Published in the prestigious journal Environmental Pollution and co-authored by ISPRA researchers, the study “Climate Change and Ocean Acidification Outweigh Local Stressors in Mediterranean Mussels: A Multi-Method Convergence Analysis” presents the results of a ten-year biomonitoring programme (2014–2023) carried out in the Ligurian Sea.
The research focused on the Mediterranean mussel (Mytilus galloprovincialis) at Gorgona Island (used as the reference site) and near an offshore regasification terminal. By integrating biomarker data, tissue metal concentrations, and high-resolution oceanographic variables, the study quantified the relative contribution of different environmental stressors affecting mussel health using five complementary statistical approaches.
The study’s main finding is that climate change—particularly ocean acidification—emerged as the primary driver of biological stress, accounting for approximately 40% of the observed variance. This significantly exceeded the contribution of metal contamination (around 30%) and the local influence of the offshore regasification terminal (approximately 13%). Notably, about 64% of the climate-related impact was found to operate indirectly by enhancing the bioaccumulation of metals.
The GOOD-OARS International Summer School 2025 aimed to equip the next generation of ocean scientists with the multidisciplinary research skills to enhance our understanding of how marine ecosystems will respond over the coming decades and support efforts to address harmful impacts on the ocean.
OA reduces calcification, compromising the UV shield and exacerbating photoinhibition in C. officinalis.
OA amplifies PSII donor-side damage, disrupts electron flow to PSI, and suppresses PSI function.
OA shifts PSII damage-repair balance toward irreversible photoinhibition by increasing damage and suppressing repair.
Abstract
Ocean acidification (OA) exerts diverse effects on marine macroalgae, with calcified species being particularly vulnerable. Due to calcified skeletons can contribute to physical screening against solar ultraviolet radiation (UVR), OA-driven calcification loss may increase exposure of the photosynthetic apparatus to UVR. Here, we cultured Corallina officinalis under ambient CO₂ (∼420 μatm) or elevated CO₂ (∼1000 μatm), with or without UVR, under natural solar radiation. Our results confirmed that OA reduced calcification and, under UVR, enhanced donor-side impairment of photosystem II (PSII), as evidenced by an increase in the relative K-step (Wk, an indicator of OEC damage) and a decrease in the maximum quantum yield of PSII (Fᵥ/Fₘ). This donor-side injury was accompanied by a reconfiguration of energy fluxes per PSII reaction center, particularly under combined OA and UVR. These impairments further extended to intersystem electron transport and limited the linear electron flow from PSII to the intersystem chain. Photosystem I (PSI) related electron transport was also functionally constrained, as evidenced by the reduced electron transfer probability and terminal reduction yield. This, together with the reduction of cyclic electron transport around PSI, resulted in over-reduction of the intersystem chain and making PSI the limiting photosystem. Together, these results indicate that OA amplified UVR-induced net photodamage and weakened PSII repair capacity in C. officinalis, while also constraining PSI-related electron transport. These findings highlight the potential vulnerability of calcified red algae under future high-CO₂, high-UVR coastal oceans.
Ocean acidification (OA) refers to the increase in the partial pressure of CO2 and decrease in the pH of seawater resulting from the absorption of atmospheric CO2 by the ocean. This study investigated OA impacts across multiple generations (F0-F3) of the copepod Acartia tonsa which were exposed to four pH conditions (8.1, 7.8, 7.6 and 7.1). Key reproductive and developmental traits were evaluated, including egg production, hatchability, development time, fecal pellet production, and sex ratio. Results showed that pH 7.1 significantly reduced egg production, hatchability and fecal pellet production, while prolonging the N–C time; N-A time remained unaffected by pH across all groups. For sex ratio, a downward trend was observed with increasing generations and decreasing pH: in F3, female proportion in pH 7.8, 7.6 and 7.1 groups was significantly lower than in the control group, and pH 7.1 and 7.6 groups had lower F3 female proportion than in the F1 generation. A. tonsa showed some tolerance under short-term acidification conditions at pH 7.1, but its physiological functions were further reduced after long-term exposure, suggesting a limited adaptive capacity. Ecologically, A. tonsa is a dominant coastal zooplankton species that links phytoplankton to higher trophic levels (e.g., fish larvae) and mediates energy flow and biogeochemical cycling. These results highlight the risks to key zooplankton populations and associated ecosystem functioning. Future studies should focus on the long-term effects of acidification on A. tonsa and combine multi-species experiments with field surveys to assess the ecological risks of OA.
