Based on four field surveys conducted from August 2022 to May 2023, seasonal distribution and dynamics of the seawater aragonite saturation state (Ωarag) were investigated in the northern coastal zone of the Northern Yellow Sea, an important fishery region, to assess impacts of ocean acidification especially in river-dominated coastal systems. Results revealed seawater Ωarag had significant spatiotemporal variability with surface values ranging from 1.42 to 3.76 in summer, 1.22 to 2.34 in autumn, 1.71 to 2.48 in winter, and 2.03 to 3.56 in spring. Subsurface seawater Ωarag was generally lower than surface values, while seawater with Ωarag < 1.5—a critical threshold for severe biological stress—were predominantly found in the nearshore areas and in the southwestern offshore bottom waters. Persistent seasonal acidification was observed across the study area. While seawater temperature played an important role in seasonal Ωarag variation, its effect was masked in the nearshore zones by river-diluted water inputs, especially in summer, and in offshore bottom waters by community respiration during summer and autumn. These mechanistic insights clarify key drivers of coastal acidification and provide a scientific basis for developing targeted strategies to detect acidification trends and ecosystem responses in anthropogenically impacted coastal regions.
Continue reading ‘Seasonal variations and key controls on seawater aragonite saturation state in the Northern Yellow Sea, China’Seasonal variations and key controls on seawater aragonite saturation state in the Northern Yellow Sea, China
Published 17 March 2026 Science Leave a CommentTags: chemistry, field, North Pacific
Coulometric readout of ion-selective electrodes for an aquatic pH probe
Published 17 March 2026 Science Leave a CommentTags: chemistry, field, Mediterranean, methods
Ion-selective electrodes are widely used for the detection of ions in aqueous solutions such as natural waters. Their origin traces back to 1909 with the invention of the pH glass electrode. Nowadays, routine pH measurements are still performed by potentiometric measurements with glass electrodes. The phase-boundary potential difference at the glass membrane-sample interface, measured against a reference electrode, relates to solution pH following the Nernst equation. While being user-friendly, they suffer from multiple drawbacks. Firstly, their sensitivity is intrinsically dictated by the Nernst equation and is limited to 59.2 mV/pH at 25 °C. This might not be sufficient for applications where high precision pH sensing is required, such as ocean acidification monitoring. Secondly, a Nernstian response can only be obtained if all the other potential differences in the overall electrochemical cell are constant over the whole experimental procedure. This is not the case when, for example, the temperature or the ionic strength of the sample change during the measurement routine. The former influences the glass electrode itself, while the latter rather affects the reference electrode via liquid junction potential variations.
This thesis presents enhancements to the potentiometric experimental setup for pH sensing with glass or polymeric membrane pH electrodes, achieved through the integration of electronic components, chemical symmetry and open liquid junctions. A dynamic electrochemical readout called constant potential coulometry is explored for in situ pH sensing in coastal waters by implementation in a submersible probe deployed in the Krka River estuary in April 2025.
Continue reading ‘Coulometric readout of ion-selective electrodes for an aquatic pH probe’Physiological responses of Swedish maerl to ocean acidification and warming
Published 17 March 2026 Science Leave a CommentTags: algae, biological response, calcification, laboratory, multiple factors, North Atlantic, photosynthesis, respiration, temperature
Maerl, (Corallinales, Rhodophyta), are free-living calcareous algae found in coastal ecosystems. They form biogenic beds with complex structures in which other species can find refuge or on which other species can settle, which highlights their importance as an ecosystem. While many species have been investigated worldwide, maerl from the Swedish west coast are poorly studied. This report investigated both acidification and warming impacts on different physiological functions of Swedish maerl, including photosynthesis, respiration and calcification. The maerl were exposed to different pH levels and temperatures in both light and dark conditions to determine their physiological thresholds, where photosynthesis and respiration were measured via oxygen fluctuations, photosynthetic efficiency via PAM fluorometry and calcification via alkalinity titrations. It was found that neither photosynthetic nor respiratory oxygen exchange showed positive or negative trends when exposed to changes in pH. On the contrary, photosynthesis peaked at the natural ambient temperature of 16°C and respiration increased with increasing temperature. Photosynthetic efficiency also did not show any trends to pH changes. However, calcification showed a significant (p < 0.05) negative response to pH in both light and dark conditions, with the response more severe in dark conditions. This suggests that decreasing pH may induce skeletal dissolution, and that photosynthesis could help buffer internal responses to external conditions. Carbonate production at ambient conditions in the light was calculated to be 556 ± 54 g CaCO3 m-2 yr-1, showing that Swedish maerl are just as, if not more, productive than maerl found elsewhere. Overall, this report showed that photosynthetic and respiratory thresholds may not be reached with acidification and that temperature increases could instead have much more severe consequences. It also showed that calcification thresholds will be met sooner rather than later, depending on acidification rates, in darker conditions for maerl found in temperate and possibly polar regions.
