Protecting seafood security by assessing the impacts of ocean acidification

Published 18 June 2026 Science , Web sites and blogs Leave a Comment

A global research network assessed how ocean acidification affects seafood to help countries build climate resilience and secure future food supplies.

The spotted rose snapper (Lutjanus guttatus), locally known as pargo mancha or pargo lunarejo, is a commercially and culturally valuable fish species in Costa Rica. (Photo: C. Sanchez-Noguera/University of Costa Rica)

Global seafood security depends on the health of our ocean. However, this vital resource is currently under threat from the ‘invisible’ process of ocean acidification.  

As the ocean absorbs more carbon dioxide from the atmosphere, its chemistry changes, making it increasingly difficult for many marine species, including shellfish and fish that billions of people rely on for protein, to grow and survive.  

To address this challenge, the IAEA launched a five-year Coordinated Research Project (CRP) in August 2019 to evaluate how changing ocean chemistry affects seafood and to explore adaptation strategies for the aquaculture and fisheries industries.

A unified scientific protocol for a global assessment

The project applied a novel, collaborative approach in which researchers from 14 countries across five continents used a common experimental protocol, allowing results to be compared and integrated into a single dataset.  

The project enabled scientists to study how locally important seafood species respond to the complex physiological stress of acidifying waters, including impacts on growth and mortality, as well as seafood quality, such as taste and texture. By focusing on species of high socio-economic importance such as oysters, mussels, shrimp and fish, the research provides a direct link between marine chemistry changes and the livelihoods of coastal communities. 

Using similar methodologies and research kits provided by the IAEA, the consortium successfully co-designed a comprehensive experimental framework. This turnkey scientific model allowed laboratories with varying levels of experience to produce high-quality data to inform policy making.  

“This project allowed us to move beyond isolated observations to a more global understanding,” said Florence Descroix-Comanducci, Director of the IAEA Marine Environment Laboratories. “By providing countries with a unified scientific framework to study ocean acidification impacts, we have empowered them to produce data that is high-quality, comparable and ready to inform national policy. We are no longer looking at individual pieces of a puzzle; we are seeing a more complete picture of ocean change.” 

The team from the University of Costa Rica organizing a public seafood tasting of the spotted rose snapper (Lutjanus guttatus) previously subjected to ocean acidification, to assess potential impacts on taste and texture. (Photo: C. Sanchez-Noguera/University of Costa Rica)

Strengthening infrastructure and informing policy

The impact of the project extends beyond the laboratory, strengthening research infrastructure and informing policy frameworks of the participating countries. 

The initiative led to the establishment of specialized laboratories for ocean acidification research in Türkiye and Cuba, as well as new monitoring stations in Argentina.  

Furthermore, the project mentored more than 30 students and early-career scientists, helping to build a skilled workforce capable of tackling future marine challenges. These enhanced capabilities have already translated into real-world policy changes. In Ecuador, for example, data generated through the project was shared with policymakers to inform articles of the National Environmental Law, which now explicitly addresses ocean acidification. 

This collaborative effort also brought science to local communities, engaging with aquaculture managers and the public through surveys and seafood-tasting events.  

“The collaborative nature of this project helped us bring the topic of ocean acidification to the attention of decision-makers in a way we couldn’t have done alone,” said Betina Lomovasky, a researcher from Argentina.  

The project has provided a solid basis for long-term food security and the sustainable management of marine resources in a changing climate. 

Marc Metian, IAEA Department of Nuclear Sciences and Applications, 16 June 2026. Article.

