Applications open: fourth winter school on ocean acidification and multiple stressors

Published 20 October 2026 Events Leave a Comment

Dates: 30 November – 11 December 2026

Location: IAEA Marine Environment Laboratories, Monaco.

Deadline for application through InTouch+ platform: 6 November 2026

The Winter School is organized by the IAEA OA-ICC in partnership with the Prince Albert II of Monaco Foundation through the OACIS Initiative (Ocean Acidification and other ocean Changes – Impacts and Solutions) and the Laboratoire d’Océanographie de Villefranche (LOV).

Introduction

Ocean acidification is a global environmental stressor that threatens marine life and the livelihoods of coastal communities. Ocean acidification is caused by increasing atmospheric carbon dioxide being absorbed by the ocean, resulting in changes to seawater carbonate chemistry, including a drop in pH. Due to global concerns about its consequences, ocean acidification is included in international policies such as Target 3 of UN Sustainable Development Goal (SDG) 14 and Target 8 of the Global Biodiversity Framework (GBF).

The IAEA’s Ocean Acidification International Coordination Centre (OA-ICC) supports IAEA Member States to minimize and adapt to OA and report towards SDG 14.3 and the GBF, with a strong focus on building capacity to study ocean acidification and related stressors and promoting international collaboration and coordination.

Ocean acidification is not happening in isolation, but in combination with other human-driven pressures, including pollution, warming, and oxygen loss. The impact of multiple ocean stressors on marine life and ecosystem function is not well understood, yet this information is crucial to inform adaptation strategies that might minimize negative effects on organisms, ecosystems, and associated socioeconomic benefits.

The Fourth Winter School on Ocean Acidification and Multiple Stressors is part of the capacity building program of the OA-ICC.  This two-week training course will provide participating scientists with a thorough understanding about key concepts and experimental design used to study the impacts of ocean acidification in the context of additional stressors.

Objectives

The aim of the Winter School is to train early-career scientists who already have experience researching ocean acidification on how to study acidification in the context of other co-occurring stressors. Through lectures and practical exercises in the laboratory, the students will gain understanding of key concepts in multiple-stressor research (e.g., What is a stressor? What is a mode of action? What is an interaction?), purposeful experimental design, and analysis of complex datasets. During the course, participants will collaborate on a joint laboratory experiment to elucidate the effects of three simultaneous drivers on marine organisms.

Target Audience

The course is open to 10-12 trainees. Priority will be given to early-career scientists with experience in marine environmental change with a focus on ocean acidification; a background in biological sciences is preferred. At least one publication in the field of marine environmental change is required.

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Participation and Registration

All persons wishing to participate in the event have to be designated by an IAEA Member State or should be members of organizations that have been invited to attend.

In order to be designated by an IAEA Member State or invited organization, participants are requested to submit their application via the InTouch+ platform (https://intouchplus.iaea.org) to the competent national authority (Ministry of Foreign Affairs, Permanent Mission to the IAEA or National Atomic Energy Authority) or organization for onward transmission to the IAEA by 6 November 2026, following the registration procedure in InTouch+:

1. Access the InTouch+ platform (https://intouchplus.iaea.org):

  • Persons with an existing NUCLEUS account can sign in to the platform with their username and password;
  • Persons without an existing NUCLEUS account can register here.

2. Once signed in, prospective participants can use the InTouch+ platform to:

  • Complete or update their personal details under ‘Complete Profile’ and upload the relevant supporting documents;
  • Search for the relevant event under the ‘My Eligible Events’ tab;
  • Select the Member State or invited organization they want to represent from the drop-down menu entitled ‘Designating Authority’ (if an invited organization is not listed, please contact InTouchPlus.Contact-Point@iaea.org);
  • If applicable, indicate whether a paper is being submitted and complete the relevant information;
  • If applicable, indicate whether financial support is requested and complete the relevant information (this is not applicable to participants from invited organizations);
  • Based on the data input, the InTouch+ platform will automatically generate the Participation Form (Form A) and/or the Grant Application Form (Form C);
  • Submit their application.

Once submitted through the InTouch+ platform, the application, together with the auto-generated form(s), will be transmitted automatically to the required authority for approval. If approved, the application, together with the applicable form(s), will automatically be sent to the IAEA through the online platform.

NOTE: The application for financial support should be made, together with the submission of the application, by 6 November 2026.

For additional information on how to apply for an event, please refer to the InTouch+ Help page. Any other issues or queries related to InTouch+ can be sent to InTouchPlus.Contact-Point@iaea.org.

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

Participants should have a university degree in marine chemistry, biology, oceanography or a related scientific field, and should be currently involved in or planning to study the ecological impact of multiple stressors, including ocean acidification. Experience with the R software is strongly encouraged.

