Application open: OA-ICC Basic Training Course on Ocean Acidification in Kingston, Jamaica

Published 19 December 2025 Courses and training , Science Closed

Dates: 16-20 March 2026

Location: Kingston, Jamaica

Deadline for receipt of application from the nominating national authority: 30 January 2026

The IAEA Ocean Acidification International Coordination Centre (OA-ICC) is holding a regional Basic Training Course on Ocean Acidification in Kingston, Jamaica from 16-20 March 2026.

Applications are open to anyone from Antigua and Barbuda, Bahamas, Barbados, Belize, Cuba, Dominica, Dominican Republic, Grenada, Guyana, Haiti, Jamaica, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Suriname, and Trinidad and Tobago.

In order 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.

This course was previously scheduled for 2025. Please note that if you previously applied to the course, your application is still being considered.

Read below for full course details:

Introduction

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

Caribbean Small Island Developing States (SIDS) are particularly vulnerable to ocean acidification due to their reliance on the ocean for food, income, and recreation. This Basic Training Course on Ocean Acidification will provide scientists from Caribbean SIDS with foundational knowledge on conducting ocean acidification monitoring and designing purposeful experiments to understand the impacts of ocean acidification on key marine organisms in the Caribbean region. By the end of the course, participants will have a better understanding of the challenges and complexities presented by ocean acidification and the critical role we all play in addressing this issue and developing solutions.

Objectives

The course aims to empower Caribbean SIDS to monitor ocean acidification and its effects on key marine species, informing both SDG 14.3 and Target 8 of the Global Biodiversity Framework, and to explore local solutions to increase the resilience to ocean acidification in the region. It will cover various topics, including theoretical aspects and best practices for the measurement of seawater carbonate chemistry, how to evaluate the impacts of ocean acidification on marine species and ecosystems, and potential solutions for minimizing its effects, including possible local adaptation measures. Guidance on how to report towards Sustainable Development Goal 14.3 and its indicator 14.3.1 on ocean acidification will be provided.

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Acidification and plastic pollution threaten Bangladesh’s blue economy

Published 2 January 2026 Media coverage Leave a Comment
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The Bay of Bengal has long been the engine of Bangladesh’s blue economy—a vast, resource-rich frontier that sustains millions of people and generates vital export earnings.

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Bangladesh’s total marine fish harvest fell to 628,622 tonnes in FY 2023–24, the lowest in nine years (Department of Fisheries – Annual Report 2024). Deep-sea trawler catches declined by 21% year-on-year (FAO), while catch per artisanal boat has dropped nearly 70% over the past two decades—from 13 tonnes in 2000 to barely 4 tonnes in 2020 (World Bank Fisheries and Aquaculture Review).

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Overfishing and IUU (Illegal, Unreported, and Unregulated) fishing are well-known problems. But two largely untold reasons lie behind this steady deterioration: acidification and plastic pollution—silent yet powerful forces that destabilise the marine ecosystem.

Acidification: An invisible enemy beneath the waves

The ocean has long served as Earth’s greatest climate regulator, absorbing nearly one-third of all carbon dioxide (CO₂) emitted by human activities (IPCC, 2023). While this process helps slow global warming on land, it comes at a devastating cost beneath the surface.

When CO₂ dissolves in seawater, it forms carbonic acid, lowering the ocean’s pH and disrupting marine chemistry.

In the early 1980s, Bay of Bengal surface waters averaged a pH of 8.3 (Indian Ocean Research Consortium). Today, coastal and estuarine zones measure between 7.9 and 8.0, with some readings as low as 7.73 (UNEP South Asia Marine Assessment). This 0.2–0.3 drop in pH represents nearly a 30% increase in ocean acidity over five decades (NOAA; IPCC).

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Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH

Published 2 January 2026 Science Leave a Comment
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Cirolanid isopods play important ecological roles as predators and scavengers, but when populations increase, they can form swarms that attack fish and humans. Understanding how the reproduction of cirolanid isopods will be affected by future warmer and more acidic oceans is therefore important. Samples of the viviparous species Cirolana harfordi were held in 4 combinations of 2 temperatures (18 and 24°C) and 2 pH levels (7.7 and 8.1), and the development of embryos and mancas was investigated by microscopic examination of each pregnant female through the transparent ventral cuticle of their thorax. Higher temperature increased the rate of development, thereby reducing pregnancy duration and accelerating the growth of mancas postpartum. By contrast, increased acidity had no significant effect on these parameters and had no deleterious effects on the development of the mancas. Higher temperature did not have a significant effect on the number of postpartum mancas after the 22 weeks that the adults spent in treatments. Increased temperature and/or lowered pH had no effect on the adult survival or growth. These data are in keeping with the hypothesis that C. harfordi may be able to withstand future warmer and more acidic oceans. Longer-term studies are needed to determine whether decreasing pregnancy durations in higher temperatures increases the number of times females can become pregnant over their lifetime, potentially leading to greater population numbers.

