Oysters are found ubiquitously in estuaries along the Georgia coast, where marsh morphology and large daily tidal fluctuations create dynamic and stressful conditions to which oysters may be locally adapted. Based on water quality data from the Sapelo Island National Estuarine Research Reserve, it is evident that changing climatic conditions are rapidly causing shifts in water quality that may be adversely affecting oyster health, especially as ocean acidification alters the carbonate buffering capacity, increasing the amplitude of daily pH variations. Importantly, the rate of change of conditions are not uniform within estuaries, varying on spatial and temporal scales. The symbiotic relationship between oysters and their internal microbiome has been increasingly analyzed as a metric for oyster health. As filter feeders, oysters continuously introduce microorganisms into their hemolymph. Core families of bacteria, including Mycoplasmataceae, have been identified to be associated with healthy oysters. The abundance of core groups, or of pathogenic genera like Vibrio, can be used as an indicator of oyster condition. Utilizing reciprocal transplant and common garden tank designs, we examined how changing variability in localized water quality conditions drive oyster health using physical and microbial indicators, including oyster growth, condition index, and shifts in microbial community dynamics. Our results suggest that low pH conditions are detrimental to oyster physiology, inducing stress, leading to a reduction in overall health and growth. Low pH causes a shift within the microbial composition, altering community dynamics, and increasing the abundance of stress-related bacteria, including Arcobacteraceae and Vibrionaceae. Drivers of oyster health and host-associated microbial dynamics are site- and scale-dependent and will need further research to fully understand which biotic or abiotic factors are most influential in oyster conditions amidst low pH conditions. Oysters are increasingly used in nature-based restoration efforts to support reef recovery and salt marsh expansion, making it critical to understand how relocation influences oyster health. Our results indicate that oyster condition is driven by destination rather than origin, with relocation success dependent on water quality at the transplant site.
Continue reading ‘The influence of localized water quality on Eastern oysters (Crassostrea virginica) and their internal microbiome under changing environmental conditions’The influence of localized water quality on Eastern oysters (Crassostrea virginica) and their internal microbiome under changing environmental conditions
Published 5 May 2026 Science Leave a CommentTags: biological response, laboratory, mollusks, morphology, North Atlantic, physiology, prokaryotes
Evaluating the role of seaweed farming in ocean acidification mitigation: insights from high-frequency observations
Published 5 May 2026 Science Leave a CommentTags: algae, biological response, field, mitigation, North Atlantic, phytoplankton
The oceanic uptake of anthropogenic CO2 has resulted in ocean acidification (OA). Macroalgae farming has the potential to mitigate OA by removing CO2 from the surface water via photosynthesis. However, continuous in-situ observations of marine carbonate chemistry related to macroalgae farming remain limited, leaving its effectiveness in addressing OA uncertain. To address these knowledge gaps, this study examined a 2-acre Saccharina latissima, sugar kelp, farm located at Point Judith, Rhode Island, as a case study to assess the potential of sugar kelp aquaculture in mitigating local OA. Over the full growing season from December 2022 to May 2023, high-temporal-resolution (every 30–60 minutes) measurements of surface temperature, salinity, dissolved oxygen and pH were taken inside and outside the kelp farm. The results demonstrate that sugar kelp farming does not significantly impact the carbonate system, thus providing negligible OA mitigation locally. Specifically, a temporary, local-scale CO2 reduction and higher pH occurred during very early kelp growth in early February, but was reversed by a higher surface CO2, exaggerating OA, starting in mid-February. Over the entire observation period, kelp growth resulted in a 5.1 ± 11.6 μatm increase of pCO2 per week compared to the control site in the surface, a signal which is small compared to the substantial natural variability. However, the minimal pCO2 difference at the kelp farm may be reflective of the relatively small cultivation area (2 acres) or depressed growth of phytoplankton, resulting from nutrient competition between the kelp and in-situ phytoplankton. This study underscores the need for future sustained observations to evaluate the impact of seaweed cultivation on OA mitigation and the carbon cycle at the ecosystem scale.
Continue reading ‘Evaluating the role of seaweed farming in ocean acidification mitigation: insights from high-frequency observations’Combined effects of ammonium and pH on sea urchin embryogenesis: insights for sediment quality assessment
Published 30 April 2026 Science Leave a CommentTags: biological response, echinoderms, laboratory, Mediterranean, multiple factors, physiology, reproduction, sediment, toxicants
Highlights
- Reduced pH enhances ammonium toxicity on sea urchin embryos in filtered seawater.
