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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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.

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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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Response of volatile halocarbons release to atmospheric deposition and ocean acidification in the tropical eastern Indian Ocean

Published 27 October 2026 Science Leave a Comment
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Highlights

  • Fe(III) inputs increased CH3I emission by photochemical and biogenic processes.
  • Nutrient inputs enhanced volatile halocarbons by boosting biogenic processes.
  • Ocean acidification enhanced CH2Br2/CHBr3 emissions by BrPO-mediated halogenation.

Abstract

Short-lived volatile halocarbons (SLVHCs) are important trace greenhouse gases and ozone-depleting substances influencing global climate. Anthropogenic activities have accelerated ocean acidification (OA) and enhanced atmospheric deposition, yet how these perturbations regulate SLVHCs production in open ocean remains unclear. Herein, we investigated the effects of OA and atmospheric deposition derived Fe(III) and nutrient input on SLVHCs production through ship-based incubation experiments at two stations in the tropical eastern Indian Ocean (10°N-10°S) from March to May 2022. Our findings revealed that nutrient addition promoted phytoplankton growth with the maximum Chlorophyll a (Chl a) increasing to 6.17 μg L−1, enhanced bromoperoxidase (BrPO) activity (by 108.3 % compared to the control group), and stimulated release of dissolved organic carbon (DOC), ultimately driving the production of CH3I, CH2Br2, and CHBr3 (by 152.0 %, 200.2 %, and 141.8 % increases, respectively). OA and Fe(III) additions promoted phytoplankton growth (Chl a up to 1.85 μg L⁻1), thereby enhancing SLVHCs production through biological and photochemical processes, whereas they exhibited no significant effects on SLVHCs production in relatively oligotrophic regions. Mechanistically, CH3I release was regulated by phytoplankton-mediated biogenic processes and photochemical processes. In contrast, CH2Br2 and CHBr3 production was predominantly associated with phytoplankton-mediated biogenic processes (BrPO-mediated halogenation). These results demonstrating that OA, Fe(III), and nutrient inputs regulate marine SLVHC production by altering phytoplankton-mediated biogenic processes and photochemical reactivity. Our study offers a novel perspective and direct evidence for quantifying the production of SLVHCs under climate change scenarios, thereby underscoring the need to reassess oceanic climate feedbacks in the context of anthropogenic forcing.

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Interactive effects of ocean acidification and benzophenone-3 on mussel physiology: a biomarker-based approach

Published 27 October 2026 Science Leave a Comment
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Highlights

  • Ocean acidification was the primary driver of biomarker responses.
  • Low pH enhanced BP3-induced cytotoxicity in hemocytes.
  • BP3 detoxification mainly involved the GST/GSH pathway.
  • Lipid peroxidation occurred in gills and digestive gland despite antioxidant response.
  • Acidification impacts biomineralization enzymes more strongly than BP3.

Abstract

Benzophenone-3 (BP3), a widely used ultraviolet (UV) filter in personal care products and industrial applications, is an emerging concern in aquatic ecosystems due to its lipophilicity, bioaccumulation potential, and toxicity to marine biota. Its occurrence in marine environments coincides with ocean acidification driven by rising atmospheric CO2 emissions, which disrupts the bicarbonate buffer system and reduces pH. This study investigated the acute effects (96 h exposure) of BP3 (at realistic concentrations of 0.2 and 2 μg/L) under 3 pH conditions (8.1- the current South Atlantic condition- and 7.6 and 7.3 as projected acidification scenarios for 2100 and 2300, respectively) in the brown mussel Perna perna. The effects were investigated through analysis of hemocyte viability and biomarkers related to detoxification (glutathione S-transferase, glutathione, glutamate cysteine ligase, and reduced glutathione), oxidative stress (antioxidant capacity against peroxyl radicals and lipid peroxidation), and biomineralization (carbonic anhydrase and Ca2+ATPase), measured in the gills, digestive gland, and mantle. Despite BP3-induced activation of glutathione-related detoxification pathways, as evidenced by increased GSH levels and GST activity, particularly in the gills, hemocyte viability decreased after BP3 exposure, with the greatest reduction at pH 7.3. Lipid peroxidation (LPO) also increased in the gills and digestive gland under acidified conditions, with the magnitude of the response varying according to BP3 concentration. CA and Ca2+ATPase activities were more strongly influenced by acidification than by BP3 exposure, although their responses were tissue-specific and, in some cases, modulated by BP3 exposure. Multivariate analyses identified pH as the primary driver of biomarker responses.