Did you know that the ocean plays a vital role in controlling the planet’s temperature, as well as providing food, minerals, and half of the oxygen we breathe? Another important role is balancing the amount of carbon dioxide gas in the atmosphere. Unfortunately, due to large emissions of carbon dioxide over the past few centuries, the ocean is becoming acidic. This process is called ocean acidification. Ocean acidification affects many sea organisms, especially those with shells, like mussels and corals, but it can also affect other animals’ sense of orientation, like fish. Scientists are discovering more about the potential impacts of ocean acidification on the marine system and, consequently, on humans and other life forms who depend on or explore the ocean. In this article, we explain why ocean acidification started, where it has been detected, its present and future impacts on marine life, and how we can help correct it.
Climate change explains ∼40% of biological stress variance in Mediterranean mussels.
Ocean acidification drives 67% of metal bioavailability changes via pH-metal speciation.
64% of climate effects on biomarkers operate indirectly through metal bioaccumulation.
Multi-method convergence (LMG, GAM, SEM, Bayesian Networks) confirms stressor ranking.
Only SSP1-2.6 keeps biological stress below the chronic-stress threshold through 2050.
Abstract
Marine coastal ecosystems face concurrent pressure from climate change and anthropogenic contamination, yet their relative contributions to biological stress remain poorly quantified. Here we present a decade-long (2014–2023) biomonitoring study on Mytilus galloprovincialis in the Ligurian Sea (NW Mediterranean), integrating quarterly biomarker measurements, heavy metal bioaccumulation data (12 metals), and high-resolution oceanographic records at a control site (Gorgona Island Marine Protected Area) and an offshore regasification terminal.
Biological stress variance was partitioned using five complementary analytical frameworks — Lindeman–Merenda–Gold (LMG) variance decomposition, Hierarchical and Generalised Additive Models (HGAM/GAM), Structural Equation Modelling (SEM), and Bayesian Networks — applied to four biomarkers: DNA damage, lysosomal membrane stability, gill tissue integrity, and immune response. A campaign-specific T0 baseline normalisation isolated environmental signals from initial population variability.
Climate change emerged as the dominant driver, consistently explaining ∼40% of variance across all methods, significantly exceeding metal bioaccumulation (∼30%), terminal influence (∼13%), and seasonal effects (∼2%). Ocean acidification was the primary climate mechanism, influencing 67% of analysed metals. Causal mediation analysis revealed that 64% of the climate effect operates indirectly through enhanced metal bioaccumulation (Climate→Metals→Biomarkers), while 36% acts directly. Climate and biological stress indices co-varied strongly (ρ = 0.78, p < 0.001), with marine heatwaves coinciding with peak biomarker responses.
Under IPCC Shared Socioeconomic Pathway (SSP) scenarios, the Biological Stress Index is projected to cross chronic-stress thresholds by 2035–2040 under the high-emission scenario (SSP5-8.5) and the intermediate-emission scenario (SSP2-4.5), with only the low-emission scenario (SSP1-2.6) maintaining stress below critical levels through 2050.
These findings challenge pollution-centric monitoring paradigms and demonstrate that CO2 mitigation now constitutes the highest-leverage intervention for marine invertebrate health in the Mediterranean.
Graphical abstract
This graphical abstract illustrates the main findings of a decade-long field study (2014–2023) on the effects of climate change and metal contamination on Mytilus galloprovincialis in the Ligurian Sea (NW Mediterranean). Three panels summarise the causal chain from environmental drivers to biological outcomes. The first panel depicts the key oceanographic trends recorded at the study site: ocean warming (+0.41°C/decade), acidification (−0.020 pH units/decade), deoxygenation, and a doubling of marine heatwave frequency after 2018. The second panel shows how pH decline enhances the bioavailability of 67% of the metals analysed, driving a predominantly indirect pathway (64%) from climate stressors to biological stress, mediated by metal bioaccumulation, as revealed by structural equation modelling and Bayesian network analysis. The final panel presents the four biomarkers used to compute the Biological Stress Index (BSI), its strong temporal correlation with the Climate Change Index (ρ = 0.78), and BSI projections to 2050 under three IPCC emission scenarios, showing that only SSP1-2.6 keeps BSI below the chronic-stress threshold throughout the projection period.