Selection will be based on merit and interest. Applications should include:

 * A motivation letter with a short description of the candidate’s research interests and how the course would benefit the applicant’s current or future research on ocean acidification and multiple stressors (max one A4 page)

  * CV with publication list

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Lagrangian drifter measurements of the effects of seaweed cultivation on seawater carbon chemistry on a nearshore coral reef in Okinawa, Japan

Published 30 October 2026 Science Leave a Comment
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Ocean acidification (OA) and deoxygenation (collectively OAD) increasingly threaten coral reefs, which support marine biodiversity and human economic activity. Seaweed farms have been proposed to locally mitigate OAD conditions by removing dissolved inorganic carbon (DIC) and enhancing pH and dissolved oxygen (DO), but empirical evidence has been limited. Here, we investigated the effects of seaweed farming on net community production (NCPDIC, NCPDO), net community calcification (NCC), and seawater chemistry on a back reef lagoon system in Onna, Okinawa, Japan. Lagrangian drifters were used to measure and calculate rates of NCP, NCC, pH, and aragonite saturation state (Ωarag) in December 2022, April 2023, January 2024, and May 2024. The April 2023 and May 2024 surveys coincided with the annual maximum extents of seaweed cultivation (0.16 and 0.14 km2 respectively). Mean NCP and NCC were positive across sessions, but had high variability. Under saturating solar radiation, we observed elevated NCPDIC and NCPDO in April 2023 compared to January 2024, and stronger increases in pH and Ωarag in April 2023 and in May 2024 than in January 2024. Changes in pH and Ωarag were driven by NCPDIC, which was itself driven by temperature and solar radiation. We noted that NCC had a minor effect on the carbonate chemistry system relative to NCP. While we observed biogeochemical signals consistent with biotically-driven OAD modulation, the lack of spring survey control groups limits our ability to decisively attribute this modulation to the seaweed farm.

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Integrated study of ocean warming, CO₂ uptake, and acidification under anthropogenic emissions

Published 30 October 2026 Science Leave a Comment
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The study examines the influence of greenhouse gas pollutants on ocean waters. A key parameter describing ocean properties is pH, whose decrease negatively affects marine flora and fauna. Ocean surface temperatures rise over time due to the absorption of anthropogenic heat, with the most significant processes occurring within the upper 10 m layer. Phytoplankton, increasingly important for addressing ecological issues, is also affected by decreasing pH levels. To quantitatively describe ocean conditions, a thermodynamic calorimetric method is proposed. Validation is performed through a comparison of calculated and observed temperature variations, as well as the estimated specific heat capacity of ocean water. Measured pH variations are also compared with calculated values. The resulting expression incorporates temperature change, absorbed heat, and CO₂ content. Phytoplankton photosynthetic activity is further assessed in relation to potential cultivation areas on the ocean surface.

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Current knowledge of marine crustaceans in Mauritius and their global importance in a changing climate

Published 30 October 2026 Science Leave a Comment
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Marine crustaceans are ecologically and socio-economically important components of coastal and marine ecosystems; however, in Mauritius, knowledge of their biodiversity, functional roles, and responses to climate change remains limited and fragmented. This narrative review synthesizes available information on Mauritian marine crustaceans, with particular emphasis on the class Malacostraca, while identifying key knowledge gaps and research priorities relevant to their ecological importance and climate-change vulnerability at both local and global scales. Although existing records document 61 crustacean families in Mauritius, these data are sparse, outdated, and largely based on historical surveys, highlighting the urgent need for updated inventories and long-term monitoring. Globally, marine crustaceans act as trophic intermediaries, ecosystem engineers, and scavengers, contributing to nutrient cycling, sediment dynamics, and habitat stability. They support fisheries, aquaculture, tourism, and cultural practices, and provide valuable bioresources such as chitin, chitosan, and other bioactive compounds with applications in regeneratiom engineering, medicine, agriculture, environmental remediation, and biotechnology. Trade patterns further emphasize their economic importance, revealing export-oriented dynamics in Mauritius, instead of local consumption, that result in a net reliance on imports. Climate change poses an escalating threat through ocean warming, acidification, and increasing environmental variability, affecting DNA repair, protein synthesis, haemolymph, metabolic performance, calcification, reproduction, immunity, behavior, and species interactions. These stressors are further compounded by habitat degradation, altered symbiotic interactions and food-web disruption. The scarcity of empirical studies from Mauritius underscores the need for integrative, multi-stressor, and long-term research to support effective conservation, fisheries management, and climate resilience.

