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CO2 hydrate deposits off Mayotte offer window into ocean carbon storage

Published 16 June 2026 Press releases Closed

CO2 hydrates releasing droplets of liquid CO2, filmed in 2021 at a depth of 1,367 meters by the Victor 6000 ROV in the Fer à Cheval area during the Geoflamme campaign aboard the Pourquoi Pas. (Image credit: Ifremer)

More than 120 CO2 hydrate deposits were discovered at the Fer à Cheval site, located 10 km east of Petite-Terre (Mayotte), during the Geoflamme expedition co-led by Ifremer and the Paris Institute of Earth Physics (IPGP) in 2021. No comparable site had ever been documented before. Published in Nature Geoscience, the study shows that this site is unique worldwide for investigating the mechanisms of transient CO2 sequestration in the ocean and the impacts of ocean acidification on biodiversity.

The data collected on these CO2 hydrates discovered in the Indian Ocean were analyzed by an international team from Ifremer, IPGP, the French Alternative Energies and Atomic Energy Commission (CEA), the French National Center for Scientific Research (CNRS), the National Oceanic and Atmospheric Administration (NOAA), and the University of Milan.

Solid CO2 Deposits at the Bottom of the Ocean

Hydrates are solid compounds similar to ice, consisting of water and gas molecules. In nature, hydrates are usually composed of methane, and it is extremely rare to find carbon dioxide hydrates on the ocean floor.

Cécile Cathalot, marine geochemistry researcher at Ifremer and the study’s lead author, said: “This is the first time we have observed clusters of CO2 hydrates that remain stable for several years on the ocean floor, of this size and in such quantities. Composed of agglomerated CO2 droplets, these domes range in height from a few centimeters to 2 meters. This discovery raises new questions about the natural mechanisms of temporary CO2 storage in the ocean. It could also fuel discussions on certain geoengineering approaches aimed at limiting climate change.”

These hydrates were observed within the active Fer à Cheval volcanic structure, located 10 km east of the island of Mayotte. Surrounded by cliffs reaching 250 meters in height, this 6 km² underwater feature is one of many structures in the underwater volcanic chain that extends east of Mayotte to the Fani Maore underwater volcano. It forms a semi-enclosed space within which CO2 released onto the seafloor accumulates periodically with the tides.

Furthermore, this site offers the conditions necessary for the formation of hydrates: the combination of cold water—here at 4 degrees Celsius—and sufficient pressure exerted by the water column at a depth of 1,400 meters.

Olivia Fandino, a specialized physical chemistry of gas hydrates researcher at Ifremer, said: “At the Fer à Cheval site, CO2 hydrates form when droplets of liquid CO2 come into contact with cold water under high pressure. A solid film then develops on their surface, the growth of which depends closely on temperature, salinity, and emission rate. What is remarkable here is that, despite the ocean currents, these hydrates were able to grow and form large, relatively stable structures.”

Structures Associated with the Fani Maore Volcano

It is likely that the emergence of these magmatic sources of liquid CO2 in the Fer à Cheval area is linked to the seismic-volcanic crisis affecting the island of Mayotte, which was notably marked by the formation of the new Fani Maoré volcano discovered in 2019. This activity likely destabilized the volcanic structure of the Fer à Cheval, which formed long before the eruption of Fani Maoré.

Unlike Fani Maoré, which has shown no activity since 2021, the Fer à Cheval site remains highly active in terms of seismicity and fluid emissions, particularly CO2.

A joint campaign conducted by Ifremer and OceanX made it possible to revisit this site of interest four years later.

Carla Scalabrin, a specialized water-column acoustics researcher at Ifremer, said: “Using the ROV Argus, deployed from the OceanXplorer vessel, we observed that the field of hydrate mounds appeared to have remained stable since 2021. The formation of these hydrates depends on the balance between incoming and outgoing carbon dioxide fluxes over time. This provides a first indication of the ability of hydrate mounds to store carbon dioxide over periods of several years.”

