Ocean acidification (OA), driven by global climate change together with pollution from organic contaminants, is increasing the ecological risk faced by coral reef ecosystems. The coral holobiont comprises diverse microbial communities that collectively support the coral host in coping with and adapting to environmental stress. However, the response of the coral holobiont to the combined stress of acidification and benzo[a]pyrene (BaP) remains poorly understood. In this study, Acropora millepora was selected as a model species to investigate the responses of coral-associated microbiomes to acidification (pH 7.8), BaP exposure (10 µg·L−1) and their combined effects. We found that while the cell density of coral-associated Symbiodiniaceae increased significantly with prolonged exposure time in all treatment groups, and there were no temporal differences in chlorophyll-a contents. The Symbiodiniaceae community was stable within all treatments, with Cladocopium as the dominant genus, and subtype C3u had the highest relative abundance (>70%). A rapid and significant increase in rare bacteria taxa was observed in the single-stress treatments (acidification, BaP), whereas prolonged exposure led to an increasing number of unique bacteria taxa in the combined-stress group in two weeks. Surprisingly, the main community structure of core coral-associated bacteria in the combined treatment group was close to that of the control group. Across all treatments, core coral-associated bacteria (including Sphingomonadaceae and Burkholderiaceae) consistently dominated the microbial community, while core coral-associated archaea exhibited more stochastic variations. Collectively, these results highlight the critical role of coral-associated microbiomes in rapidly and flexibly responding to environmental stressors, thereby contributing to the maintenance of holobiont stability under multiple stress conditions.
Continue reading ‘Transient disturbance and community convergence of coral-associated microbial communities under acidification, benzo[a]pyrene pollution, and combined stress in coral Acropora millepora’Posts Tagged 'abundance'
Transient disturbance and community convergence of coral-associated microbial communities under acidification, benzo[a]pyrene pollution, and combined stress in coral Acropora millepora
Published 9 November 2026 Science Leave a CommentTags: abundance, adaptation, archaea, biological response, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, photosynthesis, physiology, prokaryotes, toxicants
Multi-stressor-driven biotic upheaval across the PETM: a perspective from elemental and isotope ratios of foraminiferal and bulk carbonate in the southern Tethyan shelf
Published 9 November 2026 Science Leave a CommentTags: abundance, biological response, chemistry, otherprocess, paleo, protists
Highlights
- Multi-proxy reveals a sequence of ocean acidification, warming and anoxia across the PETM.
- We document pre-onset biotic stress, causing ecosystem to deteriorate before the PETM.
- Synergistic ocean warming, anoxia and acidification drove ecological reorganization.
- The study provides a geo-analogue for projecting future trajectory of ocean ecosystem.
Abstract
The Paleocene–Eocene Thermal Maximum (PETM) represents a pivotal geological analog for modern anthropogenic climate change, yet the precise temporal sequence of environmental stressors that drove severe biotic crisis remains elusive. Here, we present an integrated, multi-proxy record, including bulk carbonate and foraminiferal stable isotopes (δ13C, δ18O), and elemental ratios (Mg/Ca, B/Ca, U/Ca) from a Tethyan marine sequence (Tarfa section, Egypt), that captures the full PETM progression. Our data document four distinct phases of environmental and biotic changes. First, the pre-onset phase shows that initial foraminiferal decline is closely linked to precursor shifts in δ13C, δ18O, and early deoxygenation. This demonstrates that marine ecosystem stress began before the PETM carbon isotope excursion (CIE). Second, the PETM onset featured a severe carbonate dissolution (<1 wt%), forming a regional clay bed that caused benthic extinction and planktic decline. Third, the main body phase is characterized by a pronounced CIE (∼3.7‰), extreme warming (Mg/Ca-derived temperature increase of ∼5 °C, peaking at ∼35 °C), and pervasive deoxygenation (elevated U/Ca), which acted synergistically to drive ecological turnover and dwarfing. Lastly, the recovery phase is marked by a carbonate overshoot, gradual geochemical stabilization, and biotic rebound. Together, these findings reveal a phased cascade of stressors—initial carbon cycle instability, ocean acidification, and prolonged warming and deoxygenation—that reshaped marine ecosystems sequentially. This study therefore provides a template for understanding multi-stressor interactions and biotic resilience during rapid hyperthermal events, which has critical implications for predicting the future scenario of anthropogenic forcing.
