Applications open: Sixth International Symposium on the Ocean in a High-CO2 World

Published 28 July 2026 Events Closed

The IAEA’s Ocean Acidification International Coordination Centre (OA-ICC) (https://www.iaea.org/ocean-acidification) is cooperating on the organization of this event and has limited funds at its disposal to help meet the costs of the attendance of selected participants from eligible IAEA Member States to present their work and foster international collaboration at the conference.

The deadline to apply is Friday September 4th. To apply, applicants will need to submit their application through their national authority to the IAEA – in most cases, this will be your country’s permanent mission to the IAEA.

If you have questions on the application procedure, please contact Ms Lina Hansson (L.Hansson(at)iaea.org) or Ms Carolina Galdino (C.Galdino(at)iaea.org).

Dates: 13–16 October 2026

Location: Tākina Convention & Exhibition Centre, Wellington, New Zealand

Form A and Form C

Introduction
Held every four years, the International Symposium on the Ocean in a High-CO2 World is the largest global gathering on ocean acidification. The Symposium brings together scientists, communities, policymakers, and stakeholders from sectors such as fisheries and aquaculture to share and discuss the latest research on the impacts of ocean acidification on marine life and potential solutions to counter its effects. The Sixth edition will maintain a focus on ocean acidification but will also expand to consider other ocean climate impacts, such as ocean warming and deoxygenation, particularly in a multiple-driver context. Research on marine carbon dioxide removal interventions, which have been suggested to mitigate climate change and ocean acidification, will also be a key part of the conference. More information on the seven key themes of the conference, its 22 workshops, and the detailed programme can be found on the Symposium website (https://highco2-vi.org/).

Objectives
The purpose of the event is to provide a space for scientists from the ocean acidification (OA) research community to disseminate the results of their research, discuss joint projects with peers and engage with stakeholders. The event, held every four years, is the world’s largest conference on OA and related stressors.

Target Audience
Scientists from developing IAEA Member States. Priority will be given to early-career scientists actively working on ocean acidification, multiple stressors or marine carbon dioxide removal (mCDR). Applicants should hold a university degree in marine biology, oceanography or a related scientific field. Female scientists are encouraged to apply.

Working Language
English

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Participation and Registration
All persons wishing to participate in the event through the IAEA have to be designated by an IAEA Member State.

In order to be designated by an IAEA Member State, participants are requested to send the Participation Form (Form A) and Grant Application Form (Form C – if applicable) to their competent national authority (e.g. Ministry of Foreign Affairs, Permanent Mission to the IAEA or National Atomic Energy Authority) for onward transmission to the IAEA by 4 September.

Selected participants will be informed in due course on the procedures to be followed with regard to administrative and financial matters.

Participants are hereby informed that the personal data they submit will be processed in line with the Agency’s Personal Data and Privacy Policy and is collected solely for the purpose(s) of reviewing and assessing the application and to complete logistical arrangements where required. The IAEA may also use the contact details of Applicants to inform them of the IAEA’s scientific and technical publications, or the latest employment opportunities and current open vacancies at the IAEA. These secondary purposes are consistent with the IAEA’s mandate.

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Additional Requirements
The participants should have a university degree in marine chemistry, biology, oceanography, or a related scientific field, and must be active researchers in the ocean acidification /mCDR field or should have already received technical training on ocean acidification / mCDR by the IAEA or through other efforts.

Selection will be based on merit and motivation. Applications must include, in addition to Form A and C, if applicable:

  •  A motivation letter with a short description of research interests, motivation to participate, and plans regarding present and future research on OA and/or mCDR (max one A4 page)
  •   CV with publication list
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Tiny fossils crack a cretaceous cold case

Published 19 August 2026 Press releases Leave a Comment

Ancient ocean acidification triggered one of the ocean’s most severe extinctions

New research examining hundreds of microscope fossils offers one of the clearest examples yet of how rising CO2 can alter ocean chemistry and harm marine life. Above, Jonathan Chen, the study’s lead author, uses a fine-tipped brush to separate tiny fossils from surrounding sediment.

A 113-million-year-old marine murder mystery may finally be solved.

Using chemical clues locked inside microscopic fossils, Northwestern University scientists found evidence that ocean acidification drove one of the largest extinction events in the history of planktic foraminifera — tiny shell-building organisms that help regulate Earth’s carbon cycle.

The scientists attribute the acidification to the eruption of the Kerguelen Plateau, a massive volcanic province in the southern Indian Ocean. During the Early Cretaceous period, the volcanic province spewed vast quantities of carbon dioxide (CO2) into the atmosphere. As the oceans absorbed that CO2, seawater became more acidic, making it more difficult for marine organisms to build and maintain their shells.