Studying the Adaptation of Biodiversity to Environmental Acidification

Marjolaine Matabos, benthic ecology researcher at Ifremer, said: “The dynamics of these domes, which sequester liquid CO2 and then release it as they dissolve, will be monitored over the long term to better understand the mechanisms involved and assess their viability in the medium to long term. This monitoring, conducted during the MAYOBS missions (IPGP, IPGS, BRGM, IFREMER) and as part of the Mayotte Volcanological and Seismological Monitoring Network (REVOSIMA, IPGP), could also help determine the consequences of ocean acidification for biodiversity.”

This discovery will allow researchers to study the ability of the surrounding biodiversity to thrive and adapt to changes in the acidity of their environment.

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Large CO2 seeps and hydrate field on the seafloor offshore Mayotte Island

Published 16 June 2026 Science Closed
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Gas hydrates modulate methane and carbon dioxide benthic fluxes into the ocean and usually occur embedded in the sediment. Here we use acoustic surveys alongside optical and geochemical observations from remotely operated vehicles to show that CO2 hydrate mounds are forming directly on the seafloor atop a large liquid CO2 vent field offshore Mayotte Island. The venting, which initiated following volcanic activity in 2018, deleteriously impacts surrounding coral communities due to local acidification.

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Short communication: skin melatonin and cortisol responses to water acidification and basification within the optimal pH range in three-spined sticklebacks

Published 15 June 2026 Science Closed
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Highlights

  • Cutaneous Mel, unlike cortisol, shows high sensitivity to slight shifts in water pH.
  • Water pH was regulated by a custom-designed system controlling dissolved CO2 levels.
  • High skin Mel levels and distinct pH-dependent responses indicate local Mel synthesis.

Abstract

Fish skin functions not only as a passive protective barrier but also as an active site of key physiological processes, including a local stress response system. In fish, this system involves the hormones cortisol and melatonin (Mel), which contribute to counteracting environmental stressors and maintaining homeostasis. In this study, we examined the sensitivity of both components of the cutaneous stress response system (CSRS) in three-spined sticklebacks (Gasterosteus aculeatus) exposed to acidic (pH = 6.54) and basic (pH = 8.70) water conditions, representing the boundary values of the species’ optimal pH range, under either rapid or gradual pH change regimes. Water pH in the aquaria was precisely controlled using a custom-designed gas-exchange system regulating dissolved CO2 levels. Mel concentrations were measured in the skin, brain and eyeball, while cortisol was determined in the skin. Samples were collected during the day. Skin Mel levels were significantly higher under acidification than under basification (P = 0.036; rapid change regime), whereas cortisol remained stable across all conditions. Ocular Mel levels were not affected by treatments. Brain Mel concentrations were generally very low but tended to be slightly higher under basification than under acidification in both regimes (P = 0.05, borderline significance). The marked differences in skin Mel levels between acidic and basic pH water conditions, accompanied by stable cortisol concentrations, indicates that cutaneous Mel, but not cortisol, is highly sensitive to subtle water pH fluctuations even within the species’ optimal range.

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Cross-seasonal influence of China Coastal Current water on spring carbonate system in the northern South China Sea

Published 15 June 2026 Science Closed
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This study investigates the carbonate system in the northern South China Sea shelf off the Pearl River estuary during the spring of 2023. Contrary to the typical distribution pattern observed in river-dominated coast where dissolved inorganic carbon (DIC) increases offshore, field observations revealed higher DIC in inshore waters (> 1980 µmol kg− 1) than in offshore seawaters (< 1970 µmol kg− 1), with DIC in the coastal zone being 20.9±8.8 µmol kg− 1 higher than that offshore. An end-member mixing model indicated that the high DIC coastal water was primarily attributed to mixing with the remnant high-DIC southward winter China Coastal Current water. In addition, biological processes and air-sea CO2 exchange also played important roles. Two representative regions were examined: the inshore high-DIC region and the offshore low-DIC region. In the inshore high-DIC region, biological processes and air-sea CO₂ exchange increased DIC by 11.6 ± 3.0 (relative to air-sea CO2 equilibrium) and 1.1 ± 7.0 µmol kg− 1 (relative to conservative mixing), respectively. In the offshore low-DIC region, biological processes decreased DIC by 5.1 ± 3.5 µmol kg− 1, whereas air-sea CO2 exchange increased DIC by 9.9 ± 2.8 µmol kg− 1. Overall, this study highlights the dominant role of the cross-seasonal influence of the remnant water of the coastal current, as well as the secondary but significant contributions of biological activity and air-sea CO2 exchange to the DIC distribution in coastal regions.

