Applications open: training course on ocean alkalinity enhancement – assessing the impact on marine organisms

Published 2 April 2026 Events Closed

The IAEA Ocean Acidification International Coordination Centre is hosting a second Training Course on Ocean Alkalinity Enhancement – Assessing the Impact on Marine Organisms. The deadline to apply is Thursday April 30th (extended from what is indicated in the linked announcement). 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. Travel and lodging for all scientists accepted to the course will be covered. Priority will be given to early-career scientists with experience in marine environmental changes who have already received training on ocean acidification and seawater carbonate chemistry. Preference will be given to applicants with experience in biological response research and who are interested in conducting studies on the ecological impact of OAE. 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: 15 – 19 June 2026

Location: IAEA Marine Environment Laboratories, Monaco.

Application Forms

Introduction
The Training Course on Ocean Alkalinity Enhancement — Assessing the Impact on Marine Organisms is part of the capacity building program of the IAEA Ocean Acidification International Coordination Centre (OA-ICC). The program aims to support IAEA Member States to minimize and address the impacts of ocean acidification (Sustainable Development Goal 14.3) and study the impacts of ocean-based solutions.

The course 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).

Objectives
The ocean is under pressure from warming, acidification and oxygen loss, adversely impacting marine ecosystems and the communities and societies who depend on them. But the ocean, covering 70% of Earth’s surface, can also be a vital part of the solution and our ally to mitigate and adapt to climate change. Meeting the objectives of the Paris Agreement to limit warming to well below 2º C would not only require drastic cuts in carbon dioxide (CO2) emissions, but also the active removal of carbon CO2 on the order of 100–1000 Gt CO2 over the 21st century (IPCC, 2018). Ocean alkalinity enhancement (OAE) is a marine Carbon Dioxide Removal (mCDR) approach which is receiving growing interest from scientists, policy makers and industry. It entails the addition of alkaline materials to the sea with the goal of increasing the ocean’s potential to absorb CO2. There is limited scientific information to date about the impact that OAE might have on marine organisms and ecosystems. Building technical expertise to assess ecological impacts of OAE is critically needed to allow for informed policy decisions about this approach.

The aim of this course is to train scientists on how to perform laboratory experiments on the potential impact of OAE on marine organisms. The course includes both theoretical and practical exercises with the goals of designing purposeful experiments, analyzing complex datasets, avoiding typical pitfalls, and ensuring data comparability with other studies. Lectures on the broader context and implications of OAE will also be provided (e.g., societal and governance aspects). The course will be largely based on the 2023 Guide to Best Practices for Ocean Alkalinity Enhancement Research, especially the chapters on experimental design.

Target Audience
The course is open to 10-12 trainees. Priority will be given to early-career scientists with experience in marine environmental changes who have already received training on ocean acidification and seawater carbonate chemistry. Preference will be given to applicants with experience in biological response research and who are interested in conducting studies on the ecological impact of OAE. At least one publication in the field of marine environmental changes is required.

Working Language
English

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Participation and Registration
Scientists wishing to participate in the event must 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, participants are requested to send the Participation Form (Form A) 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 17 April 2026. Participants who are members of an organization invited to attend are requested to send the Participation Form (Form A) through their organization to the IAEA by the above deadline.
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.

Additional Requirements
The participants should have a university degree in marine chemistry, biology, oceanography, or a related scientific field, and must have already received training on ocean acidification and seawater carbonate chemistry or performed ocean acidification biological response experiments. Selection will be based on merit and interest. Your applications should include:

  • A motivation letter with a short description of your research interests, why you would like to
    participate, and your plans regarding present and future research on OAE (max one A4 page)
  • CV with publication list
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Research progress on the comprehensive response mechanisms of marine organisms to multiple environmental stressors

Published 28 April 2026 Science Leave a Comment
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The ocean constitutes a vital component of the Earth’s ecosystem, serving as the breeding and habitat ground for marine organisms. Currently, the global marine ecosystem is confronting combined threats from multiple environmental stressors, such as seawater warming, acidification, hypoxia, and microplastic pollution. Research focusing solely on individual stressors can hardly reveal the authentic response patterns of marine organisms accurately. This paper presents a comprehensive review. It systematically integrates cutting-edge research findings from recent years. The review centers on two core themes. These themes are the interactive effects of multiple environmental stressors and the response mechanisms of marine organisms. Studies indicate significant species-specific differences in organism responses to combined stress. These differences exist across various organism groups. Additionally, the interactive effects of multiple environmental stressors often induce biological responses. These responses deviate from the predictions derived from single-factor studies. The research results presented herein can provide crucial theoretical support for the conservation of marine biological resources, the restoration of biodiversity, and the protection of the marine ecological environment. Meanwhile, they lay a foundation for the establishment of predictable marine stress-response relationship models.

