Coastal upwelling zones, shaped by global change and human impacts, naturally impose hypoxia and acidification on marine species, creating selective pressures that influence physiological responses and drive phenotypic variability. Understanding these responses is crucial for predicting marine biodiversity dynamics in heterogeneous seascapes. We explored diel cycles of pH and dissolved oxygen (DO) and their influence on the metabolic performance of the kelp crab Taliepus dentatus, a species with limited larval dispersal. Kelp crabs from two environmentally contrasting sites along an upwelling seascape in central Chile—an upwelling shadow and an active upwelling zone—were studied using field sensor data and laboratory experiments. Active upwelling disrupted the regular diel pH cycle, resulting in persistently low pH (pHT ≈ 7.5) decoupled from oxygen dynamics. Experimental simulations of diel pH–DO fluctuations revealed that nocturnal low DO/low pH conditions (DO = 1 and 5 mg l⁻¹; pH = 7.5 and 7.8 for ‘upwelling’ and ‘downwelling’ conditions, respectively) reduced metabolic rates and respiratory quotient in crabs. Individuals from the active upwelling zone exhibited elevated metabolic rates, haemolymph pH and lactate accumulation under extremely low pH/low DO conditions compared with those from the upwelling shadow, suggesting site-specific physiological adjustments. These findings underscore the importance of incorporating natural variability into experimental designs and management frameworks aimed at predicting species resilience under climate change.
Continue reading ‘Diel variability and decoupled pH-oxygen dynamics drive metabolic plasticity in kelp crabs from an upwelling seascape’Posts Tagged 'biological response'
Diel variability and decoupled pH-oxygen dynamics drive metabolic plasticity in kelp crabs from an upwelling seascape
Published 25 March 2026 Science ClosedTags: biological response, chemistry, crustaceans, laboratory, multiple factors, oxygen, physiology, respiration, South Pacific
Acidification and deoxygenation matter in assessing redistribution of global cold-water coral biodiversity induced by climate change
Published 24 March 2026 Science ClosedTags: biological response, BRcommunity, corals, globalmodeling, modeling, multiple factors, temperature
The ocean is undergoing significant changes, including warming, acidification, and deoxygenation, which pose great challenges to marine biodiversity. However, most models projecting the impacts of climate change on marine species overlook predictor variables critically meaningful for species’ ecologies such as pH and dissolved oxygen. The recent release of high-resolution projections of different future climate-change scenarios offers the opportunity to explore species redistribution under multiple threats beyond ocean warming. Accordingly, we conducted a global comparative analysis to study the impact of incorporating predictor variables describing pH and dissolved oxygen into marine species distribution models. We used models trained for 268 cold-water coral species to project potential future distributions for different climate and dispersal scenarios over different time periods. We found that, irrespective of scenario or period, models using pH and dissolved oxygen projected 11.5–21.4% higher impacts of climate change than those without them. For instance, by the end of the century under a high emission scenario, models including pH and oxygen projected an average range contraction of 48.2% for cold-water corals under a no-dispersal scenario, compared with a 26.8% contraction projected by models excluding these two predictors. Given the substantial differences in the predicted distribution patterns and the biological importance of these variables, we highlight that researchers should consider more diverse sets of predictor variables when predicting future range shifts for marine biodiversity assessments under climate change.
Continue reading ‘Acidification and deoxygenation matter in assessing redistribution of global cold-water coral biodiversity induced by climate change’Experimental exposure to climate change scenarios imposed alterations on the morphological traits of sessile and low-motility marine invertebrates
Published 24 March 2026 Science ClosedTags: biological response, laboratory, Mediterranean, methods, mollusks, morphology, multiple factors, porifera, temperature
Background
Over the past 50 years, the oceans have absorbed over 90% of global warming heat, leading to warming, acidification and declining oxygen levels that are disrupting marine ecosystems and altering species distributions and productivity. The vulnerability of marine organisms to these changes depends on their biological traits, habitat conditions and adaptive capacity, influencing their growth, behaviour and overall population health. Micro-computed tomography (micro-CT) has been previously used for studying the morphological traits of marine invertebrates, which provide important insights into species functionality and responses to climate change and ocean acidification. Micro-CT enables non-destructive, high-resolution 3D analysis of internal and external structures, allowing precise measurement of traits such as density, porosity and morphology that are valuable for climate change research.
