The IAEA’s Ocean Acidification International Coordination Centre (OA-ICC) (https://www.iaea.org/ocean-acidification) is cooperating on the organization of this event and has limited funds at its disposal to help meet the costs of the attendance of selected participants from eligible IAEA Member States to present their work and foster international collaboration at the conference.
The deadline to apply is Friday September 4th. To apply, applicants will need to submit their application through their national authority to the IAEA – in most cases, this will be your country’s permanent mission to the IAEA.
If you have questions on the application procedure, please contact Ms Lina Hansson (L.Hansson(at)iaea.org) or Ms Carolina Galdino (C.Galdino(at)iaea.org).
Dates: 13–16 October 2026
Location: Tākina Convention & Exhibition Centre, Wellington, New Zealand
Introduction Held every four years, the International Symposium on the Ocean in a High-CO2 World is the largest global gathering on ocean acidification. The Symposium brings together scientists, communities, policymakers, and stakeholders from sectors such as fisheries and aquaculture to share and discuss the latest research on the impacts of ocean acidification on marine life and potential solutions to counter its effects. The Sixth edition will maintain a focus on ocean acidification but will also expand to consider other ocean climate impacts, such as ocean warming and deoxygenation, particularly in a multiple-driver context. Research on marine carbon dioxide removal interventions, which have been suggested to mitigate climate change and ocean acidification, will also be a key part of the conference. More information on the seven key themes of the conference, its 22 workshops, and the detailed programme can be found on the Symposium website (https://highco2-vi.org/).
Objectives The purpose of the event is to provide a space for scientists from the ocean acidification (OA) research community to disseminate the results of their research, discuss joint projects with peers and engage with stakeholders. The event, held every four years, is the world’s largest conference on OA and related stressors.
Target Audience Scientists from developing IAEA Member States. Priority will be given to early-career scientists actively working on ocean acidification, multiple stressors or marine carbon dioxide removal (mCDR). Applicants should hold a university degree in marine biology, oceanography or a related scientific field. Female scientists are encouraged to apply.
Working Language English
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Participation and Registration All persons wishing to participate in the event through the IAEA have to be designated by an IAEA Member State.
In order to be designated by an IAEA Member State, participants are requested to send the Participation Form (Form A) and Grant Application Form (Form C – if applicable) to their competent national authority (e.g. Ministry of Foreign Affairs, Permanent Mission to the IAEA or National Atomic Energy Authority) for onward transmission to the IAEA by 4 September.
Selected participants will be informed in due course on the procedures to be followed with regard to administrative and financial matters.
Participants are hereby informed that the personal data they submit will be processed in line with the Agency’s Personal Data and Privacy Policy and is collected solely for the purpose(s) of reviewing and assessing the application and to complete logistical arrangements where required. The IAEA may also use the contact details of Applicants to inform them of the IAEA’s scientific and technical publications, or the latest employment opportunities and current open vacancies at the IAEA. These secondary purposes are consistent with the IAEA’s mandate.
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Additional Requirements The participants should have a university degree in marine chemistry, biology, oceanography, or a related scientific field, and must be active researchers in the ocean acidification /mCDR field or should have already received technical training on ocean acidification / mCDR by the IAEA or through other efforts.
Selection will be based on merit and motivation. Applications must include, in addition to Form A and C, if applicable:
A motivation letter with a short description of research interests, motivation to participate, and plans regarding present and future research on OA and/or mCDR (max one A4 page)
Although net negative emissions of carbon dioxide (CO2) are essential to meet climate targets, little is known about how declining atmospheric CO2 levels will affect ocean acidification. Here, by analysing the acidity ([H+]) and corrosivity to aragonite (ΩArag) in eight Earth system models that made simulations under rising then falling CO2 levels, we identify the Arctic as a hotspot for delayed reversibility of ocean acidification. Under falling CO2, Arctic surface waters remain comparatively more acidic, and aragonite-corrosive conditions (ΩArag < 1) persist until atmospheric CO2 drops ~120 ppm below the threshold at which they first appeared under rising CO2. This hysteresis arises from the erosion of the natural surface-layer deficit in dissolved inorganic carbon, initially maintained by sea ice limiting air–sea gas exchange and not fully restored as sea ice recovers during CO2 decline. Thus, the Arctic Ocean experiences not only the greatest acidification but also the most delayed benefits from negative emissions.
Seawater pH measurement is essential for monitoring ocean acidification and its biogeochemical impacts. Glass electrode pH sensors are widely used for in situ applications due to their ease of operation, low power consumption, and no reagent requirements. However, their accuracy can be affected by temperature-dependent effects, particularly those associated with the internal reference solution. Conventional calibration methods based on the Nernst response do not explicitly account for temperature-induced variations in the internal solution, which may lead to systematic bias under conditions with large temperature gradients. In this study, a correction method is proposed to address temperature-dependent errors by modeling the internal pH (pHin). The model incorporates two primary temperature-dependent contributions: the intrinsic temperature dependence of the phosphate buffer and potential shifts caused by activity changes in saturated KCl. These effects are combined through the electrode response factor (fR), defined as the ratio of the observed electrode slope to the theoretical Nernst slope, to estimate pHin as a function of temperature and correct measured pH values to a reference temperature of 25 °C. Application of the method to vertical seawater profiles demonstrated a reduction in deviation from colorimetric reference measurements. The corrected results showed reduced temperature-dependent bias across depth. This approach provides a practical framework for improving the reliability of in situ glass electrode pH measurements under varying thermal conditions. The proposed method addresses equilibrium temperature-dependent effects of the internal solution but does not explicitly account for transient hysteresis, pressure effects, or long-term sensor drift.