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Light and tidal inundation and exposure regulate the sensitivity of estuarine benthic greenhouse gas fluxes to warming and ocean acidification

Published 28 April 2026 Science Leave a Comment
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Coastal sediments are globally significant sources and sinks of greenhouse gases (GHGs), yet their contributions to climate feedbacks of warming and ocean acidification remain uncertain, in part due to limited understanding of short-term variability. Here, we use a fully factorial laboratory experiment to disentangle how diel light–dark and tidal inundation and exposure interact with warming and elevated pCO2 to regulate benthic fluxes of CO2, CH4, and N2O in estuarine sediments, alongside concurrent changes in benthic oxygen exchange. While warming and pCO2 exerted strong independent effects, their influence was shaped by diel and tidal fluctuations in redox conditions and oxygen availability, reflecting shifts in metabolic balance between primary production and respiration. Light consistently limited CO2, CH4, and N2O emissions through enhanced autotrophic uptake and oxygenation, while dark promoted anaerobic production pathways. N2O showed the greatest sensitivity to the combined effects of climate forcing and redox dynamics. Despite warming-driven stimulation of benthic heterotrophy and the production of all GHGs, CO2 remained the dominant greenhouse gas, with minimal CH4 and N2O fluxes due to the limited organic matter availability within the sediment. This reflects the strong redox controls on CH4 and N2O production, which relies on both oxygen depletion and organic substrate supply. Our findings emphasize that fine-scale temporal variability can significantly shape both the magnitude and climate sensitivity of benthic GHG emissions. Capturing these fine-scale controls is essential for accurately modeling the contributions of estuarine sediments to global GHG budgets and their feedbacks.

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Ocean acidification simplifies food webs and may intensify competition between sea urchins

Published 28 April 2026 Web sites and blogs Leave a Comment

Figure: Paracentrotus lividus with its faecal pellets used to investigate diet with eukaryotic DNA metabarcoding.

Ocean acidification not only affects the physiology of marine organisms but also profoundly transforms their feeding relationships and may intensify competition between species that previously occupied distinct trophic niches. This is one of the main conclusions of the TROIA project (TROphic Interactions of two echinoderms under ocean Acidification), led by Dr. Vanessa Arranz and Dr. Sara González-Delgado from the Marine Biodiversity and Evolution (MBE) group at the Biodiversity Research Institute (IRBio) of the University of Barcelona, and funded through a PR IRBio 2024 Grant.

The study was carried out in the natural CO₂ vent system of Punta de Fuencaliente, on La Palma (Canary Islands), one of the few naturally acidified environments in the Atlantic. In this area, submarine volcanic emissions generate a pH gradient along the coast that allows researchers to simulate the oceanic conditions projected for the coming decades and to study their long-term effects on real marine communities.

The results, currently under publication, show that under acidification the isotopic niche space of the benthic community is significantly reduced. Basal carbon sources become homogenized and functional trophic diversity decreases. “Acidification simplifies the benthic food web: there is less resource variety and organisms converge towards more similar feeding strategies,” explains Dr. Sara González-Delgado.

Two species, two contrasting responses

The study focuses on two sea urchin species common in the Mediterranean and the Atlantic: Paracentrotus lividus and Arbacia lixula. The results reveal contrasting responses to acidification. While P. lividus maintains a relatively stable diet along the pH gradient, A. lixula undergoes a notable dietary shift, moving from a predominantly carnivorous diet under current conditions (around 79% animal prey) to herbivory in acidified environments. This shift leads to an increase in trophic niche overlap between the two species, rising from 0% under current conditions to more than 27% in the most acidified sites. “Arbacia lixula is highly trophically plastic, but this flexibility comes at a cost: under acidification it begins to compete for the same resources as Paracentrotus lividus,” notes Dr. Vanessa Arranz.

Combining methods to better understand diet

The project combined two complementary methodological approaches: stable isotope analysis (δ¹³C and δ¹⁵N) and eukaryotic DNA metabarcoding from fecal samples. One of the study’s key contributions is the first validation in these species of using feces as a non-invasive sample to study diet through COI gene metabarcoding.