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Coastal phytoplankton response to acidification and warming under differing levels of nutrient availability

Published 12 June 2026 Science Closed
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Ocean acidification and warming will alter phytoplankton biomass and composition, yet despite numerous studies, there are few consistent responses on which to base predictions. To determine the responses of chlorophyll-a and phytoplankton size and composition to predicted lower pH (−0.33 to −0.5) alone, and also combined with elevated temperature (+2.5–3.5 °C), two mesocosm experiments were carried out in austral spring and autumn in temperate New Zealand coastal waters. Lower pH alone had no effect on chlorophyll-a in either experiment and, as the treatment pH was lower than the pH minimum recorded in a parallel four-year time series, this lack of response in chlorophyll-a was not attributable to prior in situ exposure. Conversely, chlorophyll-a increased under lower pH and warming in both experiments, with the large (>20 µm) phytoplankton size fraction showing opposing responses under nutrient deplete and replete conditions. Diatom biomass also increased in both treatments when nutrient availability was maintained, with a dominant pennate species Cylindrotheca clostridium emerging. The results highlight the value of contextual time series for experimental interpretation, and also the importance of assessing warming and acidification together using regionally representative nutrient concentrations, for prediction of coastal phytoplankton response to climate change.

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High-resolution reconstruction of the pH-upregulation and its seasonal drivers in the temperate coral Cladocora caespitosa

Published 12 June 2026 Science Closed
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Ocean acidification (OA) and associated changes in seawater carbonate chemistry, combined with thermal stress, hampers coral calcification. By upregulating pH and dissolved inorganic carbon, corals can optimize their calcification, giving them some resilience to OA. Little is known about the seasonal- and interannual‑scale impacts of thermal stress and OA on pH upregulation and calcification in the temperate coral Cladocora caespitosa, despite it being the only zooxanthellate reef builder in the Mediterranean Sea. δ¹¹B and B/Ca were determined seasonally in C. caespitosa skeletons from two NW Mediterranean sites to reconstruct the effect of seawater temperature and pH on the carbonate chemistry of the coral calcifying fluid (CF), at a bimonthly resolution from June 2013 to August 2017 (Columbretes Islands, Spain), and June 2016 to February 2022 (Villefranche-sur-Mer, France). Cladocora caespitosa displayed a similar pH upregulation strategy to most tropical corals, albeit with an apparently lower sensitivity to seasonal environmental change. Temperature was the main driver of seasonal variability in the CF composition and coral calcification, with seawater pH having a comparatively lower seasonal variability, and acting on longer timescales. While longer coral records and investigations into inter-population variability would still be beneficial in order to fully understand the response of C. caespitosa to environmental change, our records constitute an important first step in understanding the biomineralization strategy of this ecologically important coral species.

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Response mechanism of Sepia esculenta larvae under global warming, ocean acidification and salinity fluctuation: Integrated biochemical and transcriptome profiling

Published 12 June 2026 Science Closed
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Highlights

  • Analysis based on global warming, ocean acidification and salinity fluctuation.
  • Multi-angle analysis of Sepia esculenta under temperature, pH and salinity stress.
  • Different stress enhanced the immune defense and antioxidant defense of S.esculenta.
  • The hub genes closely related to stress resistance were identified and screened out.

Abstract

The Sepia esculenta occupies a significant economic proportion in the squid family, and it is also the squid with the largest economic value in the northern sea area of China. With the occurrence of global warming, ocean acidification and ocean salinity fluctuations, it has caused serious negative effects on the development of the S. esculenta artificial breeding industry. Therefore, in the research, we employed weighted gene co-expression network analysis (WGCNA) to investigate the effects of three environmental factors, including salinity, temperature and pH, on the molecular mechanism of S. esculenta larvae, and proved the reliability of transcriptome results through physiological indicators. Enrichment analysis of each module indicated that environmental exposure markedly influenced immune function, oxidative stress responses, and other physiological processes in S. esculenta larvae. Our research elucidates the comprehensive response mechanism of S. esculenta under different environmental stresses, clarifies the significant molecular pathways essential for its growth and development.