Seagrasses provide valuable ecosystem functions, yet they are declining globally due to anthropogenic stressors. Understanding how global climate stressors like ocean acidification interact with local environmental conditions (e.g., increased nutrient pollution) to affect ecosystem dynamics can be used to inform management of these habitats. In San Francisco Bay, it is unknown how stressor interactions will affect herbivory by Ampithoe valida, an invasive amphipod that exhibits novel feeding behavior by directly consuming the tissue of Zostera marina (eelgrass), which has been linked to negative impacts on local meadows. The goal of this study was to determine how anthropogenic stressors and amphipod size influence A. valida herbivory on eelgrass in San Francisco Bay to evaluate the ecological implications for eelgrass habitats. To further understand this relationship, feeding assays first examined food preferences of A. valida of three sizes on eelgrass of two ages and epiphytic algae. Secondly, a mesocosm experiment exposed A. valida of medium and large sizes to levels of ocean acidification expected with accelerating climate change and eelgrass to levels of nutrient pollution possible from point sources along shorelines, to test if these combined stressors affect A. valida direct herbivory of eelgrass. Additionally, A. valida were collected in the field during peak eelgrass growing season in summer and early fall to determine their size distributions and provide context to the experiments. Results found that A. valida largely prefer epiphytic algae over eelgrass regardless of their size. When offered only eelgrass, medium to large individuals consumed the tissue, whereas small individuals exhibited near-zero consumption. Although small A. valida were most abundant in field collections, medium-sized individuals were also present in moderate numbers, suggesting amphipods of this size may be the primary contributors to direct eelgrass consumption in San Francisco Bay, with high-consuming large individuals less common. Mesocosm results indicated that increased nutrients reduced eelgrass aboveground morphology (leaf size) and biomass, while tissue nutrient content increased, suggesting that although nutrients were taken up, they were not used for growth. Finally, feeding assays revealed that the effects of reduced pH and nutrient additions on A. valida eelgrass herbivory varied with grazer size and experimental context. In the no-choice assay, medium-sized individuals increased consumption under reduced pH relative to ambient pH, while large individuals consumed more of the highest nutrient-enriched eelgrass tissue. In contrast, the choice assay showed higher eelgrass consumption under ambient pH relative to reduced pH, and no effect of nutrient additions. This suggests that under reduced pH A. valida may shift their feeding behavior depending on environmental context, potentially increasing consumption through compensatory feeding on lower-quality tissue when food options are limited or reducing consumption when alternative refugia and higher-quality resources are available. This also indicates that ocean acidification may primarily alter eelgrass grazing behavior among mid sized A. valida, while nutrient enrichment may increase grazing pressure from larger individuals, potentially exacerbating eelgrass vulnerability in San Francisco Bay given reduced plant performance under high-nutrient conditions.
Policymakers and researchers can better understand, mitigate, and adapt to the impact of ocean acidification on food security, ensuring a more sustainable future for blue foods and the communities that depend on them if they:
Ensure baseline measurements of acidification are taken across different ocean basins.
Research the impact of ocean acidification on fisheries, shellfish, coral and plankton and priortize seafood species of local importance.
Explore knowledge gaps in ocean acidification science and research through a food security lens.
Align and integrate ocean acidification and food security research with regional and national policy objectives.
Leverage international frameworks to direct research, policy and financing support to more adequately assist nations in prolonged responses to the impacts of ocean acidification on food security
Key takeaways:
By implementing these recommendations, policymakers and researchers can better understand, mitigate, and adapt to the impact of ocean acidification on food security, ensuring a more sustainable future for blue foods and the communities that depend on them:
Ensure baseline measurements of acidification are taken across different ocean basins.
Research the impact of ocean acidification on fisheries, shellfish, coral and plankton and prioritize seafood species of local importance.
Explore knowledge gaps in ocean acidification science and research through a food security lens.
Align and integrate ocean acidification and food security research with regional and national policy objectives.
Leverage international frameworks to direct research, policy and financing support to more adequately assist nations in prolonged responses to the impacts of ocean acidification on food security.
The IAEA accepts a limited number of interns each year. The internships are awarded to persons studying towards a university degree or who have recently received a degree (see Internship web pages for further details).
The purpose of the programme is:
To provide interns with the opportunity to gain practical work experience in line with their studies or interests, and expose them to the work of the IAEA and the United Nations as a whole;
To benefit the IAEA’s programmes through the assistance of qualified students specialized in various professional fields.
The duration of an internship is normally not less than three months and not more than one year.
Organizational Setting
The Division of IAEA Marine Environment Laboratories (NAML) comprises three separate laboratories that together constitute the IAEA’s Marine Environment Laboratories. They use nuclear and isotopic techniques to understand and propose mitigation strategies and tools for the environmental impacts of radionuclides, trace elements and organic contaminants, as well as climate change, habitat destruction and biodiversity loss.
The Radioecology Laboratory uses state-of-the-art nuclear and isotopic techniques to address Member States’ most important coastal and marine ecological challenges and needs. These include studies on biomagnification, ocean acidification, carbon cycling, seafood safety and biotoxins, often in the context of future climate-change scenarios. It hosts the Ocean Acidification International Coordination Centre.