Graphical abstract

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From population to individual: bulk and single-cell analysis reveal Fe bioavailability, limitation thresholds, and biological responses for marine diatom Chaetoceros debilis

Published 27 October 2026 Science Leave a Comment
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Highlights

  • Fe speciation and pH jointly regulated Fe bioavailability.
  • A critical bioavailable Fe limitation threshold (∼10 nM) was identified for the marine algae.
  • Single-cell analysis revealed previously hidden heterogenous Fe accumulation.
  • Fe stress induced adaptive responses including metallome remodeling.

Abstract

In marine ecosystems, Fe fundamentally regulates algal productivity and drives biogeochemical cycling in the hydrosphere, yet its environmental controls and cellular responses remain insufficiently resolved, particularly at the single-cell level. Herein, we combined bulk and single-cell analysis to systematically investigate Fe bioaccumulation process in the marine diatom Chaetoceros debilis under varying Fe species, initial pH, and concentration conditions. Fe bioavailability followed the order Fe-ethylenediaminetetraacetate > Fe-deferoxamine B > Ferrihydrite and decreased with declining initial pH, highlighting the combined control of chemical speciation and ocean acidification. A critical bioavailable Fe limitation threshold of ∼10 nM was identified, below which algal growth, pigmentation, and cell size were significantly suppressed. Under Fe limitation, cells exhibited compensatory accumulation of other metals (e.g., Zn, Mn, Cu, and Ni), indicating metallome remodeling as an adaptive strategy. Notably, single-cell analysis revealed pronounced heterogeneity in Fe accumulation within populations, with heterogeneity positively related to bioavailable Fe levels. These findings demonstrate that algal Fe accumulation is governed by coupled environmental and physiological processes and that population-level averages mask critical cell-to-cell variability and their adaptive strategies under environmental stress. This work provides mechanistic insights into how environmental chemistry regulates metal bioavailability and biological responses, offering a broadly applicable framework for understanding the environmental behavior and ecological effects of trace metals and other contaminants in aquatic ecosystems.

Graphical abstract

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Surviving together: evolutionary dependency, community dynamics, and mortality in marine microbial communities

Published 26 October 2026 Science Leave a Comment
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Oligotrophic regions of the world ocean sustain vast phytoplankton populations despite extremely low nutrient levels. However, the mechanisms governing their coexistence, interdependence, and mortality are poorly understood. This dissertation investigates how evolutionary dependency, community feedback, and regulated cell death (RCD) jointly shape the stability of marine microbial communities using the Prochlorococcus/Parasynechococcus/Alteromonas model system.

In Chapter 1, I argue that the Black Queen (BQ) hypothesis—which posits that microbes lose costly metabolic functions supplied by community partners—provides a unifying framework for understanding phytoplankton ecology. This framework helps resolve longstanding puzzles, including the paradox of the plankton and the evolutionary maintenance of RCD in unicellular organisms. Building on this framework, Chapter 2 uses transcriptomic analysis of Alteromonas in co-culture with picocyanobacteria to demonstrate that community composition induces greater changes in gene expression than pCO₂ alone. Reduced 2-phosphoglycolate/glycolate exudation by Prochlorococcus under elevated pCO₂ may disrupt the helper heterotroph effect underlying this cyanobacterium’s BQ dependency.

Chapter 3 integrates co-culture experiments, RNA-seq, metabolomics, and mathematical modeling to demonstrate that the stable coexistence of Prochlorococcus and Parasynechococcus is maintained by an “Ouroboros network” of feedback loops. In this network, resource competition, carbon exudation, BQ dependency, and possibly RCD collectively stabilize the community across environmental gradients and during adaptation to changing conditions.

Chapter 4 resolves the cellular mechanisms underlying RCD in these cyanobacteria, showing that differences in cell death modes and the number of checkpoint-linked mortality events between taxa are associated with divergent life-history strategies. These findings suggest that carbon released at these checkpoints may shape interactions with helper Alteromonas, linking individual cell death to community-level interdependencies.

