Phosphorus (P) availability constrains marine productivity, yet how ocean acidification interacts with intensifying phosphate limitation remains unresolved. Here we present multi-omics analyses of >1,000 generations of experimental diatom evolution to disentangle evolutionary and acclimation-driven responses to ocean acidification under different phosphate regimes. Long-term selection under elevated CO2 produced heritable increases in growth and carbon fixation that persisted irrespective of phosphate availability. In contrast, ocean acidification-driven reductions in particulate organic phosphorus were reversed after reciprocal transfers between selection treatments under phosphate limitation, indicating acclimation and environment-dependent P allocation. Multi-omics analyses indicate that the particulate organic phosphorus decline could be attributed to depletion of cellular P reserves and enrichment of non-P cell membrane lipids under combined ocean acidification and phosphate stress. Coastal mesocosm experiments revealed similarly reduced particulate organic phosphorus in natural phytoplankton at low-phosphate stations under ocean acidification. Global meta-transcriptomes further indicate widespread upregulation of gene expression in non-P cell membrane lipid pathways in high-pCO2 and low-phosphate regions. Earth system models predict a 211% to 2,185% decline in particulate organic phosphorus by 2100 under the under the Shared Socioeconomic Pathway (SSP)2–4.5 or SSP5–8.5 scenarios, respectively. These results show that ocean acidification could intensify nutrient imbalance and reshape global phosphorus cycling in marine ecosystems.
Continue reading ‘Ocean acidification reshapes phytoplankton phosphorus metabolism under phosphate-limited conditions’Posts Tagged 'field'
Ocean acidification reshapes phytoplankton phosphorus metabolism under phosphate-limited conditions
Published 9 November 2026 Science Leave a CommentTags: adaptation, biogeochemistry, biological response, field, globalmodeling, growth, laboratory, mesocosms, modeling, molecular biology, multiple factors, North Pacific, nutrients, otherprocess, photosynthesis, physiology, phytoplankton, protists
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’Contrasting catchment characteristics and carbonate buffering capacity shape acidification susceptibility and CO2 source-sink dynamics in tropical lagoons
Published 6 November 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, Indian, mitigation, modeling, regionalmodeling
Coastal ecosystems face increasing anthropogenic pressure, driving acidification and shifting them from carbon sinks to sources, yet comparative assessments across contrasting catchment types remain limited, particularly in the Indian Ocean region. We investigated carbonate chemistry in two contrasting tropical Sri Lankan lagoons, Negombo Lagoon, impacted by intensive anthropogenic and marsh-derived inputs, and minimally disturbed Rekawa Lagoon. In Negombo, low-pH, low total alkalinity (TA), and high-CO2 river water and acid-sulfate marsh inputs, combined with weaker carbonate buffering, intensified acidification (pH = 7.66 ± 0.45) and sustained CO2 outgassing (9.1 ± 10.2 mmol m-2 d-1). The lowest pH and weakest buffering occurred in the inner lagoon, and increased toward the seawater inlet through river-sea mixing. In contrast, catchment-derived higher-pH, higher-TA, lower-CO2 river water and strong buffering in Rekawa supported higher pH (8.31 ± 0.52) and net CO2 uptake (−1.8 ± 0.9 mmol m-2 d-1). Our simulations showed that riverine alkalinity enhancement (292–526 µmol kg-1 TA addition) mitigated acidification and CO2 outgassing in Negombo within 40–50 days. Our regional data synthesis showed that pH increased significantly with increasing TA/DIC ratio across estuaries and lagoons. These findings highlight carbonate buffering and catchment management as key strategies for mitigating coastal acidification and CO2 emissions.