Main Purpose
The objective of this internship is to contribute to various activities of IAEA’s Ocean Acidification International Coordination Centre (OA-ICC). Based at the IAEA’s Radioecology Laboratory (REL) in Monaco, the intern will work with the OA-ICC team to organize and implement upcoming activities and events (technical meetings, training courses), update OA-ICC resources (news stream and databases), and draft communication material (reports, newsletters, web stories, social media posts). As part of the activities of the OA-ICC, the intern will also help support the Secretariat of the Global Ocean Acidification Observing Network (GOA-ON), working in close collaboration with Secretariat members (one person from IOC-UNESCO and one person from the NOAA Ocean Acidification program). This includes attending weekly Secretariat meetings, helping with GOA-ON communication, contributing to the activities of the UN Ocean Decade programme OARS (Ocean Acidification Research for Sustainability), organizing quarterly meetings of the GOA-ON Executive Council, supporting regional hubs of GOA-ON (e.g. Africa, Mediterranean), and helping prepare GOA-ON activities planned for the 6th Symposium on the Ocean in a High-CO2 World, which will take place from 13-16 October 2026 in Wellington, NZ.
Functions / Key Results Expected
Work with the OA-ICC team to deliver the Centre’s annual work plan (organization and facilitation of expert meetings, capacity building and outreach activities)
Assist in communication activities of the OA-ICC (reports, web stories, newsletters, social media)
Help maintain and update OA-ICC online resources (news stream, data bases)
Help support the Secretariat of the Global Ocean Acidification Observing Network (GOA-ON)
Contribute to exploring potential non-traditional funders for OA-ICC programmes
Develop a survey to collect baseline data for a series of Key Performance Indicators of OA-ICC activities
Qualifications and Experience
Bachelor’s Degree – University degree in Marine Biology, Environmental sciences, Radioecology, Ecology or a related field.
Good background knowledge of climate and environmental change, ocean acidification, marine biology, oceanography, radioecology.
Ability to coordinate and manage projects in a timely manner.
Ability to work well within a team and in a multicultural and international context.
Project management experience is an asset.
Applicant Eligibility
Candidates must be a minimum of 20 years of age and have completed at least three years of full-time studies at a university or equivalent institution towards the completion of a first degree.
Candidates may apply up to one year after the completion of a bachelor’s, master’s or doctorate degree.
Candidates must not have previously participated in the IAEA’s internship programme.
Good written and spoken English essential; fluency in any other IAEA official language (Arabic, Chinese, French, Spanish or Russian) an asset.
Candidates must attach two signed letters of recommendation to their application.
This curriculum developed by the Mid-Atlantic Coastal Acidification Network (MACAN) brings coastal and ocean acidification into the classroom in clear, practical ways. It provides complete lesson plans, hands-on activities, and data-driven investigations that support student inquiry while aligning with Next Generation Science Standards (NGSS).
Designed for high school classrooms, the lessons can be taught as a full unit or selected individually to fit existing course needs.
Lesson 1: This section introduces the curriculum and key concepts in ocean acidification through background reading and short videos. It includes NGSS-aligned questions and transcripts that can be used in class or for flipped learning.
Lesson 2: Students learn how carbon moves through Earth’s systems and how emissions affect atmospheric CO₂. An interactive game helps reinforce sources and sinks through hands-on participation.
Lesson 3: Students explore how increased atmospheric CO₂ changes ocean pH and water chemistry. Demonstrations and guided activities help introduce the foundational processes behind ocean acidification.
Lesson 4: Through hands-on lab activities, students investigate the chemical reactions that drive ocean acidification. These labs also introduce how changes in chemistry affect shell formation in marine organisms.
Lesson 5: Students compare ocean and coastal acidification using data and infographics. The lesson emphasizes how estuaries and coastal waters experience different conditions than the open ocean.
Lesson 6: Students examine data on Mid-Atlantic species to understand how decreasing pH affects growth, reproduction, and survival. They connect changes in chemistry to impacts on living organisms.
Lesson 7: Students work individually and in groups to analyze data related to bivalve health. The lesson focuses on interpreting evidence and drawing conclusions about the effects of dissolved CO₂.
Lesson 8 Part 1: This lesson engages students in investigating declining bay scallop populations while exploring the scientific method and experimental design. Students analyze data, build critical thinking skills, and examine coastal acidification’s impacts on biological species. Lesson 8 Part 2: In Part 2, students apply the scientific method to investigate the bay scallop mystery by reviewing key steps, conducting research, developing hypotheses, and designing experiments to guide their inquiry.
Bring your students into the Pacific Northwest to discover how the ocean acts like a carbon sponge and its effects on salmon and plankton that fuel the ecosystem. This toolkit utilizes effective communication strategies to convey the significance of ocean acidification effects and empower mitigation actions within communities. Tested in classrooms, this toolkit increased ocean acidification literacy for ages 9 and older. Students can become OA Ambassadors as they apply what they know toward ocean acidification solutions.
The toolkit includes four NGSS aligned modules that can be used independently or together. Each module includes the ocean acidification literacy goal, a value that can be used to better engage or connect with students, discussion guide, and solutions students can take part. In addition, an optional script that uses specific language will guide the instructor in successful and effective ocean acidification dialogue.