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How rising ocean acidity is changing India’s coasts and fisheries

Published 1 January 2026 Press releases Leave a Comment
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The ocean has always seemed immeasurably vast and unchanging, a realm so deep and ancient that human activity could hardly make a dent in its rhythms. Scientists now warn that this assumption is outdated. While it might be calming to stand on a beach and watch the waves roll in, little do we realise that a quiet change is taking place within the familiar-looking ocean. The water is slowly turning more acidic, almost like a few extra drops of lemon in a glass of water. We cannot see it, but marine life feels it every day. For a country like India, where millions depend on the sea for food and income, this invisible change carries real consequences.

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A new scientific review from researchers at Amrita Vishwa Vidyapeetham shows ocean acidification may be just as disruptive, and in some regions even more immediate, than rising temperatures or sea level rise. Its consequences could reverberate for centuries.

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Why India cannot afford to ignore ocean acidification

India has one of the longest coastlines in Asia, and millions of people depend on the sea for income. Almost seventy percent of fishing households live near or below the poverty line, making adaptation difficult.

India’s four major coral reef systems already face temperature-related bleaching. Acidification slows coral growth and weakens reef structures, affecting shore protection, fish nurseries, and tourism.

India also has a large aquaculture sector that relies on species sensitive to pH and carbonate levels. Molluscs, crustaceans, and some finfish can face growth and survival challenges in more acidic waters. Yet India’s research output on OA remains low and scattered. Most studies focus on coral bleaching or warming. There is no national OA monitoring network, and only a few long-term coastal observations exist.

The review notes that India contributes only a fraction of global OA literature and lacks coordinated national monitoring. With 67.3 percent of India’s fishing households living at or below the poverty line, disruption to marine resources could undermine livelihoods, nutrition, and coastal stability. Without long-term pH and carbonate chemistry data, policymakers lack the scientific foundation needed to anticipate risks or design adaptation measures.

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Assessing the influence of ocean acidification on the deterioration of coral reefs in Sri Lanka

Published 1 January 2026 Science Leave a Comment
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Rising atmospheric CO2 levels have significantly increased ocean acidification (OA), endangering coral reefs, and nutrient (nitrate (NO3−), and phosphate (PO43−)) pollution also weakens the coral reef resilience. Therefore, the study evaluates the prevailing OA level over the Sri Lankan coral reef areas using the aragonite saturation state (ΩAr) and assesses the nitrate (NO3−), and phosphate (PO43−) concentrations over the coral sites. The study was conducted on coral reefs on the eastern coast (EC), southern coast (SC), northern coast (NC), and west coast (WC) of Sri Lanka from April to June 2024. A total of 63 seawater samples were collected around each coastal site for analysis. The Ω Ar were supersaturated (ΩAr> 1) and ranged from 2.98±0.04 to 4.92±0.12. Throughout the study period, the study sites had ΩAr values exceeding 2.92±0.16, indicating that the nation’s corals were resilient to deterioration, and the comparative analysis demonstrates that these sites were not vulnerable to OA. The NO3− concentrations of 2–5 µmol L− 1, from human activities, may intensify coral bleaching during heat stress. Results showed that SC (2.19±1.28 µmol L− 1) and WC (3.52±1.48 µmol L− 1) had NO3− above the permissible range, which may be due to waste discharge and high runoff. The significantly higher PO43− concentrations were reported in EC (0.35±0.07 µmol L− 1). Coral bleaching hotspot (HS) identification emphasizes how spatially distributed HS are from January to June. The OA risk assessment confirmed that climate change brought high risk to the coral reef ecosystems, which impact on the ecology and economy of Sri Lanka.