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Ecological implications in a changing ocean

The results have important implications for predicting changes in marine communities under the acidification scenarios projected by the IPCC. The study highlights the need to go beyond individual physiological effects and also consider how trophic interactions and the ecological roles of species are altered within marine ecosystems.

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Climate change resilience and positive Scope for Growth in wild adult Sydney rock oysters, Saccostrea glomerata (Gould 1850)

Published 27 April 2026 Science Leave a Comment
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Climate change resilience and positive Scope for Growth in wild adult Sydney rock oysters, Saccostrea glomerata (Gould 1850)

Oysters have ecological and economic importance worldwide as they provide ecosystem services and sustain profitable aquaculture industries. Calcifying bivalves including oysters have been found to be sensitive to ocean warming and acidification caused by anthropogenic climate change. This study tested whether adult wild Sydney rock oyster, Saccostrea glomerata, exposed to elevated pCO2 (331 μatm and 867 μatm) and temperature (24°C and 28°C) in an orthogonal design for five weeks, have resilience and can maintain sufficient scope for growth or are pushed into a suboptimal state. At the end of the exposure growth, condition index, clearance, ingestion and absorption efficiency and rates were measured and scope for growth calculated. Sydney rock oysters responded to elevated pCO2 and temperature with no change in overall growth or condition index, but significantly increased metabolic, clearance, ingestion, and absorption rates and positive Scope for Growth. Our results indicate that adult S. glomerata can cope with the moderate level of climate change stress predicted for 2100 through increased standard metabolic rate and increased energetic processes. If, however, food availability becomes limiting, and other environmental stressors interact with climate change stressors then resilience thresholds maybe breached for this economically, ecologically and indigenous significant and iconic oyster species.

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Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters

Published 27 April 2026 Science Leave a Comment
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Coccolithophores, as calcifying phytoplankton, play a critical role in the global carbon cycle by producing calcium carbonate (CaCO 3 ) in the ocean through their calcitic coccoliths. Here we examine Gephyrocapsa huxleyi (formerly Emiliania huxleyi) and related species abundance and genetic diversity along the West Coast of North America from samples taken on the 2021 NOAA West Coast Ocean Acidification (WCOA21) cruise, along the margin from British Columbia, Canada, to San Diego, California, USA. Significant carbonate chemistry gradients were observed across 17 transects, mostly in the onshore-offshore and north-to-south direction. Abundance and morphometrics of Gephyrocapsa spp. was evaluated using real-time PCR of mitochondrial cytochrome c oxidase subunit 3 ( cox3 ) gene and by microscopy. Variation in PIC concentrations, G. huxleyi and related species abundance, and coccosphere thickness were found to be associated with the gradients in carbonate chemistry and nutrient concentrations (phosphate, nitrate, nitrite, ammonium) across stations sampled during the cruise. We identified 5 unique amplicon sequence variants (ASVs) of Gephyrocapsa spp. cox3 that systematically varied in relative abundance across the California Current System. Southern California locations had greater diversity in cox3 sequences than northerly locations. These analyses represent baselines for evaluation of the impacts of future environmental changes in coastal waters along this productive upwelling regime.

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Open for submissions : Ocean acidification

Published 27 April 2026 Science Leave a Comment



Submission deadline: 02 December 2026

Ocean acidification, driven by rising atmospheric CO2 levels, alters the carbonate chemistry of seawater and reduces pH, directly affecting calcifying organisms such as corals, mollusks, and plankton. This Collection invites research on the chemical mechanisms underlying ocean acidification, including interactions between CO2, bicarbonate, and carbonate ions, as well as experimental and modeling approaches to measure and predict these changes. We also welcome research that highlights the chemical processes of biomineralization and how those processes respond to seawater acidification.

We particularly encourage studies on mitigation strategies from a chemical perspective, such as ocean alkalinity enhancement, and their effectiveness in restoring carbonate equilibria. Research exploring the chemical mechanisms linking CO2 emissions to shifts in ocean chemistry, and their downstream effects on marine ecosystems, will contribute to a more comprehensive understanding of this global challenge.

Submissions that integrate analytical chemistry, environmental chemistry, and modeling approaches are particularly welcome, as they offer insights into both fundamental chemical processes and applied solutions for maintaining oceanic chemical balance.