The new study, published in Science, marks the fifth Northwestern-led investigation to link widespread volcanic eruptions to ocean acidification and extinction, strengthening evidence for a recurring pattern that played out across more than 60 million years.

The findings also provide one of the clearest examples yet of how rising CO2 can alter ocean chemistry and harm marine life. As current-day oceans absorb human-generated CO2, the ancient events offer a natural experiment for understanding how modern ocean acidification might affect shell-building organisms and the ecosystems that depend on them.

“By examining fossils, scientists already knew surface plankton were getting smaller and building thinner shells, which suggested they were under stress,” said Northwestern’s Jonathan Chen, who led the study. “But we didn’t know that ocean acidification was responsible. By measuring the fossils’ calcium isotopes, we finally provided that missing evidence. We found a giant increase in calcium isotope ratios right as the extinction unfolded, indicating the organisms’ shells were calcifying at a much slower rate. That was the smoking gun linking ocean acidification to the severe biocalcification stress that ultimately led to their extinction.”

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Calcium isotopes link ocean acidification to Aptian–Albian foraminiferal extinctions

Published 19 August 2026 Science Leave a Comment
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Editor’s summary

About three quarters of planktic foraminifera species disappeared in the Aptian-Albian extinction event. What role might ocean acidification (OA) have played in this die-out? Chen et al. measured calcium isotope ratios in foraminifera, using them as a proxy for biocalcification and carbonate saturation (see the Perspective by Leckie). Their data reveal a dramatic reduction in calcification rates accompanied by decreases in the size, abundance, and diversity of planktic foraminifera. These results are consistent with the hypothesis that ocean acidification drove the extinctions of these organisms at the Aptian-Albian boundary. —Jesse Smith

Abstract

The second-largest extinction event in the evolutionary history of planktic foraminifera occurred at the Aptian–Albian boundary. This extinction may reflect ocean acidification (OA) associated with Oceanic Anoxic Event 1b. As calcium isotope ratios (δ44/40Ca) can track how biocalcification rates respond to OA, we measured δ44/40Ca records for planktic and benthic foraminifera, bulk carbonates, and authigenic calcite across the Aptian–Albian boundary in the South Atlantic. Benthic and bulk δ44/40Ca data display a distinct sequence of negative and positive excursions, similar to δ44/40Ca variations across other OA events. Planktic δ44/40Ca values increase markedly, tracking a reduction in calcification rates coincident with decreases in the size, diversity, and shell thickness of planktic foraminifera. These results suggest that OA drove extinctions of planktic foraminifera at the Aptian–Albian boundary.

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A hidden driver of the greenhouse effect: production mechanisms and climate implications of N2O derived from marine planktonic ammonia-oxidizing archaea

Published 18 August 2026 Science Leave a Comment
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Nitrous oxide (N2O) is a potent and long-lived greenhouse gas, and the ocean represents its primary natural source. An accurate understanding of the emission intensity and driving mechanisms of oceanic N2O directly affects the estimation of atmospheric N2O budget and the projection of climate change. Recent studies have demonstrated that ammonia-oxidizing archaea (AOA) dominate nitrification in marine environments and are thus recognized as an important biological source of marine N2O production. However, their specific metabolic pathways, regulatory mechanisms, and environmental response patterns remain poorly understood. This paper systematically reviews the spatial distribution characteristics of marine N2O and its major biogeochemical sources, with a particular focus on the potential metabolic pathways and key intermediates involved in AOA-derived N2O production. We further synthesize the current understanding of how environmental factors—including dissolved oxygen, pH, temperature, substrate availability, and organic carbon—regulate AOA nitrogen metabolism and N2O generation. In addition, we discuss the potential mechanisms underlying the shift in AOA metabolic strategies and variations in N2O yield under multifactorial coupling scenarios the scenario of multifactorial coupling. On this basis, we identify the major knowledge gaps in existing research, particularly regarding culture systems, mechanistic elucidation, in situ validation, and global-scale quantification. Finally, we proposed future research directions for AOA-derived N2O emissions under ongoing oceanic changes. This review aims to advance the understanding of the biogeochemical mechanisms governing marine N2O production and to provide a theoretical basis for improving the parameterization of marine nitrogen cycle and climate models.

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Postdoctor in Experimental evaluation of the combined effects of changes associated with ocean alkalinity enhancement (OAE) implementation

Published 17 August 2026 Jobs Leave a Comment

Reference number PAR 2026/628

The University of Gothenburg tackles society’s challenges with diverse knowledge. 58 000 students and 6800 employees make the university a large and inspiring place to work and study. Strong research and attractive study programmes attract researchers and students from around the world. With new knowledge and new perspectives, the University contributes to a better future.