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Spatiotemporal water quality dynamics in Southern U.S. coastal reserves: a long-term perspective

Published 30 October 2026 Science Leave a Comment
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Water quality monitoring in estuarine ecosystems is essential for assessing the health and sustainability of these dynamic coastal habitats, which are increasingly vulnerable to environmental change and human impacts. This study aims to characterize long-term trends and seasonal drivers of seven key water quality parameters: temperature, salinity, dissolved oxygen (DO), pH, chlorophyll-a (Chla), nitrate + nitrite (NOx), and phosphate (PO4) across four southern U.S. National Estuarine Research Reserves (Apalachicola Bay, Grand Bay, Mission-Aransas, and Weeks Bay) to identify which reserves and processes are most vulnerable to climate and anthropogenic change. Using two decades of data (1995–2020) and applying Generalized Additive Models (GAMs), we identified significant spatial and temporal patterns linked to environmental and anthropogenic factors. Results revealed a warming trend in Weeks Bay (+0.1035 °C/year, P = 0.0013), a salinity decline in Grand Bay (−0.1699 PSU/year, P = 0.033), and a salinity increase in Apalachicola Bay (+0.2055 PSU/year, P = 0.003). DO concentrations peaked in spring and dropped in summer, reflecting seasonal nutrient inputs. Grand Bay exhibited the highest Chla variability (CV=131.48%). NOx concentrations declined in Grand Bay (−0.0003 mg/L/year, P = 0.0162), while PO4 levels remained relatively stable. pH trends suggested localized acidification, particularly in Mission-Aransas (−0.0071/year, P = 0.0016). GAM results emphasized the combined effects of long-term and seasonal changes, with site-specific differences. These findings provide critical insights into estuarine functioning and highlight the need for regionally tailored management strategies to enhance resilience and biodiversity conservation in U.S. coastal reserves.

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Abrupt pH changes overestimate the responses of Chaetoceros muelleri to ocean acidification

Published 30 October 2026 Science Leave a Comment
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Ocean acidification, characterized by a gradual seawater pH decline, influences marine primary producers such as diatoms, which contribute substantially to oceanic carbon fixation. Experimental studies aiming to project climate change impacts often simulate acidification via abrupt pH shifts, potentially misrepresenting ecological and evolutionary responses. Here we conduct a long-term evolution experiment with the marine diatom Chaetoceros muelleri, comparing abrupt and gradual CO2 increases from 440 to 1000 ppm over 1100 generations. Integrating evolutionary genomics, physiological assays, elemental stoichiometry, and Earth System Modeling, we find that abrupt acidification exaggerates diatom growth and carbon fixation responses by up to 15%, driven by enhanced divergent genomic signals and persistent gene expression changes. Gradual acidification elicits weaker phenotypic and genomic shifts, aligning more closely with natural ocean conditions. These findings suggest that models based on abrupt CO2 increases may overestimate the contribution of Chaetoceros muelleri and maybe also other diatoms to productivity and biogeochemical cycling under ocean acidification, highlighting the importance of gradual pH decline in experimental designs to accurately predict marine ecosystem responses.

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Navigating uncertainty in the Pacific Arctic region: toward adaptive fisheries management under climate change and ocean acidification impacts

Published 30 October 2026 Science Leave a Comment
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Fisheries management under climate change in the Pacific Arctic Region faces profound uncertainties, particularly concerning the trajectory of environmental drivers and the biological responses of fish species to ocean acidification (OA), which affect both stock productivity and spatial distributions. Here, we employed the Dynamic Bioclimate Envelope Model to project century-scale changes in abundance, maximum catch potential, and species distributions for key commercial fish under two climate scenarios (SSP1-2.6 and SSP5-8.5) and two alternative assumptions about OA responses, namely without OA effect and with OA effect parameterized as increases in basal metabolic rate and elevated larval mortality. Fishing mortality was treated as a management control variable, and the minimax regret criterion was applied to select the fishing mortality strategy that minimizes the worst-case loss in landed value relative to the scenario-specific optimal strategy across all climate and OA response scenarios. Results indicate strong regional heterogeneity: southern LMEs (East Bering Sea, West Bering Sea, and Aleutians) experienced persistent declines in abundance and maximum catch potential, with negative responses to OA further amplifying reductions, whereas the northern LME (Northern Bering–Chukchi Seas) exhibited substantial gains. These poleward shifts were accompanied by increased spatial aggregation, highlighting that species are not only shifting northward but also becoming more spatially concentrated within suitable habitats. Assessments that ignore OA effects risk overestimating long-term yields and exposing fisheries to productivity and revenue losses. Precautionary reductions in fishing mortality consistently minimized long-term regret across most species and LMEs. These findings highlight the critical interplay between climate change, OA effects, and management decisions, providing a scientific basis for adaptive fisheries management in the rapidly changing Pacific Arctic Region.