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Yemen fisheries and climate change

Published 31 December 2025 Newsletters and reports Leave a Comment
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Yemen’s extensive coastline, encompassing the southern Red Sea, Gulf of Aden, and northwest Arabian Sea, is home to rich marine biodiversity and historically productive fisheries, crucial for the nation’s economy, food security, and livelihoods (Figure 1). However, the intersection of global climate change and a prolonged internal conflict has significantly disrupted marine ecosystems and fisheries management, exacerbating already critical challenges.

This report addresses these pressing issues through two interconnected analyses. The first examines recent climate-driven changes in marine ecosystem health indicators, providing insights into seasonal variability, long-term trends, and impacts from extreme climate events such as Cyclone Tej in 2023. The second analysis investigates the status of Yemen’s fisheries, highlighting historical trends, the impacts of conflict, and gaps in current monitoring and management practices.

Leveraging innovative methodologies, satellite remote sensing, computer vision, and collaborative in situ data collection, the report aims to present a cohesive framework for revitalizing Yemen’s marine research and fisheries management. Ultimately, the findings underscore the urgency of implementing targeted, adaptive, and evidence-based policies to sustain Yemen’s coastal ecosystems and the livelihoods dependent upon them.

The report is structured as follows: Section 1 presents analysis of seasonal variability, climate shocks and extreme events along with longer-term temporal trends on temperature, oceanic biomass and productivity, salinity and ocean acidification in Yemen’s coastal waters; Section 2 presents analysis of the fisheries sector, notably identifying the existing data gaps and the absence of reliable monitoring as a result of the ongoing unrest; based on these analyses, Section 3 proposes a framework for the creation of a dynamic fisheries monitoring and management model; and Section 4 concludes with policy recommendations.

While this study does not include formal projections, observed decadal trends across Yemen’s marine regions allow for indicative interpretation of the likely direction of change in key ecosystem indicators. The table below summarizes historical trajectories (2004 – 2024) of these variables, which may inform expectations of future biological productivity if current drivers persist.

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The role of heterotrophy in the response of Oculina arbuscula to ocean acidification

Published 31 December 2025 Science Leave a Comment
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On both tropical and temperate reefs, the calcium carbonate skeletons produced by scleractinian corals provide habitat that supports a high biodiversity of fishes and invertebrates. Ocean acidification (OA), driven by excess anthropogenic CO2 uptake, causes declines in seawater pH and carbonate ion concentration and can compromise coral calcification by causing increased energetic demands. Deciphering how corals meet this increased energetic demand is critical to predicting their future persistence. Oculina arbuscula is a facultatively symbiotic temperate coral common on subtropical reefs of the South Atlantic Bight. This coral has demonstrated calcification resilience to reduced pH conditions in both symbiotic and aposymbiotic forms, despite aposymbiotic colonies lacking access to photosynthetically-derived energy. I hypothesized that energy acquired through heterotrophy is a mechanism by which O. arbuscula obtains the resources necessary to overcome the heightened energy demand created by ocean acidification. To investigate the role of heterotrophy, a 90-day laboratory experiment was conducted exposing aposymbiotic O. arbuscula fragments to a pH of either 7.7 or 8.0 under three different feeding levels of Artemia spp. nauplii. Although fragments with greater food consumption showed significantly higher calcification rates, this effect was independent of pH. Similarly, biochemical analyses indicated that total protein and total carbohydrate stores increased with higher food consumption but were unaffected by pH exposure. In contrast, total lipid stores decreased during the experiment, regardless of pH exposure or food level, suggesting the heterotrophic contribution to lipid stores was deficient. Together, these results indicate that while heterotrophically-derived energy may not be a primary mechanism underlying the ability of O. arbuscula to sustain calcification rates under OA stress, this coral species should continue to thrive in an increasingly acidifying ocean as long as heterotrophic food resources are in abundance.