Continue reading ‘Physiological responses of Swedish maerl to ocean acidification and warming’Multi-level holobiont dysregulation increases the ecological risk of combined ocean acidification and benzo[a]pyrene pollution to the reef-building coral Porites lutea
Published 17 March 2026 Science Leave a CommentTags: archaea, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, photosynthesis, physiology, phytoplankton, prokaryotes, toxicants
Highlights
- Combined ocean acidification and BaP induce holobiont dysregulation, evidencing by a decoupled Symbiodiniaceae proliferation and a collapse of the archaeal Nanoarchaeota-Halobacterota symbiosis.
- The coral host shifts its defense strategy from antioxidant capacity to cellular homeostasis, while the bacterial community increases functional redundancy, revealing a costly acclimation mechanism.
- The multi-level dysregulation demonstrates an underestimated ecological risk, highlighting that current single-stressor risk assessments are inadequate for protecting corals under complex pollution scenarios.
Abstract
Reef-building corals are increasingly threatened by the combined effects of global climate change and localized organic pollutants. However, the holistic impacts of co-exposure to ocean acidification (OA) and benzo[a]pyrene (BaP) on coral holobionts remain poorly understood. Here, we investigated the multi-level responses of the reef-building coral Porites lutea to short-term (7-day) exposure to OA (pH 7.80), BaP (10 µg/L), and their combination, by integrating physiological measurements with microbiome profiling (ITS2 and 16S rRNA). We found that combined stress was associated with a dysregulated response in Symbiodiniaceae, characterized by a significant increase in cell density without a parallel rise in chlorophyll content, suggesting a possible compensatory but inefficient proliferation response. Despite this, the dominant symbiont Cladocopium C15 remained stable. The bacterial diversity increased (e.g., enrichment of Ruegeria and Acanthopleuribacter, decline of Endozoicomonas), which may suggest enhanced functional redundancy, while the archaeal community was significantly restructured, most notably a marked decline of the putative obligate Nanoarchaeota–Halobacterota symbiosis. At the host level, combined stress was associated with suppressed antioxidant enzyme activities (SOD/POD) but upregulated genes related to protein folding (Hsp90) and calcium homeostasis (NCX1, VAMP4). These findings suggest a complex holobiont reconfiguration under combined stress, involving a stabilized core symbiont, altered microbiomes, and a shifted host defense strategy. Our study suggests that the ecological risk of combined OA and organic pollution may not be extrapolated from single-stressor responses, indicating the need to incorporate multi-stressor frameworks into coral reef risk assessments.
Continue reading ‘Multi-level holobiont dysregulation increases the ecological risk of combined ocean acidification and benzo[a]pyrene pollution to the reef-building coral Porites lutea’Effects of rapid acidification in marine seawater: focus on Actinopterygii
Published 17 March 2026 Science Leave a CommentTags: biological response, fish, morphology, mortality, performance, physiology, reproduction, review
Highlights
- The review reports physiological, behavioural, developmental and reproductive effects.
- Studies on Actinopterygii exposure to various pCO₂ levels are integrated.
- Fishes show strong species- and life-stage
specific vulnerability to high pCO2. - Most experiments with extreme CO₂ levels are short-term, limiting current knowledge.
Abstract
The progressive acidification of the world’s oceans has led to widespread concern regarding the potential consequences for marine biosphere. As a result, most research has been focused on the steady increase of dissolved CO₂ and consequent acidification thus on calcifying species while less attention has been paid to the physiological and developmental impacts of teleost fish. However, rapid and massive release of carbon dioxide (CO₂) into the marine environment may occur due to both natural and anthropogenic causes. This review specifically examines the outcomes of rapid but confined CO₂ emissions, with a focus on their role in accelerating the local acidification of seawater and on the related effects on Actinopterygii. It examines the impacts of elevated CO₂ levels on marine fishes, also emphasizing the lack of experimental evidence on embryonic larval and larval phases, which are highly vulnerable to acid-base imbalances and related physiological disruptions. A broad review of literature published between 1963 and 2025, on fishes’ exposure to varying CO₂ conditions, highlights pronounced variability in responses across species and developmental stages. Early life phases frequently exhibit reduced survival, skeletal and sensory anomalies, and shifts in metabolic demand. Although some taxa demonstrate compensatory adjustments, the resulting energetic costs and physiological trade-offs can limit growth, reproduction, and long-term resilience. Advancing our understanding of fish vulnerability and adaptive potential under seawater acidification of marine fishes in an acidifying environment requires long-term, ecologically relevant designs and integrated approaches that link multiple life stages and biological scales.