Continue reading ‘Multi-stressor-driven biotic upheaval across the PETM: a perspective from elemental and isotope ratios of foraminiferal and bulk carbonate in the southern Tethyan shelf’Metabolic dynamics of an offshore coral reef in the central Red Sea: observations from autonomous sensors
Published 9 November 2026 Science Leave a CommentTags: abundance, algae, biogeochemistry, biological response, calcification, chemistry, community composition, corals, dissolution, field, methods, otherprocess, photosynthesis, physiology, porifera, primary production, Red Sea, respiration
Abstract
Coral reefs are increasingly threatened by local and global stressors. Traditional visual reef monitoring methods are time-intensive and provide only a snapshot of reef condition. Recent efforts aim to measure reef metabolism, or the balance of net community production (NCP) and net community calcification (NCC), as coral reef carbonate budgets shift globally toward declining NCC and greater NCP influence. Resolving these metabolic changes requires comprehensive, high-resolution biogeochemical measurements unattainable by traditional sampling alone. This work reports the novel multi-month deployment of a high-resolution, autonomous total alkalinity (TA) sensor alongside pH, partial pressure of CO2, and dissolved oxygen (DO) sensors at Cement Wreck, a central Red Sea offshore reef. Observations from the back reef and fore reef revealed strong diel variability and distinct reef-zone biogeochemical dynamics linked to contrasting benthic compositions. On the back reef, pH and DO were tightly coupled and closely matched a Redfield-based model (𝑅2=0.943), while the fore reef relationship was weaker (𝑅2=0.145). TA observations allowed characterization of the back reef carbonate system, with TA–DIC stoichiometry yielding a slope of 0.26, indicating NCP accounted for approximately 87% of observed carbonate system variability. Compared to global reefs, Cement Wreck exhibits high % NCP contribution. However, the observed 2023 TA–DIC slope closely matches those from Red Sea observations from 1997 to 2013, suggesting that while reefs around the world shift, Red Sea reefs like Cement Wreck represent a persistent metabolic state. Scaled-up autonomous deployments, like the one presented here, will better enable predictions of global reef health in future conditions.
Plain Language Summary
Globally, coral reefs are threatened by rising temperatures, changes in seawater chemistry, pollution, and overfishing. The health of coral reefs is traditionally monitored by reef community composition through visual analysis, however changes in surrounding seawater chemistry can provide insight into reef processes and holistically monitor reef health. Here, we deploy a newly developed total alkalinity (TA) sensor, alongside commercially available pH and oxygen sensors on a coral reef in the Red Sea. Autonomous sensors allow the collection of high-resolution data on reef seawater chemistry, including daily cycles and changes over time, with a cost per data point much lower than traditional discrete samples. Furthermore, the TA sensor allows us to evaluate the relative balance between the reef-building processes and reef-eroding processes occurring, which are important parameters when evaluating a reef’s present and future health. We found that the reef studied here was strongly influenced by organic production, and that this signal closely matched Red Sea observations from the last 25 years. This suggests that some Red Sea reefs may represent a persistent metabolic state rather than a recent shift. The Red Sea lacks high-resolution carbonate-system observations, and this deployment contributes to baseline understanding of Red Sea reef metabolism and carbonate budgets.
Continue reading ‘Metabolic dynamics of an offshore coral reef in the central Red Sea: observations from autonomous sensors’Relative resistance of estuarine dimethyl sulfide production to ocean acidification in the Yangtze river estuary
Published 6 November 2026 Science Leave a CommentTags: abundance, biogeochemistry, biological response, chemistry, field, North Pacific, otherprocess, phytoplankton
Dimethyl sulfide (DMS) is a climatically important sulfur gas, yet its response to ocean acidification in estuarine systems remains poorly constrained. Here, we combined three seasonal field surveys with ship-based microcosm experiments in the Yangtze River Estuary and adjacent coastal waters to resolve spatial variability in DMS cycling and assess responses to declining pH. DMS concentrations and cycling rates showed pronounced seasonal variability, remaining broadly comparable in spring and autumn but reaching maxima in summer. During the wet season, mean sea-to-air DMS fluxes estimated using two gas-transfer parameterizations were 11.5–14.3 μmol m−2 d−1, approximately 1.8–2.2 times the global ocean mean. Across all seasons, estuarine waters exhibited lower pH than adjacent coastal waters, yet DMS concentrations showed no corresponding decline. Along the pH gradient, coastal waters exhibited significant positive relationships between pH and chlorophyll a, DMS concentration, DMS accumulation rate, and DMS yield, whereas these relationships were largely absent in the estuary. The microcosm experiments further confirmed this contrast, with pH reductions of 0.2–0.4 units significantly decreasing chlorophyll a, particulate and dissolved dimethylsulfoniopropionate, and DMS in coastal waters by 11.9%–31.2%, 10.9%–24.6%, 13.0%–32.1%, and 13.9%–42.4%, respectively, but producing little response in estuarine waters. These results reveal that DMS production in the Yangtze River Estuary exhibits relative resistance to pH declines of 0.2–0.4 units across all three seasons investigated, suggesting that natural pH variability and environmental exposure history may modulate acidification responses.
Plain Language Summary
Dimethyl sulfide (DMS) is a naturally produced sulfur gas in seawater that can influence clouds and climate after being emitted to the atmosphere and oxidized to form sulfate aerosols. Previous studies have suggested that ocean acidification may reduce marine DMS production, but most evidence has come from open-ocean or relatively stable coastal environments. Here, we combined seasonal field surveys in spring, summer, and autumn with ship-based acidification experiments in the Yangtze River Estuary and adjacent coastal waters to examine how DMS production responds to declining pH. In the adjacent coastal waters, lower pH was associated with reduced phytoplankton biomass and lower DMS concentrations, and experimental acidification further suppressed DMS production. In contrast, DMS and related processes in the estuary showed limited responses to comparable pH reductions. These results demonstrate a marked difference in sensitivity to ocean acidification between the estuarine and adjacent coastal waters of the Yangtze River Estuary. Given the relative resistance of DMS production observed in estuarine waters, the contribution of the Yangtze River Estuary to future ocean-atmosphere sulfur exchange may remain relatively stable under moderate acidification.