Continue reading ‘Contrasting catchment characteristics and carbonate buffering capacity shape acidification susceptibility and CO2 source-sink dynamics in tropical lagoons’Overlooked contribution of organic alkalinity in Arctic Ocean margins biases ocean acidification estimates
Published 5 November 2026 Science Leave a CommentTags: Arctic, chemistry, field, methods
Organic alkalinity has been recognized as a potentially substantial fraction of total alkalinity in coastal waters. However, conventional assessments of ocean acidification typically neglect its contribution when calculating pH and aragonite saturation state, potentially biasing the derived values. Here, we present elevated organic alkalinity in Arctic margins, and show that failure to account for it introduces substantial biases in calculated [H+] (1% – 51%) and aragonite saturation state (1% – 117%) in the Svalbard fjords, Tanafjorden, and the Barents Sea Opening, with potential implications for the broader Atlantic sector of the Arctic margins. Regional projections based on Earth system model outputs further indicate that accounting for organic alkalinity leads to a larger and faster pH decline. These results indicate non-negligible biases in conventional ocean acidification assessments for Arctic margins and highlight the need to account for organic alkalinity in coastal waters and beyond.
Continue reading ‘Overlooked contribution of organic alkalinity in Arctic Ocean margins biases ocean acidification estimates’Africa’s first permanent Ocean Observatory: powering science, defending nature, and shaping policy for ocean governance and the blue economy
Published 5 November 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, Indian, methods
Sustained, high-resolution ocean observation is essential for understanding how marine ecosystems respond to climate variability, human pressure, and conservation action. Yet long-term observing platforms remain scarce across the Global South, limiting the capacity to detect environmental change, evaluate management interventions, and support evidence-based ocean governance. To help address this gap, we established Africa’s first permanent, multi-ecosystem Ocean Observatory in Mozambique’s Bazaruto Archipelago, operated by the Bazaruto Center for Scientific Studies (BCSS) and Kisawa Sanctuary through a novel Resort-to-Research (R2R) funding and operational model. The observatory spans ~6,850 km² of ocean habitats in the Western Indian Ocean (WIO) region, a domain nearly six times larger than Bazaruto Archipelago National Park-BANP (1,430 km²) and more than fourteen times the San Sebastian Sanctuary (472 km²). It extends ecosystem-scale monitoring beyond protected-area boundaries across coral reefs, seagrass meadows, mangroves, sandy habitats, seamounts, coastal waters, and open-ocean environments. Between 2017 and 2026, the observatory generated more than 22 million high-frequency measurements across more than 30 ocean, weather, and biodiversity variables from 14 long-term stations distributed across six ecosystem types. These records are complemented by more than 250,000 minutes of underwater soundscape recordings, more than 120,000 georeferenced species records, and over 14,000 kg of marine debris recovered through monitoring and clean-up operations. Together, these datasets constitute one of the most comprehensive long-term environmental and biodiversity time-series currently available for the WIO region. The observatory is organized around four thematic programs: ecosystem dynamics, habitat mapping, migratory populations, and marine plastics, integrating physical, chemical, biological, and anthropogenic dimensions of environmental change. This publication forms part of a paired contribution on the BCSS Ocean Observatory. The companion technical/data paper published in Frontiers in Marine Science, “Africa’s first long-term ocean observatory in the Bazaruto Archipelago for multi-ecosystem and biodiversity data,” describes the observatory architecture, sensor systems, measured variables, QA/QC procedures, metadata structure, DOI-linked repositories, FAIR data-access pathways, and reuse potential. Building on this technical foundation, the present publication examines the observatory’s broader scientific, institutional, conservation, governance, and blue-economy significance. Embedded within the R2R model, the BCSS Ocean Observatory links eco-tourism, science, education, and community stewardship to support long-term operational continuity. Its open-access, DOI-linked datasets provide a foundation for environmental reporting and future monitoring, reporting, and verification applications related to climate, weather, ocean physics and chemistry, biodiversity, and pollution. More broadly, the observatory shows how locally anchored and community-engaged science can produce actionable knowledge for conservation planning, policy support, and selected blue-economy applications, including the future development of blue bonds, biodiversity credits, or plastic credits where appropriate validation and governance frameworks exist. The BCSS Ocean Observatory and R2R model therefore provide a transferable Africa-based example of how sustained ocean observation can support environmental accountability and strengthen long-term ocean governance.