At the Department of Biological and Environmental Sciences (BioEnv) we have teaching and research activities that stretch from the alpine ecosystem, through forests, cultivated land and streams, all the way into the marine environment. In these environments we study different levels of biological organisation from genes, individuals and populations, to communities and ecosystems. We work within ecology, evolution, physiology, systematics and combinations of these fields in order to understand the impact of natural and anthropogenic changes of the environment.

The department is placed at two different localities: in Natrium at Medicinaregatan 7B in Gothenburg and at the Kristineberg marine research station operated by the Marine Infrastructure at the University of Gothenburg. The current position is placed at the Kristineberg Marine Research Station, Fiskebäckskil.

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Subject area 

Experimental evaluation of the combined effects of changes associated with ocean alkalinity enhancement (OAE) implementation

Subject area description 

Ocean Alkalinity Enhancement (OAE) is a marine Carbon Dioxide Removal (mCDR) technique that may have a significant role in facilitating large scale CO2 removal to substantially reduce global warming and ocean acidification. However considerable uncertainties and knowledge gaps remain regarding its efficacy, technological and economic viability, its environmental and ecological impacts and its governance.

This 2 years postdoctoral position is part of the EU Horizon project OAeSIS (https://oaesis.eu/), a diverse, interdisciplinary team of leading experts in natural science, law, governance and socio-economic assessments. One key aspect is quantifying the impacts of OAE on key species, communities and biodiversity, including interactions with other marine ecosystem stressors – assessing the feasibility and sustainability of OAE as a tool to counteract climate change and ocean acidification

The position specifically focuses on resolving the combined effects of changes associated with different OAE implementation methods through experiments using a range of marine organisms. This will allow to produce performance curves for key drivers associated with OAE deployments, multiple stressors experiments, and modelization of performance landscapes for different OAE methods using experimental data and literature review.

This will be done in close collaboration with key partners within the consortium, particularly with the University of Copenhagen and the International Atomic Energy Agency. The position will contribute to enabling informed decision and policy-making regarding the potential application of this leading mCDR approach as a climate mitigation tool.

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Short-term pH variability reshapes phytoplankton and microzooplankton communities in the northern Indian Ocean

Published 17 August 2026 Science Leave a Comment
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Phytoplankton and microzooplankton (MZP) are key components of marine food webs, driving carbon transfer through the microbial loop. Short-term laboratory microcosm bottle incubations using seawater from the Bay of Bengal (BoB) and Arabian Sea (AS) in 2022 examined the effects of reduced pH. Phytoplankton biomass (Chl-a) remained stable or increased by up to 12% under low pH, suggesting reduced grazing or improved prey quality. MZP diversity (Shannon index, H′) showed basin-specific responses. In the BoB (Exps. 1–2), H′ ranged 2.00–3.70 with high evenness (J′ = 0.93–1.00) and slight declines under medium acidification (ΔpH = 0.2). In contrast, the AS (Exps. 3–4) showed wider variability (H′ = 0.00–3.63) and greater sensitivity, with sharp diversity losses under stronger acidification (ΔpH = 0.4). AS assemblages showed pronounced richness declines (D′ = 2.85–0.00), whereas BoB communities remained stable. Regional and pH-related differences were linked to shifts in ciliates and dinoflagellates. Autotrophic bacteria sustained under low pH, while heterotrophic bacteria increased later, indicating altered microbial-loop functioning. Overall, pH, chlorophyll-a, and heterotrophic bacteria structured the community, accounting for > 65% of the variation. Thus, short-term acidification reshapes MZP assemblages and may modify trophic interactions across the northern Indian Ocean.

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Biological modulation of shell δ13C in Mytilus galloprovincialis and Phorcus sp.: divergent responses between CO2 vents and laboratory mesocosms

Published 17 August 2026 Science Leave a Comment
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table isotopes are fundamental proxies for deciphering past environmental conditions and carbon cycle perturbations. However, applying these geochemical tools with a forward-looking perspective can also help predict the resilience of marine biota in future acidified oceans. This study investigates carbon uptake and biomineralization pathways under reduced pH in two ecologically keystone calcifying species: the bivalve Mytilus galloprovincialis and the gastropod Phorcus sp. To unravel these mechanisms, we adopted a dual approach, comparing isotopic trajectories (δ13C) under strictly controlled laboratory mesocosms with observations from natural CO2 vent systems in Ischia, Italy. Our results reveal a striking discrepancy between settings. Under laboratory conditions, both species exhibited a significant depletion in shell δ13C as pH decreased, directly tracking seawater carbonate chemistry. Conversely, specimens from the volcanic vents displayed a paradoxical δ13C enrichment at low-pH sites (pH ~7.4). These divergent trajectories indicate that in complex natural environments, the geochemical signal of ocean acidification can be overridden by metabolic overprints and trophically driven vital processes. Consequently, while laboratory experiments are essential to isolate kinetic fractionation, natural analogues remain crucial to capture the biological resilience and complex ecological feedback of future oceans. Future research combining these geochemical trends with direct, in vivo physiological assessments will be essential to precisely constrain the underlying metabolic kinetics and refine predictive metabolic models.