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The spatial and temporal variability of dissolved inorganic carbon and total alkalinity production during early diagenesis in river dominated ocean margin sediments and their resultant effect on bottom water acidification

Published 30 October 2026 Science Leave a Comment
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Rapid anthropogenic release of CO2(g) to the atmosphere promotes global ocean acidification that is exacerbated in coastal environments by processes such as eutrophication and upwelling of low pH deep water. The decline in ocean pH through time poses a threat to marine ecosystems and the coastal communities that depend on them. Total alkalinity (TA), mainly supplied to the ocean by river discharge, allows seawater to buffer against future pH decline. Pore water DIC and TA generated in sediments during early diagenesis may be released to the overlying waters and either contribute to acidity or buffer against overlying water acidity, depending on the benthic TA to dissolved inorganic carbon (DIC) flux ratio (RTA:DIC), as RTA:DIC < 1 promotes acidification and RTA:DIC > 1 mitigates further acidification. The rapid accumulation of organic matter in river dominated ocean margin (RiOMar) sediments promotes the generation of relatively large benthic DIC and TA fluxes that may significantly influence overlying water acidification in these regions. A number of seasonally variable environmental factors such as river discharge and sediment resuspension may promote early diagenetic redox cycling in RiOMar sediments and induce seasonal RTA:DIC variability. This seasonal RTA:DIC variability is poorly characterized, however, despite their potential influence on overlying water acidification in these regions.

The present dissertation investigated how early diagenetic processes in RiOMar sediments and resultant benthic solute fluxes and RTA:DIC respond to seasonally variable environmental factors. This was accomplished using a combination of in-situ benthic flux measurements on the northern Gulf of Mexico (nGoM) continental margin and ex-situ sediment core solid phase and pore water analyses from both nGoM margin and Rhône River prodelta sediments. Overall, the results presented in this dissertation revealed significant seasonal early diagenetic and RTA:DIC variability in RiOMars that was driven by seasonally variable environmental factors such as river discharge, primary production, sediment perturbations, and bottom water hypoxia development. The largest RTA:DIC from RiOMar sediments may be promoted either 1) proximal to river deltas and in eutrophic hypoxic systems, where anerobic TA generation is high and reoxidation of reduced metabolites is low, or 2) when CaCO3 dissolution generates significant TA in pore waters.

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Connecting international ocean, climate and biodiversity governance to protect deep-sea life

Published 29 October 2026 Science Leave a Comment
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Deep-ocean biodiversity plays a fundamental role in the global carbon cycle and Earth’s climate system. Despite this critical function, international biodiversity and climate change governance frameworks have rarely considered deep-sea life to any considerable extent historically. Recent developments create opportunities to close this gap, including through the Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction (BBNJ Agreement), the Paris Agreement under the UN Framework Convention on Climate Change (UNFCCC), and the Kunming-Montreal Global Biodiversity Framework under the Convention on Biological Diversity (CBD). We review the history and developments of these conventions to date regarding how they address the interface between climate, biodiversity, and the deep ocean, and use this historical overview to identify specific opportunities and mechanisms that can be used to sustain and protect life in the deep ocean more effectively and coherently going forward. Practical suggestions include incorporating climate and carbon considerations in the creation of marine protected areas and other area-based management tools under the BBNJ Agreement, establishing cross-cutting mechanisms that can align efforts under the UNFCCC, CBD, and the BBNJ Agreement, and, under the Paris Agreement, incorporating deep-ocean actions in nationally determined contributions, reconsidering what counts as mitigation or adaptation to encourage consideration of carbon conservation actions, and ensuring that climate change mitigation efforts do not harm deep-ocean biodiversity.

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Monsoon-linked gut microbiome variation in a tropical sea urchin: a single-reef case study from the Arabian Sea

Published 29 October 2026 Science Leave a Comment
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Highlights

  • Stomopneustes variolaris gut microbiota shows clear seasonal structuring in response to monsoon-driven biogeochemical variability.
  • The gut microbiota of Stomopneustes variolaris is dominated by Bacteroidota, and most diverse during winter and spring inter-monsoon.
  • Gut microbial composition covaries with seasonal oxygen, pH, temperature, and nutrient gradients.
  • The sea urchin gut microbiome shows seasonal plasticity under monsoon-linked stress.