- In elutriates ammonium is a major driver of P. lividus embryotoxicity.
- Data support setting ammonium thresholds in sediment quality frameworks.
- Ocean acidification potentially increases ammonium toxicity for sea urchin larvae.
Abstract
Ammonium is a key component of coastal marine systems, originating from both natural and anthropogenic sources, with possible toxic effects on marine organisms depending on the concentration and pH. This study evaluates, for the first time, the combined effects of ammonium and seawater acidification on early development of the sea urchin Paracentrotus lividus under both laboratory conditions and exposure to environmental matrices derived by dredged sediments from harbor area. Embryos were incubated with increasing concentrations of ammonium in filtered seawater at pH 8.1 and 7.6, as well as in sediment elutriates from the Pescara harbor (Adriatic Sea, Italy), selected as a case study with relevant concentrations of ammonium (0.1–3.5 mg/L). A combined effect between ammonium and pH was observed, with increasing ammonium toxicity by ∼20% at pH 7. Moreover, in sediment elutriates, ammonium affect sea urchin embryo development, with EC50 ranging between 1.388 and 1.538 mg/L NH4+ at pH 8.1 and 7.6, respectively, without significant differences due to pH. Chemical analyses of sediments confirmed low levels of trace metals and organic pollutants, indicating that ammonium is the primary driver of embryotoxicity without a direct toxic effect of other contaminants. The results further underscore the need to integrate ammonium assessment into sediment quality frameworks and for management strategies, particularly in the context of future ocean acidification, to safeguard the early life stages of sensitive marine invertebrates.
Continue reading ‘Combined effects of ammonium and pH on sea urchin embryogenesis: insights for sediment quality assessment’Acidification in coastal waters of Adélie Land, Antarctica (1985–2025)
Published 29 April 2026 Science Leave a CommentTags: Antarctic, chemistry, field, modeling, regionalmodeling, sensor
Ocean acidification is expected to be particularly severe in Antarctic continental shelves due to enhanced anthropogenic carbon uptake in cold waters in response to rising atmospheric CO2, sea-ice retreat, freshening and climate-change feedbacks. Models suggest that undersaturated conditions with respect to aragonite (Ωar), a major form of calcium carbonate formed by marine species, could be reached as soon as 2052 for austral winter. Here we present new ocean carbonate system observations from cruises conducted since 2010 in the Adélie Land coastal region in East Antarctica, along with data from a BCG-Argo float and results from a neural network model for the period 1985–2025. The region is a permanent CO2 sink and was most pronounced since 2006. The CO2 sink leads to a positive increase of surface water total CO2 concentrations (CT) (+0.44 ± 0.01 µmol.kg-1.yr-1) and to a progressive decrease of pH (-0.013 per decade) and Ωar (-0.035 per decade) for the winter season. The lowest surface Ωar of 1.2 was observed in winter 2024 from the float data, a critical limit for some marine species such as pteropod. A projection of the CT concentrations in the future, based on observed anthropogenic CO2 concentrations and emissions scenarios, suggests that aragonite saturation state (Ωar = 1) will occur in surface waters as soon as 2055 in the Adélie Land region, which is part of a larger area of East Antarctica proposed as a Marine Protected Area by the Commission for the Conservation of Antarctic Marine Living Resources since the early 2010s.
Continue reading ‘Acidification in coastal waters of Adélie Land, Antarctica (1985–2025)’Ocean acidification and harmful algal blooms combine to suppress the growth and survival of North Atlantic bivalve larvae
Published 29 April 2026 Science Leave a CommentTags: algae, biological response, community composition, laboratory, mollusks, mortality, North Atlantic, otherprocess, reproduction
While harmful algal blooms (HABs) and ocean acidification (OA) are environmental factors that can impair bivalves, the manner in which these two stressors may act and interact to impact bivalve larvae is poorly understood. This study exposed larvae of hard clams (Mercenaria mercenaria) and Eastern oysters (Crassostrea virginica) to a range of pCO2 levels found in estuaries (400–3,000 µatm) and three harmful algae, Alexandrium catenella, Dinophysis acuminata, and Margalefidinium polykrikoides, at densities found during HABs (500–7,000 cells mL-1), with one HAB species exposure per experiment. The combined OA and HAB treatment significantly reduced larval survival in all 21 experiments by 91 ± 4.6% (SE) compared to controls and reduced larval sizes in 92% of experiments by 40 ± 3.5%. Cultured M. polykrikoides had a stronger negative effect on larvae than cellular equivalent bloom populations. Densities of D. acuminata >750 cells mL-1 reduced larval survival and size (p < 0.01), but the addition of OA to D. acuminata did not suppress survival further. While the combined A. catenella and OA treatment reduced larval growth and survival at all densities (p < 0.01), A. catenella alone did not impact M. mercenaria survival or size at or below 1,000 cells mL-1 and did not impact C. virginica at any density. Oyster larvae were less impacted than hard clams by OA (33 vs. 67% of experiments) and by HABs (67 vs. 100% of experiments). Given the very low survival of bivalve larvae when exposed to combined HABs and OA in all experiments (<0.1–5%), bivalve restoration and conservation efforts should seek to avoid regions that experience these co-stressors.