Marine invertebrates and fishes exhibit inconsistent body size responses to ocean acidification

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Body size is a fundamental characteristic of all living organisms that determines physiological functions and life-history traits. Ecological theory predicts that ocean acidification can cause body size reductions, confirmed by several studies reporting miniaturization in ectotherms. Based on this prediction, we would expect a broad suite of species to show similar plastic body-size responses to elevated CO2. Using four natural climate change analogues of ocean acidification across the northern and southern hemispheres, we quantified body size alterations across 18 marine invertebrate and fish taxa to test for climate-driven miniaturization. Only three species consistently showed body-size reductions under ocean acidification: one urchin and two fish species. In contrast, 15 other species, ranging from highly calcified to non-calcified, displayed unchanged or increased body sizes or inconsistent miniaturization. If body-size miniaturization responses were consistently reproducible across taxa we would have observed it more frequently, suggesting that species responses to ocean acidification are more variable than previously thought and likely vary depending on a species’ physiology and life history. Thus, rather than entire communities undergoing miniaturization, species are likely to display a spectrum of responses, with some exhibiting size reductions, others demonstrating physiological resistance to elevated CO2, and others potentially benefiting from the indirect effects of ocean acidification.

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Pteropod vulnerability to ocean acidification in the eastern Arabian Sea

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Highlights

  • First study on pteropod response to ocean acidification in the eastern Arabian Sea.
  • High pteropod abundance during fall inter monsoon season due to food availability.
  • pH in the Arabian Sea was low during south west monsoon with pHT upto 7.75
  • Pteropod shell dissolution was observed under acidified conditions
  • Protrusions through the pteropod shell were observed under acidified conditions

Abstract

The rapid rise in atmospheric CO2 and its subsequent uptake by the oceans has led to ocean acidification and other associated changes in the marine ecosystem. The recent reports of the shoaling of the aragonite saturation horizon in the northern Indian Ocean are particularly alarming, as they pose a serious threat to the survival of calcareous organisms. Pteropods, also known as sea-butterflies, are believed to be highly susceptible to ocean acidification due to their thin aragonite shell. In our study in the eastern Arabian Sea, we found low pH conditions with surface pHT as low as 7.751 during late South-west monsoon (SWM). The pteropod abundance is high during the fall inter-monsoon (FIM), suggesting that the system continues to sustain productivity even after the cessation of peak monsoon activity. This also implies that the food availability regulates pteropod abundance in the eastern Arabian Sea. As pteropods are key components of food sources for many marine species, such as fish, any changes in their abundance can have cascading effects on the marine food web. To show how pteropods will be affected in futuristic elevated CO2 conditions, a CO2 manipulation experiment was conducted in the eastern Arabian Sea during December 2024. Pteropods belonging to Creseis acicula from the eastern Arabian Sea were subjected to pHT = 7.470, and pCO2 = 1734 μatm under controlled conditions. Our findings suggest that acidification led to the dissolution of pteropod shells. Acidification also led to protrusion through the shells, and these protrusions varied in length up to 88 μm. These structural alterations represent an acute response of pteropod shells to reduced pH, highlighting their rapid vulnerability to acidification stress. These observed protrusions need to be assessed further to determine if they provide any competitive advantage in combating or minimizing the impact of ocean acidification.

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Temperature, but not acidification, influences the growth and lipid profile of juvenile sand whiting, Sillago ciliata (Cuvier 1829)

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Seafood provides an essential source of macro- and micronutrients for coastal communities worldwide. Climate change is a key threat to seafood security, altering the sizes, abundances, distributions, physiology and ecological interactions of fisheries species, and increasingly, there is evidence of impacts to seafood nutritional quality. In a 12-week mesocosm experiment, we tested the influence of projected ocean warming and acidification scenarios on the growth and lipid quality of juvenile sand whiting (Sillago ciliata), a popular fisheries species in eastern Australia. The growth of S. ciliata significantly increased (by 61% body weight) under elevated temperature (+3°C) but was not affected by acidification treatment levels. Lipidomic analysis revealed no influence of temperature or acidification on total lipid content or the composition and total proportions of lipid classes and subclasses. However, elevated temperatures significantly impacted the overall composition of fatty acids, including a shift toward higher saturation and a decline in important omega-3 fatty acids. Fish exposed to elevated temperature treatments had more saturated fatty acids than those at control temperatures, along with reduced levels of the valuable omega-3 eicosapentaenoic (C20:5) and docosahexaenoic (C22:6) fatty acids. Despite impacting fatty acid composition in S. ciliata, the increased growth of the juvenile whiting, if sustained into adulthood, under elevated temperatures, may help compensate for the overall availability of essential polyunsaturated fatty acids to support consumer nutritional requirements. These findings contribute to the growing body of evidence on variable climate resilience in nearshore species to future environmental conditions and the implications for the trophic transfer of nutrients in estuarine ecosystems.