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Ecological roles, climate-driven responses, and critical knowledge gaps of krill in the global ocean

Published 11 June 2026 Science Closed
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Human-induced global climate change and other anthropogenic stressors are fundamentally altering our oceans. Understanding the ecological and societal implications of these changes is critical for developing mitigation strategies and conservation measures. However, major components of the marine pelagic ecosystem remain poorly understood. This is true for euphausiids (“krill”), which are a crucial part of marine food webs and play an important role in elemental cycling, including in the biological carbon pump, but for which we know surprisingly little. In this review, we first provide an overview of the ecological and socio-economic value of krill, highlighting their function in marine food webs and biogeochemical cycling. Next, we describe what is currently known regarding the response of krill to climate change and other anthropogenic stressors, focusing on changes in their biogeography, physiology, life history, as well as the impacts of krill fishing and their association with pathogens and parasites. We identify five key gaps in our current knowledge of krill: (1) the effects of krill on food web dynamics and stability, (2) the effects of changing predator and/or prey communities on krill populations, (3) the identification of important krill habitats, (4) the understanding of vertical and horizontal range shifts, and (5) the combined effects of multiple climate change and other anthropogenic stressors on krill. We also highlight the krill species, regions, and habitats that are understudied. Finally, we propose strategies to improve our understanding of this ecologically important taxonomic group, including the sustained funding for time series; implementation of novel research technologies; expanding research on understudied species and regions; and creating a global community of krill researchers.

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Climate-induced coastal hazards, impacts and adaptation strategies in Global South countries: a review

Published 11 June 2026 Science Closed
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Coastal ecosystems provide a wide range of goods and services in the Global South countries. Nevertheless, climate-induced extreme events cause unprecedented impacts that result in a reduction of aquatic goods and services, destruction of infrastructure, and loss of human lives. Hence, effective management and adaptation strategies are required to sustain the benefits of coastal areas and tackle the socioeconomic impacts of climate-induced risks. This review aims to assess the impacts of climate-induced coastal hazards and adaptation strategies in Global South countries. The findings revealed that coastal flooding, cyclones, storm surges, coastal erosion, ocean acidification, algal blooms and saltwater intrusion were the main climate-induced coastal hazards in Global South countries. The South Asian countries face the highest frequency of cyclones and storm surges, while African coastal nations experience greater rainfall variability and drought-related hazards. Besides, ocean acidification disproportionately affect Small Island States. Coastal hazards had significant impacts on the fishery, water, agriculture, coastal ecosystems, and tourism sectors. Saltwater intrusion simultaneously reduces water quality and agricultural productivity, and damages coastal ecosystems. This further creates cascading effects on livelihoods and migration patterns. Studies show that the efficiency of hybrid adaptation measures outweighs the efficiency of hard, soft, and ecosystem-based adaptation measures to adapt to the impacts of coastal hazards in Global South countries. Hybrid approaches achieve 30–45% higher benefit/cost ratios than single-measure adaptations, with lower residual risks and greater ecological co-benefits. In the Global South, development sectors face unprecedented impacts from climate-induced coastal hazards due to their high exposure to coastal hazards coupled with their low economy. The vulnerability of Global South countries to coastal hazards will continue unless all stakeholders act proactively, unlike focusing on reactive adaptation measures. Moreover, an empirical investigation of the economic, social, and environmental impacts of coastal hazards in the region is vital to develop efficient adaptation plans.

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Ocean acidification effects on larval development and survival in commercially important shellfish