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Assessing the impact of riverine water on the Northwest Pacific using normalized total alkalinity

Published 30 December 2025 Science Leave a Comment
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The impact of riverine water was assessed using salinity-normalized Total Alkalinity observations of the Northwest Pacific, including the coastal areas of Japan (20–50° N, 120–160° E). The observational data included surface carbonate parameters obtained from decades of surveys conducted by volunteer cargo ships and research vessels in this area. This study uses data and statistical methods (e.g., re-gridding and Fourier regression) like those in a previous study that analysed air-sea CO2 flux but focuses instead on the diffusion of normalized Total Alkalinity from land. First, the seawater area affected by riverine water was identified using an Empirical Orthogonal Function analysis of normalized Total Alkalinity. The differences in normalized Total Alkalinity and Dissolved Inorganic Carbon from the surrounding area were then analysed to evaluate the potential drivers, such as riverine water supply, advection effects, and biological activities. In addition, the impact of riverine water on oceanic CO2 uptake and acidification in the study area was assessed. The analysis showed that riverine water was the main cause of the higher total Alkalinity compared to the surrounding area, whereas its contribution to the increase in Dissolved Inorganic Carbon was relatively minor. The supply of riverine water had little effect on oceanic CO2 uptake throughout the year. The supply of riverine water had a minor effect on pH but contributed to coastal acidification, as indicated by a decrease in the calcification index (Ωarg, the aragonite saturation state) by 0.09±0.01 over the past 20 years, even after accounting for the buffering effect of riverine Total Alkalinity, which reduced the overall decrease by approximately 71 %. The results of this study are expected to be further improved by enhancing observations, such as the vertical profiles of carbonate parameters, and are expected to expand to other sea areas and be applied to global budgets.

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Shell proteome plasticity assists oyster larval biomineralization in adverse carbonate chemistry

Published 30 December 2025 Science Leave a Comment
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Bivalve planktonic development is a critical phase during which larvae must secrete the first calcium carbonate shell, the prodissoconch I (PD I). As PD I formation is in close contact with seawater, this process can be negatively affected by adverse seawater carbonate chemistry. It is hypothesized that bivalves can regulate shell formation under environmental stress through biologically controlled biomineralization involving a complex extracellular shell proteome. However, the plasticity of this regulatory mechanism during PD I development is unknown. We assessed the PD I shell proteome of the Hong Kong oyster (Magallana hongkongensis) in carbonate chemistry that was adverse or favorable for biomineralization to understand the regulatory capacity of larval shell formation. While survival rates were not affected in adverse carbonate chemistry, there were significant changes, including the upregulation of several calcium-binding proteins and downregulation of proton-generating processes and putative calcification inhibitors. With 198 sequences, the oyster larval shell proteome was twice to over six times larger than those reported for other bivalve species at the same developmental stage. However, in adverse carbonate chemistry, the oyster larval shells were thinner and smaller, and protein diversity decreased to 131 sequences, with overall lower functional redundancy and reduced expression of structural proteins, indicating potential trade-offs. The proteomic and shell structural data also suggest that direct cellular control and biologically induced mechanisms, which will require further investigation, may be involved in PD I formation.

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Ventilation and buffering capacity effects on ocean acidification in low oxygen environments

Published 30 December 2025 Science Leave a Comment
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Ocean acidification results from oceanic uptake of anthropogenic CO2 (ΔCant). Weak carbonate buffering capacity (high Revelle factor, RF) amplifies acidification, but its role in persistently low-oxygen, poorly ventilated regions is unclear. Here we compare preindustrial to present changes in partial pressure of CO2 (pCO2), hydrogen ion concentration ([H+]), pH, aragonite saturation state (Ωara), and RF within permanent oxygen minimum zones (OMZs) versus well-ventilated regions. We find that acidification is negligible in the least-ventilated, poorly buffered lower OMZs, but detectable in moderately ventilated upper OMZs. In upper OMZs, pCO2 and [H+] increase faster while Ωara, pH, and RF change more slowly than in adjacent well-ventilated regions. Our analysis reveals that limited ΔCant delivery by ventilation ultimately constrain acidification in low-oxygen regions. Accordingly, low-oxygen regions with poor ventilation will experience less acidification than well-ventilated regions, and different metrics (notably [H+] versus Ωara) respond distinctly due to their different definitions and sensitivities.