Abstract

Tropical coastal ecosystems of the Eastern Arabian Sea (EAS) experience pronounced monsoon-driven shifts in water-column biogeochemistry, yet their influence on the gut-associated microbiomes of benthic invertebrates remains poorly understood. Sea urchins are ecologically important grazers in reef-associated habitats, and their gut microbiota may reflect both environmental and dietary variability. Here, we provide an exploratory characterisation of the gut-associated microbiome of the sea urchin Stomopneustes variolaris from the Grande Island archipelago (Goa, India) across four monsoon-associated periods: Winter monsoon (WM), Spring-inter monsoon (SIM), Summer monsoon (SM), and Fall-inter monsoon (FIM). Using 16S rRNA gene sequencing, we analysed gut tissue and gut digesta from S. variolaris alongside environmental samples (seawater, sediment, and seaweed). Bacteroidota dominated the urchin gut microbiome, whereas Proteobacteria were more abundant in environmental samples. Gut microbial diversity was highest in WM and SIM and lowest during SM and FIM. Exploratory analyses indicated that gut microbial composition varied temporally, with taxa affiliated with sulphur-cycling lineages more prevalent during sampling points associated with low-oxygen monsoon phases (SM and FIM) and Firmicutes and organic matter-associated taxa more prominent during comparatively oxygenated periods (WM and SIM). Ordination analyses suggested an association between gut and environmental microbial assemblages and gradients in dissolved oxygen, temperature, pH, nutrients, and pCO2. This study provides baseline insights into the gut microbiome of a tropical echinoid from an understudied region and highlights monsoon-associated patterns in microbial community composition, forming a foundation for future functional and experimental investigations.

Graphical abstract

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Unlocking spatial ecological assessment for tropical seagrass habitats using a new rapid assessment method (SEARAM)

Published 29 October 2026 Science Leave a Comment
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Highlights

  • Rapid and standardized assessment of tropical seagrass ecological state.
  • Multimetric index combining structure and vitality indicators.
  • Spatial mapping of seagrass fragmentation and degradation.
  • Links between habitat condition, environment, and megafauna.
  • A practical tool for coastal monitoring and impact mitigation.

Abstract

Seagrass meadows are key coastal ecosystems supporting biodiversity, carbon storage, and essential trophic functions, yet they are increasingly threatened by anthropogenic and climatic pressures. Based on the Seagrass Meadows Rapid Assessment Method (SEARAM), a standardized protocol grounded in seagrass biodiversity indicators (SBIs), we developed a reliable and operational index to assess seagrass ecological state at high spatial resolution. Using 536 circular plots and 144 faunal stations across three intertidal reef habitats in Mayotte (Western Indian Ocean), SEARAM integrates structural and vitality sub-indices into a composite seagrass ecological state index (SESI), spatialized by geostatistical interpolation and analyzed using ANOVA, PCA, and multiple regression models. Results revealed highly fragmented meadows dominated by Halodule uninervis and Halophila ovalis, with low canopy height (5 ± 2 cm) and substantial epiphyte loads (37 ± 17%). The inner fringing reef flat showed the poorest ecological state (SESI = 4.8 ± 0.7/10), whereas the barrier reef (5.4 ± 0.8/10) and exposed fringing reef flat (5.6 ± 0.8/10) exhibited moderate scores. Key environmental drivers (turbidity, grain size, pH), significantly explained spatial patterns of seagrass structure and vitality, confirming the influence of sediment and light regimes. Functional relationships were also demonstrated between seagrass condition and associated fauna, particularly green turtle density and dugong feeding traces. SEARAM proved to be a rapid and robust tool for diagnosing tropical seagrass states. Its multimetric framework connects benthic condition to habitat suitability for megafauna, offering an operational foundation for ecological monitoring, management, and impact mitigation within the Avoid–Reduce–Offset (ARO) doctrine.

Graphical abstract

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Closer to danger: southern Ocean pteropods build their shells deeper in the water column during winter-spring

Published 29 October 2026 Science Leave a Comment
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Shelled pteropods are at risk from ocean acidification, with known effects on their shell durability and calcification. Pteropods typically form their aragonitic shells over specific depth ranges known as the “calcification depth,” which varies depending on species and habitats. Some Southern Ocean waters are already undersaturated with respect to aragonite and this could negatively affect shelled pteropods. However, the calcification depths of pteropods have not been determined nor used to infer consequences of changing seawater carbonate chemistry in the Southern Ocean. In this study, we analyzed the stable oxygen isotopic composition of Limacina rangii shells, collected by sediment traps in the sub-Antarctic zone, to estimate their calcification depth. Shallow calcification depths (13–126 m) were detected in summer–autumn, while L. rangii calcified their shells deeper in the water column during winter–spring (302–525 m). Recent shoaling of the aragonite saturation horizon is likely to negatively affect pteropods that calcify their shells in deep water. Such shoaling could affect pteropod calcification, shell integrity and threaten population viability.