Continue reading ‘Effects of rapid acidification in marine seawater: focus on Actinopterygii’An invisible threat in Long Island’s waters
Published 16 March 2026 Media coverage Leave a CommentTags: fisheries, North Atlantic
For generations, the waters surrounding Long Island have defined its identity — from the wide-open waterfronts of the South Shore to the shellfish beds of the North Shore. But beneath the surface, a quieter transformation is underway.
Ocean acidification is often called climate change’s “evil twin,” and refers to the lowering of the water’s pH, the scale used to measure the concentration of hydrogen ions in the water. While global warming refers to rising temperatures, acidification describes a shift in seawater chemistry.
…
On Long Island, acidification is not driven by global carbon emissions alone. Local factors intensify the problem. Nitrogen discharged from wastewater, septic systems and fertilizer runoff flows into bays and harbors, fueling harmful algal blooms. When those blooms die and decompose, the process consumes oxygen and releases additional carbon dioxide in the water, further lowering pH.
The result is a compounding effect: global atmospheric carbon dioxide combined with local nitrogen pollution accelerates acidification in shallow, enclosed estuaries.
Warming waters add another layer of stress. As temperatures rise, marine organisms’ metabolic demands increase, but warmer water holds less dissolved oxygen. Together, warming and acidification can weaken shellfish during their most vulnerable larval stages, making it harder for them to survive and build shells.
For Long Island’s oyster and clam farmers — industries that have experienced both revival and setbacks in recent decades — these chemical changes aren’t just theoretical. They are measurable, seasonal and, increasingly, part of daily operations.
Continue reading ‘An invisible threat in Long Island’s waters’Enhanced carbon burial in seagrass meadows under ocean acidification revealed by carbon dioxide vents
Published 16 March 2026 Science Leave a CommentTags: algae, biogeochemistry, biological response, field, Mediterranean, phanerogams, vents
Seagrass meadows are natural carbon sinks, yet the effect of ocean acidification on their carbon burial capacity remains poorly understood. Here we investigated natural carbon dioxide vents in Ischia, Italy to assess how seawater pH influences carbon burial in an area dominated by the seagrass Posidonia oceanica. Organic carbon burial rates (mean ± standard error) between 1954 – 2021 were low under ambient conditions (1.5 ± 0.5 g m-2 yr-1) but increased sharply under acidified conditions (7 ± 1 g m-2 yr-1), reaching sevenfold higher values under extreme acidification (10 ± 3 g m-2 yr-1). Stable isotopes suggest that these patterns reflect changes in the relative contribution of seagrass, macroalgae, and epiphytes to buried carbon. These findings reveal that ocean acidification can substantially alter coastal carbon cycling, potentially through shifts in community composition, with important implications for understanding past and future feedbacks between seagrass ecosystems and the marine carbon cycle.
Continue reading ‘Enhanced carbon burial in seagrass meadows under ocean acidification revealed by carbon dioxide vents’Marine heatwaves, ocean warming and acidification reshape reef fish gut microbiomes
Published 16 March 2026 Science Leave a CommentTags: biological response, BRcommunity, community composition, field, fish, molecular biology, multiple factors, North Pacific, otherprocess, physiology, prokaryotes, temperature, vents
Extreme climatic events and gradual climate change are increasingly anticipated to interact and reshape ecological communities. However, the combined effects of ocean warming, acidification and marine heatwaves on host‐associated microbial communities and their potential role in host adaptation remain poorly understood. Here, we assessed shifts in gut microbiome communities and their associations with physiological performance in one tropical ( Abudefduf vaigiensis ) and one subtropical ( Microcanthus strigatus ) reef fish species, across three temperate reefs representing natural analogues of climate change: a present‐day baseline (‘cool reef’), a chronically warmed reef (‘warm reef’) and a reef experiencing combined warming and extreme acidification (‘extreme reef’). We also examined gut microbiome changes in A. vaigiensis before and during a severe marine heatwave. A. vaigiensis had lower gut microbiome evenness and diversity at the warm (43% and 44% decrease, respectively) and extreme (38% and 31% decrease) reefs compared to the cool reef, and its gut microbiome community shifted at the extreme reef with a 122% increase in abundance of opportunistic bacteria Vibrio. A. vaigiensis also had lower gut microbiome richness at the warm (42% decrease) and extreme (52% decrease) reefs during the heatwave compared to pre‐heatwave individuals. In contrast, M. strigatus showed higher microbiome evenness (99% increase) and diversity (98% increase) at the warm reef compared to the cool reef; however, these gains were lost at the extreme reef, with microbiome diversity and evenness returning to cool reef levels. Microbiome changes in both species were generally not associated with their physiological performance (protein content, oxidative stress, antioxidant capacity or body condition). Our findings suggest that marine heatwaves, ocean warming and acidification can reshape reef fish gut microbiomes, driving simplification in Abudefduf vaigiensis but distinct restructuring in Microcanthus strigatus . We conclude that climate‐driven microbiome reshuffling may alter host–microbiome relationships and functions in fishes in a future ocean.