Science education plays a key role in helping students to become responsible citizens, capable of making appropriate decisions based on scientific information, participating in discussions on socio-scientific issues (SSIs), and taking action in the context of climate change. Thus, achieving scientific literacy in general and practising scientific argumentation skills – as part of scientific literacy – in particular, are essential. Therefore, the pilot study presented here focusses on improving upper secondary students’ (ISCED 3) scientific argumentation skills by implementing Toulmin’s Argumentation Pattern (TAP) in the chemistry classroom. We focus on chemistry education to better understand subject-specific argumentation in chemistry classrooms. This pilot study is part of an interventional study that aims to implement TAP as a construction mechanism to improve students’ scientific argumentation skills. Our study is embedded in the SSI of human-induced ocean acidification. In order to gain insight into students’ scientific argumentation patterns and develop adequate teaching materials, we asked 29 upper secondary students to write well-founded arguments to confirm a claim about calcification of coral skeletons made in a newspaper headline. Students’ arguments were constructed prior to and following the provision of support material based on TAP. These arguments were analysed with regards to their formal quality using qualitative content analysis. Our findings indicate that TAP aligned well with our participants’ intuitive arguments. We discuss our findings and propose how using TAP can contribute to teaching and learning chemistry-specific argumentation skills.
The Gulf is dynamic and productive, supporting corals, fish, shellfish and other marine life that sustain the region’s fisheries, biodiversity and economies. Join us for a Gulf of America Coastal Acidification Network (GCAN) webinar highlighting a new interactive Story Map that illustrates how researchers are monitoring ocean and coastal acidification across the Gulf. Pallavi Tummeti and Dr. Natalia López Figueroa will provide an overview of the Story Map and guide discussion about tracking acidification in the Gulf. Learn about the the data, research projects, and regional partnerships featured in this interactive resource.
Climate change is increasingly reshaping the sustainable development of the ocean through ocean warming, deoxygenation, acidification, and other compounding stressors. Against this backdrop, environmental impact assessment (EIA) has become a pivotal governance instrument for anticipating and reducing the climate-related impacts of human activities at sea. From the United Nations Convention on the Law of the Sea (UNCLOS) to the Agreement on Biodiversity Beyond National Jurisdiction (the BBNJ Agreement), regulatory expectations for marine EIAs are moving toward more structured thresholds, procedural workflows, and reporting obligations. At the same time, rapid advances in climate artificial intelligence (climate AI), such as machine-learning forecasting, deep-learning nowcasting, and agentic AI workflows, are expanding the ability to produce timely, high-resolution, and probabilistic climate information from heterogeneous climate data streams. These capabilities can strengthen climate-related EIAs by combining short-term forecasting and nowcasting for early warning, long-term observation and monitoring for dynamic baselines, and scenario-based climate modelling for impact estimation and decision support. Climate AI can therefore be integrated throughout the EIA workflow rather than appended as an auxiliary layer, translating climate data into regulatory evidence under changing marine-climate conditions. To ensure regulatory robustness and accountability, implementation should be grounded in evidence standards and quality assurance, transparent and auditable documentation, human oversight, responsibility allocation, and formal mechanisms for cross-institutional data sharing. We argue that a standards-driven, AI-enabled EIA framework can improve the relevance, reviewability, and robustness of marine EIA decisions, supporting long-term ocean sustainability under accelerating climate risks.
South Africa’s coastal zone comprises diverse ecosystems and species, and provides important benefits to people. It is also under significant pressure from numerous activities that take place on land, in estuaries, and in the sea, and that are rarely considered together. Here, we review the pressures on coastal biodiversity in South Africa, taking a cross-realm perspective. The pressures are reviewed under 10 themes: biological resource use; energy production and mining; pollution; coastal development; transportation and service corridors; natural systems modifications (sand-flow disruptions, estuarine hydrological regime change, livestock grazing and browsing); human intrusions and disturbance; aquaculture, agriculture and plantation forestry; invasive and other problematic species and diseases; and climate change, severe weather and ocean acidification. Many of these are intense or pervasive cross-realm pressures, often with cumulative, synergistic impacts that are collectively causing habitat fragmentation and loss, declines in species richness and abundance, altered animal behaviour, reduced ecosystem resilience, and declines in capacity to provide ecosystem services. However, the inter-connected nature of these pressures also means that integrated coastal management provides opportunities to address multiple pressures and impacts cross-realm. Sustainable development that is mindful of long-term climate projections is imperative in the coastal zone to safeguard this national asset into the future.
Widespread shifts in seawater chemistry are occurring across spatial and temporal scales, with important consequences for coastal ecosystems. Giant kelp (Macrocystis pyrifera) forests elevate seawater pH and dissolved oxygen (DO) through photosynthesis, potentially providing short-term refugia from ocean acidification and deoxygenation. However, whether these effects persist across contrasting environmental settings remains unclear. Here, we assess how biological and oceanographic conditions regulate giant kelp-mediated modification of seawater chemistry across multiple sites.