Continue reading ‘Relative resistance of estuarine dimethyl sulfide production to ocean acidification in the Yangtze river estuary’Multiscale pH fluctuations on a stable algal reef community (SE Sardinia, Tyrrhenian Sea)
Published 5 November 2026 Science Leave a CommentTags: abundance, algae, biogeochemistry, biological response, bryozoa, chemistry, cnidaria, community composition, corals, field, Mediterranean, otherprocess, porifera
Highlights
- Mean Tyrrhenian surface pH is 8.33, but drops to 8.07 at Capo Carbonara coralligenous.
- High-frequency pH fluctuations are twice the open-sea mean multidecadal pH decrease.
- Intrusion of Atlantic water and Saharan dust outbreaks affect local pH variability.
- Coralligenous assemblage had long-lived, stable components and seasonal turf development.
- Future shifting boundaries of variability by OA may impair Coralligenous tolerance.
Abstract
The Mediterranean Sea is threatened by ocean acidification and warming, in combination with habitat loss, pollution, invasive species, and overexploitation. Assessing local high-frequency pH variability in the context of relevant basin-scale time series data is essential to understand ecosystem vulnerability. We report the results of the Italian national pH monitoring based on the Marine Strategy Framework Directive, and the pH dynamics observed at Capo Carbonara. An experimental station equipped with a pH sensor and CTD probe was deployed at 32 m depth on a sandy bottom bordered by Coralligenous assemblages. Physical and biogeochemical variables were continuously recorded over 345 days and analyzed through additive time series decomposition. The benthic assemblages were surveyed by photographic and destructive sampling in summer and autumn 2016 and spring 2017 on algal reef and sandy bottom, to describe the biological components undergoing and contributing to the pH fluctuations. Seasonal pH variability ranged up to 0.2 units annually and 0.1 units daily, with maxima in January and minima in August, while the range of pH on the basin scale had higher mean values and exceeded local variability. Assemblage changes were driven by algal turf development and the invasive Caulerpa cylindracea. Coralligenous taxa appear stable, despite the substantial natural pH variability, shaped by meteo-marine conditions, water mass circulation, Saharan dust inputs, and benthic biological processes, with primary producers and calcifiers exerting a key influence. The ongoing trend of increasing temperatures and decreasing pH may threaten the Coralligenous ability to cope with the shifting future boundaries of such variability.
Continue reading ‘Multiscale pH fluctuations on a stable algal reef community (SE Sardinia, Tyrrhenian Sea)’Oxidative stress as a potential mechanistic link between climate change and aquatic biodiversity loss
Published 4 November 2026 Science Leave a CommentTags: abundance, adaptation, algae, biological response, calcification, community composition, corals, echinoderms, fish, light, mollusks, mortality, multiple factors, nutrients, otherprocess, oxygen, performance, photosynthesis, physiology, phytoplankton, plastics, protists, reproduction, review, temperature, zooplankton
Climate change is rapidly altering aquatic ecosystems through rising temperatures, ocean acidification, hypoxia, ultraviolet radiation, salinity fluctuations, and interacting environmental stressors. These changes impose substantial physiological challenges on aquatic organisms, with oxidative stress representing an important mechanistic pathway linking environmental disturbances to biological responses across multiple levels of organization. This review synthesizes current evidence on oxidative stress responses associated with climate change-related environmental stressors across aquatic taxa, including fish, aquatic invertebrates, corals, phytoplankton, macroalgae, amphibians, and polar and deep-sea organisms. We examine the mechanisms underlying reactive oxygen species production, disruption of antioxidant defenses, and oxidative damage, while critically evaluating biochemical, molecular, and omics-based biomarkers for environmental stress assessment. Particular emphasis is placed on how oxidative stress may translate from cellular and organismal responses into changes in growth, reproduction, behavior, survival, species distributions, population dynamics, community structure, biodiversity, and ecosystem resilience. We also highlight limitations of current biomarker approaches, including species-specific variability, methodological inconsistencies, and difficulties in extrapolating laboratory findings to natural ecosystems. Future research should prioritize integrated multi-biomarker and multi-stressor approaches, long-term ecological monitoring, standardized protocols, and the integration of omics, environmental DNA, remote sensing, and artificial intelligence. Overall, oxidative stress biomarkers provide complementary tools for assessing climate-change impacts on aquatic biodiversity and ecosystem resilience.
Continue reading ‘Oxidative stress as a potential mechanistic link between climate change and aquatic biodiversity loss’Coupled increases in pelagic fish productivity and export productivity during the Paleocene-Eocene Thermal Maximum
Published 3 November 2026 Science Leave a CommentTags: abundance, biogeochemistry, biological response, fish, globalmodeling, modeling, otherprocess, paleo
Ocean productivity is sensitive to climate change, and its decline in recent decades has profoundly impacted the biosphere. Yet its long-term trajectory under global warming remains a topic lacking consensus. To address this question, we use paired ichthyolith and marine barite accumulation rates to investigate marine productivity and associated biological responses during the Paleocene-Eocene Thermal Maximum. We find a widespread increase in pelagic fish productivity, particularly in the Pacific and North Atlantic, that closely tracks export productivity in trend and spatial pattern, suggesting this increase was fueled by enhanced carbon export from the surface ocean. Model simulations support the observed trend, demonstrating that under elevated pCO2 conditions, the effects of enhanced nutrient supply can outweigh the suppressive effects of ocean stratification on export productivity. Our findings highlight that the long-term response of marine productivity to sustained greenhouse warming may differ fundamentally from the short-term declines observed in the modern ocean.