Module
Description
I. Our Ocean: The Giant Sponge
Students learn how the ocean absorbs carbon dioxide and the difference between regular and uncontrolled amounts through a guided demonstration.
II. Our Changing Ocean
Students make the connection between carbon dioxide in the ocean and increased acidity. With a simple experiment, they compare ocean acidity now with the past.
III. Swim, Snack, Sink
Students learn about the impacts of increased acidity on the plankton that feed the food web through an interactive activity.
IV. Senseless Salmon!
Students understand the impacts of ocean acidification on a salmon’s ability to smell to migrate and avoid predators through a game.
Alexandrium blooms occurred with normoxic conditions and moderate pH (7.5-8.0).
Alexandrium blooms occurred with moderate pCO2 (400 – 1,000 µatm) and saturating conditions for aragonite.
Dinophysis blooms co-occurred nocturnal acidification (8.71 to 13.6 hr d−1) and hypoxia (0.52 to 3.88 hr d−1).
Dinophysis blooms co-occurred with high pCO2 (1,000 – 3,500 µatm) and undersaturated aragonite (Ωar < 1).
The co-occurrence of nocturnal hypoxia, acidification, Ωar undersaturation, and HABs coupled is a significant threat for marine life.
Abstract
While harmful algal blooms (HABs), hypoxia, and ocean acidification are common occurrences in coastal zones, research investigating the co-occurrence and interactions between these processes has been lacking. Here, we documented the initiation, peak, and demise of eight distinct HAB events caused by Alexandrium catenella and Dinophysis acuminata over a two-year period in two estuaries (Northport Harbor and Cold Spring Harbor, NY, USA). We concurrently characterized the dynamics of carbonate chemistry, including pCO2 and the saturation state of aragonite (Ωar), pH, dissolved oxygen (DO), and general environmental conditions in space and time. HABs occurred in succession and reached high densities with A. catenella blooms exceeding 104 cells L−1 being succeeded by D. acuminata blooms exceeding 106 cells L−1. A. catenella blooms occurred during spring months under generally normoxic conditions with moderate levels of pCO2 (400 – 1,000 µatm), only brief periods of acidification (pH < 7.5), mostly saturating conditions for aragonite, and an absence of hypoxia. In contrast, D. acuminata blooms, which occurred in summer, consistently co-occurred with bouts of extended nocturnal acidification (8.71 to 13.6 hr d−1) and hypoxia (0.52 to 3.88 hr d−1) coupled with higher levels of pCO2 (1,000 – 3,500 µatm), and undersaturating conditions for aragonite (Ωar < 1). During both blooms, nearshore locations hosted higher cell densities, lower pH and DO, and higher pCO2 compared to open water regions. The co-occurrence of multiple stressors including nocturnal hypoxia, acidification, Ωar undersaturation, and HABs, coupled with strong diel cycling of DO, pH, and pCO2, especially during D. acuminata blooms, represents a significant and previously unrecognized threat for marine life.
Absorption of CO2 by global oceans is decreasing pH resulting in ocean acidification (OA). Impacts on shellfish have been documented in ecologically and commercially important species. We examined the influence of diet and OA between two populations of red abalone (Haliotis rufescens) a species of aquaculture importance and declining wild populations. Populations experience different exposure histories: strong upwelling (Van Damme, California [VD]) historically exposed to low-pH conditions and weak-intermittent upwelling (Santa Barbara, California [SB]). Abalone were cultured under control-pH or OA-conditions and fed crustose coralline algae (CCA) or diatoms used in aquaculture. We tested treatment effects of population, settlement diet, and OA-exposure on survival as influenced by larval-energy stores. Survival in both populations was enhanced by CCA when cultured under both treatment conditions; however, by later stages, this effect remained only for SB. SB had reduced post-settlement survival when cultured under OA-conditions, whereas post-settlement survival of VD was not. Diet affected the relationship between larval-energy and post-settlement survival; a positive relationship when fed diatoms and a negative relationship with CCA. The relationship between larval energy and post-settlement survival was stronger in VD. CCA enhanced juvenile growth in SB cultured abalone at both three-months and one-year post-settlement. Settlement diets can reduce the impacts of OA on early-life stages of abalone, but population differences driven by underlying energetics affect the consistency of this outcome. These findings illuminate the impacts from OA, suggesting populations may be at risk, and inform strategies for developing and sustaining shellfish aquaculture in the face of changing ocean conditions.