Methodology
Hourly measurements of seawater pH, DO and temperature were collected during spring–summer 2022–23 using paired deployments inside and outside giant kelp forests at one site in central Chile and four sites in Tasmania, Australia. The influence of giant kelp density was also evaluated at two sites in southern Chile and three sites in Tasmania. An upwelling index was calculated for the central Chile site to assess the influence of regional oceanographic forcing on kelp-associated seawater chemistry patterns.
Key Results
Hourly pH and DO were higher inside giant kelp forests than outside at the central Chile site and at one Tasmanian site. At these locations, stronger daytime pH–DO relationships indicated that photosynthetic carbon uptake exceeded night-time respiration, generating a net positive metabolic signal. In Tasmania, giant kelp density was positively associated with hourly pH and DO, whereas no such relationship was detected in southern Chile. At the central Chile site, kelp-associated effects intensified during a strong upwelling event, reducing the severity of low pH and DO conditions.
Conclusions
Giant kelp forests can locally buffer short-term fluctuations in seawater pH and DO, but this capacity is highly site-dependent and influenced by giant kelp density and environmental conditions. Overall, our findings suggest that continued loss of giant kelp forests in Tasmania may reduce their potential to provide short-term refugia, while in Chile the strength of kelp-mediated seawater chemistry modification is likely to remain strongly influenced by variability in upwelling and freshwater inputs.
The Mediterranean Sea (MedSea) is highly sensitive to climate-driven changes in temperature, oxygen, and pH, among other variables. To better assess these long-term trends, we developed CARIMED (CARbon, tracers, and ancillary data In the MEDiterranean Sea), the first comprehensive, harmonised data synthesis product for the MedSea. CARIMED integrates hydrographic, inorganic carbon, transient tracer, and ancillary measurements from 46 research cruises spanning the period from 1976 to 2018, containing observations for the entire water column across all MedSea sub-basins. A substantial component of the data was retrieved from fragmented or locally archived historical records, thus consolidating previously inaccessible measurements. Following global synthesis approaches, CARIMED applies a quality-controlled, and bias-adjusted framework. A key adaptation was the secondary quality control (2QC) procedure, specifically tailored to the MedSea’s unique hydrography, utilising sub-basin divisions and supplementary checks (including statistical consistency assessments) to resolve complex, often contradictory, inter-cruise offsets. This rigorous process minimised systematic biases, yielding a dataset with improved consistency, and highlights the urgent need for adapted standard operating procedures and reference materials to address the MedSea biogeochemical particularities. CARIMED delivers two complementary, freely available products: the aggregated original cruise data product (https://doi.org/10.20350/digitalCSIC/17785, García-Ibáñez et al., 2025) and the final bias-adjusted data synthesis product (https://doi.org/10.25921/cp5b-zq67, Álvarez et al., 2025; hosted at https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/oceans/CARIMED/, last access: 26 June 2026). This essential resource establishes a new benchmark for assessing long-term biogeochemical trends, validating regional ocean models, and supporting climate-change mitigation and adaptation strategies in this rapidly changing semi-enclosed basin.
Acute acid stress (pH 4.5) preferentially impairs later mating stages in medaka, rather than causing a generalized reproductive collapse.
Early initiation phases (following and courtship) are relatively less affected, whereas progression to the crossing stage and spawning is strongly suppressed.
General locomotion and territorial aggression show no detectable change under acute acidification.
Females exhibit increased ammonia excretion and oxygen consumption, indicating sex-specific physiological strain under acid stress.
The behavioral impairment is consistent with an energy reallocation toward acid–base homeostasis, reducing investment in energetically costly terminal mating behaviors.
Abstract
Environmental acidification poses a significant threat to aquatic organisms, yet the underlying mechanisms of how acid stress disrupts complex social and reproductive behaviors remain incompletely understood. In the present study, we investigated the behavioral and physiological responses of adult Japanese medaka (Oryzias latipes) under acute acid exposure (pH 4.5, 24 h). Our results showed that acute acid stress reduced mating success, with a stronger impairment observed in the transition to the crossing stage and subsequent spawning, while the earlier, male-driven stages of following and courtship were relatively less affected under the present experimental conditions. This reproductive impairment did not coincide with detectable changes in generalized emotional-like behavior. Fish showed normal performance in the novel tank test and maintained territorial aggression. Physiologically, we observed a clear sexual dimorphism. Under acid stress, males maintained relatively stable MO₂ and JAmm, whereas females showed elevated MO₂ and JAmm. These findings suggest that reproductive impairment may be more pronounced in energetically demanding mating stages and may be associated with sex-dependent physiological strain. We further propose that the increased metabolic cost of acid-base regulation in females could shift energy allocation, and that high-cost coordination behaviors may be reduced in order to maintain short-term survival. This study provides evidence linking bioenergetics, acid-base regulation, and reproductive behavior in a teleost model under acidification.
Retraction: D.L. Dixson, P.L. Munday, G.P. Jones, “ Ocean Acidification Disrupts the Innate Ability of Fish to Detect Predator Olfactory Cues,” Ecology Letters 13 no. 1, (2010): 68–75, https://doi.org/10.1111/j.1461-0248.2009.01400.x.