Continue reading ‘Africa’s first permanent Ocean Observatory: powering science, defending nature, and shaping policy for ocean governance and the blue economy’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)’Anthropogenic CO2-induced seawater acidification suppressed dimethylsulfide emissions in the northwestern Pacific marginal seas
Published 4 November 2026 Science Leave a CommentTags: biogeochemistry, biological response, community composition, field, North Pacific, phytoplankton, prokaryotes
Marine dimethylsulfide (DMS) emissions exert a pivotal control on climate regulation via aerosol formation. Nevertheless, the biogeochemical cycle of DMS under seawater acidification remains poorly understood. Here we present integrated biogeochemical analyses that combine field observations, historical datasets, process-based modeling, and ship-based incubation experiments to elucidate pH-dependent regulatory mechanisms governing the cycling of DMS and its precursor dimethylsulfoniopropionate (DMSP) across the northwestern Pacific marginal seas. Our findings identify pH as the key driver of DMS spatial variability; moreover, DMS removal processes are highly sensitive to pH. Structural equation modeling reveals pH-driven cascading impacts on DMS mediated by dinoflagellate biomass. Incubation experiments further demonstrate that decreasing pH reduces high DMSP-producer abundance and suppresses both DMS biological production and removal rates, collectively inhibiting net DMS accumulation. These findings indicate that seawater acidification under the high-emission SSP5-8.5 scenario will reduce global marginal seas DMS emissions by 35%–66% by 2100, which may intensity regional and global warming. Our research provides new insights into the feedback mechanisms linking marine sulfur biogeochemical cycles and global climate change.
Continue reading ‘Anthropogenic CO2-induced seawater acidification suppressed dimethylsulfide emissions in the northwestern Pacific marginal seas’Active calcifying fluid pH upregulation facilitates resilience of the coral Tubastraea aurea to ocean acidification
Published 4 November 2026 Science Leave a CommentTags: biological response, corals, dissolution, field, morphology, North Pacific, physiology, vents
Ocean acidification poses a critical threat to marine calcifiers, yet the physiological mechanisms allowing certain species to thrive in high-CO₂ environments remain poorly understood. Kueishan Island (Taiwan) provides a unique natural laboratory to address this gap. While nearby non-vent reefs support diverse coral communities, the strongly acidified hydrothermal vent fields at Kueishan Island are dominated by the azooxanthellate coral Tubastraea aurea. Here, we tested whether this persistence is driven by regulation of the calcifying microenvironment. Using skeletal boron isotope (δ¹¹B) composition and scanning electron microscopy (SEM), we reconstructed calcifying-fluid pH (pHCF) and assessed skeletal microstructure in specimens from the vent site (HV, pH ~6.6) and a reference site (FU, pH ~8.0). Despite a ~1.4-unit difference in ambient seawater pH (pHSW), the estimated pHCF was indistinguishable between sites (HV 8.45 ± 0.02, FU 8.38 ± 0.01), resulting in a markedly larger ΔpH (pHCF − pHSW) at the vents. While SEM analysis revealed no gross dissolution at the resolution examined, vent colonies were smaller than reference counterparts, suggesting possible growth constraints under extreme conditions (exploratory given limited colony replication). These findings indicate that T. aurea maintains elevated pHCF in exceptionally low-pH seawater, highlighting a physiological capacity that could contribute to skeletal maintenance under future acidified oceans.
Continue reading ‘Active calcifying fluid pH upregulation facilitates resilience of the coral Tubastraea aurea to ocean acidification’Community metabolism generates chemical legacies that alter coral physiology
Published 3 November 2026 Science Leave a CommentTags: biogeochemistry, biological response, communityMF, corals, field, mesocosms, multiple factors, photosynthesis, physiology, primary production, respiration, South Pacific
Coral reefs are among the world’s most diverse ecosystems and contribute substantially to ocean productivity and the carbon budget. Disturbances are shifting reefs to altered community states, yet how these new communities indirectly alter organismal physiology by modifying the local biogeochemical environment remains largely unknown. We investigated this biogeochemical feedback in a 25-d mesocosm experiment in Mo’orea, French Polynesia. We exposed the common coral Porites rus to the biogeochemical environments generated by three distinct communities representative of recent benthic states in this system: coral-, macroalgae-, and crustose coralline algae-enriched relative to a seawater-only control. While net community production was similar among communities, net community calcification was lowest in the macroalgae-enriched state. Across treatments, community metabolism drove changes in the organic and inorganic carbon pool, with net community production increasing both pH and dissolved organic carbon. Using structural equation modeling, we tested how these community-generated chemical legacies propagated through coral physiology. Elevated pH increased chlorophyll a content, which increased endosymbiont density, tissue biomass, gross photosynthesis, and respiration through a series of indirect pathways. Dissolved organic carbon had no detectable effect on downstream corals at 25 d. These results reveal a mechanistic pathway linking disturbance-driven shifts in benthic communities to coral performance. Altered community metabolism modifies local carbon chemistry, which reshapes symbiont physiology and ultimately influences host metabolic function. By identifying the pathways through which community states engineer their chemical environment, this study provides a framework for predicting coral performance and ecosystem trajectories as reefs transition away from coral-enriched states.