Continue reading ‘Coupled increases in pelagic fish productivity and export productivity during the Paleocene-Eocene Thermal Maximum’Time-variant bioeconomic risks on a gastropod fishery affected by uncertain ocean acidification trajectories
Published 3 November 2026 Science Leave a CommentTags: abundance, biological response, chemistry, field, fisheries, growth, modeling, mollusks, mortality, North Pacific, otherprocess, regionalmodeling, socio-economy
Introduction: In the north-eastern Pacific, high-value abalone fisheries, which are sensitive to pH variations, require in situ pH data to properly assess the bioeconomic effects of their possible dynamic trajectories under alternative fishing mortalities.
Methods: In situ pH data were collected every 15 min using a HOBO® MX2501 sensor in the La Bocana pink abalone fishing grounds and compared them with Argo float and Copernicus Marine Service observations. The observed pH distribution was fitted to the Extreme Value Minimum distribution based on the Anderson–Darling goodness-of-fit statistic. Stochastic pH trajectories were generated through 10,000 Monte Carlo replications under three IPCC ocean acidification scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) and three fishing mortalities (FD = 0.02, 0.04, and 0.06). These trajectories were incorporated into a dynamic age-structured bioeconomic model by making individual growth and age-specific natural mortality functions dependent on pH. Biomass and resource rent per boat were projected from 2025 to 2100, and linear mixed-effects models, sensitivity analyses, and 95% confidence intervals were used to evaluate temporal responses and parameter uncertainty. Dynamic risks were estimated as the probability that biomass and resource rent fell below their respective limit reference points (LRPs: 190 t and USD 15,000 yr-1) across scenarios and fishing mortalities.
Results: The results indicate considerable variability in pH measurements between remote and in situ sources, which may introduce a proportional bias into the bioeconomic modeling if local observations are absent. Also, the effects of ocean acidification on H. corrugata biomass, survival, and fishery resource rent increase with time, IPCC pH scenario, and alternative exploitation intensity. Under the current exploitation rate (FMSY = 0.06), effects were negligible in the short term under SSP1-2.6, whereas by 2100 pH-related growth effects decreased by 4%, 13%, and 26% under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. Over the same period, pH effects on survival rates resulted in a slight increase of 2.14% under SSP1-2.6, but reductions of 6.48% and 22% under SSP2-4.5 and SSP5-8.5, respectively, while age-specific biomass peaks declined by up to 20% and 44% under SSP2-4.5 and SSP5-8.5. Mixed-effects models confirmed significant effects of pH scenario, exploitation rate, and time on biomass and resource rent, including significant interactions (all p < 0.001). By 2100, annual resource rent per small-scale boat was significantly higher under SSP1-2.6 than under SSP2-4.5 and SSP5-8.5 by USD 3,083 and USD 7,482, respectively (p < 0.0001). Under FMSY, the risk of biomass falling below its LRP was <25% during 2025–2040 but increased to 34% and 54% under SSP2-4.5 and SSP5-8.5, respectively, by 2100; corresponding risks for resource rent increased to 27% and 48%.
Discussion: These results indicate that ocean acidification may substantially increase the long-term bioeconomic vulnerability of the fishery, particularly under high-emission scenarios. Management actions to mitigate the undesired bioeconomic effects of OA will likely depend on the fishery authority’s risk attitude (i.e., degree of risk aversion) and corresponding exploitation-rate strategy selection.
Continue reading ‘Time-variant bioeconomic risks on a gastropod fishery affected by uncertain ocean acidification trajectories’Climate-driven habitat loss of Chinese sturgeon in the Northwestern Pacific and implications for marine protected area design
Published 3 November 2026 Science Leave a CommentTags: abundance, biological response, fish, methods, modeling, multiple factors, North Pacific, nutrients, otherprocess, oxygen, regionalmodeling, salinity, temperature
Highlights
- Ensemble modeling integrates eleven algorithms to predict sturgeon habitat suitability.
- Temperature is the dominant driver, followed by pH and total suspended matter.
- Suitable habitats are projected to disappear completely by 2100 under SSP5–8.5.
- Static protected areas must transition to climate-adaptive zoning strategies.