The above article, published online on 21 December 2009 in Wiley Online Library (onlinelibrary.wiley.com), has been retracted by agreement between the Editor-in-Chief, Peter H. Thrall; and John Wiley & Sons Ltd. A third-party complainant alerted the publisher to their observation of a statistically implausible variance in the data. The authors were contacted regarding the concerns raised. After evaluating the full dataset provided by the authors, an investigation by members of the journal’s editorial team determined that the data provided contained substantial errors, including repeated blocks, missing data, and structural errors. The authors acknowledged the inconsistencies with the data and provided an explanation, which included carelessness during manuscript reorganization, and they also asserted that the reported data anomalies did not affect the overall published results. The authors maintain that the errors were not a result of intentional data fabrication, but rather, poor standards of data handling and quality control. However, neither the publisher nor the editor has confidence in the article, primarily because the data provided during the investigation were not consistent with the observation methods described in the article. Therefore, because the journal has no basis on which to affirm confidence in the published results, the article must be retracted. The authors have been informed of the retraction.
Invasive macroalgae reduced P. oceanica seedling biomass and leaf development.
Macroalgal invasion depleted carbohydrate reserves in seedling roots and rhizomes.
Elevated CO2 increased rhizome starch but did not mitigate invasion impacts.
Root microbiome diversity declined markedly under macroalgal invasion.
Future CO2 enrichment unlikely to buffer invasion stress at recruitment stage.
Abstract
Seagrass seedlings are key to meadow recovery under global change, as they enable recolonization of degraded areas and provide genetic variability needed for adaptation. While invasive macroalgae increasingly threaten seagrass communities, elevated CO2 has been proposed to enhance seagrass performance and potentially buffer other stressors. Here, we conducted a mesocosm experiment to test the combined effects of two invasive macroalgae (Lophocladia trichoclados and Caulerpa cylindracea) and elevated CO2 on Posidonia oceanica seedlings. CO2 enrichment increased carbohydrate reserves in rhizomes and induced subtle shifts in root-associated microbiomes. In contrast, invasive macroalgae had consistently negative effects on seedling development and physiology and strongly altered both above- and belowground microbial communities. Despite its potential to stimulate seagrass productivity, elevated CO2 did not mitigate the detrimental impacts of invasive macroalgae. These findings indicate that future CO2 conditions may not offset invasion-driven stress at the recruitment stage, highlighting the need for targeted management efforts to limit macroalgal proliferation and support seagrass meadow regeneration.
Ocean acidification threatens coral reefs by reducing seawater pH and carbonate saturation state. Crustose coralline algae are particularly vulnerable because their high-magnesium calcite skeletons dissolve more readily than coral aragonite skeletons. However, this dissolution may increase alkalinity and buffer reef-water chemistry. Here we show, using repeated low-tide observations and in situ incubations in a shallow reef system in the southern Great Barrier Reef, that reef-water pH varies by more than one unit over the day (7.47 – 8.61), reaching levels comparable to those projected for the end of this century. Nighttime respiration promotes dissolution of high-magnesium calcite produced by crustose coralline algae, increasing alkalinity and helping maintain seawater supersaturated with respect to aragonite. At the same time, isolated coral incubations experience a greater decline in pH and aragonite saturation state in the absence of this buffering effect. These findings suggest that high-magnesium calcite-producing communities may help partially buffer reefs against future acidification.
More than a dozen Mendocino County schools will be hosting a new program providing students an opportunity to learn about their ocean environment as well as a unique art experience. The students will be dyeing fabric using purple sea urchin spines.
Workshop student, Sarah Burstein of Arcata, looks at live sea urchins in salt water, during a sea urchin natural dye workshop taught by Margaret Seelie, at Fibershed Learning Center in Pt. Reyes, Saturday, July 25, 2026. (Darryl Bush/For The Press Democrat)
The workshops, presented by Seelie Studio of Oakland, include an educational component that addresses the need to harvest vast numbers of the overblown populations of purple sea urchins because they are decimating the California kelp forests.
Bay Area artist Margaret Seelie is the founder and head dyer at Seelie Studio. She was introduced to natural dye through a fun wine and crafts evening.
Margaret Seelie, founder of Seelie Studio, looks at a purple sea urchin while wearing a light pink beanie dyed with sea urchin pigment, during her sea urchin natural dye workshop at Fibershed Learning Center in Pt. Reyes, Saturday, July 25, 2026. (Darryl Bush/For The Press Democrat)
“I went to a friend’s art studio one night for this, you know, like wine and crafts thing,” she said. “A woman brought indigo dye and I indigo dyed a pillowcase and that was the beginning of the end for me. I loved it. That’s when my infatuation with plant and nature-based dyes began.”
She said she began dyeing everything she could get her hands on using the indigo plant. “That just became my medium,” she said.
Live purple sea urchins are shown in front of a jar of liquid containing sea urchin pigment as Margaret Seelie, founder of Seelie Studio, teaches a sea urchin natural dye workshop at Fibershed Learning Center in Pt. Reyes, Saturday, July 25, 2026. (Darryl Bush/For The Press Democrat)
Discovering purple urchins
In 2022, Seelie learned that sea urchins had eaten around 95% of the kelp forest off the California coast. The urchin populations are so out of control from a lack of predators that a whole movement has been created around the need to harvest as many sea urchins as possible in order to bring down their populations and give the kelp beds a chance to revive. That stuck with her and informed her path toward a unique new business that help increase the harvesting of sea urchins while also educating the public to the problems their overpopulation poses.
A chance encounter inspired that new altruistic venture. She was doing natural dyeing for Santa Cruz surfer and shaper Ashley Lloyd’s line of beachwear called Unfurling. Through Lloyd she met Noyo Harbor Master Anna Neumann who was making dye from sea urchins.