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Shifts of tentacles-associated prokaryotes of Anemonia viridis along a natural pH gradient

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Highlights

  • A. viridis tentacle microbiomes were studied under changing natural pH conditions.
  • Notable shifts in the abundance of specific taxa emerged in the acidified sites.
  • Differences in seawater emphasized the host’s unique microbial signature.
  • Rickettsiales predominance suggested a specialized ecological role in symbiosis.
  • Further research is needed to discern the role of microbes for host resilience.

Abstract

Marine hydrothermal vents are extreme environments that naturally select for organisms with strong resistance and the ability to cope with special conditions of acidification. Sea anemones are an interesting example that are able to buffer intracellular pH conditions. In this study, the influence of a natural pH gradient on microbial communities associated with Anemonia viridis (Cnidaria, Anthozoa) tentacles was investigated. We hypothesized that exposure to a natural pH gradient would be associated with changes in the structure and activity of A. viridis-associated microbial communities, potentially contributing to the host’s resilience in hydrothermal environments. Microbial enzymatic activities within anemones’ tentacles were investigated by incubation with fluorogenic compounds. The leucine amino peptidase activity was highest in the tentacles of specimens living in more acidified sites. A microbial biodiversity loss was observed in bacterial symbionts from less acidified to more acidified sites, with a reduction of relative abundance in certain groups (i.e., Planctomycetota, Firmicutes, and Desulfobacterota). Results obtained by a metabarcoding approach provided interesting insights into the taxonomic shifts of the A. viridis holobiont system in naturally acidified environments.

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A systematic bias in float pH leads to overestimation of derived pCO2 and underestimation of carbon uptake by the Southern Ocean

Published 17 June 2026 Science Leave a Comment
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The carbon flux estimated from biogeochemical Argo float data indicates a lower annual carbon uptake by the Southern Ocean compared to fluxes derived from other observations (e.g., ship and aircraft measurements). The root cause of this discrepancy remains controversial, with growing evidence suggesting that potential biases in float-derived pCO2 may be a plausible explanation. Here, we perform a multi-variable comparison of vertical profiles between float- and ship based-data and reveal consistent discrepancies in pH, pCO2 and dissolved inorganic carbon, which are not found in other variables such as dissolved oxygen, nitrate and total alkalinity. Our findings are consistent with a previously unrecognized negative bias in float pH driving a positive offset in float-derived pCO2. The float-derived surface pCO2 is, on average, biased high by 15 ± 3 µatm compared to ship data, representing a larger magnitude of bias than previously recognized. Biases exist in both surface and deep waters, including old deep waters containing minimal anthropogenic carbon. A more sophisticated adjustment for float pH, involving multiple cross-reference depths, may be required for accurate estimation of air-sea CO2 exchange in the Southern Ocean.

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Response of HAB-forming microalgae competition to ocean acidification, warming, and changing light fields