New information
The present manuscript describes micro-CT imaging datasets generated to investigate the effects of climate change on the morphological structure of two benthic marine invertebrates: the low-motility gastropod Hexaplex trunculus (Linnaeus, 1758) and the sessile sponge Chondrilla nucula Schmidt, 1862. Both species are considered particularly vulnerable to environmental stressors. To date, no study has investigated the effects of ocean warming and acidification on sponges using micro-CT technology. Using a common garden experimental design, individuals from geographically distinct populations exposed to different natural environmental regimes were subjected to combined warming and acidification scenarios to assess their morphological responses and adaptive capacity.
Continue reading ‘Experimental exposure to climate change scenarios imposed alterations on the morphological traits of sessile and low-motility marine invertebrates’Tolerance of egg and yolk-sac larval yellowfin sole (Limanda aspera) to ocean warming and acidification
Published 23 March 2026 Science ClosedTags: biological response, fish, fisheries, growth, laboratory, morphology, mortality, multiple factors, North Pacific, physiology, reproduction, temperature
Yellowfin sole (Limanda aspera) support the largest flatfish fishery in the world and contribute substantially to the eastern Bering Sea (EBS) flatfish catch. The EBS has been warming and acidifying, trends that are expected to intensify into the future. Sustainable management of yellowfin sole requires an understanding of how yellowfin sole respond to environmental change, which can be assessed through controlled laboratory investigations. Across four independent trials, yellowfin sole embryos and larvae were incubated at one of six experimental treatments spanning three temperatures (9°C, 12°C, and 15°C) and two pCO2 target levels (low and high), and a range of organismal and physiological responses were measured. Embryonic daily mortality rates and metabolic rates increased with increasing temperature but were not affected by ocean acidification. At- hatch and at- yolk absorption, morphometric measurements (length, dry weight, myotome height, and yolk area) were temperature- sensitive, but the response differed across the four trials. There was a consistent increase in length- based growth and yolk absorption rates with increasing temperature across trials. All morphometric and rate- based measurements were not affected by ocean acidification. Yellowfin sole metabolic enzyme activities were measured at- yolk absorption. Lactate dehydrogenase (anaerobic metabolism) and β- hydroxyacyl CoA dehydrogenase (fatty acid metabolism) both increased with increasing temperature, indicating elevated energy demand. Citrate synthase (aerobic metabolism) declined with increasing pCO2 levels, indicating potential metabolic suppression. Overall, embryonic and larval yellowfin sole demonstrated relatively high tolerance to ocean warming and acidification. We hypothesize the variation in temperature responses across the trials may be driven by maternal effects, which could support tolerance to future ocean conditions.
Continue reading ‘Tolerance of egg and yolk-sac larval yellowfin sole (Limanda aspera) to ocean warming and acidification’Ocean acidification disrupts the biomineralization process in the oyster Crassostrea virginica via intracellular calcium signaling dysregulation
Published 20 March 2026 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, morphology, North Atlantic, physiology, reproduction
Calcium is a key component in the shell and skeleton structure, serving as a second messenger for regulating biomineralization across many species. Ocean acidification (OA) is well-studied for causing shell dissolution in marine bivalve species by disordering calcium deposition. However, the regulatory pathway of calcification affected by OA remains unclear. This study assessed eastern oyster (Crassostrea virginica) to determine how calcium signaling responds to elevated pCO2 and influences shell formation. Under elevated pCO2, increased calcium influx was found in mantle epithelial cells, followed by the upregulation of calmodulin, a primary sensor of intracellular calcium. Expression levels of shell matrix proteins (SMPs), representing shell construction conditions, were significantly upregulated in the CO2-induced mantle cells. Larval C. virginica exhibited developmental stage-dependent alterations in calcium signaling and SMPs disarrangement stimulated by pCO2. Pharmaceutical blockage of the calcium binding on calmodulin induced abnormal expression of downstream genes and shell matrix changes consistent with those caused by elevated pCO2. Restored SMPs expressions in CO2-treated mantle cells were achieved by rescuing the level of calcineurin, a downstream effector of calmodulin. These findings suggest that shell deformities under OA are primarily caused by the disruption of the calcium-calmodulin signaling pathway in mantle epithelial cells.