In conclusion, these findings converge on a new resolution to the paradox of the plankton: coexistence in resource-limited environments emerges from interdependent metabolic exchanges, feedback, and regulated cell death shaped by multilevel selection. I propose that together, these processes form an “altruistic bargain” in which stability arises from self-constraint rather than competition alone. Because these interactions are environmentally sensitive, climate change, including warming and acidification, may disrupt the dependencies that sustain microbial diversity and ecosystem function in the world ocean.

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Large-scale water-sediment regulation (Yellow River) substantially reshapes organic carbon mineralization pathways and benthic fluxes in sediment of a river-dominated sea (Bohai Sea)

Published 26 October 2026 Science Leave a Comment
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Large-scale hydrological engineering has fundamentally altered the rhythm of land-to-ocean material transport globally, yet the mechanistic response of coastal benthic biogeochemistry to these “pulse” events remains poorly quantified. Here, we investigated the transient impacts of the annual Yellow River Water-Sediment Regulation (WSR), a massive anthropogenic flood, on sediment organic carbon (OC) mineralization and benthic fluxes in the Bohai Sea (BHS) by combining geochemical analyses with sediment incubations. Results indicated that the WSR enhanced sediment OC mineralization rates by an average factor of 1.65, driven primarily by pulsed input of labile OC and probably also reflecting a priming effect. This stimulation reconfigured dominant diagenetic pathways: significantly elevating the role of dissimilatory iron reduction at the expense of both aerobic respiration and sulfate reduction. In addition, pulsed nitrate inputs promoted denitrification, establishing it as an important OC mineralization pathway. Concurrently, diffusive nutrient fluxes increased by a factor of 1.9–5.1 following the WSR, and the mean ratio of total alkalinity to dissolved inorganic carbon fluxes decreased from 1.34 to 0.96. This shift in the ratio signifies a reduced capacity for carbonate buffering in the bottom waters, which could exacerbate seasonal bottom-water acidification. Collectively, our findings demonstrate that short-term anthropogenic perturbations can rapidly reprogram sediment diagenesis and benthic fluxes, thereby perturbing carbon and nutrient cycling as well as benthic-pelagic coupling in river-dominated coastal systems.

Plain Language Summary

The annual Water-Sediment Regulation of the Yellow River is one of the world’s largest engineered flow manipulations, rapidly delivering huge amounts of freshwater and sediment into the Bohai Sea (BHS). While much is known about its effects on the water column ecochemistry, how such a large-scale human intervention alters organic carbon degradation and chemical exchange in seafloor sediments has remained unclear. By combining field measurements and laboratory experiments, we show that this event strongly enhances sediment carbon degradation rates and shifts the dominant pathways, favoring iron reduction and nitrate reduction processes. These changes drive substantial increases in benthic fluxes of dissolved inorganic carbon and nutrients (ammonium, silicate, and phosphate) into overlying waters. Notably, the regulation reduces the ratio of alkalinity to inorganic carbon flux, implying a temporary decline in the capacity of the sea to absorb atmospheric CO2. Our findings provide critical insights by revealing that large-scale human-regulated river discharges can rapidly reshape coastal sediment biogeochemistry. These results have important implications for carbon and nutrient cycling, offering valuable references for understanding not only the BHS but also other river-dominated coastal systems worldwide.

Continue reading ‘Large-scale water-sediment regulation (Yellow River) substantially reshapes organic carbon mineralization pathways and benthic fluxes in sediment of a river-dominated sea (Bohai Sea)’

Hypoxia and acidification antagonistically suppress nitrification but enhance its N2O production in coastal waters

Published 26 October 2026 Science Leave a Comment
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The concurrent intensification of hypoxia and acidification poses a growing threat to estuarine-coastal ecosystems globally, yet their interactive impacts on nitrification, a key process in the nitrogen (N) cycle and a substantial source of nitrous oxide (N2O), remain poorly understood. This knowledge gap hinders reliable projections of future N cycling and climate feedbacks in these critical ecosystems. Here, we demonstrate that along the estuarine-coastal continuum, the co-occurrence of hypoxia and acidification suppresses nitrification rates but stimulates nitrification-derived N2O emissions—although their combined effect is lesser than the sum of their individual effects. Metatranscriptomic analysis provided molecular evidence for these isotopically traced responses and uncovered critical microbial coping strategies through transcriptional adjustments in metabolic pathways for energy conservation and stress tolerance. This previously overlooked interaction disrupts microbial N cycling with potential impacts on N2O emissions and climate feedbacks, highlighting the necessity to revise predictive models by incorporating such multistressor dynamics.