Abstract
The conservation of endangered anadromous fishes depends on understanding their full-lifecycle habitat requirements, yet the marine phase of Chinese sturgeon (Acipenser sinensis) remains a critical knowledge gap despite over 90% of its lifespan occurring at sea. We integrated multi-source occurrence data (satellite tagging, bycatch records, environmental DNA, and online databases) and applied an ensemble modeling framework (Biomod2 with eleven algorithms) to predict habitat suitability across the Northwestern Pacific Ocean (100°E–150°E, 10°N–55°N). After collinearity filtering, seven key environmental drivers were retained, among which mean temperature contributed most, followed by maximum pH, total suspended matter and mean silicate. The ensemble model achieved high predictive performance (median TSS = 0.944) and identified the Changjiang Estuary and coastal waters of Zhejiang and Jiangsu provinces as current distribution hotspots. Under the high-emission scenario (SSP5–8.5), suitable habitats are projected to disappear completely by 2100, accompanied by a significant northward contraction. These projections should be regarded as a potential worst-case scenario under high-emission conditions rather than a deterministic forecast. These findings demonstrate that business-as-usual emissions would eliminate viable marine habitat for this critically endangered species. Conservation priorities should therefore focus on (1) protecting benthic prey resources in the Changjiang Estuary and Zhoushan Archipelago as core refugia, and (2) transitioning from static marine protected areas to dynamic, climate-adaptive zoning informed by real-time habitat predictions. The ensemble modeling approach developed here is transferable to other data-limited, endangered marine species facing similar climate threats.
Continue reading ‘Climate-driven habitat loss of Chinese sturgeon in the Northwestern Pacific and implications for marine protected area design’Long-term stress induced by low bicarbonate alkalinity causes intestinal oxidative stress, gut microbiota imbalance and metabolic disorder in Scylla paramamosain
Published 3 November 2026 Science Leave a CommentTags: abundance, biological response, community composition, crustaceans, fisheries, molecular biology, morphology, mortality, North Pacific, otherprocess, physiology, prokaryotes
Highlights
- Low bicarbonate induces acid-base imbalance and oxidative stress
- Opportunistic pathogen Klebsiella is a potential biomarker of the LB group.
- Low bicarbonate affects chitin synthesis and gut barrier.
- Low bicarbonate affects NDAA and gut microbiota.
Abstract
To investigate the effects of low bicarbonate alkalinity on intestinal health of Scylla paramamosain, we systematically evaluated the growth survival, intestinal antioxidant enzyme activities, and expression profiles of genes involved in immunity, inflammation, apoptosis and osmoregulation under low alkalinity conditions. Meanwhile, integrated intestinal microbiome and metabolome analyses were performed. The results showed that low bicarbonate alkalinity significantly reduced the survival and molting rates of S. paramamosain. It markedly elevated the activities of intestinal SOD, CAT and GSH-Px, as well as the expression levels of inflammation-related genes (IL-16, RELISH, LITAF), apoptosis-related genes (CASPASE7, BAX, BCL2) and osmoregulation-related genes (NKA, NHE, Cl−/HCO₃−), while suppressing the expression of immune genes (proPO, ALF1, LZM) (P<0.05). Low bicarbonate alkalinity disrupted the intestinal microbiota structure of S. paramamosain, accompanied by a decreased abundance of the phylum Bacteroidota and a significant increase in the abundance of the genus Klebsiella (P<0.05). A total of 714 differential metabolites were identified by metabolomic analysis, which were mainly annotated into Fatty Acyls, Glycerophospholipids, and Steroids and steroid derivatives. Multiple carbohydrate metabolism pathways were significantly enriched and participated in the regulation of Fructose 6-Phosphate (F6P). Integrated microbiome-metabolome analysis revealed that N,N-dimethyl arachidonoyl amine (NDAA) may cooperate with intestinal microorganisms to regulate the stress tolerance of S. paramamosain under low bicarbonate alkalinity stress. Based on the physiological and biochemical characterization of the intestine, this study elucidated the adaptive characteristics of S. paramamosain under low bicarbonate alkalinity. The findings provide important theoretical basis and practical significance for the saline-alkaline aquaculture of S. paramamosain.
Continue reading ‘Long-term stress induced by low bicarbonate alkalinity causes intestinal oxidative stress, gut microbiota imbalance and metabolic disorder in Scylla paramamosain’Current knowledge of marine crustaceans in Mauritius and their global importance in a changing climate
Published 30 October 2026 Science Leave a CommentTags: abundance, biological response, community composition, crustaceans, fisheries, otherprocess, performance, physiology, reproduction, review
Marine crustaceans are ecologically and socio-economically important components of coastal and marine ecosystems; however, in Mauritius, knowledge of their biodiversity, functional roles, and responses to climate change remains limited and fragmented. This narrative review synthesizes available information on Mauritian marine crustaceans, with particular emphasis on the class Malacostraca, while identifying key knowledge gaps and research priorities relevant to their ecological importance and climate-change vulnerability at both local and global scales. Although existing records document 61 crustacean families in Mauritius, these data are sparse, outdated, and largely based on historical surveys, highlighting the urgent need for updated inventories and long-term monitoring. Globally, marine crustaceans act as trophic intermediaries, ecosystem engineers, and scavengers, contributing to nutrient cycling, sediment dynamics, and habitat stability. They support fisheries, aquaculture, tourism, and cultural practices, and provide valuable bioresources such as chitin, chitosan, and other bioactive compounds with applications in regeneratiom engineering, medicine, agriculture, environmental remediation, and biotechnology. Trade patterns further emphasize their economic importance, revealing export-oriented dynamics in Mauritius, instead of local consumption, that result in a net reliance on imports. Climate change poses an escalating threat through ocean warming, acidification, and increasing environmental variability, affecting DNA repair, protein synthesis, haemolymph, metabolic performance, calcification, reproduction, immunity, behavior, and species interactions. These stressors are further compounded by habitat degradation, altered symbiotic interactions and food-web disruption. The scarcity of empirical studies from Mauritius underscores the need for integrative, multi-stressor, and long-term research to support effective conservation, fisheries management, and climate resilience.