Potential topics for submission include, but are not limited to:

  • Carbonate chemistry and bicarbonate equilibria
  • Marine chemical modelling
  • Mitigation strategies for ocean acidification
  • Methods of marine carbon dioxide removal, including ocean alkalinity enhancement and direct ocean removal
  • Analytical chemistry of seawater
  • Developments in sensing technologies, such as biosensors and field-effect transistors
  • Chemical processes of biomineralization and its respond to seawater acidification
  • Chemical interactions, exchange, and transport at the air-water interface

This Collection supports and amplifies research related to SDG 14: Life Below Water.

All manuscripts submitted to this journal, including those submitted to collections and special issues, are assessed in line with our editorial policies and the journal’s peer review process. Reviewers and editors are required to declare competing interests and can be excluded from the peer review process if a competing interest exists.

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Real-time acidification monitoring through Sofar buoy and SAMI-pH integration

Published 23 April 2026 Science Leave a Comment
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Ocean acidification (OA) impairs the ability of corals to build and maintain reef structures by reducing calcium carbonate deposition and accelerating the dissolution of existing frameworks. OA conditions can result from both natural pH fluctuations, driven by diel and seasonal variability in biological activity and water quality, and long-term increases in atmospheric CO2 absorption. Accurate characterization of OA requires precise, high-frequency time-series data, particularly in nearshore ecosystems where benthic community metabolism can cause rapid, localized shifts in carbonate chemistry. However, continuous, high-resolution pH monitoring remains challenging, and most existing technologies lack real-time feedback capabilities. Here, we present a real-time acidification monitoring system that integrates a Sofar Spotter buoy with a Sunburst SAMI-pH sensor. The system delivers continuous environmental data (benthic pH and temperature, surface temperature, wind, wave height, and barometric pressure) and sensor health diagnostics (battery levels and cellular connectivity status) to a public-facing dashboard. This system enables real-time access to high-frequency pH data and provides a modular and cost-effective alternative to larger, more complex platforms such as MAPCO2 buoys. Increased accessibility supports broader and more scalable monitoring efforts, supporting scientists, resource managers, and policymakers in tracking diel, seasonal, and long-term OA dynamics.

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Seawater acidification accelerates growth but hastens decline in batch cultures of the marine diatom Thalassiosira pseudonana

Published 22 April 2026 Science Leave a Comment
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Diatoms are characterized by rapid cell division and a high capacity to adapt to environmental variability, and some species can form blooms when environmental conditions are favorable. Previous studies have largely focused on the bloom development phase, during which biomass accumulates rapidly, whereas the decline phase-despite its critical role in carbon export and microbial loop dynamics-has received far less attention. Here, we tracked changes in cell density and inorganic carbon utilization characteristics throughout the entire course of a simulated Thalassiosira pseudonana bloom under ambient (420 μatm) and elevated pCO2 (1000 μatm) conditions. Inhibitors of carbonic anhydrase and direct bicarbonate transporters were applied to investigate the characteristics of inorganic carbon utilization. The relationship between photosynthetic rate and inorganic carbon concentration was measured to assess inorganic carbon affinity. The simulated T. pseudonana bloom was characterized by rapid cell density accumulation, reaching a peak within 10 days, followed by a rapid decline without a distinct stationary phase. As the bloom progressed, photosynthetic rate and the maximum quantum yield of photosystem II declined, whereas the inorganic carbon affinity increased. Elevated CO2 enhanced growth and maximum quantum yield during the acceleration phase but resulted in an 86% higher fitted death rate during the decline phase. Regarding the relationship between photosynthetic rate and dissolved inorganic carbon concentration, elevated CO2 increased the maximum photosynthetic rate and half-saturation constant only during the acceleration phase. Collectively, these results indicate that seawater acidification can influence both biomass accumulation and decline intensity in diatom blooms, with potential consequences for carbon sequestration and its redistribution among biogeochemical pools.

Continue reading ‘Seawater acidification accelerates growth but hastens decline in batch cultures of the marine diatom Thalassiosira pseudonana’

Ocean acidification induces neuronal hyperexcitation and anxiety-like behaviour in marine medaka via ASIC activation