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Physiological responses of Atlantic surfclams (Spisula solidissima) to moderate ocean acidification across thermal regimes

Published 23 October 2026 Science Leave a Comment
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Highlights

  • Interactive effects of warming and acidification tested in surfclams.
  • Growth, feeding, and metabolic rates measured after 6-week exposure.
  • Moderate acidification had limited effects under warming conditions.
  • Surfclams showed resilience to near-future ocean acidification.
  • Multi-stressor design improves ecological relevance of lab studies.

Abstract

Understanding marine organismal responses to co-occurring climate stressors is critical for predicting changes in ecosystems and commercial fisheries. The Atlantic surfclam supports a major commercial fishery in the Northeastern United States, where ocean warming and acidification are rapidly altering marine habitats. To evaluate how changing ocean conditions may affect bivalve physiology, surfclams were exposed to conditions reflective of ocean warming and acidification, respectively. One-year-old surfclams were exposed to nine conditions in a fully crossed design of temperature (ambient, +2 °C, and + 5 °C) and pH (7.88 ± 0.05, 7.76 ± 0.05, and 7.51 ± 0.07) for six weeks in a flow-through laboratory experiment using natural seawater. We quantified several physiological responses including growth, feeding, digestion, respiration rates, and shell weight and thickness to assess organismal performance across treatments.

Surfclams generally exhibited resistance to moderate ocean acidification across warming, but non-thermally stressful, temperatures. No effects of ocean acidification were observed on surfclam growth or respiration, although other physiological metrics (shell thickness and absorption rate) decreased with decreasing pH at some temperatures. These findings provide experimentally-derived insight into species-specific responses to interacting climate stressors. Further, the experimental design highlights the importance of integrating natural environmental variability into laboratory studies and studying multiple environmental stressors concurrently. This study contributes a basis for refining models of surfclam growth and distribution in potential future climate scenarios, with implications for sustainable fisheries management.

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Ocean warming and acidification reveal transcriptional plasticity in the gastropod Hexaplex trunculus

Published 23 October 2026 Science Leave a Comment
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Coastal ecosystems, particularly in the rapidly warming Mediterranean Sea, are increasingly impacted by climate change driven by ocean warming and acidification. Calcifying marine invertebrates are especially vulnerable, yet their molecular responses remain poorly understood. Gene expression dynamics in the ecologically and commercially important gastropod Hexaplex trunculus were investigated under simulated scenarios combining elevated temperature and reduced pH. High-throughput RNA sequencing was used to generate a de novo assembly of the foot transcriptome, followed by differential gene expression analyses to characterize molecular responses to individual and interactive stressors under high-emission (RCP 8.5) projections. The foot tissue – central to locomotion, adhesion, and environmental interaction – exhibited pronounced transcriptional changes in genes associated with calcium signaling, ion transport, aerobic respiration, muscle contraction, and transmembrane transport. Ocean acidification emerged as the dominant driver of transcriptional change, inducing substantial shifts in metabolic demand and ion regulatory pathways, which might suggest increased energetic costs and potential functional constraints. The results demonstrate marked transcriptional plasticity in H. trunculus under combined climate stressors. By providing foundational transcriptomic resources for this species and mechanistic insight into its response to projected environmental changes, this study advances the understanding of molecular processes in vulnerable Mediterranean gastropods and informs ecological assessment efforts in rapidly warming marine ecosystems.

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Flinders University research links ocean acidification to diatom health and carbon cycling

Published 23 October 2026 Press releases Leave a Comment

New research from Flinders University shows how changes in diatoms (microalgae) could further undermine the foundation of aquatic life’s food webs—as well as vital deep-sea carbon capture or sequestration.

A new study published in Marine Ecology used high-tech methods to test common microalgal species to assess how various stressors, including acidification from excessive carbon dioxide (CO2) levels, affect absorption of trace metals and therefore undermine their overall health and role in Earth’s carbon cycling.

Although microscopic, the single-celled algae diatoms that live in oceans, lakes, rivers, and even damp soil are among the most important organisms on Earth, as they produce a significant portion of oxygen in the atmosphere.