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How ocean acidification makes marine fish reproduction vulnerable: physiological mechanisms and ecosystem consequences

Published 29 October 2026 Science Leave a Comment
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Highlights

What are the main findings?

  • Ocean Acidification (OA) disrupts the HPG axis, reducing sex steroids and vitellogenesis.
  • OA impairs gamete quality, sperm motility, egg integrity, and Ca²⁺ signaling.
  • pH decline may weaken Dax1 repression of P450arom, but this remains unvalidated.
  • OA plus warming often worsens reproductive dysfunction; multigenerational recruitment effects are still unknown.

What is the implication of the main finding?

  • OA threatens fish recruitment, community structure, and fishery productivity/food security.
  • Long-term, multigenerational, multi-stressor field studies are needed for effective management.

Abstract

Ocean acidification, driven by the absorption of anthropogenic carbon dioxide into seawater, poses a significant threat to marine environments and biodiversity. This comprehensive review examines the specific impacts of acidification on the reproductive physiology of fish, integrating recent advances in our understanding of gonadal development, gametogenesis, and early embryonic development. We synthesize current findings on how altered carbonate chemistry disturbs the reproductive system from gametogenesis and fertilization to larval development and beyond. Our analysis reveals that ocean acidification affects multiple physiological pathways, including disruption of the hypothalamic–pituitary–gonadal (HPG) axis, impairment of calcium signaling, and alterations in sex hormone synthesis. We propose a mechanistic model in which pH reduction may weaken Dax1-mediated repression of P450arom transcription, thereby dysregulating aromatase activity and leading to sex hormone imbalance that impairs gonadal development; however, this proposed mechanism requires direct experimental validation under ocean acidification, as the net outcome may be modulated by additional regulatory layers such as epigenetic modifications and other transcription factors. Furthermore, we discuss the synergistic effects of ocean acidification with temperature elevation and other stressors, which often exacerbate reproductive dysfunction. This review concludes that no multi-generational study has yet evaluated HPG axis disruption to population-level recruitment failure, a critical gap for fishery resource assessment. We emphasize the critical importance of multi-generational and field-based studies to fully understand these impacts, which is essential for forecasting consequences for global marine biodiversity and the long-term sustainability of fisheries.

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Coastal benthic ecosystems in a changing ocean: a mini review

Published 29 October 2026 Science Leave a Comment
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Coastal benthic ecosystems are shaped by the combined effects of climate change and anthropogenic pressures. Ocean warming, acidification, and deoxygenation interact with eutrophication, pollution, bottom trawling, and coastal development, altering biodiversity, habitat structure, and functioning from shallow coasts to continental margins. Benthic communities, comprising infaunal and epifaunal taxa, regulate key processes including nutrient cycling, sediment dynamics, and carbon burial, thereby underpinning benthic-pelagic coupling and biogeochemical dynamics. Rising temperatures and marine heatwaves drive widespread losses of habitat-forming species, while ocean acidification constrains calcification. Warming, acidification, hypoxia, eutrophication, and pollution increasingly simplify assemblages, and alter trophic pathways and performance. Interactions among stressors can amplify organismal sensitivity and push ecosystems towards ecological thresholds. However, many knowledge gaps remain. Recent methodological advances, including environmental DNA metabarcoding, automated imaging, trait-based analyses, and multi-stressor experiments, are improving the detection of ecosystem changes at large and our mechanistic understanding of ecosystem responses to ongoing change. By summarizing the various stressors that benthic habitats and taxa face, their interactions and potential outlooks, this review provides a concise synthesis of current understanding and identifies key knowledge gaps for future research and management under accelerating climate change.

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When oceans acidify: metal toxicity, uptake–depuration, and ion homeostasis in the copepod Nitokra sp.

Published 28 October 2026 Science Leave a Comment
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Highlights

  • Seawater pH affected metal toxicokinetics, but not toxicity in Nitokra sp.
  • Seawater pH affected Cu, Zn and Cd toxicokinetics, but not toxicity in Nitokra sp.
  • The highest bioconcentration factor was observed for Cu at pH 8.1.
  • Acute Cu, Cd, and Zn exposure did not reduce significantly copepod Ca or Na at pH 8.1 and 7.6.
  • Copepod Ca declined 48 h after Cd exposure ended, indicating Cd-induced ionic imbalance.