Continue reading ‘Community metabolism generates chemical legacies that alter coral physiology’Assessment of sediment and water regimes in island ecosystems of the Gulf of Mannar: implications for ecological monitoring
Published 3 November 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, Indian
Island ecosystems are highly dynamic, and this study examined sediment and water regimes across four coral islands in the Gulf of Mannar to evaluate their ecological significance. Sediment and water samples were collected from four islands, with sediment analyses covering grain size, calcium carbonate (CaCO₃), organic carbon, organic matter, and key water parameters: pH, salinity, temperature, conductivity, dissolved oxygen (DO), turbidity, and total dissolved solids (TDS). Standardized protocols ensured consistency, and data analysis (ANOVA, correlation, regression, Principal Component Analysis (PCA)) was used to assess spatial variability and interrelationships. Sediment composition varied significantly (p< 0.05) in terms of sand, silt, clay, calcium carbonate, organic carbon, and organic matter, with regression analysis revealing a positive trend for silt and negative trends for the other components. PCA (KMO = 0.402; Bartlett’s p< 0.0001) revealed two principal components explaining 87.05% of total variance, with Component 1 linked to sand, organic carbon, and organic matter, and Component 2 to silt, clay, calcium carbonate, and organic matter. Water parameters also varied significantly (p< 0.05); conductivity (r = 0.369) and temperature (r = 0.302) correlated with island location, while temperature was strongly associated with conductivity (r = 0.478) and TDS (r = 0.405). PCA (Kaiser-Meyer-Olkin (KMO) = 0.563; Bartlett’s p< 0.0001) identified ionic strength and thermal regime as key environmental drivers. These findings establish critical baseline data, offering a robust framework that demonstrates how sedimentary composition and physicochemical parameters jointly regulate benthic-pelagic interactions and ecosystem resilience. Overall, island-specific sediment and water patterns exert strong control on ecological processes, providing early detection of environmental shifts and strengthening evidence-based adaptive management. The study offers valuable insights for ecological monitoring and conservation within the Gulf of Mannar region.
Continue reading ‘Assessment of sediment and water regimes in island ecosystems of the Gulf of Mannar: implications for ecological monitoring’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’Lagrangian drifter measurements of the effects of seaweed cultivation on seawater carbon chemistry on a nearshore coral reef in Okinawa, Japan
Published 30 October 2026 Science Leave a CommentTags: algae, chemistry, field, mitigation, socio-economy
Ocean acidification (OA) and deoxygenation (collectively OAD) increasingly threaten coral reefs, which support marine biodiversity and human economic activity. Seaweed farms have been proposed to locally mitigate OAD conditions by removing dissolved inorganic carbon (DIC) and enhancing pH and dissolved oxygen (DO), but empirical evidence has been limited. Here, we investigated the effects of seaweed farming on net community production (NCPDIC, NCPDO), net community calcification (NCC), and seawater chemistry on a back reef lagoon system in Onna, Okinawa, Japan. Lagrangian drifters were used to measure and calculate rates of NCP, NCC, pH, and aragonite saturation state (Ωarag) in December 2022, April 2023, January 2024, and May 2024. The April 2023 and May 2024 surveys coincided with the annual maximum extents of seaweed cultivation (0.16 and 0.14 km2 respectively). Mean NCP and NCC were positive across sessions, but had high variability. Under saturating solar radiation, we observed elevated NCPDIC and NCPDO in April 2023 compared to January 2024, and stronger increases in pH and Ωarag in April 2023 and in May 2024 than in January 2024. Changes in pH and Ωarag were driven by NCPDIC, which was itself driven by temperature and solar radiation. We noted that NCC had a minor effect on the carbonate chemistry system relative to NCP. While we observed biogeochemical signals consistent with biotically-driven OAD modulation, the lack of spring survey control groups limits our ability to decisively attribute this modulation to the seaweed farm.