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Hydrogeochemistry of submarine groundwater discharge along a Bruneian coastline: iron and aluminum enrichment along with coastal acidification

Published 30 December 2025 Science Leave a Comment
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Submarine groundwater discharge (SGD) and its influence on coastal acidification and trace-metal enrichment have not been studied in Borneo. This study characterizes SGD from northwest Borneo into the South China Sea, focusing on iron (Fe) and aluminum (Al) inputs, hydrogeochemical controls on their mobility, and SGD’s role in coastal acidification. Samples were collected along transects at Tungku and Empire beaches, spanning the peritidal to subtidal zones, as well as from streams, pools, and beach sand. SGD contained elevated Fe and Al (Tungku: 4.07 mg/L Fe, 1.31 mg/L Al; Empire: 2.12 mg/L Fe, 0.38 mg/L Al), identifying these as key SGD-derived trace metals. pH was near-neutral in many samples (minimum 6.6), rising from 7.72 (Tungku) and 7.48 (Empire) in SGD to 8.11 and 8.01 in adjacent seawater, creating steep pH gradients favoring Al and Fe precipitation. Acid sulfate soils and high dissolved organic matter enhance groundwater acidity and trace-metal mobility. Major-ion chemistry indicates dominance of non-carbonate alkalis (SO₄²⁻ + Cl⁻ >CO₃²⁻ + HCO₃⁻; Na⁺ + K⁺ >Ca²⁺ + Mg²⁺) and low phosphate and nitrate, with mixed freshwater–saline contributions. The combination of low pH, elevated Fe and Al, and anthropogenic disturbance may degrade coastal and groundwater quality, affecting marine biogeochemical cycles, biodiversity, and ecosystem functioning. Overall, SGDs in Brunei deliver acidic, Fe- and Al-enriched water, contributing to coastal acidification and contamination, with implications for regional climate resilience.

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Aquaculture of seaweeds (Saccharina latissima, Ulva spp., Gracilaria spp.) significantly improves the growth of co-cultivated bivalves in mesotrophic, but not eutrophic, estuaries

Published 29 December 2025 Science Leave a Comment
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The co-cultivation of seaweeds with bivalve shellfish is a potential strategy for protecting bivalve crops against anthropogenic coastal acidification and hypoxia. We co-cultivated seaweeds and bivalves using a succession of seaweed species according to season (winter, Saccharina latissima → spring, Ulva spp. → summer, Gracilaria spp.) together with eastern oysters (Crassostrea virginica) and blue mussels (Mytilus edulis). Bivalves and seaweeds were deployed in two estuaries that contrasted in trophic state, one mesotrophic and one eutrophic. In all five experiments in the mesotrophic system, cocultivation with seaweeds significantly increased weight- and/or shell-based growth of bivalves (p < 0.05). Growth rate increases for C. virginica were modest, with weight-based growth improving by 17–21% and shell-based growth improving by 3–27% with seaweed co-culture of all macroalgal species. For M. edulis, the effect was large; co-culture with S. latissima caused 47% and 114% increases in shell- and weight-based growth rates, respectively. In the four experiments in the eutrophic estuary, co-culture with seaweeds did not significantly improve bivalve growth. Seaweed cultivation significantly improved water quality metrics (increased pH and dissolved oxygen (DO); p < 0.05 in all cases) in and around the seaweed sites at both locations, although increases in pH and DO were modest, and even in control treatments, there were no prolonged periods of harmful pH or DO levels. An abundance of macroalgal detritus may have bolstered the diets of co-cultivated bivalves in the mesotrophic estuary, a hypothesis supported by lower chlorophyll a concentration, and therefore lower planktonic food levels, at that site. Given that seaweeds display species-specific allelopathic effects against phytoplankton, it is also possible that the presence of seaweeds altered the phytoplankton community to the benefit of the bivalves. Regardless, the findings here demonstrate that co-cultivation with seaweeds can accelerate the growth of bivalves.

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Ecological stability of late Maastrichtian benthic foraminifera amidst Deccan volcanism

Published 29 December 2025 Science Leave a Comment
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Highlights

  • Benthic foraminifera assemblage at Bidart reveal a stable, mesotrophic late Maastrichtian seafloor.
  • K/Pg boundary at Bidart shows signs of ecological stress and taphonomic dissolution.
  • Deccan-induced calcification stress was restricted to surface ocean and had minimal impact on benthic foraminifera.
  • Robust test ratio and fragmentation index together serve as effective taphonomic proxies.

Abstract

The late Maastrichtian witnessed profound disruptions in biogeochemical cycles, leading to the fifth mass extinction at the Cretaceous–Paleogene (K/Pg) boundary. At Bidart section (France), the final ∼60 kyr of the Maastrichtian coincide with mercury (Hg) peaks, low magnetic susceptibility, evidence of biological stress and taphonomic alteration in planktic foraminifera, indicative of an ocean acidification event. While this event primarily appears to be a surface-ocean phenomenon, previous studies also documented a minor rise in benthic foraminiferal test fragmentation beginning 0.5 m below the K/Pg boundary, with a pronounced spike at the boundary itself.