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ICM and ICATMAR deploy an oceanographic buoy off Somorrostro beach to monitor ocean acidification

Published 17 August 2026 Web sites and blogs Leave a Comment

The automated station, resulting from a participatory budgeting process and an agreement with the Barcelona City Council, records currents, pH, temperature, and real-time meteorological data off this iconic Barcelona beach.

The buoy has been moored approximately 1.5 kilometres from the coastline / ICATMAR.

The Institute of Marine Sciences (ICM-CSIC), in collaboration with the Catalan Research Institute for Ocean Governance (ICATMAR), has deployed a state-of-the-art automated oceanographic buoy off Barcelona’s Somorrostro beach. This new infrastructure has been designed to monitor a wide range of essential marine parameters in real time, including currents, temperature, salinity, and water pH. Additionally, the device features an integrated weather station that will continuously measure various atmospheric variables directly at the sea surface, serving as a key tool for studying climate change along the Catalan coast.

The action addresses a strategic need to expand permanent observation systems and stems directly from the prior experience gained by ICM-CSIC technical and scientific staff. The institution already had a solid background in this field, thanks to the instrumentation of a signaling buoy in the Medes Islands marine park (Girona) and the installation of a complex mooring system next to the Casablanca oil platform (Tarragona). These prior experiences were fundamental in refining the logistical and technological aspects of this new station, tailoring the design to its specific location to overcome the battery, communication, and security limitations detected in previous infrastructures.

An institutional push driven by public engagement

The feasibility and acquisition of the buoy’s instrumentation were made possible through an institutional collaboration agreement signed between the Spanish National Research Council (CSIC), the Barcelona City Council, and the public company Barcelona Cicle de l’Aigua S.A. The origin of this agreement dates back to February 2020, when the city council launched a pioneering citizen participation initiative within the framework of municipal participatory budgeting. Among the winning proposals submitted by residents in the Ciutat Vella district was the initiative titled “BCN pel Mediterrani. Canvi Climàtic” (BCN for the Mediterranean: Climate Change). Aligned with the Climate Emergency Declaration issued by the city of Barcelona in January of that same year, the proposal received a dedicated budget allocation of 200,000 euros, fully earmarked for deploying a buoy to comprehensively monitor coastal acidification in Catalonia.

Since this project fully aligned with the strategic plans of both ICM-CSIC and ICATMAR to roll out permanent coastal monitoring stations, both organizations formed an alliance to pool their resources, infrastructure, and expertise. A multidisciplinary team of technical and scientific staff from ICATMAR, the ICM-CSIC Oceanographic Engineering Service, and other institute departments participated in the development and assembly of the infrastructure. Thanks to this collaborative effort, ICATMAR funded the physical structure and the complex mooring line; the scientific instruments were financed through funds from the City Council and Barcelona Cicle de l’Aigua; and the internal electronics, real-time communication systems, and safety devices were provided directly by ICM-CSIC.

Acidification Monitoring

The location selected for the buoy is no coincidence. It has been moored approximately 1.5 kilometers offshore, directly in front of Somorrostro beach. This point holds significant scientific value for ICM-CSIC, as the research center has been conducting monthly oceanographic sampling here uninterruptedly for over 25 years. The arrival of this automated device represents an extraordinary qualitative leap forward, turning periodic site visits into continuous, automated data collection. The main objective is to establish a high-resolution time series on water acidity off a major metropolitan area like Barcelona, allowing immediate assessment of human impacts on the marine ecosystem.

Due to its geographical proximity to the shipping lanes entering and leaving the Port of Barcelona, project leaders carefully adjusted the buoy’s technical specifications and its electronic and optical signaling systems. This process was carried out in strict compliance with the legal requirements of the Port Authority of Barcelona and the Directorate-General for Coastal Policies of the Catalan Government, ensuring full safety for both commercial and recreational navigation in the area.

With the deployment of this equipment—now integrated into ICATMAR’s meteo-marine observation network along the Catalan coastline—the scientific community gains an unprecedented technological ally to decode how the Barcelona coastline responds to the challenge of the climate emergency. 

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Choose Your Own (O)Adventure education tool released

Published 17 August 2026 Educational Materials , Resources , Web sites and blogs Leave a Comment
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Choose Your Own (O)Adventure brings an interactive experience for your own learning pathway.

The NOAA Ocean Acidification Program is excited to announce the launch of “Choose Your Own (O)Adventure,” a new interactive tool to help you discover ocean and coastal acidification resources tailored to your specific interests and goals.