Continue reading ‘Lagrangian drifter measurements of the effects of seaweed cultivation on seawater carbon chemistry on a nearshore coral reef in Okinawa, Japan’Spatiotemporal water quality dynamics in Southern U.S. coastal reserves: a long-term perspective
Published 30 October 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, North Atlantic
Water quality monitoring in estuarine ecosystems is essential for assessing the health and sustainability of these dynamic coastal habitats, which are increasingly vulnerable to environmental change and human impacts. This study aims to characterize long-term trends and seasonal drivers of seven key water quality parameters: temperature, salinity, dissolved oxygen (DO), pH, chlorophyll-a (Chla), nitrate + nitrite (NOx), and phosphate (PO4) across four southern U.S. National Estuarine Research Reserves (Apalachicola Bay, Grand Bay, Mission-Aransas, and Weeks Bay) to identify which reserves and processes are most vulnerable to climate and anthropogenic change. Using two decades of data (1995–2020) and applying Generalized Additive Models (GAMs), we identified significant spatial and temporal patterns linked to environmental and anthropogenic factors. Results revealed a warming trend in Weeks Bay (+0.1035 °C/year, P = 0.0013), a salinity decline in Grand Bay (−0.1699 PSU/year, P = 0.033), and a salinity increase in Apalachicola Bay (+0.2055 PSU/year, P = 0.003). DO concentrations peaked in spring and dropped in summer, reflecting seasonal nutrient inputs. Grand Bay exhibited the highest Chla variability (CV=131.48%). NOx concentrations declined in Grand Bay (−0.0003 mg/L/year, P = 0.0162), while PO4 levels remained relatively stable. pH trends suggested localized acidification, particularly in Mission-Aransas (−0.0071/year, P = 0.0016). GAM results emphasized the combined effects of long-term and seasonal changes, with site-specific differences. These findings provide critical insights into estuarine functioning and highlight the need for regionally tailored management strategies to enhance resilience and biodiversity conservation in U.S. coastal reserves.
Continue reading ‘Spatiotemporal water quality dynamics in Southern U.S. coastal reserves: a long-term perspective’The spatial and temporal variability of dissolved inorganic carbon and total alkalinity production during early diagenesis in river dominated ocean margin sediments and their resultant effect on bottom water acidification
Published 30 October 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, Mediterranean, North Atlantic, sediment
Rapid anthropogenic release of CO2(g) to the atmosphere promotes global ocean acidification that is exacerbated in coastal environments by processes such as eutrophication and upwelling of low pH deep water. The decline in ocean pH through time poses a threat to marine ecosystems and the coastal communities that depend on them. Total alkalinity (TA), mainly supplied to the ocean by river discharge, allows seawater to buffer against future pH decline. Pore water DIC and TA generated in sediments during early diagenesis may be released to the overlying waters and either contribute to acidity or buffer against overlying water acidity, depending on the benthic TA to dissolved inorganic carbon (DIC) flux ratio (RTA:DIC), as RTA:DIC < 1 promotes acidification and RTA:DIC > 1 mitigates further acidification. The rapid accumulation of organic matter in river dominated ocean margin (RiOMar) sediments promotes the generation of relatively large benthic DIC and TA fluxes that may significantly influence overlying water acidification in these regions. A number of seasonally variable environmental factors such as river discharge and sediment resuspension may promote early diagenetic redox cycling in RiOMar sediments and induce seasonal RTA:DIC variability. This seasonal RTA:DIC variability is poorly characterized, however, despite their potential influence on overlying water acidification in these regions.