To investigate the effects of ocean acidification (OA) on macroalgae, we conducted in situ surveys along a natural CO2 vent gradient in Shikine Island, Japan, together with complementary laboratory culture experiments. The in-situ surveys revealed that near the CO2 vent (where pH dropped by 0.37), macroalgal diversity and species-richness were less than half those at the reference sites under ambient pH conditions. Nevertheless, the rates of CO2 assimilation of several common macroalgae increased from the reference site to the areas near the CO2 vent. This enhancement coincided with decreased photosynthetic CO2 affinity, reflecting that the acidified area down-regulated CO2-concentrating mechanisms in the algae. Measured photosystem II activity revealed that macroalgae at reference sites had lower electron transport rate and light utilization efficiency. The laboratory culture experiments, in which the dominant species (Gelidium elegans and Dictyopteris undulata), were cross-exposed to ambient and elevated CO2 conditions, further demonstrated that the stress near the CO2 vent significantly exacerbated photoinhibition under high light stress. Our results demonstrate that reduced pH and high sunlight act synergistically to impair macroalgal photosynthesis through exacerbated photoinhibition. This effect was more pronounced in red algae (e.g., G. elegans) than in brown algae (e.g., D. undulata). These different physiological responses provide a mechanistic explanation for an observed community shift, from red algal dominance in ambient pCO2 areas to brown algal dominance near the vent. Our findings imply that future OA, when combined with high-light stress, may selectively disadvantage high-light-sensitive species, thereby altering macroalgal community structure in coastal waters.
The dynamics of calcium carbonate structures in marine organisms (skeletons and shells) has become increasingly important due to heightened interest in marine environmental acidification. Research into molluscan shell corrosion and calcification in response to acidification is typically carried out in laboratory-controlled settings, which often overlooks the intricate interactions found in natural environments. Mollusks inhabiting intertidal zones are especially susceptible to intense shell weathering caused by tidal cycles of heating, cooling, wetting, and drying, exacerbated by solar radiation during periods of air exposure. We investigated the effect of sun exposure (solar radiative heating) on both outer shell corrosion and inner shell compensatory calcification in the tropical oyster, Saccostrea scyphophilla. Shell properties were compared between oysters from neighboring populations in sun-exposed and shaded habitats. Habitat temperatures were measured using iButtons, and right shell valve corrosion was quantified. Compensatory calcification was assessed through measurements of shell thickness, shell density, shell compression strength, and mineralogical properties. Our results revealed that oysters in the sun that experience global irradiance, higher temperature peaks and broader daily temperature ranges (averaging an increase of 10 °C) show considerably greater outer shell surface corrosion (87%) compared to shaded oysters (31%) that experience only diffuse irradiance. Sun-exposed shells also become thickened in the midsection and around the adductor muscle, and they are slightly stronger, indicating compensation for the outer shell loss. These findings highlight the need for caution when interpreting molluscan shell dynamics based on laboratory marine acidification protocols that fail to account for the many natural environmental factors influencing shell formation and dissolution.
This study evaluated how the combination of ocean warming, acidification, and deoxygenation (“deadly trio”) affects the early development of the fish Sparus aurata. Embryos and recently hatched larvae were exposed to increased temperature (Δ + 4 °C; 22 °C), elevated CO2 levels (pCO2 ~1000 μatm, Δ − 0.4 units; pH 7.7), and reduced oxygen (Δ − 60% O2 saturation; 3 mg O2 L −1). Deoxygenation emerged as the primary stressor, significantly reducing hatching rates, larval survival, and heart rates. These effects were further intensified when combined with warming and acidification. Acidification alone also reduced larval phototactic behavior by 50%, while exposure to all three stressors eliminated phototactic responses entirely. Overall, the results demonstrate that multiple climate-related stressors together severely harm fish early life stages, emphasizing the need to study combined environmental changes to better predict future impacts of climate change on marine fish populations and ecosystem functioning.
Abstract
The interaction between increased dissolved carbon dioxide, rising temperatures, and oxygen loss—the so-called “deadly trio”—is expected to strongly affect marine biota over the coming years, undermining ocean services and uses. Nonetheless, no study has so far scrutinized the cumulative impact of these three stressors on fish embryos and larvae. To fill this knowledge gap, we conducted a fully multi-factorial experiment to investigate the effects of warming (+4 °C: 22 °C), acidification (Δ − 0.4 pH units: 7.7 pH, pCO2 ~1000 μatm), and deoxygenation (Δ − 60% O2 saturation: 3 mg O2 L−1) on physiological and behavioral responses of the commercially important species Sparus aurata. Deoxygenation was the primary factor reducing hatching rates (64.25%), survival (46.71%), and heart rates (31.99%) of recently hatched larvae, being generally further exacerbated when combined with warming and acidification. No larvae exposed to the interaction of the three treatments reacted to the phototactic behavior test. However, acidification alone caused a 50% reduction in phototactic behavior. Our findings demonstrate that the deadly trio is detrimental to early fish development, impacting several key features at this critical life stage, and the need to assess the impacts of stressors’ interaction on marine taxa to better predict future ecosystem responses to ocean changes.
Minister of Water, Environment and Climate Change, Hon. Matthew Samuda, provides details about the outcomes of the 11th Our Ocean Conference held in Mombasa, Kenya, during a Post-Cabinet Press Briefing at Jamaica House on Wednesday (June 24). Photo: Adrian Walker.