Continue reading ‘Marine heatwaves, ocean warming and acidification reshape reef fish gut microbiomes’Stony coral symbioses show variable responses to future ocean conditions
Published 16 March 2026 Science Leave a CommentTags: adaptation, biological response, BRcommunity, community composition, corals, laboratory, mesocosms, multiple factors, North Pacific, otherprocess, phytoplankton, temperature
Coral reefs support over a quarter of marine species and nearly a billion people worldwide but are also among the ecosystems most threatened by anthropogenic impacts. There is long-standing debate about whether coral symbioses will be disrupted or respond adaptively under future ocean conditions. Using a factorial 2.5-year future-ocean mesocosm experiment across eight coral species representing the major coral lineages, we tracked symbiont community shifts within replicate fragments from the same individual coral. Some corals exhibited stochastic divergence consistent with dysbiosis, whereas others showed deterministic, thermally adaptive shifts. Heat stress generally reduced symbiont diversity and promoted predictable restructuring, supporting deterministic processes under moderate stress but stochastic dysbiosis under extreme conditions. We propose that adaptive and stochastic responses represent endpoints along a continuum of host-orchestrated symbiont sorting. This study bridges coral reef ecology with broader host–microbiome theory, offering an integrated perspective on how symbiotic systems may respond to environmental change.
Continue reading ‘Stony coral symbioses show variable responses to future ocean conditions’Temperature and pH-dependent potassium currents of muscles of the stomatogastric nervous system of the crab, Cancer borealis
Published 13 March 2026 Science Leave a CommentTags: biological response, crustaceans, laboratory, molecular biology, multiple factors, North Atlantic, physiology, temperature
HIGHLIGHTS
- Cancer borealis stomach muscles are sensitive to temperature and pH.
- Warming or alkalizing hyperpolarizes fibers and reduces synaptic response amplitude.
- qRT-PCR detects K2P gene transcripts CbKCNK1 and CbKCNK2 in muscles.
- CbKCNK1 and CbKCNK2 are candidates for the temperature and pH-dependent conductances.
SUMMARY
Marine crustaceans such as the crab Cancer borealis experience fluctuations in temperature and pH, yet their stomatogastric neuromuscular system must remain functional for feeding. We examined 16 of ∼40 stomach muscle pairs and found that warming consistently hyperpolarized muscle fibers (∼10 mV per 10°C) and reduced excitatory junctional potentials and currents. Muscle responses were also strongly influenced by extracellular pH, with an optimal range between pH 6.7 and 8.8; outside this window, abnormal activity emerged. Voltage-clamp analysis of gastric muscle gm5b revealed a temperature- and pH-sensitive conductance with a reversal potential near the potassium equilibrium potential and insensitivity to tetraethylammonium and barium, arguing against classical voltage-gated potassium channels. Quantitative RT-PCR detected expression of two putative two-pore domain potassium (K2P) channels in these muscles. Together, these results suggest that muscle excitability in C. borealis is shaped by temperature- and pH-sensitive potassium currents consistent with contributions from K2P channels.
Continue reading ‘Temperature and pH-dependent potassium currents of muscles of the stomatogastric nervous system of the crab, Cancer borealis’Environmental controls and nonlinear responses of the diatom-dinoflagellate ratio in Jiaozhou Bay
Published 13 March 2026 Science Leave a CommentTags: abundance, biological response, BRcommunity, chemistry, community composition, field, North Pacific, otherprocess, phytoplankton
Highlights
- Dia/dino abundance, biomass, and diversity ratios exhibited similar temporal patterns;
- All ratios showed considerable heterogeneity without a consistent distributional trend;
- Dia/dino ratios responded distinctly to DO, nutrients, and their interactions;
- Shifting seawater properties exerted large influence on diatom-dinoflagellate dynamics.