Skip the search for quality ocean acidification resources

Instead of wading through an ocean of information, access high-quality resources founded on the best available science and teaching best practices through. Whether you are an educator looking for classroom-ready materials, a student researching a project, or simply someone interested in learning more about how our oceans are changing, this tool makes finding information easier than ever. Dive into our curated collection for ocean and coastal acidification background, classroom ready, or regional and species-specific resources.

What you can do with Choose Your Own (O)Adventure

Our interactive feature in the gallery helps you quickly navigate our curated library to find the exact resources you need or you can browse our full CYOA collection.

  • Filter by Interest: Quickly navigate our curated library to find exactly what you need.
  • Search by Category: Browse resources based on specific criteria, including region, species, or grade level.
  • Find Vetted Content: Access background information and educational tools that have been vetted for teaching and communication best practices.

We invite you to explore the gallery on your own or follow a personalized learning path tailored to your specific interests and goals into our curated collection and follow a personalized learning path to unlock new insights about ocean and coastal acidification.

Also available is our full, searchable resources collection where you can find these materials, multimedia, reports and more.

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Persistence of Arctic Ocean acidification under negative emissions

Published 14 August 2026 Science Leave a Comment
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Although net negative emissions of carbon dioxide (CO2) are essential to meet climate targets, little is known about how declining atmospheric CO2 levels will affect ocean acidification. Here, by analysing the acidity ([H+]) and corrosivity to aragonite (ΩArag) in eight Earth system models that made simulations under rising then falling CO2 levels, we identify the Arctic as a hotspot for delayed reversibility of ocean acidification. Under falling CO2, Arctic surface waters remain comparatively more acidic, and aragonite-corrosive conditions (ΩArag < 1) persist until atmospheric CO2 drops ~120 ppm below the threshold at which they first appeared under rising CO2. This hysteresis arises from the erosion of the natural surface-layer deficit in dissolved inorganic carbon, initially maintained by sea ice limiting air–sea gas exchange and not fully restored as sea ice recovers during CO2 decline. Thus, the Arctic Ocean experiences not only the greatest acidification but also the most delayed benefits from negative emissions.

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Method for correcting the temperature dependence of field-type glass electrode pH sensors

Published 14 August 2026 Science Leave a Comment
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Seawater pH measurement is essential for monitoring ocean acidification and its biogeochemical impacts. Glass electrode pH sensors are widely used for in situ applications due to their ease of operation, low power consumption, and no reagent requirements. However, their accuracy can be affected by temperature-dependent effects, particularly those associated with the internal reference solution. Conventional calibration methods based on the Nernst response do not explicitly account for temperature-induced variations in the internal solution, which may lead to systematic bias under conditions with large temperature gradients. In this study, a correction method is proposed to address temperature-dependent errors by modeling the internal pH (pHin). The model incorporates two primary temperature-dependent contributions: the intrinsic temperature dependence of the phosphate buffer and potential shifts caused by activity changes in saturated KCl. These effects are combined through the electrode response factor (fR), defined as the ratio of the observed electrode slope to the theoretical Nernst slope, to estimate pHin as a function of temperature and correct measured pH values to a reference temperature of 25 °C. Application of the method to vertical seawater profiles demonstrated a reduction in deviation from colorimetric reference measurements. The corrected results showed reduced temperature-dependent bias across depth. This approach provides a practical framework for improving the reliability of in situ glass electrode pH measurements under varying thermal conditions. The proposed method addresses equilibrium temperature-dependent effects of the internal solution but does not explicitly account for transient hysteresis, pressure effects, or long-term sensor drift.

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Deep dive: evaluating students’ use of Toulmin’s argumentation pattern in chemistry classrooms for constructing scientific arguments about ocean acidification

Published 14 August 2026 Science Leave a Comment
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Science education plays a key role in helping students to become responsible citizens, capable of making appropriate decisions based on scientific information, participating in discussions on socio-scientific issues (SSIs), and taking action in the context of climate change. Thus, achieving scientific literacy in general and practising scientific argumentation skills – as part of scientific literacy – in particular, are essential. Therefore, the pilot study presented here focusses on improving upper secondary students’ (ISCED 3) scientific argumentation skills by implementing Toulmin’s Argumentation Pattern (TAP) in the chemistry classroom. We focus on chemistry education to better understand subject-specific argumentation in chemistry classrooms. This pilot study is part of an interventional study that aims to implement TAP as a construction mechanism to improve students’ scientific argumentation skills. Our study is embedded in the SSI of human-induced ocean acidification. In order to gain insight into students’ scientific argumentation patterns and develop adequate teaching materials, we asked 29 upper secondary students to write well-founded arguments to confirm a claim about calcification of coral skeletons made in a newspaper headline. Students’ arguments were constructed prior to and following the provision of support material based on TAP. These arguments were analysed with regards to their formal quality using qualitative content analysis. Our findings indicate that TAP aligned well with our participants’ intuitive arguments. We discuss our findings and propose how using TAP can contribute to teaching and learning chemistry-specific argumentation skills.