Jamaica signed on to four key international environmental partnerships during the 11th Our Ocean Conference in Mombasa, Kenya, held from June 16 to 18.
The agreements are the Caribbean Ocean Coordination Mechanism, the Ocean Acidification Alliance, the Action in Blue Regional Network, and the Mangrove Breakthrough.
Minister of Water, Environment and Climate Change, Hon. Matthew Samuda, provided the details during Wednesday’s (June 24) Post-Cabinet Press Briefing at Jamaica House.
He explained that the Caribbean Ocean Coordination Mechanism is a platform that “shares the burden of environmental management of our shared Caribbean Sea”.
Anchored by the United Nations Environment Programme (UNEP), the mechanism places Jamaica in a leadership position to manage many of the issues that face Caribbean nations, he pointed out.
As it relates to Ocean Acidification Alliance, he explained that it is a network of scientists who are “specifically focused on the issue of ocean acidification, which is critical to the health of our coral reefs, fisheries and, indeed, to tourism”.
The nation also joined the Action in Blue Regional Network, which is focused on coordinating the protection of 30 per cent of the Caribbean Sea.
“That is something that Jamaica would have lobbied for from as far back as 2015, when Jamaica joined what is called the High Ambition Coalition for Nature, which led the way in calling for 30 per cent protection of our marine environment,” the Minister stated.
Meanwhile, through the Mangrove Breakthrough, which is managed by an alliance chaired by Colombia and Jamaica, the country will be working with partner nations and institutions to strengthen efforts on mangrove protection and restoration.
The Minister noted that Jamaica needs support in protecting its mangroves, especially along the south coast “where we are exposed to heavy storm surge in times of storms and have low coastal defences”.
Meanwhile, the Minister noted that while in Kenya, he had a bilateral meeting with the Green Climate Fund, which is also currently in Jamaica for a technical mission.
“While there, it was announced that Jamaica was approved for an additional US$2.1-million grant being managed by the CCCCC (Caribbean Community Climate Change Centre), which is the CARICOM unit that manages climate change, to assist Jamaica with getting projects ready for submission for significant grant funding,” Mr. Samuda shared.
The grant is titled ‘Catalysing Climate Action by building Jamaica’s NDA Capacity & Country Investment Platform’.
CARICOM has indicated that it will help Jamaica access international climate financing and develop a pipeline of projects needed to protect its people, economy and environment.
Posidonia oceanica is a foundation seagrass species endemic to the Mediterranean Sea, where it forms highly productive meadows that support biodiversity, coastal protection and long-term blue carbon storage. However, these ecosystems are increasingly threatened by the combined effects of climate change and local anthropogenic pressures, including ocean warming, marine heatwaves, ocean acidification, hypersalinity and thermal pollution. Despite growing evidence of the vulnerability of P. oceanica to environmental change, the mechanisms underlying its acclimation capacity, resilience and potential vulnerability thresholds remain only partially understood, particularly under multiple-stressor scenarios.This study investigates the responses of P. oceanica to climate change-related stressors across multiple levels of biological organization, integrating evidence from meta-analysis, controlled mesocosm experiments, molecular analyses and field observations. Special attention is given to the role of environmental history in shaping population-specific responses, comparing plants exposed to contrasting environmental conditions and assessing their phenological, physiological, metabolic and molecular performance under single and combined stressors.By linking organismal, molecular and meadow-scale responses, this work provides new insights into the capacity of P. oceanica to cope with future climate scenarios and local anthropogenic disturbances. The findings contribute to identifying resilience mechanisms and vulnerability patterns in Mediterranean seagrass ecosystems, supporting the development of more effective monitoring, management and conservation strategies under ongoing global change.
The coastal Ocean Data Analysis Product in North America (CODAP-NA) Version 2026 represents a major expansion of coastal ocean carbonate chemistry synthesis for North American continental margins. Compared to CODAP-NA Version 2021 (61 cruises, 3,391 profiles, and 28,206 data rows), the updated product integrates newly available cruise observations spanning more than four decades, substantially increasing both the spatial and temporal coverage of coastal biogeochemical measurements across all North American continental shelves. This version of the CODAP-NA is composed of 32,250 oceanographic profiles from 446 research cruises covering all continental shelves in North America (U.S. west coast, U.S. east coast, Gulf of Mexico, and Alaska coast). Data for 14 variables (temperature; salinity; dissolved oxygen concentration; dissolved inorganic carbon concentration; total alkalinity; pH on the Total Scale; carbonate ion concentration; fugacity of carbon dioxide; and concentrations of silicate, phosphate, nitrate, nitrite, nitrate plus nitrite, and ammonium) have been subjected to extensive quality control. Funding for this work comes from the National Oceanic and Atmospheric Administration (NOAA) Ocean Acidification Program.