Published 21 April 2026 Science Leave a Comment
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Ocean acidification presents a significant threat to marine life, yet its neurobiological mechanisms remain poorly understood. This study examined how acid-sensing ion channels (ASICs) mediate neuronal excitability and anxiety-like behaviour in marine medaka (Oryzias melastigma) under elevated CO2 concentrations (1000 and 1900 ppm). Transcriptomics revealed early upregulation of asic1a (4 days), while RT-qPCR demonstrated increased asic1a, asic1b, asic2 and asic4a (7 days), with only asic1a sustained at 30 days. Immunofluorescence confirmed heightened Asic2 in emotion-processing brain regions following acidification. Transmission electron microscopy unveiled distinct ultrastructural alterations: widened synaptic clefts, thinned postsynaptic densities, and decreased mitochondrial aspect ratios. Mitochondrial membrane potential assays revealed a reduction in membrane potential in response to acidification. Electrophysiological recordings showed increased neuronal firing count in the dorsolateral telencephalon under acidification, behavioural assessments revealed significant anxiety-like phenotypes, effects that were fully rescued by ASIC inhibition. These results indicated that temporal specificity in ASIC subtype expression in acidification response. The interplay of synaptic and mitochondrial dysfunction, neuronal hyperexcitability, and behavioural alterations suggested acidification impaired both synaptic transmission efficiency and mitochondrial function, destabilizing neural circuits. This study systematically elucidates the neurotoxic effects of ocean acidification on marine fish, providing critical scientific evidence for predicting the ecological impacts of climate change on marine organisms.

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Decadal shifts in hypoxia and acidification reveal changing anthropogenic pressures on bottom waters of a coastal shelf

Published 20 April 2026 Science Leave a Comment
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Coastal systems provide habitat that sustains valuable shellfisheries but are subject to dissolved oxygen (DO) and/or carbonate chemistry impairment from anthropogenic pressures such as eutrophication and increasingly, climate change. Although extreme events can have disproportional negative ecological impacts, their ephemeral nature and a lack of baseline monitoring data make them challenging to characterize. Through assessments of historical records and a series of modern-day cruises, this study documented the magnitude and extent of summer hypoxia and acidification in the coastal shelf bottom waters of an urban shelf ecosystem, the New York Bight, before and during a devastating hypoxic event in 1976 and at present. In 1974, the most severe DO (2.39 mg L−1) and carbonate chemistry [pHN: 7.47; aragonite saturation state (ΩAr): 0.45] conditions occurred as a halo around a now derelict sewage disposal site, while averaging 4.43 mg L−1 (DO), 7.84 (pH), and 1.25 (ΩAr) across the region that August. During the mass mortality event of 1976, extremely low DO (< 1 mg L−1), pHN (< 7.5), and ΩAr (< 0.5) levels were observed across bottom waters during summer. Comparisons of modern subsurface chemistry to that of 1974—a year with ocean dumping but no mass mortality—indicated increases in bottom water DO, with evidence to suggest that ocean acidification has dampened the concomitant increases in ΩAr over the intervening half-century. This study highlights the impacts of ocean dumping and the threat of ocean acidification to systems that are experiencing or recovering from coastal hypoxia.

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Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea

Published 20 April 2026 Science Leave a Comment
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Highlights

  • Miniaturization coincides with reduced species diversity and elevated chlorophyll a.
  • Declining pH and reduced dissolved inorganic nitrogen are key drivers for smaller cells.
  • Salinity, dissolved oxygen and cooling jointly reshape phytoplankton community structure.

Abstract

Phytoplankton are tiny drifting photosynthetic organisms that support marine food webs and help control the global carbon cycle. However, it remains unclear how ongoing environmental changes are altering their cell size, species diversity, and chlorophyll a concentration in coastal seas. In this study, we investigated changes in phytoplankton cell size, species diversity, and chlorophyll a concentration along the Yellow Sea coast of China from 2021 to 2024, based on fourteen research cruises conducted at twenty-six coastal stations. We then employed statistical models to explore how individual and combined environmental factors were related to those biological features. We observed a clear shift to predominance of smaller cells, a reduction in species diversity, and an increase in chlorophyll a concentration. pH and reduced dissolved inorganic nitrogen were strongly associated with smaller cell size, while higher salinity and higher oxygen were associated with lower diversity. Lower surface water temperature and higher dissolved oxygen were associated with higher chlorophyll a concentrations. Overall, our findings suggest that interacting changes in pH, nutrient supply, temperature, salinity, and oxygen are associated with a simpler phytoplankton community structure, smaller mean cell size, and higher biomass levels in the Yellow Sea coastal region, with potential consequences for local food webs and carbon cycling.

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Effects of ocean acidification on the growth, shell integrity, and vulnerability to thermal stress and predation in Pacific oysters (Magallana gigas), and bay mussels (Mytilus spp.)