Diatoms account for 40%–50% of primary production in oceans, and they contribute to organic carbon being exported to the deep ocean by fixing CO2 from near-surface waters, says senior author Professor Sophie Leterme, director of the ARC Industry Transformation Training Centre for Biofilm Research and Innovation at Flinders University’s College of Science and Engineering.

“We showed that changes in the ocean pH can affect the growth, abundance and elemental composition of these diatoms,” said Professor Leterme. “We need to investigate how these changes interplay between various trace elements and can lead to broader ecological impacts, such as disruption to marine food webs, reduced carbon and silicon export, and increased microbial and nutrient activity.”

Rising carbon emissions affect pH levels in seawater, which can alter planktonic algae’s absorption of trace elements including iron, zinc, and cadmium, which are essential for inorganic carbon acquisition.

The dissolution of CO2 into the ocean has already induced a global drop in pH of 0.1 units since the end of the Industrial Revolution, and values are expected to drop another 0.3–0.6 units by the end of this century.

Diatom species are great bio-indicators, often used to assess water quality and boost understanding of how ongoing ocean acidification and rising water temperatures downgrade their physiology and functioning—which have important consequences for the future of oceans.

The Flinders researchers say a better understanding of how these complex processes work in seawater will help find solutions, including the development of novel biofilms to reduce shipping pollution in harbors.

Using seawater samples collected in South Australia’s Gulf St Vincent and from the CSIRO algae collection, the researchers’ highly sensitive neutron activation analysis was used in experimental setups on the species Thalassiosira pseudonana and Nitzschia navis-varingica.

The experiments, supported by ANSTO expertise, showed how trace metal uptake by marine diatoms could be applied to other marine organisms’ absorption of a wide range of other elements in the environment.

“While a higher abundance and growth of diatoms might be beneficial to reduce carbon dioxide levels, the impact of lower concentrations of major and trace elements in the environment is not well understood.”

The research article—’The impact of ocean acidification on the sorption of trace metals by diatoms‘ (2026) by Sophie C Leterme, Tamar Jamieson, Alessandra Mazzoli, Angus Hambrook, Rachel S Popelka-Filcoff, John Bennett, and Attila Stopic—has been published in Marine Ecology (Wiley). DOI: 10.1111/maec.70112.

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Planetary Health Check 2026 finds mounting pressures across Earth’s life support systems

Published 23 October 2026 Press releases Leave a Comment

Seven breached Planetary Boundaries continue to worsen as record ocean heat, droughts, floods, wildfires and extreme heat reveal an Earth system under strain, according to the latest Planetary Health Check. The annual update is authored by more than 60 scientists, and produced by the Planetary Boundaries Science Lab at the Potsdam Institute for Climate Impact Research (PIK).

The Planetary Boundaries describe the interconnected Earth-system processes that must remain within safe limits to preserve the planet’s stability and resilience. Seven of the nine Planetary Boundaries are now transgressed, with ocean acidification the latest to breach its boundary in 2025. All seven are now at their highest recorded levels of transgression.

The seven transgressed boundaries are: climate change, change in biosphere integrity, land system change, freshwater change, modification of biogeochemical flows, introduction of novel entities and ocean acidification. Only the stratospheric ozone depletion and atmospheric aerosol loading boundaries have shown improvement over the last decade. However, the authors caution that global progress may mask unsafe aerosol levels persisting in some regions.

“The diagnosis is unambiguous. Pressure is rising across every Planetary Boundary already outside the safe operating space. It means that the risk of large-scale, persistent and potentially irreversible change is increasing, while our margin for error in tackling these problems is shrinking,” commented Boris Sakschewski, PIK scientist and lead author of the report.

“We do not have the luxury of time, but we do have the knowledge, capacity and solutions to change course. Accelerating action to return to the safe operating space across all Planetary Boundaries is essential to protect lives and livelihoods, and to deliver on the promise of shared future prosperity,” said Johan Rockström, PIK Director and co-author of the report.

A year of extreme events highlights escalating risks

The report comes after 12 months marked by extremes across land and oceans. Human-caused warming intensified several major weather extremes, while degraded ecosystems, water stress, land-use change, exposure and social vulnerability often magnified their impacts.

Pakistan’s 2025 monsoon floods affected more than 6.9 million people. Global ocean heat content reached a new record in 2025, with Hurricane Melissa rapidly ramping up to a Category 5 Hurricane and striking Jamaica after passing over exceptionally warm seas. January 2023 to September 2025 saw bleaching-level heat stress impacting approximately 84.4 percent of the world’s coral reef area, making it the largest global coral-bleaching event observed to date.