Continue reading ‘Ocean acidification disrupts the biomineralization process in the oyster Crassostrea virginica via intracellular calcium signaling dysregulation’Influence of ocean warming and acidification on juveniles of the true giant clam, Tridacna gigas, and its microalgal symbionts
Published 19 March 2026 Science ClosedTags: biological response, BRcommunity, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, phytoplankton, reproduction, temperature
Uncontrolled carbon dioxide emissions from human activities contribute to ocean warming and acidification. These alterations in ocean chemistry threaten marine organisms, such as the true giant clam, Tridacna gigas, which is already imperiled due to overharvesting and habitat destruction. To gain an understanding of the physiological and molecular responses of T. gigas and its symbiotic dinoflagellates to ocean warming and acidification, we subjected juvenile individuals to different treatments simulating predicted seawater pH (7.6 and 8.0) and temperature (28°C, 30°C, 32°C and 34°C) levels for the next century. Juvenile giant clams were able to tolerate sustained exposure to temperatures of up to 32°C and pH as low as 7.6, while exposure to higher temperature (34°C), regardless of pH level, resulted in total mortality after a week. However, symbiosis was compromised even in the sublethal treatments, as indicated by the decrease in Symbiodiniaceae density and changes in symbiont gene expression. Symbionts significantly upregulated genes involved in splicing, translation, fatty acid metabolism, and DNA repair, which may constitute an adaptive response, while downregulating genes involved in photosynthesis and transmembrane transport, suggests impaired transfer of photosynthates to the host. These findings demonstrate the vulnerability of the juvenile T. gigas holobiont to heat stress, highlighting the critical importance of continued conservation and management alongside efforts to mitigate global changes in ocean conditions to safeguard this iconic marine bivalve.
Continue reading ‘Influence of ocean warming and acidification on juveniles of the true giant clam, Tridacna gigas, and its microalgal symbionts’Differential impacts of ocean acidification and alkalinization on shell microstructure and molecular responses in Mytilus edulis
Published 18 March 2026 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, morphology, mortality, North Pacific
Anthropogenic CO2 emissions are intensifying ocean acidification (OA), disrupting carbonate chemistry and threatening marine calcifiers such as mussels. Ocean alkalinity enhancement (OAE) has been proposed as a marine carbon dioxide removal (mCDR) strategy that can also mitigate OA, but its ecological safety for aquaculture species remains poorly understood. Here, we examined the short-term (21 days) responses of the blue mussel Mytilus edulis to OA (pH 7.3) and NaOH-based OAE (pH 9.0) using integrated shell microstructure analysis and transcriptomics. The results showed that while survival rates were unaffected, OA caused marked shell degradation and activated stress-related molecular pathways, whereas OAE enhanced shell integrity and stimulated growth-associated processes. Across treatments, a core set of biomineralization-related genes (e.g., VWA7, CA14, ALPL) exhibited expression shifts, suggesting central roles in carbonate homeostasis. In contrast, differential regulations of genes such as CA10 and VWDE revealed pH-specific responses. Notably, OAE induced minimal disruption of biomineralization and alleviated OA-related damage, highlighting its potential to support mussel aquaculture under future ocean conditions. While model simulations and plankton-scale experiments suggest global benefits of OAE, this study provides direct organism-level experimental evidence linking shell ultrastructure and transcriptomic responses under OA and OAE conditions. These findings offer mechanistic insights into mussel resilience and provide a critical empirical basis for evaluating the ecological safety of OAE as both a carbon sequestration strategy and a tool for sustainable aquaculture.