Published 17 April 2026 Science Leave a Comment
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The ocean is absorbing approximately one third of the anthropogenic carbon dioxide (CO₂) emissions to the atmosphere. As a result, the pH of the ocean is declining steadily, a phenomenon known as ocean acidification (OA). This decline in pH and the associated reductions in calcium carbonate saturation states of the water can have widespread consequences for marine life, particularly to calcifying organisms. In this thesis, I aim to understand the effects of OA on the growth, shell integrity, and susceptibility to secondary stressors like heatwaves or predation, of two important shellfish species in British Columbia, Pacific oysters (Magallana gigas) and bay mussels (Mytilus spp.). I also aim to identify potential tipping points beyond which the biological responses of these shellfish to OA rapidly become more pronounced. I reared oysters and mussels in experimental mesocosms, in four pCO₂ treatments for eight-weeks to determine growth. I subsequently exposed these OA-acclimated animals to a secondary stressor by simulating heatwave conditions to assess thermal tolerance, and by introducing a predatory sea star to assess vulnerability to predation. Finally, shell condition was visually assessed, and shells were mechanically crushed to determine integrity. I found that OA decreased the growth of both oysters and mussels. No tipping point was observed for oyster growth, but reduced growth only emerged at the highest levels of OA in mussels. Sensitivity to atmospheric warming was not increased after exposure to acidic conditions for either species, although oysters had a considerably higher thermal tolerance than mussels. Mussel vulnerability to predation did increase, although the relationship was complex and depended on predator size. OA negatively affected shell strength, and possible tipping points emerged for this response metric in both species. Overall, OA was shown to negatively affect both species, but patterns of effect and the presence of potential tipping points depended on the species and the response metric. Understanding how these ecologically and commercially important bivalves are responding to OA is important for understanding how changing ocean chemistry will affect marine ecosystems, and to inform aquaculture managers on mitigation strategies.

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Synergistic effects of ocean acidification and thermal stress on shell biomineralization and parasitism in the white clam Leukoma asperrima (Bivalvia: Veneridae)

Published 17 April 2026 Science Leave a Comment
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Ocean acidification (OA) and global warming are fundamentally altering the biomineralization processes of calcifying marine organisms. This study evaluates shell malformations and parasitism in the white clam Leukoma asperrima at Bique Beach, Panama, from December 2024 to November 2025. Environmental parameters (pH, temperature) were monitored monthly across two sampling stations (n=1100). Results indicate that 13.6% of the population exhibited shell malformations, and 6.3% were parasitized by the pea crab Pinnotheres pisum. A strong positive correlation was found between pH and healthy individuals (r=0.97, p<0.001), whereas critical pH levels (min. 5.75) were associated with increased shell fragility and dissolution. Despite thermal tolerance observed up to 35.7°C, the synergistic effect of OA and local stressors compromises the structural integrity of L. asperrima, threatening the sustainability of this socio-economic resource in the Tropical Eastern Pacific.

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Webinar: “communicating ocean acidification in a changing world”

Published 17 April 2026 Events Leave a Comment

Webinar: “Communicating Ocean Acidification in a Changing World”

📅 Wednesday April 22, 2026 |  🕐 12:00pm- 1:30pm EST | 📍Online Event

Register here

For more than a decade, scientists and NGO partners have tried to communicate the basics of ocean acidification. What is it? What is it caused by? Why should we care? What should we do? 

Join the discussion around the evolving landscape of communicating climate change and ocean acidification in a rapidly changing world and media environment. Presentations and panelists will discuss:

  • How ocean acidification has been communicated or covered in the press.
  • Challenges that we need to overcome as a community to inspire more action against climate and ocean change.
  • Recommendations to improve our communications about ocean acidification impacts and response.
  • New roles for creative mediums in storytelling about climate and ocean change.

The panelists joining us have been key players on the new Creative Communications programme and approach the OA Alliance has taken on. We will have with us:

Emily Knight, Director of Outreach & Engagement, Blue Convergence Fund

Laura Secorun, Managing Director, Meridian Consulting

Mónika Naranjo-Shepherd, Director, Luma Storytelling

Akira Biondo, Director of Operations, PangeaSeed

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Register now: life on the extremes: why ocean acidification hits differently on the coasts

Published 16 April 2026 Events Leave a Comment
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Tuesday, May 19, 2026 – 7:00pm – 8:30pm

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Event Details

The ocean and other water bodies absorb nearly a third of human-emitted carbon dioxide (CO2). However, once dissolved, CO2 lowers the water’s pH, and makes it more acidic—a phenomenon known as ocean acidification. In coastal waters like Chesapeake Bay, acidification plays out differently than in the open ocean. In this talk, SERC ecologist Whitman Miller will explore the surprising role marine biota play in coastal acidification. He’ll also reveal how emerging technology and automated measurements are painting a new, more dynamic picture of coastal water bodies, where chemistry can shift drastically between day and night, between tides and between seasons—and what these shifts mean for life in coastal waters more broadly.