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“I met Anna and I was just totally enamored of the fact that she was doing this work and then also her as a person,” Seelie said. “She’s a total badass, she’s a fisherwoman. Growing up on boats myself, I know it’s not the most glamorous place to be at times, so I just thought she was a great grace.”
Inspired by the colors Neumann was creating, Seelie decided to see if she could figure out how to coax color from these incredible creatures. “With my background as a natural dyer and environmentalist, I used my understanding of how a shift in Ph levels can create strong bonds between dye and fabric, but also how it can disrupt and break down calcium carbonate in marine animals.”
She was trying to figure out how to get the sea urchins to experiment with when she was left a gift by the sea. She had been surfing down south and a king tide left the sand covered with sea urchins. “I filled an empty water bottle with dried spines and urchin bits and I brought them back to San Francisco and made sea urchin dye in my kitchen,” she said.
That would inevitably be the start of a new direction for Seelie. Up to this point she had been doing production natural dye work for clients on the side while working a tech job. But in January of 2023 she was caught up in a large wave of layoffs. She decided to found Seelie Studio, based on her work with urchin dye.
Spines and shells from the purple sea urchins contained in a jar are later ground into powder to form the dye, are shown as Margaret Seelie, founder of Seelie Studio, teaches a sea urchin natural dye workshop at Fibershed Learning Center in Pt. Reyes, Saturday, July 25, 2026. (Darryl Bush/For The Press Democrat)
So far, all of the sea urchins she’s been using have been from kelp restoration projects, which helps to fund those projects. She said they haven’t needed that many for their educational workshops. But now she’s working on launching the world’s first urchin dye kits which will require a lot more sea urchins. She’s currently in talks with divers and organizations to determine who she will be using for urchins going forward.
Seelie said her goal from day one was to try and create incentive for people to want urchins and the infrastructure to make them available. “So it’s a really exciting moment to finally need a lot of urchins, because there’s a lot of them,” she said.
Once Seelie receives sea urchins, she takes them to her studio in Oakland to process them.
“They go from a live animal to a purple spines,” she said.
Teaching others
For the urchin dye workshops she hosts she includes an educational component about the overpopulation of sea urchins and the decimation of the kelp forests off the California coast. Seelie said the urchins provide an opportunity for many satellite lessons that are rich with material. She said the urchin dye itself is both a chemistry and an ecology lesson because the sea urchin dye is actually a version of ocean acidification.
“So it’s really exciting because you get to see this sort of accelerated breaking down process of the calcium carbonate,” she said. “Sea urchin shells and spines are made of calcium carbonate. When you create the dye with them, the calcium carbonate breaks down and releases the color.”
Seelie said it’s very similar to what happens when ocean acidification happens. “The pH of the ocean changes due to warming and the change in the pH of the ocean creates an inhospitable environment for animals with shells, and they basically can’t grow shells that are strong and hard enough to survive,” she said. “There’s a lot of lessons around the sea urchin dye, but to me, I think that is kind of the most magical and impactful because you’re seeing this happen.”
Global warming has caused a rise in ocean temperature and acidification, which collectively wreak havoc on marine animals. However, the combined ramifications of these stressors on energy metabolism, oxidative balance, and DNA integrity remain inadequately studied in teleosts. The present study aims to unravel the combined effects of warming (34°C) and acidification (pH 7.7) on energetic balance, antioxidant defense, and DNA stability in Mystus gulio at two intervals (15th and 45th day). Furthermore, the Effect Addition model was used to disentangle potential additive or non-additive effects of the combined stressors. Elevated temperature and acidification induced a marked energetic imbalance, as mirrored by suppressed ingestion and absorption rates, reduced scope for growth, and elevated excretion. Oxidative stress biomarkers revealed significant upregulation of SOD, CAT, and GST under combined treatment, which ultimately led to augmented lipid peroxidation. Genotoxic assessment delineated progressive upsurges in tail DNA (%) and olive tail moment, indicating compromised genomic stability. The integrated biomarker response consisted of six parameters, RR, ER, SOD, CAT, GST, and LPO, further corroborating that elevated temperature, alone and in combination with acidification, posed the highest cumulative physiological burden. Furthermore, the model assessment indicated that the interaction between warming and acidification varied among different biomarkers. Collectively, these findings corroborate that concurrent thermal and low pH perturbations destabilise physiological processes, oxidative instability, and DNA damage, which may undermine growth potential and jeopardise population structure and destabilise trophic relationships. The present study provides a mechanistic understanding of the impacts of multiple stressors and offers a robust integrative framework to predict fish vulnerability under future climate-driven oceanic vicissitudes.