Continue reading ‘Differential impacts of ocean acidification and alkalinization on shell microstructure and molecular responses in Mytilus edulis’Novel in situ CO2 enrichment system reveals seagrass meadows are a refugium against coastal acidification for North Atlantic bivalves
Published 18 March 2026 Science ClosedTags: biological response, BRcommunity, chemistry, growth, laboratory, mollusks, mortality, North Atlantic, phanerogams
While the accumulation of anthropogenic CO2 in the atmosphere is causing a decline in global ocean pH, many eutrophic estuaries are already experiencing acidification due to accelerated respiration driving the consumption of dissolved oxygen (DO) and production of CO2, decreasing available carbonate ions (CO32-) and threatening marine calcifiers. Here, a novel in situCO2 enrichment system was constructed to examine the effects of coastal acidification on the growth and survival of two species of North Atlantic bivalves (Argopecten irradians and Crassostrea virginica) in two distinct estuarine habitats: a seagrass meadow and an unvegetated sandy bottom in an open water estuary. The in-situ system captured natural diel dynamics as ambient chambers displayed chemistry nearly identical to the surrounding water, while CO2-enriched, acidified chambers maintained a consistent ~Δ 0.3–0.5 pH offset. At the unvegetated sandy bottom site, A. irradians and C. virginica displayed significant reductions in growth and survival in the acidified chambers (pHT = 7.3–7.5; saturation state of aragonite, ΩAr = 0.6–0.9) relative to ambient conditions (pHT = 7.6–7.9; ΩAr = 1.6–2). At the seagrass site, while growth of A. irradians and C. virginica in the acidified treatments (pHT = 7.3–7.7; ΩAr = 0.7) receiving the same delivery of CO2 was, again, significantly slowed compared to the control (pHT = 7.5–8.1; ΩAr = 2 – 2.8), the growth reduction, mortality rates, and levels of acidification were attenuated compared to the sandy bottom experiment, evidencing the ability of seagrass to buffer seawater and serve as a potential acidification refuge for bivalves. Collectively, the novel experimental CO2 enrichment system constructed for this project demonstrates that coastal acidification can have deleterious effects on marine bivalve populations, and that future conditions as well as the habitat refuge offered by seagrasses must be considered when developing management and restoration plans for temperate estuaries.
Continue reading ‘Novel in situ CO2 enrichment system reveals seagrass meadows are a refugium against coastal acidification for North Atlantic bivalves’The economic impact of climate change on coral reef in the Main Hawaiian Islands
Published 18 March 2026 Science ClosedTags: biological response, communitymodeling, corals, modeling, multiple factors, North Pacific, socio-economy, temperature
Coral reefs are highly diverse and productive ecosystems that provide a wide range of ecosystem services, including recreation, coastal protection, and marine biodiversity. Climate change impacts, including ocean warming and acidification, pose a significant threat to coral reefs and the ecosystem services they provide. The variability of these impacts underlines the need to develop more spatially explicit tools in coastal ecosystem management that integrate and assess potential ecological and socio-economic outcomes. To address this, a spatially explicit predictive ecological model is applied to project changes in coral reef cover, using downscaled data from Shared Socioeconomic Pathway (SSP) climate scenarios. Based on these projections, welfare impacts of changes in recreational value are estimated across different populations and landscapes. Cumulative welfare losses for Hawaiʻi residents range from $1.5 to $3.3 billion in 2024$ by 2100. Counterintuitively, cumulative welfare losses are higher under optimistic emissions scenarios, where coral reef degradation is less severe than higher emission scenarios, because more people will experience smaller ecological losses. The approach incorporates site-specific characteristics, income distribution, and projected regional population growth to connect ecological change with welfare outcomes. EJScreen is used to assess variation in welfare impacts, identifying disadvantaged communities based on demographic and environmental indicators such as poverty, minority status, and exposure to environmental risks. These findings can inform policy and resource allocation by supporting ecosystem management strategies that account for both ecological dynamics and community-level socio-economic conditions.
Continue reading ‘The economic impact of climate change on coral reef in the Main Hawaiian Islands’Physiological responses of Swedish maerl to ocean acidification and warming
Published 17 March 2026 Science ClosedTags: 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 ClosedTags: 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 ClosedTags: 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’Enhanced carbon burial in seagrass meadows under ocean acidification revealed by carbon dioxide vents
Published 16 March 2026 Science ClosedTags: 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 ClosedTags: 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 ClosedTags: 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 ClosedTags: 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 ClosedTags: 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’Eco-evolutionary dynamics of planktonic calcifying communities under ocean acidification
Published 12 March 2026 Science ClosedTags: 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’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 ClosedTags: 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’Multifactorial neural disruption in the brain of the Senegalese sole (Solea senegalensis) under ocean acidification
Published 11 March 2026 Science ClosedTags: 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’