Published 17 June 2026 Science Leave a Comment
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In recent years, the East China Sea (ECS) has experienced frequent harmful algal blooms (HABs), driven by the complex interplay of climate change—specifically ocean warming and acidification—and eutrophication-induced light attenuation. Despite their ecological significance, the interactive effects of these environmental stressors on the competitive dynamics between bloom-forming microalgae remain poorly understood. This study aimed to elucidate how warming, reduced light, and elevated CO2 influence the competition between two dominant diatoms. We conducted controlled monoculture and mixed-culture experiments using two key species: Skeletonema costatum and Chaetoceros curvisetus. The experimental design incorporated varying levels of CO2, temperature, and light intensity to simulate future coastal scenarios. Growth rates, peak cell densities, and successional patterns were monitored to assess competitive outcomes under multiple stressors. Monoculture results indicated that high temperature and low light intensity promoted the growth of both species. However, in mixed cultures, these conditions significantly accelerated the time to reach peak density and induced a definitive successional shift from S. costatum to C. curvisetus. Notably, while the general successional pattern was consistent, elevated CO2 further enhanced the competitive advantage of C. curvisetus, particularly when combined with high-temperature and low-light scenarios. These findings suggest that the synergy of future warming, declining light availability, and intensified ocean acidification in the ECS will likely favor C. curvisetus over S. costatum. This shift may increase the frequency of HAB events dominated by C. curvisetus, driving significant climate-related restructuring of phytoplankton communities in coastal ecosystems.

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Sea to shining sea: NOAA launches dual coastwide ocean acidification research missions

Published 17 June 2026 Program , Science , Web sites and blogs Leave a Comment

NOAA Ship Ronald H. Brown during the 2021 West Coast Ocean Acidification research cruise with a NOAA mooring measuring ocean chemistry in the foreground. Credit: NOAA

This June, NOAA’s Ocean Acidification Program (OAP) launches two major research missions at sea to track how changing ocean chemistry is affecting marine life along both the East and West coasts of the United States. 

OAP’s East Coast (ECOA-4) and West Coast (WCOA 2026) Ocean Acidification research cruises collect the highest quality information that serve as vital benchmarks for research, monitoring and modeling in each region. By coupling ocean chemistry, biology and physics, researchers are able to better understand how ocean acidification impacts marine life. Each coastwide cruise occurs every four years on average. Data collected during these cruises “serve as a vital back-bone to NOAA’s ocean acidification observing enterprise allowing us to document the primary drivers and risks of acidification along much of the nation’s coastal waters,” says OAP Acting Director Dwight Gledhill. 

Tracking potential El Niño effects

This year’s missions are particularly timely as a predicted El Niño builds during the missions. This concurrence provides a unique opportunity to assess how these conditions affect ocean chemistry and marine ecosystems. El Niño is a natural variation in sea temperature that occurs when weaker than normal trade winds occur. Warmer conditions can shift where marine species occur – and where people need to fish – and significantly alter ecosystems and fisheries. If conditions develop as predicted, ECOA-4 and WCOA 2026 will both capture how El Niño conditions affect ocean acidification and impacts to marine resources. 

Delivering critical information on two coasts

The ECOA-4 research cruise will survey the Atlantic seaboard from Florida to Canadian waters and launches first in early June for a 50-day journey. WCOA 2026 departs from San Diego, CA and heads north to Washington over a month of sampling. Both coastal research cruises collect coastwide data of ocean biogeochemical and physical conditions and how conditions are affecting marine resources. Research cruises are needed to obtain the quality and breadth of measurements required to infer long-term changes and to see how marine life responds to ocean acidification.

Already, each coast has experienced the effects of ocean acidification on fisheries, aquaculture and ecosystems. The data collected by ECOA-4 and WCOA 2026 are fundamental to validating ocean models and forecast changes in ocean acidification and other conditions like hypoxia and warming to better prepare for future impacts to valued fisheries and ecosystems. 

East Coast Atlantic sea scallop fishermen are working together with researchers to develop research and adaptive management strategies addressing the impacts of ocean acidification and warming. The information also validates ocean and other models such as the Chesapeake Bay Environmental Forecast System (CBEFS) used by resource managers, shellfish growers and fishermen. The West Coast, which first saw devastating impacts to oyster farming, now produces forecasts through J-SCOPE that incorporate measures of ocean acidification and other ocean conditions into integrated ecosystem assessments and fisheries management. Research of economically, ecologically and culturally valuable species like Dungeness crab, krill and oysters also benefit from the data produced by these coast-wide research missions.