Continue reading ‘Current knowledge of marine crustaceans in Mauritius and their global importance in a changing climate’Navigating uncertainty in the Pacific Arctic region: toward adaptive fisheries management under climate change and ocean acidification impacts
Published 30 October 2026 Science Leave a CommentTags: abundance, Arctic, biological response, fish, fisheries, modeling, mortality, otherprocess, policy, regionalmodeling
Fisheries management under climate change in the Pacific Arctic Region faces profound uncertainties, particularly concerning the trajectory of environmental drivers and the biological responses of fish species to ocean acidification (OA), which affect both stock productivity and spatial distributions. Here, we employed the Dynamic Bioclimate Envelope Model to project century-scale changes in abundance, maximum catch potential, and species distributions for key commercial fish under two climate scenarios (SSP1-2.6 and SSP5-8.5) and two alternative assumptions about OA responses, namely without OA effect and with OA effect parameterized as increases in basal metabolic rate and elevated larval mortality. Fishing mortality was treated as a management control variable, and the minimax regret criterion was applied to select the fishing mortality strategy that minimizes the worst-case loss in landed value relative to the scenario-specific optimal strategy across all climate and OA response scenarios. Results indicate strong regional heterogeneity: southern LMEs (East Bering Sea, West Bering Sea, and Aleutians) experienced persistent declines in abundance and maximum catch potential, with negative responses to OA further amplifying reductions, whereas the northern LME (Northern Bering–Chukchi Seas) exhibited substantial gains. These poleward shifts were accompanied by increased spatial aggregation, highlighting that species are not only shifting northward but also becoming more spatially concentrated within suitable habitats. Assessments that ignore OA effects risk overestimating long-term yields and exposing fisheries to productivity and revenue losses. Precautionary reductions in fishing mortality consistently minimized long-term regret across most species and LMEs. These findings highlight the critical interplay between climate change, OA effects, and management decisions, providing a scientific basis for adaptive fisheries management in the rapidly changing Pacific Arctic Region.
Continue reading ‘Navigating uncertainty in the Pacific Arctic region: toward adaptive fisheries management under climate change and ocean acidification impacts’From population to individual: bulk and single-cell analysis reveal Fe bioavailability, limitation thresholds, and biological responses for marine diatom Chaetoceros debilis
Published 27 October 2026 Science Leave a CommentTags: abundance, biological response, laboratory, metals, multiple factors, otherprocess, physiology, protists
Highlights
- Fe speciation and pH jointly regulated Fe bioavailability.
- A critical bioavailable Fe limitation threshold (∼10 nM) was identified for the marine algae.
- Single-cell analysis revealed previously hidden heterogenous Fe accumulation.
- Fe stress induced adaptive responses including metallome remodeling.
Abstract
In marine ecosystems, Fe fundamentally regulates algal productivity and drives biogeochemical cycling in the hydrosphere, yet its environmental controls and cellular responses remain insufficiently resolved, particularly at the single-cell level. Herein, we combined bulk and single-cell analysis to systematically investigate Fe bioaccumulation process in the marine diatom Chaetoceros debilis under varying Fe species, initial pH, and concentration conditions. Fe bioavailability followed the order Fe-ethylenediaminetetraacetate > Fe-deferoxamine B > Ferrihydrite and decreased with declining initial pH, highlighting the combined control of chemical speciation and ocean acidification. A critical bioavailable Fe limitation threshold of ∼10 nM was identified, below which algal growth, pigmentation, and cell size were significantly suppressed. Under Fe limitation, cells exhibited compensatory accumulation of other metals (e.g., Zn, Mn, Cu, and Ni), indicating metallome remodeling as an adaptive strategy. Notably, single-cell analysis revealed pronounced heterogeneity in Fe accumulation within populations, with heterogeneity positively related to bioavailable Fe levels. These findings demonstrate that algal Fe accumulation is governed by coupled environmental and physiological processes and that population-level averages mask critical cell-to-cell variability and their adaptive strategies under environmental stress. This work provides mechanistic insights into how environmental chemistry regulates metal bioavailability and biological responses, offering a broadly applicable framework for understanding the environmental behavior and ecological effects of trace metals and other contaminants in aquatic ecosystems.
Graphical abstract
Surviving together: evolutionary dependency, community dynamics, and mortality in marine microbial communities
Published 26 October 2026 Science ClosedTags: abundance, adaptation, biological response, community composition, growth, laboratory, light, molecular biology, mortality, multiple factors, nutrients, otherprocess, photosynthesis, physiology, phytoplankton, primary production, prokaryotes, reproduction, respiration, temperature
Oligotrophic regions of the world ocean sustain vast phytoplankton populations despite extremely low nutrient levels. However, the mechanisms governing their coexistence, interdependence, and mortality are poorly understood. This dissertation investigates how evolutionary dependency, community feedback, and regulated cell death (RCD) jointly shape the stability of marine microbial communities using the Prochlorococcus/Parasynechococcus/Alteromonas model system.