Abstract

Mechanisms governing metal kinetics help maintain trace element levels required for physiological functions and ion regulation in aquatic organisms. However, both essential and non-essential metals can become toxic at excessive concentrations. Water physicochemical properties, including pH and dissolved anions, influence metal speciation, bioavailability, and toxicity. Under acidic conditions, bioavailability may increase as H+ competes with metal cations for binding sites, increasing free metal ions. Greater bioavailability may also disrupt uptake of essential macronutrients such as calcium (Ca) and sodium (Na) through competition at biotic binding sites. In the present study, we assessed the toxicity (half maximal lethal concentration [LC50]), toxicokinetics (bioaccumulation at the 10% lethal concentration [LC10] followed by depuration), and the impacts on Ca and Na levels of cadmium (Cd), copper (Cu), and zinc (Zn) in the estuarine copepod Nitokra sp. at pH 8.1 (natural) and pH 7.6 (acidified, as projected by the Intergovernmental Panel on Climate Change). All tested metals followed typical dose–response toxicity curves, with Cu being the most toxic, followed by Cd and Zn, with no significant differences between pH 8.1 and 7.6. Contrary to our hypothesis, bioconcentration factors were higher at pH 8.1 than at pH 7.6. Metal exposure did not significantly affect Ca and Na, but trends suggest early physiological disturbance, with Ca decreasing with exposure to Cd or Zn and increasing with exposure to Cu. During elimination, Ca levels were higher in Cu-exposed copepods than in Cd-exposed ones and similar to controls, suggesting that Cd competes with Ca at the cellular level.

Graphical abstract

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Ocean acidification: historical progression, feedbacks, and future projections

Published 28 October 2026 Science Leave a Comment
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Ocean acidification is increasingly recognized as a dynamic driver of Earth system change, rather than a passive chemical response to anthropogenic CO₂ uptake. Over the past decade, key research discoveries—including perturbations to surface ocean seasonal cycles, accelerated subsurface trends, and growing relevance of the biological carbon pump—have fundamentally reshaped our understanding of ocean acidification. They have also revealed critical deficiencies in how Earth System Models represent seasonality, vertical carbon distributions, and the calcium carbonate cycle. Leveraging observational advances to address model deficiencies is essential for improving future carbon cycle projections and the understanding of associated ecological impacts.

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The climate observing system – ocean acidification

Published 28 October 2026 Science Leave a Comment
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The ocean has absorbed approximately one-quarter of anthropogenic carbon dioxide (CO2) emissions since the industrial era, moderating atmospheric warming while driving significant changes in marine carbonate chemistry. Collectively referred to as ocean acidification (OA), these changes include declining seawater pH, reduced carbonate ion availability, and decreasing calcium carbonate saturation states, with consequences for marine ecosystems, biogeochemical cycles, and ocean services. Detecting and quantifying OA is challenging because anthropogenic trends are superimposed on substantial natural variability across a wide range of spatial and temporal scales. Consequently, no single variable, platform, or observing approach can adequately characterize OA.

This chapter reviews the principal components of the contemporary OA observing system and the methodologies used to quantify changes in marine carbonate chemistry. It introduces the marine carbonate system and the analytical methods used to measure key OA variables, including pH, dissolved inorganic carbon (DIC), total alkalinity (TA), and partial pressure of CO2 (pCO2). The chapter examines the role of sustained time-series stations in detecting long-term trends and distinguishing anthropogenic change from natural variability, highlighting evidence for widespread acidification across open-ocean, coastal, polar, and marginal seas. The complementary contributions of surface underway observations, repeat hydrography programs, and autonomous observing platforms are reviewed, including major international initiatives such as SOCONET, SOCAT, GO-SHIP, GLODAP, and Biogeochemical-Argo (BGC-Argo). Particular emphasis is placed on how these observing elements provide complementary information across spatial and temporal scales and together form an integrated OA observing system.

Finally, the chapter discusses uncertainty assessment, trend attribution, data integration, and the role of international coordination mechanisms, including GOOS, GCOS, IOCCP, and GOA-ON. It further examines how OA observations support climate assessments, model evaluation, ecosystem-risk assessments, Sustainable Development Goal (SDG) 14.3.1 reporting, and emerging monitoring, reporting, and verification needs associated with marine carbon dioxide removal.

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Elevated pCO2 promotes growth but compromises PSII repair and antioxidant balance in the bloom-forming diatom Skeletonema costatum under ultraviolet radiation

Published 28 October 2026 Science Leave a Comment
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Highlights

  • Elevated pCO2 stimulates growth but not UV photoprotection in Skeletonema costatum.
  • Ocean acidification constrains PSII repair and PsbA turnover under UVR.
  • Trade-off between carbon-sequestration capacity and antioxidant defense raises UV sensitivity.