Published 10 June 2026 Science Closed
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This paper studies the consequences of ocean acidification (OA) on the growth and survival of the larvae of commercially significant shellfish species such as oysters, mussels, and scallops. The authors of the study are particularly concerned with the negative processes of OA with respect to the growth of larvae, shell development, and behavior, which result in decreased survival rates, particularly the consequences of the reduced availability of calcium carbonate on the weakening of shells and larvae, which are preyed upon. The paper also studies the interference with the behavior of larvae, particularly with respect to the adequate detection of sites to settle, which is harmful to recruitment success. Additionally, the study looks at the OA-induced metabolic stress, where the larvae are expected to expend higher energy to maintain homeostasis at the expense of growth and immunity. By focusing on this issue, the paper outlines the OA’s impacts on the shellfish populations and industries. The paper also looks at the available soft measures, such as the implementation of buffering solutions to limit the acidification in hatcheries, the use of genetic selection to incorporate acidification-resistant traits, and coastal management measures to limit local sources of acidification. The paper also suggests some potential new ways to increase the resilience of shellfish stock, including more flexible adaptive aquaculture practices. With commercial shellfish interests emerging, this paper fills some of the more critical gaps in the existing literature and offers insight into the impact of OA on the sustainability of the shellfish industry. It also provides OA mitigation strategies to preserve shellfish stocks in a changing climate.

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Dialogue, inclusion, and adaptation in a remote marine sanctuary: evidence from Flower Garden Banks

Published 10 June 2026 Science Closed
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Interdisciplinary, stakeholder-engaged research is increasingly being used for managing climate change in social-ecological systems. We apply a Collaborative Adaptive Experimental Governance lens to the Flower Garden Banks National Marine Sanctuary, a remote, relatively pristine coral reef system ~130–190 km offshore in the Gulf of Mexico, where biodiversity protection coexists with recreation and offshore energy. We coupled participatory social science with climate and ecosystem modeling to inform dialogue with decision-makers and users. First, we generated scenarios using Community Earth System Model2-LE ocean temperature and aragonite saturation state to characterize warming and acidification; translated heat stress into a variability-based coral bleaching index; and projected demersal and pelagic fish biomass. We then conducted 37 semi-structured interviews (managers, oil and gas, commercial and recreational fisheries, dive operators, Non-governmental organizations, and science/education), employed multi-coder reliability, and triangulated findings with policy and legal documents. Results highlight the centrality of the Sanctuary Advisory Council in structuring inclusive dialogue, co-producing recommendations, and supporting outreach in distant coastal communities. Multi-level coordination among NOAA, the Gulf of Mexico Fishery Management Council, and the Bureau of Ocean Energy Management enabled boundary expansion and reconciled conservation with industry and fishing interests. Key barriers to adaptive responses include offshore remoteness and logistics, limited public awareness, funding constraints, trust deficits, and procedural delays; pressures that intersect with warming, acidification, and episodic hypoxia. Our study shows that remote marine protected areas can operationalize inclusive, experimental governance to align science and management, but sustained investment in monitoring, restoration capacity, boundary-spanning outreach, and cross-agency coordination is needed.

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Optimization of UV-Vis spectrophotometer (OCaPI) parameters for measuring the pH and pCO2 of the ocean carbonate system in seawater to assess ocean acidification (Mediterranean Sea)

Published 9 June 2026 Science Closed
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Automating the measurement of carbonate system parameters is essential for improving our understanding of biogeochemical processes in marine regions. The portable OCaPI (Ocean Carbon Parameters Instrument) is designed to perform simultaneous and accurate measurements of hydrogen ion concentration (pH) and partial pressure of carbon dioxide (pCO2)1 in the ocean environment. Optimizing the parameters of the UV-Vis spectrophotometer (integration time, scan-to-average, boxcar) facilitates the quantification of ocean acidification, with significantly improved measurement accuracy and reliability. The results obtained are consistent with existing techniques and offer a simplified approach to data collection, even under challenging conditions. This work, based on design principles, performance, and preliminary results obtained in the Mediterranean Sea, paves the way for the integration of these optimized techniques into long-term monitoring programs. This will contribute to a better understanding of the impacts of climate change on marine ecosystems and to improved management in the face of ocean acidification.

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Ocean acidification alters hypoxia sensitivity and oxyregulation in reef-building corals

Published 9 June 2026 Science Closed
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Coastal marine ecosystems are increasingly threatened by multiple stressors such as ocean acidification and deoxygenation, but how these co-occurring stressors interact is often poorly understood. This is especially true for tropical coral reefs where deoxygenation is an emerging yet understudied threat. Using hypoxia response curves combined with rigorous pH control, we show that acidification alters hypoxia sensitivity and oxyregulation of reef-building corals in a species-specific manner: three species exhibited increased sensitivity to various degrees, while the fourth showed enhanced tolerance. Consequently, acidification pushes critical hypoxia thresholds into oxygen regimes already prevalent on reefs today, potentially driving shifts in community composition and accelerating risks to reef resilience as these stressors intensify in the future. Our findings challenge assumptions of uniform coral vulnerability under multi-faceted climate change, emphasizing the need for trait-based approaches and to account for stressor interactions in predictive models to better anticipate coral reef futures under rapid climate change.