This event is part of the Smithsonian Environmental Research Center (SERC)’s free evening science talks, and it will be recorded! Closed captions will be available during the live stream and on the recording. By signing up on Zoom, you’ll be able to watch live and receive a link to the recording a few days after the live stream. SERC seeks to showcase a wide variety of topics and perspectives for its evening science talks. Views expressed during these talks belong to the individual speakers and not the Smithsonian.

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HELCOM strategic approach to ocean acidification

Published 16 April 2026 Newsletters and reports Leave a Comment
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Acidification of the global oceans is a major trend. In the past, a well-documented trend of increasing alkalinity has partly counter acted drivers of acidification in the Baltic Sea. However, decrease in pH has been observed in areas of intense respiration of organic matter and hypoxia. General long-term projection indicates intensified acidification of the Baltic Sea.

There is uncertainty in how ocean acidification may impact the Baltic Sea ecosystem in the future. Developing a shared view of the current evidence base would be a first step in HELCOM. This could inform future work on adapting policies or developing new measures. In order to understand ocean acidification of the Baltic Sea, there is a need to better understand the carbon-cycle. Monitoring and measurements of carbon parameters are central to the assessment of eutrophication, a topic which has been a focus area of HELCOM for decades. Alkalinity of the Baltic Sea waters is a key element to be addressed and is a focus area for this strategic approach. There could be differences in alkalinity between surface- and deep-waters that would need to be better understood, and there are knowledge gaps in how the Baltic Sea functions in terms of alkalinity sources and sinks.

The HELCOM Baltic Sea Action Plan 2021 sets the scene for this HELCOM strategic approach to ocean acidification; “Although acidification is currently not a major trend in the Baltic Sea ecosystem, it is an advancing and significant trend in the world’s oceans, directly connected to carbon dioxide emissions. The long-term forecast for the Baltic Sea also projects an increased acidification, but neither the carbon chemistry of the Baltic Sea nor possible impacts of acidification on biota are fully understood yet, and mitigation measures have not been considered so far. “

The role of HELCOM is to facilitate a science-policy dialogue on how ocean acidification affects the Baltic Sea ecosystem and related services, and to explore options for adaptation to this pressure and encourage actions to reduce CO2 emissions by taking action on climate change.

HELCOM also has a role in coordinating environmental monitoring in the Baltic Sea. An overarching aim of this strategic approach is to develop a future monitoring programme that is optimised on the regional scale in terms of spatial and temporal scope.

This strategic approach describes how HELCOM will use its existing structures to assess and address the emerging pressure of ocean acidification. HELCOM will collaborate with other organisations and institutions to create an evidence base to inform policy actions and measures. HELCOM will coordinate work between its subsidiary bodies to ensure best available scientific knowledge is used to create a coherent response to ocean acidification.

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Quantifying the role of land-based inputs on coastal ocean acidification from a tropical semi-arid region

Published 15 April 2026 Science Leave a Comment
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The land-based inputs in the form of river discharge, wastewater runoff, and submarine groundwater discharge (SGD) are among the major land-based natural pathways for the Coastal Ocean Acidification (COA). This study evaluates the direct influence of these land-based drivers, along with the aerosol deposition, and in-situ biogeochemical processes on COA along a highly populated tropical coastal area. The results suggest that spatially, aerosol deposition and in-situ biogeochemical processes in Kutch region are the major (72%) contributors to COA. In contrast, cumulative land runoff significantly (70%) contributes to COA in South Gujarat. Among these drivers, river water mixing causes the most significant pH decrease (0.093), while wastewater input results in the minimum pH drop (0.016) along the Gujarat coast. The seasonal nature of river water discharge, compared to continuous seepage of both fresh and recirculated (saline) SGD, highlights the role of SGD in COA. These findings align with the global studies represented SGD as one of the prominent land-based drivers for COA. Additionally, the low annual average pH (~ 7.954) along the Gujarat coast is attributed to the region’s macrotidal characteristics, which facilitate the release of sediment bound CO2, leading to a reduction in pH levels. The findings from the current study emphasis the need for comprehensive data collection on physicochemical and biogeochemical parameters to accurately assess COA dynamics and quantification of spatial and seasonal impacts of each driver along the India’s west coast.