The present dissertation investigated how early diagenetic processes in RiOMar sediments and resultant benthic solute fluxes and RTA:DIC respond to seasonally variable environmental factors. This was accomplished using a combination of in-situ benthic flux measurements on the northern Gulf of Mexico (nGoM) continental margin and ex-situ sediment core solid phase and pore water analyses from both nGoM margin and Rhône River prodelta sediments. Overall, the results presented in this dissertation revealed significant seasonal early diagenetic and RTA:DIC variability in RiOMars that was driven by seasonally variable environmental factors such as river discharge, primary production, sediment perturbations, and bottom water hypoxia development. The largest RTA:DIC from RiOMar sediments may be promoted either 1) proximal to river deltas and in eutrophic hypoxic systems, where anerobic TA generation is high and reoxidation of reduced metabolites is low, or 2) when CaCO3 dissolution generates significant TA in pore waters.
Continue reading ‘The spatial and temporal variability of dissolved inorganic carbon and total alkalinity production during early diagenesis in river dominated ocean margin sediments and their resultant effect on bottom water acidification’Monsoon-linked gut microbiome variation in a tropical sea urchin: a single-reef case study from the Arabian Sea
Published 29 October 2026 Science Leave a CommentTags: biogeochemistry, biological response, community composition, echinoderms, field, Indian, molecular biology, otherprocess, physiology, prokaryotes
Highlights
- Stomopneustes variolaris gut microbiota shows clear seasonal structuring in response to monsoon-driven biogeochemical variability.
- The gut microbiota of Stomopneustes variolaris is dominated by Bacteroidota, and most diverse during winter and spring inter-monsoon.
- Gut microbial composition covaries with seasonal oxygen, pH, temperature, and nutrient gradients.
- The sea urchin gut microbiome shows seasonal plasticity under monsoon-linked stress.
Abstract
Tropical coastal ecosystems of the Eastern Arabian Sea (EAS) experience pronounced monsoon-driven shifts in water-column biogeochemistry, yet their influence on the gut-associated microbiomes of benthic invertebrates remains poorly understood. Sea urchins are ecologically important grazers in reef-associated habitats, and their gut microbiota may reflect both environmental and dietary variability. Here, we provide an exploratory characterisation of the gut-associated microbiome of the sea urchin Stomopneustes variolaris from the Grande Island archipelago (Goa, India) across four monsoon-associated periods: Winter monsoon (WM), Spring-inter monsoon (SIM), Summer monsoon (SM), and Fall-inter monsoon (FIM). Using 16S rRNA gene sequencing, we analysed gut tissue and gut digesta from S. variolaris alongside environmental samples (seawater, sediment, and seaweed). Bacteroidota dominated the urchin gut microbiome, whereas Proteobacteria were more abundant in environmental samples. Gut microbial diversity was highest in WM and SIM and lowest during SM and FIM. Exploratory analyses indicated that gut microbial composition varied temporally, with taxa affiliated with sulphur-cycling lineages more prevalent during sampling points associated with low-oxygen monsoon phases (SM and FIM) and Firmicutes and organic matter-associated taxa more prominent during comparatively oxygenated periods (WM and SIM). Ordination analyses suggested an association between gut and environmental microbial assemblages and gradients in dissolved oxygen, temperature, pH, nutrients, and pCO2. This study provides baseline insights into the gut microbiome of a tropical echinoid from an understudied region and highlights monsoon-associated patterns in microbial community composition, forming a foundation for future functional and experimental investigations.
Graphical abstract
Unlocking spatial ecological assessment for tropical seagrass habitats using a new rapid assessment method (SEARAM)
Published 29 October 2026 Science Leave a CommentTags: biological response, community composition, field, Indian, methods, otherprocess, phanerogams
Highlights
- Rapid and standardized assessment of tropical seagrass ecological state.
- Multimetric index combining structure and vitality indicators.
- Spatial mapping of seagrass fragmentation and degradation.
- Links between habitat condition, environment, and megafauna.
- A practical tool for coastal monitoring and impact mitigation.