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Tracking acidification in the gulf – a new story map

Published 14 August 2026 Events Leave a Comment

The Gulf is dynamic and productive, supporting corals, fish, shellfish and other marine life that sustain the region’s fisheries, biodiversity and economies. Join us for a Gulf of America Coastal Acidification Network (GCAN) webinar highlighting a new interactive Story Map that illustrates how researchers are monitoring ocean and coastal acidification across the Gulf. Pallavi Tummeti and Dr. Natalia López Figueroa will provide an overview of the Story Map and guide discussion about tracking acidification in the Gulf. Learn about the the data, research projects, and regional partnerships featured in this interactive resource.

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From climate data to regulatory decisions: integrating climate AI into marine EIAs

Published 13 August 2026 Science Leave a Comment
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Climate change is increasingly reshaping the sustainable development of the ocean through ocean warming, deoxygenation, acidification, and other compounding stressors. Against this backdrop, environmental impact assessment (EIA) has become a pivotal governance instrument for anticipating and reducing the climate-related impacts of human activities at sea. From the United Nations Convention on the Law of the Sea (UNCLOS) to the Agreement on Biodiversity Beyond National Jurisdiction (the BBNJ Agreement), regulatory expectations for marine EIAs are moving toward more structured thresholds, procedural workflows, and reporting obligations. At the same time, rapid advances in climate artificial intelligence (climate AI), such as machine-learning forecasting, deep-learning nowcasting, and agentic AI workflows, are expanding the ability to produce timely, high-resolution, and probabilistic climate information from heterogeneous climate data streams. These capabilities can strengthen climate-related EIAs by combining short-term forecasting and nowcasting for early warning, long-term observation and monitoring for dynamic baselines, and scenario-based climate modelling for impact estimation and decision support. Climate AI can therefore be integrated throughout the EIA workflow rather than appended as an auxiliary layer, translating climate data into regulatory evidence under changing marine-climate conditions. To ensure regulatory robustness and accountability, implementation should be grounded in evidence standards and quality assurance, transparent and auditable documentation, human oversight, responsibility allocation, and formal mechanisms for cross-institutional data sharing. We argue that a standards-driven, AI-enabled EIA framework can improve the relevance, reviewability, and robustness of marine EIA decisions, supporting long-term ocean sustainability under accelerating climate risks.

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Pressures on coastal biodiversity in South Africa: a cross-realm review

Published 13 August 2026 Science Leave a Comment
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South Africa’s coastal zone comprises diverse ecosystems and species, and provides important benefits to people. It is also under significant pressure from numerous activities that take place on land, in estuaries, and in the sea, and that are rarely considered together. Here, we review the pressures on coastal biodiversity in South Africa, taking a cross-realm perspective. The pressures are reviewed under 10 themes: biological resource use; energy production and mining; pollution; coastal development; transportation and service corridors; natural systems modifications (sand-flow disruptions, estuarine hydrological regime change, livestock grazing and browsing); human intrusions and disturbance; aquaculture, agriculture and plantation forestry; invasive and other problematic species and diseases; and climate change, severe weather and ocean acidification. Many of these are intense or pervasive cross-realm pressures, often with cumulative, synergistic impacts that are collectively causing habitat fragmentation and loss, declines in species richness and abundance, altered animal behaviour, reduced ecosystem resilience, and declines in capacity to provide ecosystem services. However, the inter-connected nature of these pressures also means that integrated coastal management provides opportunities to address multiple pressures and impacts cross-realm. Sustainable development that is mindful of long-term climate projections is imperative in the coastal zone to safeguard this national asset into the future.

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Giant kelp-associated variation in coastal seawater chemistry across contrasting sites in Chile and Tasmania

Published 13 August 2026 Science Leave a Comment
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Background and Aims

Widespread shifts in seawater chemistry are occurring across spatial and temporal scales, with important consequences for coastal ecosystems. Giant kelp (Macrocystis pyrifera) forests elevate seawater pH and dissolved oxygen (DO) through photosynthesis, potentially providing short-term refugia from ocean acidification and deoxygenation. However, whether these effects persist across contrasting environmental settings remains unclear. Here, we assess how biological and oceanographic conditions regulate giant kelp-mediated modification of seawater chemistry across multiple sites.