Abstract
Diatoms and dinoflagellates are widely recognized as key indicators of marine ecosystem status and play central roles in ecosystem functioning and biogeochemical cycling. Yet how these two major phytoplankton groups adjust to changing coastal environments, and whether such adjustments occur coherently in different ecological dimensions, remains poorly constrained. Hence, we studied the temporal and spatial dynamics of diatom-dinoflagellate (dia/dino) ratios in Jiaozhou Bay during 2021 and 2024, integrating abundance-, carbon biomass-, diversity-, and richness-based metrics. Although abundance, biomass, and diversity ratios exhibited broadly similar temporal trajectories, the richness ratio displayed an opposite pattern, highlighting a decoupling between numerical dominance and species composition. Spatially, all four ratios exhibited significant heterogeneity, without a consistent nearshore-offshore gradient, reflecting complex local regulation. Correlation analyses revealed distinct controls on dia/dino ratios. The abundance ratio increased under conditions of elevated dissolved inorganic nitrogen (DIN) and reduced dissolved oxygen (DO), whereas the diversity ratio was associated with high DIN and low dissolved inorganic phosphorus (DIP). In contrast, the carbon biomass ratio was primarily linked to reduced DO and lower pH, while the richness ratio responded most strongly to the combined influence of low DO and elevated DIP. These contrasting responses indicated that dia/dino ratios captured different facets of phytoplankton community reorganization rather than reflecting a single environmental driver. Overall, our results suggested that the balance between diatoms and dinoflagellates in Jiaozhou Bay emerged from the coupled and nonlinear interactions among nutrient availability and oxygen dynamics. This study highlighted the dia/dino balance as an integrative indicator of coastal ecosystem condition and implied the importance of considering multiple ecological dimensions when assessing phytoplankton responses to ongoing eutrophication and environmental change.
Continue reading ‘Environmental controls and nonlinear responses of the diatom-dinoflagellate ratio in Jiaozhou Bay’A holistic approach to evaluating climate vulnerability of French Polynesia pearl oyster farming: bridging communities and scientific knowledge
Published 13 March 2026 Science Leave a CommentTags: fisheries, socio-economy, South Pacific
Highlights
- A holistic assessment of climate vulnerability of black pearl aquaculture social-ecological system.
- Co-definition of adaptation strategies by scientific/institutional actors and local communities of French Polynesia.
- A list of scientifically robust and locally relevant vulnerability criteria potentially transferable to other Pacific pearl-producing countries.
- Interviewees consistently identify climate change as a factor that amplifies existing weaknesses in the pearl farming sector.
- COVID-19 exposed the sector’s dependence on global markets.
Abstract
While there is wide consensus about the reliance of climate projections at global scale, there is still uncertainty about changes at finer scale and even less on the effects of such fluctuations for local economies and societies. The vulnerability of social-ecological systems (SES) to climate change is a framework that takes into account the strong link between environment and local communities that depend on ecosystem services to ensure their livelihoods. This study explores the vulnerability of pearl farming SES to climate change, combining scientific insights with local knowledge from French Polynesian communities. A preliminary list of eighty-two criteria of exposure, sensitivity and adaptive capacity, identified through a targeted scoping review, was used to develop the interview guide that informed fifty-six face-to-face interviews and workshops conducted in 2020 and 2025. Using a combination of ranking questions and open-ended responses, the results highlight differences in the perceived exposure between scientific/institutional actors and local communities, which is reflected in the degree of sensitivity of the SES to climate drivers. Expectedly, the priorities given to adaptation measures were also different. The thematic analysis of the responses, however, shows that the two parties are aware of their own limitations in understanding the effects of climate change and recognise the need to fill mutual gaps through a collaborative production of knowledge. By integrating complementary forms of knowledge, this approach may help overcome the limitations of vulnerability assessments based exclusively on scientific expertise, and support the development of climate policies that are scientifically sound and socially accepted.