Ocean warming and coastal acidification often co-occur in nearshore embayments, yet their joint associations with zooplankton remain difficult to characterize because responses are frequently nonlinear and spatially heterogeneous. In this study, we developed an integrated quantitative framework for characterizing joint warming-acidification exposure in Jiaozhou Bay. Based on six cruises conducted at nine stations in May (spring) and August (summer) from 2022 to 2024, we characterized zooplankton communities using abundance, biomass, Shannon-Wiener diversity (H′), and Pielou’s evenness (J). We further introduced a joint-exposure indicator, the Acid-Heat Vector Intensity Index (AHIvec), which summarizes joint temperature-pH departure based on standardized anomalies of temperature and pH. Generalized additive models (GAMs) were then applied to examine nonlinear response patterns and zone-specific associations between environmental gradients and zooplankton community attributes. Within the 2022–2024 observation window, sea surface temperature was generally higher in 2024 than in 2022, whereas surface pH was generally lower; however, these patterns should be interpreted as short-term observations rather than formal long-term trend estimates. Zooplankton also showed pronounced spring-summer and spatial variability. Notably, abundance showed pronounced temporal variation and generally increased with temperature, whereas biomass peaked at intermediate temperatures (∼20–22 °C) and declined thereafter, indicating a mismatch between abundance and biomass. Although pH-related associations were weaker than temperature-related associations, they became more evident at the lower end of the observed pH range (approximately 7.7–7.9). The AHIvec gradient was associated with contrasting zone-specific patterns in zooplankton community attributes. Overall, recent temperature-pH variations were associated with changes in zooplankton abundance, biomass, and diversity in Jiaozhou Bay. The AHIvec + GAM framework provides a monitoring-oriented complement to direct temperature-pH analyses for characterizing joint exposure in coastal ecosystems.
Genome-wide data revealed a mahimahi evolutionary history shaped by vicariance, ocean currents and local environments, needing models, functional genomics and selection tests for climate adaptation
This study examined the worldwide population structure of the cosmopolitan pelagic fish Coryphaena hippurus using a dataset of 8.7 million SNPs and complete mitochondrial genomes. The analyses reveal, for the first time, four genetically distinct populations corresponding to the major oceanic basins: the Atlantic, Pacific, Indian Ocean and Mediterranean Sea. Photo of Atlantic mahimahi by NOAA Fisheries.
The processes that generate and sustain marine biodiversity are still incompletely understood, especially in open-ocean systems where high dispersal potential is expected to prevent strong population differentiation. Understanding how evolutionary forces shape divergence or speciation in such environments requires detailed knowledge of a species’ life history and its interactions with key environmental variables.
In a study by Píndaro Díaz Jaimes and coworkers – at the Universidad Nacional Autónoma de México, the Tecnológico de Monterrey, and the Instituto Politécnico Nacional in Mexico; Universitat Pompeu Fabra in Spain, and the University of Palermo in Italy – the authors applied a genome-wide approach to examine the global population structure of the cosmopolitan pelagic dolphinfish or mahimahi (Coryphaena hippurus), an important commercial species. A comprehensive dataset comprising 8.7 million single-nucleotide polymorphisms together with complete mitochondrial genomes was generated during this research.
The analyses reveal, for the first time, four genetically distinct populations that correspond to the major oceanic basins: the Atlantic, Pacific, Indian Ocean and Mediterranean Sea. The Mediterranean population carries a unique genomic signature, most probably reflecting historical isolation and limited contemporary gene flow through the Strait of Gibraltar.
Despite this clear inter-basin structure, genome-wide data also retain extensive signals of historical connectivity. Results of various tests show significant excess allele sharing (meaning that two groups of individuals carry the same version or allele of a particular gene or DNA segment), particularly between the Indo-Pacific and Atlantic groups. In addition, phylogenetic network analyses (drawing evolutionary relationships that allows for mixing between groups, not just simple branching) show multiple migration events. These results underline the lasting influence of ancestral gene flow on present-day genetic patterns.
At finer geographic scales, modest but statistically significant structure was detected within both the Atlantic and Pacific basins. Seascape genomic analyses (how genetic differences in marine species are linked to the environment around them) further demonstrate that environmental gradients – including salinity, phosphate concentration, pH and others – are significantly associated with genomic variation, indicating that ecological factors play a role in shaping population differentiation across heterogeneous marine habitats.
Fig. 1: Graphical summary of the study. Adapted from the original.
Relevance of research findings to the industry
For fisheries managers and the fishing sectors, the discovery of four basin-scale genetic populations is important. Stocks that look continuous on a map may in fact be demographically independent. Management plans that treat all dolphinfish as a single global unit risk over-harvesting one basin while under-utilizing another.
Knowing that Mediterranean fish are particularly distinct and that Atlantic and Pacific populations also show internal structure gives managers a clearer basis for setting regional catch limits, seasonal closures or size regulations. The environmental associations also hint that climate-driven changes in salinity or nutrient levels could alter population boundaries in the future, which both industry and regulators should monitor.
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Perspectives
This research demonstrates that even highly dispersive oceanic species can maintain meaningful genetic structure. Future studies should combine these genomic results with ocean-circulation models to assess how currents move larvae and adults between basins. Functional genomic approaches and tests for loci under selection would help identify which genes allow each population to cope with local conditions and with rapid environmental change.
Expanding sample sizes, especially from under-represented regions of the Indian Ocean and southern Pacific, would refine the picture further. Overall, the four genetic groups identified in this study provide a solid starting point for designing management units that better match the true biology of the species.
Modeling ocean acidification and warming effects on Atlantic Sea scallop growth for adaptive management
Results of this study show that warming stress is stronger than previously recognized, especially in the southern Mid-Atlantic, while ocean acidification appears first in the north. Together these stressors shrink the optimal growth range of sea scallops, showing the value of the spatially coupled DEB model for adaptive fisheries management. Photo of a sea scallop (Placopecten magellanicus) – which has over 100 blue eyes along the edge of its mantle to sense light intensity – by Dann Blackwood, USGS (Public domain, via Wikimedia Commons).