Methodology

Hourly measurements of seawater pH, DO and temperature were collected during spring–summer 2022–23 using paired deployments inside and outside giant kelp forests at one site in central Chile and four sites in Tasmania, Australia. The influence of giant kelp density was also evaluated at two sites in southern Chile and three sites in Tasmania. An upwelling index was calculated for the central Chile site to assess the influence of regional oceanographic forcing on kelp-associated seawater chemistry patterns.

Key Results

Hourly pH and DO were higher inside giant kelp forests than outside at the central Chile site and at one Tasmanian site. At these locations, stronger daytime pH–DO relationships indicated that photosynthetic carbon uptake exceeded night-time respiration, generating a net positive metabolic signal. In Tasmania, giant kelp density was positively associated with hourly pH and DO, whereas no such relationship was detected in southern Chile. At the central Chile site, kelp-associated effects intensified during a strong upwelling event, reducing the severity of low pH and DO conditions.

Conclusions

Giant kelp forests can locally buffer short-term fluctuations in seawater pH and DO, but this capacity is highly site-dependent and influenced by giant kelp density and environmental conditions. Overall, our findings suggest that continued loss of giant kelp forests in Tasmania may reduce their potential to provide short-term refugia, while in Chile the strength of kelp-mediated seawater chemistry modification is likely to remain strongly influenced by variability in upwelling and freshwater inputs.

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CARIMED (CARbon, tracers, and ancillary data In the MEDiterranean Sea): a ship-based data synthesis product – overview and quality control procedures

Published 12 August 2026 Science Leave a Comment
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The Mediterranean Sea (MedSea) is highly sensitive to climate-driven changes in temperature, oxygen, and pH, among other variables. To better assess these long-term trends, we developed CARIMED (CARbon, tracers, and ancillary data In the MEDiterranean Sea), the first comprehensive, harmonised data synthesis product for the MedSea. CARIMED integrates hydrographic, inorganic carbon, transient tracer, and ancillary measurements from 46 research cruises spanning the period from 1976 to 2018, containing observations for the entire water column across all MedSea sub-basins. A substantial component of the data was retrieved from fragmented or locally archived historical records, thus consolidating previously inaccessible measurements. Following global synthesis approaches, CARIMED applies a quality-controlled, and bias-adjusted framework. A key adaptation was the secondary quality control (2QC) procedure, specifically tailored to the MedSea’s unique hydrography, utilising sub-basin divisions and supplementary checks (including statistical consistency assessments) to resolve complex, often contradictory, inter-cruise offsets. This rigorous process minimised systematic biases, yielding a dataset with improved consistency, and highlights the urgent need for adapted standard operating procedures and reference materials to address the MedSea biogeochemical particularities. CARIMED delivers two complementary, freely available products: the aggregated original cruise data product (https://doi.org/10.20350/digitalCSIC/17785, García-Ibáñez et al., 2025) and the final bias-adjusted data synthesis product (https://doi.org/10.25921/cp5b-zq67, Álvarez et al., 2025; hosted at https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/oceans/CARIMED/, last access: 26 June 2026). This essential resource establishes a new benchmark for assessing long-term biogeochemical trends, validating regional ocean models, and supporting climate-change mitigation and adaptation strategies in this rapidly changing semi-enclosed basin.

Continue reading ‘CARIMED (CARbon, tracers, and ancillary data In the MEDiterranean Sea): a ship-based data synthesis product – overview and quality control procedures’

Preferential impairment of later mating stages and sex-dependent metabolic shifts in Japanese medaka exposed to acute acidification

Published 12 August 2026 Science Leave a Comment
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Highlights

  • Acute acid stress (pH 4.5) preferentially impairs later mating stages in medaka, rather than causing a generalized reproductive collapse.
  • Early initiation phases (following and courtship) are relatively less affected, whereas progression to the crossing stage and spawning is strongly suppressed.
  • General locomotion and territorial aggression show no detectable change under acute acidification.
  • Females exhibit increased ammonia excretion and oxygen consumption, indicating sex-specific physiological strain under acid stress.
  • The behavioral impairment is consistent with an energy reallocation toward acid–base homeostasis, reducing investment in energetically costly terminal mating behaviors.

Abstract

Environmental acidification poses a significant threat to aquatic organisms, yet the underlying mechanisms of how acid stress disrupts complex social and reproductive behaviors remain incompletely understood. In the present study, we investigated the behavioral and physiological responses of adult Japanese medaka (Oryzias latipes) under acute acid exposure (pH 4.5, 24 h). Our results showed that acute acid stress reduced mating success, with a stronger impairment observed in the transition to the crossing stage and subsequent spawning, while the earlier, male-driven stages of following and courtship were relatively less affected under the present experimental conditions. This reproductive impairment did not coincide with detectable changes in generalized emotional-like behavior. Fish showed normal performance in the novel tank test and maintained territorial aggression. Physiologically, we observed a clear sexual dimorphism. Under acid stress, males maintained relatively stable MO₂ and JAmm, whereas females showed elevated MO₂ and JAmm. These findings suggest that reproductive impairment may be more pronounced in energetically demanding mating stages and may be associated with sex-dependent physiological strain. We further propose that the increased metabolic cost of acid-base regulation in females could shift energy allocation, and that high-cost coordination behaviors may be reduced in order to maintain short-term survival. This study provides evidence linking bioenergetics, acid-base regulation, and reproductive behavior in a teleost model under acidification.