Continue reading ‘A holistic approach to evaluating climate vulnerability of French Polynesia pearl oyster farming: bridging communities and scientific knowledge’Eco-evolutionary dynamics of planktonic calcifying communities under ocean acidification
Published 12 March 2026 Science Leave a CommentTags: adaptation, biological response, BRcommunity, calcification, communitymodeling, growth, modeling, mortality, otherprocess, performance, phytoplankton, primary production, zooplankton
Increasing emissions of CO2 into the atmosphere are causing ocean acidification, threatening calcifying organisms. In this study, we model the physiological responses of coccolithophorids to acidification to understand the ecological and evolutionary outcomes of a system in interaction with zooplankton. Assuming a trade-off between growth and protection against grazing, we show that calcification has bivalent effects on transfers between two trophic levels and that acidity can strongly alter energy transfers. Taking into account the evolution of calcifying phenotypes in response to acidification, we show that the system outcome contrasts with previous results. While the effect of evolution depends on how calcification affects grazing, it nevertheless follows that acidification leads to a decrease in calcifying capacity. This evolutionary decrease may be progressive, but can also lead to tipping points where abrupt shifts may occur. Such a counter-selection of calcification in turn affects ecosystem functioning, enhancing energy transfers within the system and modifying carbon fluxes. We discuss how such eco-evolutionary changes may impact food webs integrity, carbon sequestration into the deep ocean and therefore endanger the carbon pump stability.
Continue reading ‘Eco-evolutionary dynamics of planktonic calcifying communities under ocean acidification’Trophic status and climatic stressors in the shallow coral reefs of the Cuban marine shelf
Published 12 March 2026 Science Leave a CommentTags: chemistry, field, North Atlantic
The “Bojeo a Cuba” expedition (summer 2023) provided a synoptic, national-scale snapshot of oceanographic conditions around Cuba’s shallow coral reefs during a regional marine heatwave. At 66 sites across six regions, we evaluated key climatic stressors (sea surface temperature, pH, alkalinity) and trophic status indicators. Satellite-derived SST during each site’s sampling week revealed significantly warmer waters on the southern shelf (mean = 30.93 °C) than the northern shelf (mean = 29.21 °C, P < 0.01). In situ SST was consistently high (mean = 30.52 °C), documenting the heatwave’s intensity. pH (mean = 8.12) and total alkalinity (mean = 2343 µmol kg⁻¹) indicated a currently balanced carbonate system. Concentrations of dissolved inorganic nitrogen and phosphorus were below our methods’ quantification limits (1.61 µmol L⁻¹ for P-PO₄³⁻), while chlorophyll-a (mean = 0.04 µg L⁻¹) consistently classified waters as oligotrophic. This study establishes a critical summer baseline, confirming oligotrophic conditions while documenting the severity of thermal stress during the 2023 heatwave—the most immediate and uniform threat to Cuban reefs. Our findings underscore the vulnerability of these ecosystems to extreme warming events within the context of long-term Caribbean warming trends.
Continue reading ‘Trophic status and climatic stressors in the shallow coral reefs of the Cuban marine shelf’Effects of long-term exposure to ocean acidification on the Patagonian scallop Zygochlamys patagonica (P.P. king, 1832), a strategic fishery resource in the Southwest Atlantic ocean
Published 12 March 2026 Science Leave a CommentTags: biological response, dissolution, fisheries, laboratory, mollusks, morphology, mortality, South Atlantic
Highlights
- Scallops were resilient to low pH within the present range of natural variability.
- Negative impacts were observed under true ocean acidification scenario, including:
- Increased mortality & decreased shell mass condition index
- Dissolution of the external shell surface modifying shell ornamentation
- Shell disarticulation leading to the lost ability to swim
- During depuration time were observed:
- A recovery of the scallops’ vital functions when the stressor (low pH) was not present
- No recovery for shell mass condition index, shell ornamentations and disarticulated scallops
- No new disarticulated scallops
Abstract
Ocean acidification (OA) is a global process leading to a decrease in seawater pH. It is a direct consequence of the increase in CO2 emissions due to human activities with documented impacts on marine species and ecosystems. Effects of a long-term OA exposure (6 months) followed by a 2 months depuration period were evaluated on the Patagonian scallop Zygochlamys patagonica, an important seafood species of the Southwest Atlantic Ocean. Scallops were exposed to three target pHs, (1) pH 7.93, the mean annual pHT at the sampling site, (2) pH 7.83, the minimum value of the natural variability recorded at the sampling site and, (3) pH 7.53, a 0.3 pH unit below the minimum pH. Mortality, shell growth, and shell mass, adductor muscle mass and gonadal mass condition indices were measured at the beginning of the experiment and after 3, 6 and 8 months of exposure. Decreased pH led to a significant increase in mortality and decrease in the shell mass condition index. Shell growth was minimal over the course of the experiment with no effect of pH. The external shell surface showed a gradual dissolution and discolouration over the 6 months exposure to low pH. Shell disarticulation due to ligament damage was also observed in 29% of the animals exposed to low pH after 6 months resulting in loss of swimming ability of scallops, whereas no disarticulated animals were recorded in the high pH treatment. These results show the vulnerability of this species to future OA conditions with implications for the ecosystem services it provides, such as a decline in scallop numbers, greater vulnerability to predation and lower quality of commercial products.
