat stress
Over the last decade, mass coral bleaching events have increased in both frequency and severity, leading to higher mortality rates among coral populations worldwide.
Study lead author Kerri Dobson completed the research as a graduate student in earth sciences at Ohio State University. She noted that this study offers hope by suggesting that some coral species may be more resilient to these extreme environmental changes.