A detailed investigation of benthic foraminifera in biozone CF1 at Bidart section (France) reveals a diverse and balanced assemblage preceding the K/Pg boundary, with minimal taphonomic alterations. At the K/Pg boundary, infaunal populations diminished, diversity declined sharply, test fragmentation intensified, yet paradoxically, the absolute abundance of genera rose markedly. Preferential preservation is evident in the dominance of robust taxa (Cibicidoides spp., Coryphostoma spp.), while a high fragmentation index reflects strong taphonomic dissolution and time-averaging. A plausible explanation for this could be CO2-rich waters mixing into the ocean interior over 100–1,000 years, driving dissolution during the ∼10,000-year deposition of the K/Pg boundary red clay. The stark contrast between the planktic and benthic census and morphometric data at Bidart section clearly constrains any Deccan-related calcification stress to the surface mixed layer. Lastly, the integrated planktic and benthic considerations re-emphasize a need to carefully separate taphonomic signals from true ecological stress.

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An autonomous pH sensor for real-time high-frequency monitoring of ocean acidification in estuarine and coastal areas

Published 26 December 2025 Science Leave a Comment
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In situ pH sensing is crucial for the real-time monitoring of ocean acidification and investigations into the marine carbon cycle. Although ion sensitive field-effect transistor (ISFET) has been proven suitable for marine pH monitoring, its supply and implementation remain challenging. An underwater pH sensor for environmental analysis (uSEA-pH) based on ISFET was developed herein, incorporating a modified commercial laboratory pH probe through engineering design. Laboratory characterization demonstrated that uSEA-pH exhibited a Nernstian response (slope −57.60 ± 1.05 mV/pH, R2 > 0.999), rapid response time (∼7 s), and low measurement uncertainty (<0.01 pH). The sensor supports a sampling frequency of 1 Hz with an average power consumption of only 0.72 W. Its compact design (self-contained with battery: Φ15 × 45 cm; miniaturized version: Φ6.4 × 21 cm) facilitates deployment on various observational platforms. During high-frequency underway monitoring in the Pearl River Estuary and Dongshan Bay, uSEA-pH successfully detected subtle pH variations (<0.05 pH). In extended in situ deployments, buoy-mounted uSEA-pH reliably recorded tidal-driven pH fluctuations in Dapeng Bay (27 days) and Xiamen Bay (7 days), generating over 2.3 million field measurements. This study presents a viable, robust, and high-resolution approach for continuous pH monitoring in estuarine and coastal areas.

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Compound hypoxia with heat or acidification stress induces synergistic and additive effects on coral physiology

Published 26 December 2025 Science Leave a Comment
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As climate change accelerates, coastal marine ecosystems are increasingly exposed to co-occurring stressors whose combined effects are nonlinear and difficult to predict. Deoxygenation is a rapidly intensifying yet underrecognized threat to coral reefs that interacts with heat and acidification to alter coral physiology and stress resilience. However, the effects of hypoxia-related compound events on corals are largely unknown, underscoring the need for multi-stressor studies. Here, we conducted two extended-exposure experiments (12–17 days) across the coral species Porites furcata, Porites astreoides and Siderastrea siderea, to disentangle the individual and combined effects of low dissolved oxygen (hypoxia) with either heat or acidification. We measured eight phenotypic traits related to growth, metabolism, and symbiosis health to test whether hypoxia imposes energetic constraints or other physiological stress that amplify the effects of heat or acidification. Standardized effect size analysis across 24 stressor–trait combinations revealed 13 additive, 10 synergistic, and only one antagonistic response. Hypoxia consistently suppressed dark respiration by 37–49% across species and altered photophysiology in the two Porites species, whereas acidification alone had minimal effects, particularly in S. siderea. Heat stress caused the most pronounced declines across nearly all traits, and when combined with hypoxia, it produced the highest number of synergistic interactions. In contrast, the combination of hypoxia and acidification largely resulted in additive responses, suggesting that independent physiological mechanisms underlie these effects. All corals showed strong metabolic depression under hypoxia which is likely beneficial as a short-term adaptive response but may impose energetic constraints in the long-term. These findings highlight deoxygenation as critical yet often overlooked drivers of coral reef vulnerability. More multi-stressor experiments across a range of species are urgently needed to improve predictions of reef resilience under future ocean conditions, where compound stress events are expected to become more frequent and severe.