In 2026, Western Europe experienced its hottest June-July period on record, accompanied by drought across France, Spain, Germany and the United Kingdom, with major wildfires across Europe and Canada. Record-breaking heat was also recorded in Japan, South Korea and parts of the Middle East.

Hindou Oumarou Ibrahim, Chair of the Planetary Guardians said, “Read that list again: Pakistan, the Caribbean, Europe, the reefs beneath our oceans. These are not separate emergencies; the planet is telling us, in every region at once, that it is out of balance. As Chair of Planetary Guardians, I hear this same story wherever I go, whether from a pastoralist watching the rains fail season after season or a coastal community watching the sea rise. The 2026 Planetary Health Check puts data behind what communities on the frontlines already know from living it. We do not have the luxury of treating these as separate crises any longer.”

“Any kind of movement requires patience, trust, and the will to keep going, even when it may be easier to stop. The 2026 Planetary Health Check tells us we need that same collective resolve now, applied to the whole planet. Seven of nine boundaries are broken, and no single nation can restore them alone; this is a peace process the entire world must commit to, together, starting now,” said Juan Manuel Santos, former President of Colombia and Co-Vice Chair of the Planetary Guardians.

Natural carbon sinks under pressure

Vegetation and soils absorb a substantial share of human carbon dioxide emissions, but repeated heat, drought, fire and ecosystem degradation can reduce carbon uptake and, in some regions, turn ecosystems from sinks into carbon sources.

This year’s report discusses whether the models that we use to calculate the land carbon sink may overestimate its resilience.

“Our path to net zero emissions relies on functioning carbon sinks. Current observations raise the alarm that our planet may be losing its buffering capacity against the increasing pressures we’re putting on it,” Sakschewski said.

Planetary Boundaries Science (PBScience), 2026: Planetary Health Check 2026. Potsdam Institute for Climate Impact Research, Potsdam, Germany.

Link once published: https://www.planetaryhealthcheck.org/

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Global projections of coral reef sediment dissolution in the 21st century

Published 22 October 2026 Science Leave a Comment
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Abstract

Coral reefs build carbonate frameworks, but ocean acidification threatens to reverse this role by accelerating dissolution of permeable reef sediments. We combined Earth system model projections across five emission pathways with an aragonite saturation state-dissolution relationship to project global reef sediment dissolution through 2100. Under stringent mitigation, less than 2% of reef area experiences dissolution by 2100, compared with 30% under intermediate emissions and nearly all reefs under high emissions. Cumulative calcium carbonate loss reaches 2.5 gigatonnes under the highest-emission pathway, accompanied by 0.7 gigatonnes of potential carbon dioxide uptake that is globally negligible but signals framework degradation. Model-derived aragonite saturation states exceeded in situ observations in most regions, suggesting that reef sediment dissolution may begin earlier than gridded projections indicate. The southern Central Pacific emerges as a candidate acidification refugium warranting reef-scale evaluation. Continued high emissions could shift reefs from net carbonate accretion toward widespread structural loss.

Plain Language Summary

Human carbon emissions are making the oceans more acidic, threatening not only living corals but also the carbonate sand and rubble that help build and support reef structures. Using climate model projections and reef observations, we estimated how reef sediment dissolution may change worldwide through 2100. Under high-emission scenarios, nearly all coral reefs are projected to experience sediment dissolution by the end of the century, with cumulative calcium carbonate losses reaching 2.5 billion metric tons. Although this process can absorb carbon dioxide, the amount is far too small to meaningfully slow climate change and instead reflects the physical breakdown of reef structures. The southern Central Pacific may acidify more slowly and could offer some protection, but local water chemistry and heat stress must be evaluated before the region can be considered a reliable refuge.