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When fish lose their crowd: how ocean acidification quietly dismantles the social lives of reef fish

Published 8 June 2026 Web sites and blogs Closed

Sampling on the acidified reef. In contrast to the structurally complex control reefs, the seafloor here is relatively flat and dominated by turf algae — habitat that supports far fewer fish and much smaller shoals. Photo by Manabu Ooue and provided by the authorship team.

This blog post is provided by Angus Mitchell and colleagues and tells the #StoryBehindThePaper for the article, “Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification”, which was recently published in the Journal of Animal Ecology. In their study, Mitchell and colleagues reveal the hidden impact that climate change can have on the social lives and shoaling behaviour of reef fish.

Watch a reef long enough and you realise that fish are almost never alone. They move in groups, feed in groups, and react to danger as a group. For small reef fish, being part of a shoal is a survival strategy. More eyes spot predators sooner. More bodies mean any one fish is less likely to be the unlucky one. And fish in bigger groups tend to be bolder, as they forage more efficiently, stay out in the open more, and spend less time hiding.

When we started looking at how climate change affects fish behaviour on reefs experiencing ocean acidification and warming in Japan, we assumed we would find the usual story. Warmer water and rising acidity would alter fish behaviour, make them more cautious, or accelerate their activity levels. That seemed like the obvious prediction.

It turned out to be different — or at least, for schooling species.

…

Warming and acidification had little direct effect on behaviour

Across all reef types, even during the heatwave, the fish behaved in much the same way. They kept feeding. They did not suddenly become more nervous. The direct effects of warming, acidification, and heatwave stress on individual behaviour were mostly minimal.

You could read that as good news. Fish holding their own against climate change. But when we looked at what actually caused how the fish were behaving, the answer was not temperature or water chemistry at all. It was how many fish were in the shoal.

Fish in bigger shoals foraged more and hid less. Fish in smaller shoals were more cautious, regardless of the reef conditions around them. Shoal size, not climate stress, was mediating the behaviours we observed.

That sent us back to ask a different question: why were shoals so much smaller on the acidified reef?

What acidification actually does to a reef

On non-acidified reefs, the benthos is structurally complex, a mix of algae, encrusting organisms, and vertical relief that gives reef fish the three-dimensional habitat they rely on. On our acidified reef, that structure was largely gone. The seafloor was dominated by short turf algae, flat and featureless.

There were far fewer fish. Not because the fish were sick or behaving strangely, but because the habitat could not support the same densities we observed on non-acidified reefs. With fewer fish around, the shoals that did form were much smaller: up to 79% smaller than shoals on nearby control reefs. And with smaller shoals came more cautious behaviour across the board.

Continue reading ‘When fish lose their crowd: how ocean acidification quietly dismantles the social lives of reef fish’

Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification

Published 8 June 2026 Science Closed
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  1. Social context is a critical yet underexplored determinant of behavioural resilience to climate change. Group living can buffer individuals against environmental stress through enhanced vigilance, reduced predation risk and improved foraging efficiency.
  2. However, whether these behavioural expressions persist under chronic (warming, acidification) and acute (marine heatwaves) climate stressors remains unclear. Using natural climate analogues spanning present-day, ocean warming and combined warming–acidification reefs, we quantified how shoal size influences behavioural expression in a range-extending reef fish (Pomacentrus coelestis).
  3. Across all climate conditions, fish in larger shoals consistently exhibited higher foraging and activity levels and reduced risk-avoidance behaviours, whereas direct effects of warming, acidification and heatwaves on behaviour were negligible.
  4. In contrast, ocean acidification most likely constrained collective behaviour indirectly by simplifying benthic habitats, where fish densities were 84% lower than at the warming reef, resulting in shoals that were up to 79% smaller than the Warming and Control reefs.
  5. Combined, our data suggest that shoal size mediates behavioural expression between foraging and predator avoidance and that acidification-driven habitat simplification can alter behavioural expression indirectly by reducing fish densities and the formation of large shoals.
  6. We conclude that climate change can indirectly modify behavioural expression in shoal-forming fishes through habitat-driven erosion of social structure.
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Systematic review of chemistry educational strategies and curriculum integration in ocean acidification