In Chapter 1, I argue that the Black Queen (BQ) hypothesis—which posits that microbes lose costly metabolic functions supplied by community partners—provides a unifying framework for understanding phytoplankton ecology. This framework helps resolve longstanding puzzles, including the paradox of the plankton and the evolutionary maintenance of RCD in unicellular organisms. Building on this framework, Chapter 2 uses transcriptomic analysis of Alteromonas in co-culture with picocyanobacteria to demonstrate that community composition induces greater changes in gene expression than pCO₂ alone. Reduced 2-phosphoglycolate/glycolate exudation by Prochlorococcus under elevated pCO₂ may disrupt the helper heterotroph effect underlying this cyanobacterium’s BQ dependency.
Chapter 3 integrates co-culture experiments, RNA-seq, metabolomics, and mathematical modeling to demonstrate that the stable coexistence of Prochlorococcus and Parasynechococcus is maintained by an “Ouroboros network” of feedback loops. In this network, resource competition, carbon exudation, BQ dependency, and possibly RCD collectively stabilize the community across environmental gradients and during adaptation to changing conditions.
Chapter 4 resolves the cellular mechanisms underlying RCD in these cyanobacteria, showing that differences in cell death modes and the number of checkpoint-linked mortality events between taxa are associated with divergent life-history strategies. These findings suggest that carbon released at these checkpoints may shape interactions with helper Alteromonas, linking individual cell death to community-level interdependencies.
In conclusion, these findings converge on a new resolution to the paradox of the plankton: coexistence in resource-limited environments emerges from interdependent metabolic exchanges, feedback, and regulated cell death shaped by multilevel selection. I propose that together, these processes form an “altruistic bargain” in which stability arises from self-constraint rather than competition alone. Because these interactions are environmentally sensitive, climate change, including warming and acidification, may disrupt the dependencies that sustain microbial diversity and ecosystem function in the world ocean.
Continue reading ‘Surviving together: evolutionary dependency, community dynamics, and mortality in marine microbial communities’Long-term coral responses to high CO2: insights from volcanic vents and semi-enclosed bays
Published 20 October 2026 Science ClosedTags: abundance, adaptation, biological response, community composition, corals, mortality, multiple factors, North Pacific, otherprocess, oxygen, physiology, South Pacific, temperature, vents
This chapter provides a comprehensive review of natural laboratories used to study the effects of ocean acidification (OA) on coral reefs, emphasizing volcanic CO2 vents and semi-enclosed bays. It examines key environmental conditions at these study sites and their implications for coral physiology, biodiversity, and reef resilience. Two prominent natural analogues are highlighted: the Shikine Island warm-temperate shallow CO2 vent system in Japan and the semi-enclosed lagoon of Bouraké in New Caledonia.
Shikine Island represents a unique high-latitude coral environment influenced by the Kuroshio Current. The island’s CO2 vents provide a natural setting to investigate the community level effects of ocean acidification and how elevated CO2 levels interact with ocean warming and influence coral tropicalization. Findings suggest that while some corals persist at high CO2 levels, biodiversity declines significantly, with sensitive species unable to establish stable populations. Corals growing in these conditions exhibit reduced calcification, and the community structure shifts toward simpler, lower-complexity ecosystems dominated by turf algae. These results indicate that ocean acidification may act as a constraint on the poleward expansion of tropical corals, counteracting warming-induced range shifts.
In contrast, the semi-enclosed lagoon of Bouraké experiences extreme environmental fluctuations in pH, oxygen, and temperature, providing a window into the multifactorial stressors coral reefs may face in the future. Despite prolonged exposure to acidified, hypoxic, and thermally variable waters, corals in Bouraké demonstrate remarkable resilience. The system harbors diverse coral assemblages, with species exhibiting metabolic adjustments, increased heterotrophy, and shifts in symbiotic algae communities. This site suggests that coral ecosystems can develop physiological adaptations that enhance their survival in extreme conditions, offering valuable insights into the potential for long-term acclimatization.
By comparing these two contrasting natural analogues, this chapter highlights the complex interplay between acidification, warming, and other environmental stressors on coral reefs. While both sites provide critical insights into the future of coral ecosystems, they also underscore the urgent need for continued research and conservation efforts to mitigate the effects of climate change on marine biodiversity.
Continue reading ‘Long-term coral responses to high CO2: insights from volcanic vents and semi-enclosed bays’A key seawater acidification-enriched gut bacterium, Pseudoalteromonas carrageenovora P1, enhances growth performance, antioxidant status, and disease resistance in sea cucumbers under seawater acidification
Published 28 September 2026 Science ClosedTags: abundance, adaptation, biological response, BRcommunity, echinoderms, fisheries, laboratory, molecular biology, morphology, North Pacific, otherprocess, physiology, prokaryotes
Highlights
- First discovery of Pseudoalteromonas enrichment in A. japonicus gut under acidification.
- The dominant strain P. carrageenovora P1 was successfully isolated.
- P. carrageenovora P1 activates host antioxidant and immune pathways to bolster stress resilience.