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RETRACTION: Ocean acidification disrupts the innate ability of fish to detect predator olfactory cues

Published 12 August 2026 Science Leave a Comment
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Retraction: D.L. Dixson, P.L. Munday, G.P. Jones, “ Ocean Acidification Disrupts the Innate Ability of Fish to Detect Predator Olfactory Cues,” Ecology Letters 13 no. 1, (2010): 68–75, https://doi.org/10.1111/j.1461-0248.2009.01400.x.

The above article, published online on 21 December 2009 in Wiley Online Library (onlinelibrary.wiley.com), has been retracted by agreement between the Editor-in-Chief, Peter H. Thrall; and John Wiley & Sons Ltd. A third-party complainant alerted the publisher to their observation of a statistically implausible variance in the data. The authors were contacted regarding the concerns raised. After evaluating the full dataset provided by the authors, an investigation by members of the journal’s editorial team determined that the data provided contained substantial errors, including repeated blocks, missing data, and structural errors. The authors acknowledged the inconsistencies with the data and provided an explanation, which included carelessness during manuscript reorganization, and they also asserted that the reported data anomalies did not affect the overall published results. The authors maintain that the errors were not a result of intentional data fabrication, but rather, poor standards of data handling and quality control. However, neither the publisher nor the editor has confidence in the article, primarily because the data provided during the investigation were not consistent with the observation methods described in the article. Therefore, because the journal has no basis on which to affirm confidence in the published results, the article must be retracted. The authors have been informed of the retraction.

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Invasive macroalgae exert stronger effects than elevated CO₂ on seagrass (Posidonia oceanica) seedling performance and associated microbiomes

Published 11 August 2026 Science Leave a Comment
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Highlights

  • Invasive macroalgae reduced P. oceanica seedling biomass and leaf development.
  • Macroalgal invasion depleted carbohydrate reserves in seedling roots and rhizomes.
  • Elevated CO2 increased rhizome starch but did not mitigate invasion impacts.
  • Root microbiome diversity declined markedly under macroalgal invasion.
  • Future CO2 enrichment unlikely to buffer invasion stress at recruitment stage.

Abstract

Seagrass seedlings are key to meadow recovery under global change, as they enable recolonization of degraded areas and provide genetic variability needed for adaptation. While invasive macroalgae increasingly threaten seagrass communities, elevated CO2 has been proposed to enhance seagrass performance and potentially buffer other stressors. Here, we conducted a mesocosm experiment to test the combined effects of two invasive macroalgae (Lophocladia trichoclados and Caulerpa cylindracea) and elevated CO2 on Posidonia oceanica seedlings. CO2 enrichment increased carbohydrate reserves in rhizomes and induced subtle shifts in root-associated microbiomes. In contrast, invasive macroalgae had consistently negative effects on seedling development and physiology and strongly altered both above- and belowground microbial communities. Despite its potential to stimulate seagrass productivity, elevated CO2 did not mitigate the detrimental impacts of invasive macroalgae. These findings indicate that future CO2 conditions may not offset invasion-driven stress at the recruitment stage, highlighting the need for targeted management efforts to limit macroalgal proliferation and support seagrass meadow regeneration.

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Crustose coralline algae buffer shallow reef environments from dissolution

Published 11 August 2026 Science Leave a Comment
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Ocean acidification threatens coral reefs by reducing seawater pH and carbonate saturation state. Crustose coralline algae are particularly vulnerable because their high-magnesium calcite skeletons dissolve more readily than coral aragonite skeletons. However, this dissolution may increase alkalinity and buffer reef-water chemistry. Here we show, using repeated low-tide observations and in situ incubations in a shallow reef system in the southern Great Barrier Reef, that reef-water pH varies by more than one unit over the day (7.47 – 8.61), reaching levels comparable to those projected for the end of this century. Nighttime respiration promotes dissolution of high-magnesium calcite produced by crustose coralline algae, increasing alkalinity and helping maintain seawater supersaturated with respect to aragonite. At the same time, isolated coral incubations experience a greater decline in pH and aragonite saturation state in the absence of this buffering effect. These findings suggest that high-magnesium calcite-producing communities may help partially buffer reefs against future acidification.

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