International institutions managing fisheries and climate change operate in silos, leaving a critical gap in protection for communities dependent on blue foods.
London, 18th June 2026 – A new study, launched during Our Oceans Conference being held in Mombasa, finds that international governance frameworks are poorly equipped to address the combined threat of ocean acidification (OA) and blue food insecurity — despite both issues becoming increasingly urgent for global sustainability. The research, published in Environmental Research: Food Systems, maps the international governance landscape for both issues and finds that, while the two policy domains overlap significantly, they are rarely addressed together.
Annika Frosch, lead author and Research Fellow at the UCL Energy Institute Shipping and Oceans Research Group, said: “Without coordinated action across climate and food systems, the growing impacts of ocean acidification will continue to undermine fisheries and aquaculture that underpin global nutrition and livelihoods.”
The thematic nodes represent issue areas related to blue food security (blue) and ocean acidification (green). The nodes in the centre are those that apply to both blue food security and ocean acidification, and issues that were identified as critical governance areas at the OA-blue food nexus. The fisheries, aquaculture, and climate change nodes represented in red are discussed further in the paper.
Blue foods — fish, shellfish, and algae sourced from marine and freshwater environments — provide essential nutrients to millions of people worldwide, and global consumption has grown more than fivefold over the past 60 years. At the same time, ocean acidification, driven primarily by rising CO₂ emissions, is already harming shellfish aquaculture and fisheries, degrading coral reef ecosystems, and altering the nutritional quality and safety of seafood. Communities in the Global South, which rely most heavily on blue foods for daily protein, face the greatest risks — yet also receive the least research attention and policy support.
Using a structured review of international governance literature and a thematic mapping exercise, the researchers identified thirteen policy domains relevant to blue food security and ten relevant to ocean acidification, seven of which overlap — including fisheries and aquaculture, biodiversity, climate change, and land-based pollution.
Despite this overlap, the study finds that most international actors and instruments treat the two issues in isolation. A detailed examination of two central institutions — the Food and Agriculture Organization (FAO) and the UN Framework Convention on Climate Change (UNFCCC) — illustrates the problem clearly:
The FAO lacks an explicit mandate to govern ocean acidification. When OA is mentioned in FAO instruments, it typically appears as one item in a longer list of climate stressors, rather than being treated as a distinct and direct threat to food security.
The UNFCCC addresses ocean acidification only indirectly, through its broader CO₂ mitigation goals. Neither the UNFCCC nor the Paris Agreement explicitly names OA, and it does not feature as a core governance priority. Food security is referenced in UNFCCC objectives but is not linked to OA even in documents that mention both.
The study also highlights a troubling asymmetry: blue food security tends to receive legal and political recognition, while ocean acidification remains largely confined to scientific discussion — making coordinated policy action harder to achieve.
Keiko Nomura, co-author and Postdoctoral Researcher at the University of Colorado Boulder, said “Our findings suggest that ocean acidification remains more visible in scientific discussions than in international policy frameworks. Bridging this science-policy divide could help improve governance of climate risks to blue food systems.”
The paper makes recommendations for policy makers to bridge these governance gaps, including:
Strengthening FAO instruments to treat OA as a distinct climate-related stressor to fisheries and aquaculture, including through binding policies, vulnerability thresholds for key species, and the promotion of socioeconomic strategies.
Developing a dedicated OA workstream or technical body under the UNFCCC
Incentivising countries to include OA monitoring and adaptation measures in their Nationally Determined Contributions (NDCs)
Creating formal institutional links and coordination between climate bodies and marine science and fisheries organisations modelled on the Joint Capacity-building Programme of the three ‘Rio Conventions’, adapted for the OA–blue food security nexus
Inken Dressler, co-author and European Programme Lead at the International Alliance to Combat Ocean Acidification (OA Alliance): “The siloed recognition and approach to ocean acidification and blue food security hinders effective governance of both issues. To bridge this gap, closer cooperation between existing frameworks such as the UNFCCC and FAO must be achieved.”
The researchers note that some Pacific Island nations — including Fiji and the Solomon Islands — are already leading the way by integrating ocean acidification into their national climate strategies and fisheries management plans, demonstrating what more coherent governance could look like.
The study accompanies Dr Frosch’s new book ‘Navigating the Souring Seas: The Global Experimentalist Governance of Ocean Acidification’ which explores how OA is being addressed at the global stage. Bridging science, law, and international policy, this interdisciplinary book provides a clear overview of the scientific background of OA and maps the international governance landscape, identifying it as a regime complex. Through detailed interview-based case studies of the Ocean Acidification Alliance and the International Maritime Organization, the book evaluates real-world efforts to govern OA and highlights how flexibility, learning, and multilevel collaboration, can enhance their effectiveness.