- P. carrageenovora P1 significantly enhances resistance to V. splendidus 21,915 infection in A. japonicus.
Abstract
The sea cucumber (Apostichopus japonicus) is a key mariculture species of high economic value in East Asia. However, Ocean acidification, resulting from the increased uptake of anthropogenic CO₂ by seawater, severely impairs its growth, survival, and reproductive performance, thereby threatening the sustainable development of this aquaculture industry. The gut microbiota play a critical role in host adaptation to environmental stress; however, their involvement in mediating A. japonicus responses to seawater acidification remains unclear. Therefore, this study first compared the gut microbial communities of juvenile and adult A. japonicus under acidified and ambient seawater conditions. The results showed that Pseudoalteromonas abundance was significantly enriched under seawater acidification, from which the dominant strain, Pseudoalteromonas carrageenovora P1, was screened and isolated. This strain, when supplied as a dietary supplement under seawater acidification, improved A. japonicus growth performance and intestinal morphology, activated the Keap1-Nrf2-ARE and NF-κB pathways, enhanced antioxidant capacity and immune function, and increased resistance against Vibrio splendidus 21915 infection. Moreover, P. carrageenovora P1 modulated gut microbial structure by promoting beneficial bacteria such as Lutibacter while suppressing potential pathogens, including Vibrio, thereby maintaining intestinal homeostasis under acidification stress. This study reveals the important value of the gut microbiota of A. japonicus in regulating environmental tolerance of benthic invertebrates, and also provides a scientific reference for stress resistance regulation and health maintenance in A. japonicus aquaculture under seawater acidification.
Comparative responses of coastal Arabian sea plankton to different ocean acidification simulation methods
Published 16 September 2026 Science ClosedTags: abundance, biological response, BRcommunity, community composition, Indian, laboratory, otherprocess, phytoplankton, prokaryotes, zooplankton
Ocean acidification (OA) is expected to alter marine phytoplankton communities by modifying seawater carbonate chemistry, with important implications for marine food webs and biogeochemical cycling. In this study, we tested the hypothesis that comparable pH reductions achieved through different acidification methods generate distinct carbonate chemistry conditions and consequently different biological responses. A 5-day microcosm experiment was conducted using natural phytoplankton assemblages collected from the coastal Eastern Arabian Sea. OA was simulated by HCl addition (acid), CO2 enrichment (CO2), and acid–base manipulation. Changes in carbonate chemistry, nutrients, phytoplankton community composition, pigments, bacteria, microzooplankton, and organic carbon pools were monitored. As expected, the three manipulation methods produced significantly different carbonate chemistry conditions despite comparable pH reductions. Repeated-measures ANOVA and Tukey’s post hoc analyses confirmed significant treatment effects for pH, pCO2, DIC, HCO3−, CO32−, and total alkalinity. By Day 5, CO2 enrichment significantly increased total phytoplankton abundance and promoted microplankton dominance, driven by bloom-like proliferation of Thalassiosira sp., whereas picoplankton declined significantly. Conversely, pennate diatoms, cyanobacteria, dinoflagellates, and coccolithophores exhibited weak or negative responses. Concurrent changes in phosphate, nitrite, autotrophic bacteria, and microzooplankton indicated that nutrient availability, microbial recycling, and grazing interacted with carbonate chemistry to regulate phytoplankton succession. Our findings demonstrate that phytoplankton responses in the oligotrophic Eastern Arabian Sea are governed by the combined effects of carbonate chemistry, nutrient dynamics, and ecological interactions rather than pH alone.
Continue reading ‘Comparative responses of coastal Arabian sea plankton to different ocean acidification simulation methods’Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters
Published 27 April 2026 Science ClosedTags: 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 (CaCO3) 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’Responses of reef fish populations to similar environmental changes across distant oceanic islands
Published 9 April 2026 Science ClosedTags: abundance, adaptation, biological response, chemistry, field, fish, otherprocess, South Atlantic
Oceanic islands are among the most remote and understudied regions of the planet, yet they harbour unique reef fish communities that are increasingly vulnerable to global environmental change. Because these islands are geographically isolated, their populations are often assumed to respond mainly to local environmental conditions. However, by analysing temporal patterns in oceanographic variables across two distant systems (3204 km apart) in the South Mid-Atlantic Ridge (both encompassed by marine protected areas—MPAs), we found that temporal alignment in environmental conditions was associated with coordinated shifts in counts of nine reef fish populations in each study area. Among the evaluated variables, pH emerged as the most influential factor. Despite the divergent responses among reef fishes, possibly reflecting differences in physiological plasticity, shared temporal patterns in pH appeared central to parallel population patterns observed across assemblages. Increases in sea surface height and chlorophyll-a played secondary roles, potentially benefiting some populations, although such effects may be transient. These results suggest that climate-driven convergence in environmental conditions can override geographic isolation, promoting similar biological responses that may reduce resilience and increase extinction risk. Given that both islands are legally protected, our findings highlight that even MPAs are not insulated from large-scale oceanographic stressors, underscoring the need for long-term monitoring and adaptative conservation strategies for remote reef systems.
Continue reading ‘Responses of reef fish populations to similar environmental changes across distant oceanic islands’