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Short-term focus: phased response of Zostera marina seedlings to the combined stress of marine heatwave and ocean acidification

Published 25 December 2025 Science Leave a Comment
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Marine heat wave (MHW) and ocean acidification (OA) caused by global climate change occur frequently and intensify, which cause damage to the stability of seagrass bed. However, the understanding of the phased-impacts of sudden temperature and acidification changes on seagrass is limited. The study conducted phenomic, transcriptomic and metabolomic analyses to investigate the short-term response mechanisms of Zostera marina seedlings to sudden temperature and acidification incerease. The results showed that Z. marina seedlings activated an integrated metabolic response involving fatty acid metabolism, carbohydrate metabolism and amino acid metabolism to modulate cell membrane properties, enhance thermotolerance and maintain developmental stability. What is noteworthy is that the continuous high expression of the ABC transporters play a crucial role in resisting stress. The study is helpful to clarify the short-term phased response of Z. marina seedlings to the combination of MHW and OA, and have significant importance for the protection and restoration of seagrass beds.

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Charlie loves science: ocean acidification and our coastline (video)

Published 25 December 2025 Media coverage Leave a Comment

Ocean acidification, while not directly tied to climate change, is an issue that is becoming more problematic as the burning of fossil fuels pumps more carbon dioxide into the atmosphere. The carbon dioxide emitted into the atmosphere builds up and dissolves into the oceans, where it reacts with water to create carbonic acid.

Upwelling zones, water coming from the ocean floor to the surface, tends to be more acidic than the water in the mid to top levels of the ocean. Coastal ecosystems have adapted to tolerate the naturally low pH levels of the water. However, the addition of dissolved carbon dioxide at the surface is leading to a higher concentration of acidic water in coastal ecosystems, especially around strong upwelling zones. Ecosystems are not prepared to tolerate the speed of change and could suffer severe consequences if measures aren’t taken to reduce the amount of carbon dioxide in the atmosphere.

For more information on this study, you can find the full news release here.

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Tiny cup corals show accelerating ocean acidification in the Salish Sea (radio)

Published 24 December 2025 Media coverage Leave a Comment
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Ocean acidification is sometimes described as climate change’s evil twin. The ocean absorbs carbon dioxide from fossil fuel emissions, causing the water to become more corrosive.  

“Ocean acidification is already impacting the growth of oysters, clams, plankton, which in turn are important food sources for salmon, seabirds and other marine organisms,” said Mary Margaret Stoll, who just received her Ph.D. from the University of Washington and is the lead author on a new study of ocean acidification, published in the journal Nature Communications.

Stoll said her love of chemistry, physics and biology led to a fascination with ocean acidification. She joined a project that was looking broadly at how ocean acidification is unfolding in the Salish Sea, which borders British Columbia and Washington state. The wind and ocean currents here cause regular upwellings of carbon rich waters from the deep, influenced by the powerful California Current that causes similar conditions off that coast.

To better understand the region’s chemical trajectory, Stoll got to work with a set of artifacts that were collected 130 years ago: the skeletons of native orange cup corals. Naturalists aboard the USS Albatross — a tall ship on a mission to survey halibut for the federal government — had the foresight to keep them.

Stoll said she’s still amazed that this un-commissioned collection was available to her in the archives of the Smithsonian.

“These corals were incredibly well preserved, and there was so much information attached to them as well — about the depths of collection and where they were collected, and when they were collected, how they were cleaned and preserved,” Stoll said.

Stoll and her team painstakingly practiced their knife skills before slicing tiny samples from the 130-year-old specimens in their lab at the University of Washington. Then, they followed the path that the USS Albatross had sailed through the Salish Sea to get modern coral samples that matched those locations, depths and species.