Published 8 June 2026 Science Closed
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This systematic literature review examines the trends and developments in ocean acidification education research from 2011 to 2025. Using the PRISMA methodology, 30 articles from the Scopus database were analyzed to identify key themes, research gaps, and future directions in teaching and learning about ocean acidification. The findings reveal a growing interest in integrating ocean acidification into science education curricula, with a significant emphasis on inquiry-based learning, technology-enhanced instruction, and interdisciplinary approaches. The United States leads research production (51 authors), followed by Spain, Sweden, and Greece. Key educational innovations include virtual reality applications, computational modelling, hands-on laboratory experiments, and collaborative learning strategies. With an average of 23.37 citations per document, this field has a substantial academic impact. However, challenges persist in terms of public awareness, teacher preparation, and curriculum integration. The review identifies the critical need for enhanced pedagogical resources, professional development programs, and assessment tools to effectively teach ocean acidification as a climate change issue. These findings provide valuable insights for educators, curriculum developers, and policymakers seeking to strengthen ocean and climate change education in formal and informal settings.

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Assessing recent anthropogenic carbon dioxide and acidification in the Ross Sea, Antarctica

Published 5 June 2026 Science Closed
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Over the past decade, the East Ross Sea has experienced a significant decline in sea ice, enabling direct observational studies of regional carbon dynamics. The accumulation rate of anthropogenic CO2 in the East Ross Sea is up to six times higher than the long-term Industrial Era mean due to the inflow of seawater from the Amundsen Sea by accelerated glacial melting. In contrast, the West Ross Sea exhibited comparatively smaller changes. Measurements of dissolved inorganic carbon and stable carbon isotope indicate that, over the period 2011–2020, changes in δ13C (Suess effect) and anthropogenic CO2 were 0.20 ± 0.06‰ and −5 ± 2 μmol kg−1 in the West Ross Sea, and −0.15 ± 0.01‰ and 9 ± 1 μmol kg−1 in the East Ross Sea. These findings suggest rapid acidification in the East Ross Sea, with aragonite undersaturation likely to occur by the mid-2030s, accompanied by an expected pH decrease of ∼0.2 units by the end of the century.

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Climate change impact on the socioeconomic conditions and well-being of the South Asian small-scale fishermen: a review

Published 5 June 2026 Science Closed
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Climate change is a major threat to the small-scale fishing communities, particularly in South Asia, a region characterized by widespread coastlines, extreme population density, and high dependence on marine resources for food, income, and employment. This review synthesizes findings from peer-reviewed articles published between 2000 and 2025 to analyse the climate change impact on socioeconomic conditions and well-being of the small-scale fishermen. The review identifies a range of climatic stressors, such as rising sea surface temperatures, ocean acidification, sea level rise, and extreme weather events, that are severely disrupting marine ecosystems and fish availability. These ecological shifts directly affect the livelihoods, income stability, and food security of fishing communities, escalating existing vulnerabilities like poverty, indebtedness, and limited occupational mobility. The study categorizes the impacts into physical, economic, and social dimensions, highlighting issues such as declining catch volumes, increased operational costs, infrastructure destruction, and disruptions in food supply and nutrition. It also examines local and regional adaptation responses, ranging from ecosystem-based solutions, such as mangrove restoration and cage aquaculture, to institutional and behavioural shifts, including migration, livelihood diversification, and early warning systems. While some adaptations enhance resilience, others pose sustainability challenges. This review highlights the pressing need for targeted policy interventions that support sustainable adaptation, enhance institutional frameworks, and prioritize vulnerable fishing communities in climate resilience planning.