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Future projections of compound events around the Main Hawaiian Islands

Published 15 April 2026 Science Leave a Comment
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The consequences of overlapping environmental stressors — referred to as compound events — may be more harmful to marine ecosystems than as individual stressors. Using recently conducted submesoscale-permitting future projections for the Main Hawaiian Islands, we present the first assessment of future compound events for Hawaiian waters. Our analysis focuses on surface and sub-surface heat-stress, ocean acidification, and low-oxygen events and is based on three different greenhouse gas emission scenarios. We show that a large fraction of ocean around Hawai‘i will be subject to compound events in the near future. However, the projected event characteristics such as duration and intensity vary substantially across the region suggesting that potential ecosystem impacts may differ over short distances. Our results reveal that these spatial differences are mainly driven by considerably different magnitudes of natural variability in ocean physics and chemistry across the domain driven by mesoscale processes, while anthropogenic trends exhibit only minor spatial differences. Our analysis demonstrates that small-scale tidal variability can significantly mitigate compound events in near-shore regions including some designated Marine Protected Areas. Overall, our findings highlight the need for high-resolution numerical models as well as for an extended observation network for robust future projections of local extreme events.

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NOAA PMEL scientists provide analysis and expertise for 2026 California Coast and Ocean Assessment report

Published 14 April 2026 Web sites and blogs Closed
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California’s 2026 Coast and Ocean Assessment was released in March by the California Ocean Protection Council (OPC), in partnership with the California Ocean Science Trust. This coast and ocean assessment is the result of the work of more than 120 scientific experts from academic institutions, state and federal agencies including NOAA, NGOs, and Tribes.

The report features the OA (ocean acidification) indicators analysis from NOAA PMEL Carbon Program scientists Adrienne Sutton and Simone Alin (starting on page 85). NOAA OAP (Ocean Acidification Program) funded coastal time-series moorings provided the foundation for the annual “trend” analysis and indicator development, led by Adrienne Sutton. Simone Alin, a long-time co-lead of WCOA cruises, served as West Coast OA subject matter expert.

NOAA teams were key to the development of the assessment report. OAP provided long-term coastal monitoring and data management, with significant partnership and synergy from the Global Ocean Monitoring and Observing (GOMO) Program-funded observation and data analysis efforts throughout the global ocean. Pacific Marine Environmental Laboratory (PMEL) supports lead researchers/primary investigators to engage with diverse coastal ocean interest holders, including fishery and water quality managers like the consortium of West Coast managers who requested the assessments in this report.

The 2026 report was initiated three years ago to codevelop ocean health indicators that could be used by the multiple California State agencies, non-governmental organizations, and tribal groups. These indicators provide the state with unified, comparable status and trend information, enabling better cross-organization collaboration.

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Effects of pH on phytoplankton growth and diversity in a tropical coastal ay: an experimental study

Published 14 April 2026 Science Closed
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This research was intended to investigate the effects of reduced pH on the growth rates and diversity of phytoplankton in the coastal waters of Visakhapatnam in the Bay of Bengal. A short-term (six days) microcosm experiment was conducted with different pH conditions such as ambient (control-in situ pH), pH 8.0 (0.2 pH units drop from in situ pH) and pH 7.8 (0.4 pH units drop from in situ pH) corresponding to low, medium, and high future pH decline scenarios, respectively, to study the direct acidification impact on phytoplankton. The results revealed that the phytoplankton communities exhibit a wide range of responses including changes in growth rate during incubation. From the two treatments, a more pronounced response was observed in pH 7.8 conditions compared to the present pH scenario. Some phytoplankton communities exhibited positive growth responses to acidification, while others showed negative reactions in terms of biodiversity. Notably, Pseudo-nitzschia sp. became dominant during acidification, whereas larger centric diatoms such as Skeletonema spp., Chaetoceros spp., Rhizosolenia sp., Dactyliosolen fragilissimus, and Ditylum brightwellii showed no significant growth response to upcoming acidified conditions. This indicates a diverse array of physiological tolerance among the plankton species to environmental shifts. This study recommends further research to explore the impact of ocean acidification on other planktonic species in the coastal waters of Bay of Bengal.

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