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Differing proteome responses to ocean acidification between two common pocilloporid corals

Published 24 December 2025 Science Leave a Comment
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Ocean acidification threatens coral reef ecosystems by challenging calcification processes fundamental to reef accretion. Yet many corals continue to calcify under elevated pCO2, suggesting species-specific physiological plasticity and potential cellular compensations. Here, we use label-free quantitative proteomics to investigate proteomic responses of two common pocilloporid corals, Stylophora pistillata and Pocillopora damicornis, with known differential resistance to ocean acidification after two months at moderate (~ 940 ppm) and high (~ 2,800 ppm) pCO2 compared to the control (~ 480 ppm). S. pistillata exhibited extensive proteomic restructuring under high pCO2, marked by widespread declines of energy-generating pathways, yet selective increase of proteins involved in ion transport, cytoskeletal stability, and stress responses. This indicates a strategy of general metabolic suppression coupled with targeted investment into essential cellular functions, potentially sustaining calcification despite reduced overall metabolic capacity. In contrast, P. damicornis showed much less proteomic adjustment, primarily involving structural proteins and those potentially linked to cellular redox balance, signifying a moderate, targeted strategy for physiological stability. These divergent responses highlight contrasting modes of resistance (plasticity versus stability). Integrated with physiological data, our findings clarify cellular mechanisms controlling calcification, demonstrating the value of proteomics in coral ecophysiology and providing new insights into species-specific vulnerability under future ocean conditions.

Continue reading ‘Differing proteome responses to ocean acidification between two common pocilloporid corals’

Effects of long-term ocean acidification exposure on the structural, mineralogical, and mechanical properties of sea urchin (Echinometra spp.) skeletons at a natural volcanic CO2 seep

Published 23 December 2025 Science Leave a Comment
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Two decades of mesocosm studies document generally negative effects of ocean acidification (OA) on adult sea urchin growth, feeding performance, skeletal structure, and strength. Whether experimental observations hold true in natural systems will determine whether they can be extrapolated to predict responses under ecologically relevant contexts. Here, we employ a suite of imaging, chemical, and mechanical techniques to examine the skeletal properties of two closely related sea urchin species (genus Echinometra) living at a natural carbon dioxide (CO2) seep in Japan. Test plates and spines from urchins living under elevated CO2 conditions were thinner, more porous, and had less biomineral than those at reference sites; however, tooth structure was resilient to elevated CO2. The magnesium content of the test and spines did not differ between sites; however, they exhibited reduced nanohardness and became more brittle under elevated CO2. Together, altered structural and mechanical properties may compromise the protective function of urchin skeletons at the CO2 seep. These responses have implications for ecosystem structure if urchin function is suppressed at the population level. Future work might explore the repeatability of these findings across successive species and localities to recognize generality, its limits, and the conditions that mediate the influence of OA.

Continue reading ‘Effects of long-term ocean acidification exposure on the structural, mineralogical, and mechanical properties of sea urchin (Echinometra spp.) skeletons at a natural volcanic CO2 seep’

Interactive effects of ocean acidification and benthic biofilm composition on the early development of the European abalone Haliotis tuberculata

Published 23 December 2025 Science Leave a Comment
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Ocean acidification (OA) and associated shifts in carbonate chemistry represent major threats to marine organisms, particularly calcifiers. OA effects can be influenced by other environmental variables, including the biotic environment. This study investigated the individual and interactive effects of OA and algal density, acting through biofilm composition, on post-larval and juvenile abalone (Haliotis tuberculata). In a three-month factorial experiment, abalone were exposed from metamorphosis onward to two pH conditions (ambient 8.0 and reduced 7.7) and two initial densities of the green alga Ulvella lens on settlement plates. Biofilm biomass and composition were characterised using spectral reflectance and HPLC pigment analysis. Biological (density, length), physiological (respiration rate), behavioural (hiding response) and shell parameters (colour, surface corrosion, strength) of abalone were measured throughout the experiment. Biofilm biomass and composition remained relatively stable under both pH conditions, though greater variability in algal biomass occurred at low initial Ulvella density. Post-larval density and total length decreased significantly under low pH, while high Ulvella density reduced juvenile length at 80 days, likely due to competition between algal groups. A pH × Ulvella interaction affected shell fracture resistance and colouration, but not metabolism or behaviour, indicating that juvenile abalone maintained vital functions. Overall, the results confirm the sensitivity of early H. tuberculata stages to moderate OA (−0.3 pH units) and highlight indirect macroalgal effects through changes in diatom communities. In natural environments, the capacity of abalone to cope with future OA will depend on complex trade-offs between direct acidification effects and food-related biotic interactions.

Continue reading ‘Interactive effects of ocean acidification and benthic biofilm composition on the early development of the European abalone Haliotis tuberculata’

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