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Assessing the skill of a biogeochemical model tailored to a global coupled forecasting system: a case study for the Bay of Bengal carbon cycle

Published 22 October 2026 Science Leave a Comment
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To achieve real-time prediction of surface ocean carbonaceous variables in the Indian Ocean, we integrate an extended-range coupled forecast system with a global ocean biogeochemistry model incorporating an explicit carbon cycle. The physical ocean state is provided by the Indian Institute of Tropical Meteorology Extended Range Prediction for Applications to Society (IITM-ERPAS) coupled model, which drives the Ocean Tracer Transport Model (OTTM) with phosphate-dependent biology and OCMIP-II-type carbonate chemistry (hereafter referred to as OTTM-ERPAS-BGC). Daily mean outputs from IITM-ERPAS are used to drive the biogeochemical simulations. Model skill is evaluated against in situ observations of surface partial pressure of CO₂ (pCO₂) and pH from the Bay of Bengal Ocean Acidification (BOBOA) mooring (90°E, 15°N) over the period 2013-2018. The model successfully reproduces observed variability, with strong and statistically significant correlations (r = 0.65 for pCO₂ and r = 0.80 for pH; p < 0.001). Based on this performance, a coherent region of influence (87.5°E-92.5°E, 12.5°N-17.5°N) is identified to further assess model skill against BOBOA time-series observations, climatological products and other derived datasets of pCO₂ and pH in terms of seasonal cycle, subseasonal variability and long-term trends. Seasonal cycle analysis reveals that the updated Takahashi climatological pCO₂ product is systematically underestimated by ∼18 ± 3 μatm compared to BOBOA observations, OTTM-ERPAS-BGC simulations and other derived products. Subseasonal variability exhibits pronounced intraseasonal signals, with significant spectral peaks at 13-41 days for pCO₂ and 17-41 days for pH, reflecting dominant intraseasonal modulation of the Bay of Bengal carbon cycle. Long-term trends indicate a robust increase in pCO₂ (2.02 μatm yr⁻¹) and a concomitant decline in pH (-0.00253 yr⁻¹), consistent with progressive acidification of the basin. The decomposition analysis demonstrates that dissolved inorganic carbon (DIC) and total alkalinity (ALK) exert dominant and complementary controls on pCO₂ and pH variability, respectively, while sea surface temperature (SST) plays a secondary role. Overall, this study demonstrates that coupling extended-range physical forecasts with ocean biogeochemical models provides a viable pathway for the operational prediction of carbon variables. Such capability is critical for the early detection of ocean acidification and hypercapnia hotspots, with significant implications for marine ecosystem management and climate services in the Indian Ocean.

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Climate change and fish reproduction: a meta-analysis of global laboratory-based experimental evidence across species and ecosystems

Published 22 October 2026 Science Leave a Comment
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Climate change is altering fish reproduction by disrupting spawning cycles, reducing egg viability, and altering reproductive behaviours essential for population sustainability, to our knowledge, this is the first synthesis to integrate laboratory-based evidence for temperature, hypoxia, ocean acidification, and their combined exposure across reproductive performance, physiological, developmental, and molecular endpoints, and across freshwater, brackish, and marine habitats. Following PICOS and PRISMA criteria, we synthesised 779 effect sizes (740 retained after outlier exclusion) from 80 controlled laboratory studies (38,500 observations; 54 species; 28 countries). A three-level multilevel model accounting for non-independence among effect sizes drawn from the same study showed a significant overall negative effect of climate stressors on fish reproduction (Hedges’ g = −0.421, 95% CI: −0.631 to −0.210, p < 0.001; I² = 94.9%, decomposed into 36.3% between-study and 58.6% within-study heterogeneity). Hypoxia was the dominant and statistically distinct driver (g = −1.145, 95% CI: −1.648 to −0.643, p < 0.0001), most severely impairing gonadal development and sperm quality. The overall warming effect did not reach significance once non-independence was accounted for (g = −0.221, 95% CI: −0.448–0.006, p = 0.057), an uncertain negative trend rather than confirmed impairment, although tropical freshwater species showed significant subgroup-specific declines in reproductive physiology and genetic parameters. Ocean acidification showed a small positive effect (g = 0.199, 95% CI: 0.056–0.343, p = 0.006) that was not robust under robust variance estimation (p = 0.133) and is interpreted with caution. Combined multi-stressor exposure showed a negative trend (g = −0.901, 95% CI: −1.992–0.190, p = 0.106) that did not reach significance, based on only three studies. A formal omnibus test confirmed that stressor categories differ significantly in their effects (QM = 18.61,df = 3, p = 0.0003), with hypoxia statistically distinct from both temperature and ocean acidification. Leave-one-out and cumulative meta-analyses confirmed the robustness of the overall finding.

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