Effective climate-ready fisheries management depends on robust predictions of how species will respond to environmental change across broad spatial scales. Bioenergetic approaches such as Dynamic Energy Budget (DEB) models link physiological processes to environmental conditions and can therefore forecast organismal growth under future climate scenarios.
In a recent study by Halle M. Berger and colleagues (University of Connecticut and NOAA Northeast Fisheries Science Center and Océanopolis in France) the scientists presented the first large-scale integration of a DEB model with downscaled regional oceanographic simulations. This coupling allows resolving spatiotemporal patterns and examine how climate stressors appear at biogeographic, economic and oceanographic scales that matter for management.
The researchers calibrated a DEB model for the Atlantic Sea scallop (Placopecten magellanicus) using output from a realistic oceanographic–biogeochemical model of the Northeast U.S. continental shelf. The model was used to project the combined effects of ocean acidification (OA) and warming on individual growth both historically and through the coming century. It successfully reproduced observed historical patterns in age at harvest size and maximum attainable size.
At mid-century (2035–2050), scallop growth was projected to increase across most of the region, with the exception of the southern Mid-Atlantic; OA effects remained confined to the deep Gulf of Maine. By the end of the century (2080–2095) under a high-emissions scenario, scallops were expected to grow more rapidly yet reach smaller maximum sizes. The results indicate that warming stress is more severe than previously recognized, especially in the southern Mid-Atlantic. Warming impacts appear first in the south, whereas OA stress precedes warming in the north.
Overall, together these stressors progressively shrink the geographic area that supports optimal growth, and the results of this study demonstrate the value of a spatially explicit, climate-forced DEB model as a practical tool for guiding adaptive fisheries management.
Fig. 5: Mean (± SD) dry flesh mass (top row) and shell height (bottom) of experimental juvenile scallops exposed to low (503 microatm – the microatmosphere is a unit of pressure equal to one-millionth of an atmosphere – black symbols), moderate (805 microatm, yellow symbols), or high (1168 microatm; red symbols) pCO2 (data from Pousse et al. 2023) used to calibrate the model. In ocean science (especially ocean acidification studies), a microatm is the standard unit used to express the partial pressure of carbon dioxide (pCO₂) in seawater. Typical surface ocean values today are around 400–450 microatm. Adapted from, and with additional information in the original publication.
Relevance of research findings to the industry
For the scallop fisheries industry, the most immediate value of the work is its ability to flag which fishing grounds are likely to become less productive and which may temporarily improve. Southern mid-Atlantic beds face the earliest risk of slower growth and smaller maximum size, while some northern areas may see short-term gains before acidification becomes limiting. Processors, vessel operators and managers can use these regional signals when planning long-term investments, lease decisions or rotational closures.
The finding that animals may grow faster yet end up smaller also has direct economic consequences: smaller scallops command lower prices and may require changes in gear or processing methods. Because the model is spatially explicit, it can be updated as new climate projections or survey data become available, giving the industry a living tool rather than a one-time snapshot.
Perspectives
Results of this study demonstrate that linking bioenergetic models to regional ocean forecasts is both feasible and useful for climate-ready management. Future work could refine the food-supply component of the model, incorporate density-dependent effects, and assess additional emission scenarios. Expanding the approach to other shellfish or finfish would allow multi-species comparisons and more integrated ecosystem planning.
Managers should consider that waiting until declines appear in the catch is no longer necessary. The spatial patterns of stress are already projected; adaptive measures – such as shifting effort northward, adjusting size limits, or protecting residual high-growth habitats – can be designed now. Overall, the model developed provides a practical bridge between climate science and the day-to-day decisions that will hopefully keep the Atlantic Sea scallop fishery viable through the coming decades.
Genetic connectivity varies within basins, revealing hidden substructure.
Abstract
The origin and maintenance of marine biodiversity remain poorly understood, particularly in highly connected oceanic environments where extensive dispersal is expected to limit population differentiation. Evolutionary processes driving population divergence or speciation frequently depend on a proper knowledge of species’ life history and its interaction with major environmental variables. Using a genome-wide approach, we investigated the global population structure of the cosmopolitan pelagic fish Coryphaena hippurus Linnaeus, 1758, generating a dataset of 8.7 million SNPs and complete mitochondrial genomes.
Our results reveal, for the first time, four genetically differentiated populations, corresponding to major oceanic basins: Atlantic, Pacific, Indian and Mediterranean Sea. The Mediterranean population exhibited a distinct genomic signature, likely resulting from historical isolation and restricted contemporary exchange through the strait of Gibraltar. Despite this structure, genome-wide analyses uncovered extensive signals of historical connectivity among basins. D-statistics and f4-ratio tests detected significant excess allele sharing, particularly between Indo-Pacific and Atlantic populations, while phylogenetic network reconstruction in TreeMix supported multiple migration events, highlighting the role of ancestral gene flow in shaping global genetic patterns.
At finer scales, a limited but significant intra-oceanic structure was detected within both Atlantic and Pacific basins. Seascape genomic analyses revealed that environmental gradients such as salinity, phosphate concentration, light availability (PAR, Kd), and pH are significantly associated with genomic variation, suggesting that ecological factors contribute to population differentiation across heterogeneous marine environments.