Continue reading ‘Effects of long-term exposure to ocean acidification on the Patagonian scallop Zygochlamys patagonica (P.P. king, 1832), a strategic fishery resource in the Southwest Atlantic ocean’Ocean acidification at the crossroads I: harmonizing unpurified and purified meta-cresol purple spectrophotometric pHT measurements based on absorbance data
Published 11 March 2026 Science Leave a CommentTags: chemistry, field, methods
Consistent monitoring of seawater spectrophotometric pH on the total hydrogen ion scale (pHT) has been questioned by an evolving method, with changes in parameterization and the purity of the meta-cresol purple (mCP). Using real seawater samples, we demonstrate that spectrophotometric pHT measurements obtained with unpurified (UNPUR) and purified (PUR) mCP can be harmonized to within 0.003 pH units, the climate-goal threshold. This agreement is only achieved when mCP impurities at 434 nm are quantified for both the UNPUR and PUR mCP, assuming no impurities affect 545 nm absorbances, and impurity-corrected absorbance data at 434 nm are used in the same parameterization to calculate pHT. We applied this approach to a ship-based pHT time series transitioning from UNPUR to PUR mCP measurements. Our results show that previous claims suggesting that UNPUR mCP underestimates pHT in the upper pH range are misleading, as they were based on the inappropriate use of absorbances obtained with UNPUR mCP with a parameterization developed for PUR mCP. In fact, our data reveal better agreement between UNPUR and PUR pHT in the upper pH range of seawater, while UNPUR mCP tends to overestimate pHT in the lower pH range. These findings highlight the urgent need for the global chemical oceanography community to establish a spectrophotometric pHT method with full traceability to the International System of Units (SI), along with affordable and distributed certified reference materials and characterized purified mCP. This work supports the need for harmonization efforts to ensure the reliability of pHT data in global synthesis products.
Continue reading ‘Ocean acidification at the crossroads I: harmonizing unpurified and purified meta-cresol purple spectrophotometric pHT measurements based on absorbance data’‘Irreversible loss’: how climate change is threatening Europe’s sunken civilisations
Published 11 March 2026 Press releases Leave a CommentTags: Mediterranean, vents
Climate change is endangering the health of Europe’s oceans, and it’s not just marine life that is affected.
A new study warns that precious underwater cultural heritage is being threatened by ocean acidification.
The research found that materials that make up many archaeological treasures are at risk of deterioration when water pH levels drop.
The research, coordinated by the University of Padua in Italy, examined how ocean acidification, a direct consequence of climate change, can accelerate the decay of submerged archaeological sites.
The scientists studied how quickly historical materials deteriorate through dissolution and biological decay in marine environments, and then integrated these findings with large-scale climate models, lead researcher Luigi Germinario explains.
The results were concerning. While stone degradation was minimal in pre-industrial times and remains relatively limited today, rising emissions could trigger an exponential increase in deterioration rates.
These changes would be “irreversible over the coming decades and centuries, influenced by the materials’ properties and shifting dynamics of biocolonisation” – the growth of microorganisms on the surfaces of submerged structures – Germinario told Italian national newspaper La Repubblica.
The study, published in Communications Earth & Environment, warned that “ocean acidification will pose a severe challenge to protecting underwater cultural heritage, making conservation and adaptation policies more urgent than ever.”
Continue reading ‘‘Irreversible loss’: how climate change is threatening Europe’s sunken civilisations’Multifactorial neural disruption in the brain of the Senegalese sole (Solea senegalensis) under ocean acidification
Published 11 March 2026 Science Leave a CommentTags: biological response, fish, laboratory, molecular biology, physiology
Global ocean acidification, driven by rising atmospheric CO2, threatens marine ecosystems and biodiversity, with increasing evidence of disruptive effects on fish neurobiology and behaviour. However, the precise mechanisms underlying these impacts remain largely unresolved. Here, we reveal how chronic exposure to future-predicted CO2 levels disrupts brain function in the marine teleost Solea senegalensis. Using an integrative approach combining electrophysiology, immunohistochemistry and transcriptomics, we demonstrate that elevated CO2 induce a complex multifaceted disruption in brain physiology.