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Geographic variation in proteomic responses to ocean acidification in a cold-water coral (Balanophyllia elegans)

Published 16 June 2026 Science Leave a Comment
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In the face of a rapidly changing climate, assessing organismal responses to future stressors in the context of current, natural exposure to stress could provide key insights to understanding marine ecosystem resilience. I used Balanophyllia elegans, a cold-water, solitary, azooxanthellate coral as a model to better understand how varying oceanographic conditions across its geographic range have shaped its ability to tolerate and potentially adapt to current and future ocean acidification conditions. I collected B. elegans individuals from four sites across 2,500km of their range and subjected them to two pH treatments to investigate site-specific protein expression in response to low pH. Using proteomic analysis, I found that corals from each site responded differentially to low pH, mainly through changes in regulation of metabolism, calcification, and homeostasis-related proteins. Additionally, health condition varied significantly between sites after exposure to low pH, providing further evidence of site-specific responses. These results demonstrate site-specific variation in responses and tolerance to low pH, a pattern that could inform future investigations into environmental-driven adaptive expression. Such site-specific responses highlight the importance of multi-source studies for predicting a species’ ability to navigate future climate changes.

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Climate change is redefining tetrodotoxin accumulation and ecological dynamics in pufferfishes

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Marine pufferfishes are globally distributed and ecologically important organism notable for accumulating tetrodotoxin [TTX], a potent neurotoxin with wide ecological ramifica-tions. Unlike many endogenous defences, TTX in pufferfishes is acquired indirectly via microbial and trophic pathways, linking pufferfish toxicity to the dynamics of marine mi-crobial assemblages and food webs. Anthropogenic climate change principally ocean warming, deoxygenation, and acidification is rapidly reshaping marine environments in ways that are likely to intensify and redistribute TTX exposure. Observational and experimental studies indicate that elevated seawater temperatures favour the proliferation of thermophilic, toxin-producing bacteria [e.g., Vibrio spp.], increase the abundance of toxic prey, and raise TTX burdens in pufferfish tissues seasonally and spatially. Concurrently, warming-driven range shifts have promoted poleward expansions of several tropical and subtropical puffer species, producing novel sympatric assemblages, hybridization events, and “cryptic” toxic phenotypes that complicate species identification and risk assess-ment. These biogeographic rearrangements, together with altered prey communities and microbial composition, reconfigure the trophic pathways by which TTX is transferred and concentrated in higher trophic levels. Early evidence also links multistressor conditions elevated temperature combined with hypoxia or acidification to altered developmental success and changes in toxin allocation during reproduction, suggesting potential popu-lation-level consequences. This review synthesizes current global evidence on cli-mate-linked changes in pufferfish TTX dynamics, integrating microbial ecology, trophic transfer, life-history shifts, and biogeography. We highlight [i] mechanistic pathways by which warming and associated ocean changes increase environmental TTX availability, [ii] how shifting species ranges and hybridization alter toxicity patterns across regions, and [iii] key methodological advances [e.g., high-resolution LC-MS/MS, metagenomics] needed to resolve open questions. We identify critical research gaps long-term field moni-toring, integrated microbial–trophic mapping, and multistressor population studies and recommend synthesis strategies that link environmental monitoring to toxin surveillance. Understanding pufferfish toxification as a climate-sensitive ecological process [not a static species trait] is essential to anticipate how marine toxin landscapes will change in the Anthropocene and to develop timely, science-based monitoring frameworks.

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CO2 hydrate deposits off Mayotte offer window into ocean carbon storage

Published 16 June 2026 Press releases Leave a Comment

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.

Continue reading ‘CO2 hydrate deposits off Mayotte offer window into ocean carbon storage’

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

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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 Leave a Comment
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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.

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

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

Published 15 June 2026 Science Leave a Comment
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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 Leave a Comment
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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

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

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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