Abstract

Diatoms serve as key marine primary producers, driving global biogeochemical cycles, but their physiological performance is increasingly challenged by ocean acidification (OA) and enhanced ultraviolet radiation (UVR). This study investigated how OA caused by elevated pCO2 (1000μatm) modulates the UVR sensitivity of the bloom-forming diatom Skeletonema costatum. Elevated pCO2 significantly enhanced the specific growth rate by ~11.6%; it did not significantly aggravate the UVR-induced decline in Fv/Fm, but it constrained PSII repair and PsbA turnover, as indicated by lower rate constants for PSII repair (Krec, s−1) and PsbA removal (KPsbA, s−1), and was associated with a greater net decline in total PsbA content under PAR + UVR. Although elevated pCO2 upregulated the relative maximal electron transport rate (rETRmax) and light-saturation parameter (Ik), and maintained a higher RbcL/PsbA ratio consistent with a possible role of carbon assimilation as a downstream sink, it did not enhance the sustained non-photochemical quenching (NPQs). Furthermore, under elevated pCO2, CAT activity had a lower baseline; although CAT increased under UVR relative to PAR, its absolute activity remained lower, indicating an imbalanced antioxidant response. Collectively, these findings reveal a physiological trade-off: elevated pCO2 promotes growth and carbon-sequestration capacity but simultaneously compromises photoprotective mechanisms. Consequently, S. costatum grown under elevated pCO2 becomes more susceptible to UVR-induced photoinhibition, potentially suppressing photosynthetic production during surface blooms and influencing bloom persistence and carbon export.

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OA pumpkin stencils

Published 28 October 2026 Art , Web sites and blogs Leave a Comment

Looking for last-minute pumpkin carving ideas? Get creative with the OA pumpkin stencils! Download our designs and bring a touch of ocean science to your pumpkin creations.

Click the images below to download the stencils.

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The data diaries: MAPCO2 buoys (video)

Published 28 October 2026 Art , Web sites and blogs Leave a Comment

In this episode, we follow carbon data points as they are collected by a buoy at the surface of the ocean and transmitted to scientists. Not only do these global measurements of carbon dioxide help us understand the rate of exchange between our ocean and atmosphere, but they also inform the health of ecosystems that communities around the world rely on.

With support from NOAA’s Global Ocean Monitoring and Observations Program and Ocean Acidification Program, scientists at NOAA’s Atlantic Oceanographic and Meteorological Laboratory, Pacific Marine Environmental Laboratory and other labs and programs aid international efforts to monitor the global ocean’s accumulation of atmospheric carbon as part of the carbon cycle.

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From response to resilience: celebrating 15 years of NOAA’s Ocean Acidification Program

Published 27 October 2026 Web sites and blogs Leave a Comment

Fifteen years ago, oyster hatcheries on the West Coast faced an invisible crisis. Oyster larvae were dying by the billions from an unknown culprit, threatening a multi-million dollar industry and families’ livelihoods. Oyster growers turned to scientists to uncover the hidden threat – changing ocean chemistry that brought more corrosive waters to western shores.

Now, our nation is no longer flying blind. Congressional action empowered NOAA’s Ocean Acidification Program (OAP) to better understand ocean and coastal acidification (OA) and its ecological and economic impacts.

Highlights include:

  • OAP’s work helps harvesters of the nation’s most valuable shellfish fisheries understand a changing ocean and how they can adapt to keep up production.
  • OAP established the first-ever dedicated national ocean acidification observing network
  • Our science has advanced from from collecting observations to putting them to use in models and forecasts that enable community and industry planning.
  • OAP leads interagency coordination and outreach to on-the-ground communities most impacted by a ocean acidification.

Key Insight: Hatcheries on the West Coast were pumping in local water during upwelling, a natural process that has been delivering more corrosive waters to the surface due to OA. Technological advances allow hatcheries to measure acidity in real-time, and adjust the acidity of the water to protect oysters as they grow. Today, OAP helps growers prepare for continued OA from investigating practices from seawater to genes.

Recognizing the severe ecological and economic threats posed by OA, Congress passed the Federal Ocean Acidification Research and Monitoring Act (FOARAM) of 2009, officially establishing NOAA’s Ocean Acidification Program. Recently reauthorized under the CHIPS and Science Act of 2022, this mandate charged OAP with the critical mission to monitor ocean chemistry, understand its impacts on marine life, and give communities the information and tools they need to adapt.

From water chemistry to resilience

This year marks OAP’s fifteenth year on the frontlines of ocean acidification. Our understanding has evolved far beyond the initial identification of this ocean crisis. A robust observing network that powers modern forecasts now stands. This set the foundation to then unravel the complex sensitivities of many marine species, and deliver essential tools that communities rely on to secure their livelihoods and futures.

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Continue reading ‘From response to resilience: celebrating 15 years of NOAA’s Ocean Acidification Program’

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