Seawater carbonate system measurements in the Mediterranean Sea are relatively scarce, especially in its eastern basin. This study describes the monthly variations of carbonate system parameters in the open sea and coastal water column of the eastern Mediterranean Sea during the period February 2018 to January 2019. Water samples were collected for analysis of Total Alkalinity and pHT at the shallow coastal THEMO1 and the deeper open-water THEMO2 (1,500 m bottom depth) stations off the Mediterranean coast of Israel. In the surface layer (<25 m), TA increased with salinity at a rate of +72 μmol·kg−1 and the pCO2(SW) was strongly and positively correlated with temperature. During summertime, surface waters were highly super-saturated with respect to atmospheric pCO2 (pCO2(SW) ∼ 600 μatm), while during winter they were only slightly super-saturated. The estimated net annual CO2 flux from the surface of the eastern Mediterranean Sea to the atmosphere during the study period was +2.8 Tg C·y−1, which is three times greater than a previous estimate made for this region (0.9 Tg C·y−1), and is attributed to the smaller volume of Atlantic water input in the present study compared to the previous one as well as the substantially shallower total dissolved inorganic carbon enriched core of the Levantine Intermediate Water in this study. Based on these results, it is still expected that future warming and salinization, reduced Atlantic Water influx to the eastern Mediterranean Sea, and increased stratification will increase the flux of CO2 to the atmosphere in this region.
Plain Language Summary
This study investigated annual variations in atmospheric CO2 flux from the surface of the eastern Mediterranean Sea based on monthly seawater sampling and carbon chemistry analyses conducted at two locations off the Mediterranean coast of Israel from February 2018 to January 2019. The results indicate that the southeastern Mediterranean Sea was a net source of CO2 to the atmosphere. This behavior was largely driven by seasonal changes in seawater temperature, which controls the saturation concentration of dissolved CO2 in seawater. During summer months, warm surface waters were a strong source of CO2 to the atmosphere, while during winter they were a weak sink. The study estimates that approximately 2.8 million tons of carbon were released annually from the sea to the atmosphere during the study period. This revised and more comprehensive estimate is ∼3 times higher than previous estimates reported for the same region. The increase is suggested to result from recent changes in regional circulation, particularly a reduced inflow of Atlantic Ocean waters into the eastern Mediterranean Sea. Based on these findings, continued warming, increasing salinity, and enhanced stratification of the eastern Mediterranean Sea are expected to further intensify CO2 release to the atmosphere in the future.
Low salinity linked to warming may intensify coastal pH reduction.
Low salinity reduced righting and emergence in the limpet Patelloida pygmaea.
Low salinity reduces Mg/Ca ratios in newly formed shell layers.
Low pH increases shell thickness and Mg/Ca ratios despite dissolution.
CHS2 upregulation suggests compensatory resistance to low pH.
Abstract
Rising anthropogenic carbon dioxide emissions have driven ongoing ocean warming and associated climate changes. In the Yellow Sea, this warming is associated with enhanced monsoonal rainfall, which increases freshwater inputs and lowers coastal salinity. Increased freshwater input can weaken seawater buffering capacity, thereby leading to lower pH conditions in coastal environments. Here, we examined the effects of low pH and low salinity on the intertidal limpet Patelloida pygmaea. Adult limpets were exposed for 31 days to four experimental artificial seawater conditions combining two pH levels (8.0 and 7.5) and two salinity levels (30 and 21 psu). Survival and condition factor were not influenced by pH or salinity. However, low salinity reduced righting and emergence behavior. In addition, the Mg/Ca ratio in the M + 1 layer was lower at 21 psu than at 30 psu. Low pH resulted in a thicker M + 2 layer with higher Mg/Ca ratios despite shell dissolution, potentially helping to maintain shell integrity. While there was no change in heat shock protein (HSP70) expression, these shell modifications were accompanied by an upregulation of chitin synthase (CHS2) genes under low pH. These findings suggest that P. pygmaea is negatively influenced by low pH and low salinity, but also demonstrate compensatory mechanisms that enhance resistance to low pH.
Talcott Mountain Academy | 7th grade | 12 years old
About the Idea
Meet Raji. Raji created an innovative coastal solution that uses algae and natural calcium buffers to lower ocean acidity and boost marine health
Why did you enter the 3M Young Scientist Challenge?
I entered the 3M Young Scientist Challenge because I wanted to do something real with my research. Studying ocean acidification in a classroom is one thing, but this competition gave me a reason to go further, to actually design an experiment, collect real data, and test whether my idea could hold up under scrutiny. I also entered because climate change feels urgent to me in a way that is hard to ignore. The oceans are absorbing carbon at a rate that is changing their chemistry, and that affects billions of people. I wanted to work on something that mattered, not just something that would earn a grade. The 3M Young Scientist Challenge specifically appealed to me because it is not just about having a good idea. It rewards students who communicate science clearly and think about real-world impact. That is exactly what I was trying to do with this project.
What is your favorite invention of the last 100 years, and why?
My favorite invention of the last 100 years is the autonomous underwater vehicle (AUV), such as those developed by organizations like Saildrone and the Woods Hole Oceanographic Institution. These AUVs (like Saildrone’s carbon-neutral ocean drones) allow scientists to collect real-time data on ocean chemistry, pH levels, and CO₂ absorption in remote and challenging environments—critical for understanding and addressing ocean acidification. Their ability to operate autonomously for months at a time makes them game-changers for monitoring the health of our oceans.
In 15 years I hope to be…
In 15 years, I hope to be a NASA aerospace engineer designing systems that monitor ocean health and climate change from space. My research taught me that the most significant climate breakthroughs happen when different fields work together, and I want to build the tools that make that possible.