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The Chesapeake Bay is getting more acidic. Scientists are studying what that means for local aquaculture

Published 5 June 2026 Web sites and blogs Closed

Oyster farming lines at Lambert Shellfish on the Eastern Shore in Virginia on May 28, 2026. Katherine Hafner/WHRO News

Shellfish farmers are working with the Virginia Institute of Marine Science to better understand the looming issue.

Shellfish such as clams, crabs and oysters need tiny building blocks called calcium carbonate ions to grow and thrive.

These particles are essential to build sturdy shells that protect marine creatures from predators – and make them more appealing for human diners.

But rising acidity tied to climate change is making it harder for shellfish to access those fundamental building blocks.

The issue caught officials’ attention in the late 2000s when acidic corrosion caused mass die-offs of baby oysters in the Pacific Northwest.

Researchers at William & Mary’s Batten School and Virginia Institute of Marine Science have teamed up with local shellfish farmers to learn more about how changing conditions could impact the aquaculture industry in coastal Virginia.

“We know the threat exists,” said Emily Rivest, an associate professor in ecosystem health at the Batten School and VIMS. “This gives us the opportunity to try to get ahead of it to understand how to build our resilience and prevent those kinds of dramatic negative impacts.”

The project is funded by a $1.2 million grant from the National Oceanic and Atmospheric Administration’s Ocean Acidification Program.

The ocean absorbs about a third of the climate-warming carbon dioxide humans release into the atmosphere. That causes a cascade of chemical changes underwater, including reducing pH levels.

For millions of years, the ocean’s pH remained relatively stable at 8.2 on the pH scale, which ranges to 14, the most basic. Since the start of the Industrial Revolution, it has dropped to 8.1. Because the scale is logarithmic, that represents a nearly 30% increase in acidity, according to NOAA.

In much of the Chesapeake Bay, the rate of change is happening even more quickly, particularly in the middle, VIMS previously found.

One factor is freshwater. When freshwater surges into the bay, it lowers the amount of salt in the water, which makes it more susceptible to acidity, Rivest said. That has sometimes affected restored oyster reefs on the western side of the Eastern Shore.

Pollution from nutrients washing off land into the bay compounds the issue by triggering algae that produce carbon dioxide when eaten by bacteria, Rivest said.

Luckily, natural variability in the Chesapeake Bay “has shaped the eastern oyster to be a very tough and resilient species,” Rivest said.

Lab tests indicate local oysters are “much more tolerant of acidification” than out West. The question is: What is their breaking point?

…

Continue reading ‘The Chesapeake Bay is getting more acidic. Scientists are studying what that means for local aquaculture’

A screening approach for aquaculture breeders based on sperm performance under climate change-related stress

Published 4 June 2026 Science Closed
Tags: , , , , , , ,

Highlights

  • Temperature rise reduced European sea bass and Senegalese sole sperm motility.
  • Gilthead seabream sperm showed lower variation under acidification and warming.
  • Challenge tests allowed differentiation among males based on sperm performance.
  • Approach provides a screening framework for sperm performance.

Abstract

We aimed to develop a screening approach to differentiate among males of European sea bass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), and Senegalese sole (Solea senegalensis) based on sperm performance under environmental acidification and temperature increase. Sperm samples were selected using a CASA system, and three challenge tests were applied. The first one consisted of sperm activation with artificial seawater (ASW) across a pH range (7.6–8.2). The second assessed activation at species-specific temperatures. The third test evaluated the combined effect of ASW pH (7.8 and 8.2) and different temperatures. Results from the third challenge test revealed differences in sperm performance under environmental variations, allowing differentiation among males. For this purpose, sperm motility values obtained for each sample under species-specific natural environmental conditions were used as references, and variations in motility were compared across challenge conditions. Different levels in the criteria (regarding the different percentages of motility variation) were applied to differentiate among males. The temperature increase affected the sperm kinetic parameters of European sea bass and Senegalese sole, while gilthead seabream sperm showed lower variation under seawater acidification and rising temperatures. The challenge test allowed differentiation among males based on sperm performance under environmental variations and represents a preliminary screening approach. However, these results are based on in vitro conditions and should be interpreted as a first proxy, requiring further validation to establish links with reproductive performance in vivo.

Continue reading ‘A screening approach for aquaculture breeders based on sperm performance under climate change-related stress’

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