Contrary to the prevailing GABAA receptor reversal hypothesis, which predicts Cl− loss and heightened excitatory signalling under high CO2, we observed increased Cl− and HCO3− in cerebrospinal fluid and suppressed neural excitability. Immunohistochemistry revealed reduced expression of glial fibrillary acidic protein across multiple brain regions, suggesting glial impairment. Furthermore, transcriptomic profiling of the olfactory bulb uncovered immune modulation, downregulation of neural excitability genes, and upregulation of neuroplasticity, ciliary, and anti-inflammatory pathways, hallmarks of cellular stress adaptation. Notably, genes involved in circadian regulation and thyroid signalling were also dysregulated, pointing to broader neuroendocrine disruption.
These findings challenge simplistic models of ocean acidification impact, unveiling a cascading interplay of enhanced GABAergic inhibition, immune shifts, glial dysfunction, and disrupted timekeeping mechanisms, likely contributing to the behavioural impairments under high CO2.
Unlike prior studies relying on behavioural assays or direct physiological proxies, our integrative approach, combining direct cerebrospinal fluid ionic measurements, electrophysiology, immunohistochemistry and transcriptomics, unveils a multifactorial physiological cascade. Our work advocated for integrative neurophysiological frameworks to predict marine fish resilience and vulnerability in a rapidly changing ocean.
Continue reading ‘Multifactorial neural disruption in the brain of the Senegalese sole (Solea senegalensis) under ocean acidification’Two decades of skeletal density decline in Pocillopora spp. corals in the Mexican Pacific Ocean: insight into a tropical eastern Pacific acidification scenario?
Published 10 March 2026 Science Leave a CommentTags: biological response, chemistry, corals, field, morphology, North Pacific
Corals demonstrate vulnerability to environmental changes, exhibiting the capacity to substantially modify coral calcification. In this study, we estimated declines in the density of Pocillopora coral species in the Mexican Pacific. The samples utilized in this study encompass both recently collected corals and those stored in Mexican repositories collected in the northeastern and southern Mexican Pacific regions. Density estimates indicate a 28.6% decline in coral density over the past 23 years (−0.0227 g CaCO3 cm-3 y-1) in the southern Mexican Pacific, while at the entrance to the Gulf of California, density has decreased by 15.4% over the past 20 years (−0.017 g CaCO3 cm-3 y-1). A comprehensive evaluation of environmental data reveals that the observed decline in Pocillopora skeletal density in Mexican Pacific reefs is concomitant with decreases in Ωar and pH, and an increase in ocean temperature on a substantial regional scale. When considered in conjunction with the previously documented reductions in coral growth of Pocillopora spp. skeletons in the eastern Tropical Pacific, our findings indicate a potential decline in CaCO3 production within the region’s reef systems. The results of this study underscore the significance of generating long-term series of coral growth parameters for relevant reef-building species and the carbonate system in key and representative coastal areas, particularly those that are already challenging for coral survival and reef maintenance.
Continue reading ‘Two decades of skeletal density decline in Pocillopora spp. corals in the Mexican Pacific Ocean: insight into a tropical eastern Pacific acidification scenario?’Consequences of rising atmospheric CO₂ on ocean acidification and dissolved carbon cycling: a systematic review
Published 10 March 2026 Science Leave a CommentTags: chemistry, review
Increasing atmospheric CO2 and temperature diminish ocean pH and raise the amounts of dissolved inorganic and organic carbons, causing wide-ranging shifts in marine water carbon chemistry and predicting the impacts on long-term ecosystems. This review aimed to determine the ocean chemistry and spatial variation of CO2 at a global scale, as well as to predict the influences of anthropogenic and natural changes on marine ecosystems. The literature has demonstrated that the southern polar oceans, Antarctica, and any coastal zone are predominantly susceptible to marine acidification and the dissolved carbon cycle. Based on 355 studies conducted over the last 30 years, this investigation found that marine acidification and the dissolved cycle are complex and poorly understood phenomena. These two facts and climate change are very interrelated, and the potential of these threats is very spatial, seasonal, stratified, and complex also. It was found that the atmospheric CO2 has increased by about 50% since preindustrial times and excess CO2 raise the seawater acidity through some equilibrium reactions in aqueous medium. The study observed that over the past half-century, the marine surface water acidity has risen by 30%, and predicted that by 2100, it will increase to 150. Moreover, this study critically reviewed the actual rules of marine dissolved organic and inorganic carbon on the global carbon cycle and marine acidification and vice versa. Such a major change in ocean chemistry will already have wide consequences for marine life and ocean ecosystems.
Continue reading ‘Consequences of rising atmospheric CO₂ on ocean acidification and dissolved carbon cycling: a systematic review’