Continue reading ‘Ocean acidification and harmful algal blooms combine to suppress the growth and survival of North Atlantic bivalve larvae’Research progress on the comprehensive response mechanisms of marine organisms to multiple environmental stressors
Published 28 April 2026 Science Leave a CommentTags: biological response, corals, fish, mollusks, multiple factors, plastics, review, toxicants
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.
Continue reading ‘Research progress on the comprehensive response mechanisms of marine organisms to multiple environmental stressors’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 CommentTags: biogeochemistry, biological response, Indian, laboratory, light, multiple factors, physiology, primary production, respiration, sediment
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.
Continue reading ‘Light and tidal inundation and exposure regulate the sensitivity of estuarine benthic greenhouse gas fluxes to warming and ocean acidification’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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Continue reading ‘Ocean acidification simplifies food webs and may intensify competition between sea urchins’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 CommentTags: biological response, growth, laboratory, mollusks, multiple factors, physiology, temperature
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.
Continue reading ‘Climate change resilience and positive Scope for Growth in wild adult Sydney rock oysters, Saccostrea glomerata (Gould 1850)’Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters
Published 27 April 2026 Science Leave a CommentTags: abundance, biogeochemistry, biological response, chemistry, field, molecular biology, morphology, North Pacific, phytoplankton
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.
Continue reading ‘Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters’
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.
Continue reading ‘Open for submissions : Ocean acidification’Real-time acidification monitoring through Sofar buoy and SAMI-pH integration
Published 23 April 2026 Science Leave a CommentTags: chemistry, field, methods
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.
Continue reading ‘Real-time acidification monitoring through Sofar buoy and SAMI-pH integration’Seawater acidification accelerates growth but hastens decline in batch cultures of the marine diatom Thalassiosira pseudonana
Published 22 April 2026 Science Leave a CommentTags: biological response, growth, laboratory, photosynthesis, physiology, phytoplankton
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 ClosedTags: biological response, fish, laboratory, molecular biology, performance, physiology
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.
Continue reading ‘Ocean acidification induces neuronal hyperexcitation and anxiety-like behaviour in marine medaka via ASIC activation’Decadal shifts in hypoxia and acidification reveal changing anthropogenic pressures on bottom waters of a coastal shelf
Published 20 April 2026 Science ClosedTags: chemistry, field, North Atlantic
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.
Continue reading ‘Decadal shifts in hypoxia and acidification reveal changing anthropogenic pressures on bottom waters of a coastal shelf’Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea
Published 20 April 2026 Science ClosedTags: biological response, community composition, field, morphology, North Pacific, otherprocess, physiology, phytoplankton
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.
Continue reading ‘Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea’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 ClosedTags: biological response, laboratory, mesocosms, mollusks, morphology, mortality, multiple factors, North Pacific, predation, temperature
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.
Continue reading ‘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.)’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 ClosedTags: biological response, BRcommunity, crustaceans, field, mollusks, morphology, North Pacific
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.
Continue reading ‘Synergistic effects of ocean acidification and thermal stress on shell biomineralization and parasitism in the white clam Leukoma asperrima (Bivalvia: Veneridae)’Webinar: “communicating ocean acidification in a changing world”
Published 17 April 2026 Events Closed
Webinar: “Communicating Ocean Acidification in a Changing World”
📅 Wednesday April 22, 2026 | 🕐 12:00pm- 1:30pm EST | 📍Online Event
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
Continue reading ‘Webinar: “communicating ocean acidification in a changing world”’Register now: life on the extremes: why ocean acidification hits differently on the coasts
Published 16 April 2026 Events ClosedTags: North Atlantic
Tuesday, May 19, 2026 – 7:00pm – 8:30pm
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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Continue reading ‘Register now: life on the extremes: why ocean acidification hits differently on the coasts’