Abstract
Seagrass meadows are key coastal ecosystems supporting biodiversity, carbon storage, and essential trophic functions, yet they are increasingly threatened by anthropogenic and climatic pressures. Based on the Seagrass Meadows Rapid Assessment Method (SEARAM), a standardized protocol grounded in seagrass biodiversity indicators (SBIs), we developed a reliable and operational index to assess seagrass ecological state at high spatial resolution. Using 536 circular plots and 144 faunal stations across three intertidal reef habitats in Mayotte (Western Indian Ocean), SEARAM integrates structural and vitality sub-indices into a composite seagrass ecological state index (SESI), spatialized by geostatistical interpolation and analyzed using ANOVA, PCA, and multiple regression models. Results revealed highly fragmented meadows dominated by Halodule uninervis and Halophila ovalis, with low canopy height (5 ± 2 cm) and substantial epiphyte loads (37 ± 17%). The inner fringing reef flat showed the poorest ecological state (SESI = 4.8 ± 0.7/10), whereas the barrier reef (5.4 ± 0.8/10) and exposed fringing reef flat (5.6 ± 0.8/10) exhibited moderate scores. Key environmental drivers (turbidity, grain size, pH), significantly explained spatial patterns of seagrass structure and vitality, confirming the influence of sediment and light regimes. Functional relationships were also demonstrated between seagrass condition and associated fauna, particularly green turtle density and dugong feeding traces. SEARAM proved to be a rapid and robust tool for diagnosing tropical seagrass states. Its multimetric framework connects benthic condition to habitat suitability for megafauna, offering an operational foundation for ecological monitoring, management, and impact mitigation within the Avoid–Reduce–Offset (ARO) doctrine.
Graphical abstract
Large-scale water-sediment regulation (Yellow River) substantially reshapes organic carbon mineralization pathways and benthic fluxes in sediment of a river-dominated sea (Bohai Sea)
Published 26 October 2026 Science ClosedTags: biogeochemistry, chemistry, field, North Pacific
Large-scale hydrological engineering has fundamentally altered the rhythm of land-to-ocean material transport globally, yet the mechanistic response of coastal benthic biogeochemistry to these “pulse” events remains poorly quantified. Here, we investigated the transient impacts of the annual Yellow River Water-Sediment Regulation (WSR), a massive anthropogenic flood, on sediment organic carbon (OC) mineralization and benthic fluxes in the Bohai Sea (BHS) by combining geochemical analyses with sediment incubations. Results indicated that the WSR enhanced sediment OC mineralization rates by an average factor of 1.65, driven primarily by pulsed input of labile OC and probably also reflecting a priming effect. This stimulation reconfigured dominant diagenetic pathways: significantly elevating the role of dissimilatory iron reduction at the expense of both aerobic respiration and sulfate reduction. In addition, pulsed nitrate inputs promoted denitrification, establishing it as an important OC mineralization pathway. Concurrently, diffusive nutrient fluxes increased by a factor of 1.9–5.1 following the WSR, and the mean ratio of total alkalinity to dissolved inorganic carbon fluxes decreased from 1.34 to 0.96. This shift in the ratio signifies a reduced capacity for carbonate buffering in the bottom waters, which could exacerbate seasonal bottom-water acidification. Collectively, our findings demonstrate that short-term anthropogenic perturbations can rapidly reprogram sediment diagenesis and benthic fluxes, thereby perturbing carbon and nutrient cycling as well as benthic-pelagic coupling in river-dominated coastal systems.
Plain Language Summary
The annual Water-Sediment Regulation of the Yellow River is one of the world’s largest engineered flow manipulations, rapidly delivering huge amounts of freshwater and sediment into the Bohai Sea (BHS). While much is known about its effects on the water column ecochemistry, how such a large-scale human intervention alters organic carbon degradation and chemical exchange in seafloor sediments has remained unclear. By combining field measurements and laboratory experiments, we show that this event strongly enhances sediment carbon degradation rates and shifts the dominant pathways, favoring iron reduction and nitrate reduction processes. These changes drive substantial increases in benthic fluxes of dissolved inorganic carbon and nutrients (ammonium, silicate, and phosphate) into overlying waters. Notably, the regulation reduces the ratio of alkalinity to inorganic carbon flux, implying a temporary decline in the capacity of the sea to absorb atmospheric CO2. Our findings provide critical insights by revealing that large-scale human-regulated river discharges can rapidly reshape coastal sediment biogeochemistry. These results have important implications for carbon and nutrient cycling, offering valuable references for understanding not only the BHS but also other river-dominated coastal systems worldwide.
Continue reading ‘Large-scale water-sediment regulation (Yellow River) substantially reshapes organic carbon mineralization pathways and benthic fluxes in sediment of a river-dominated sea (Bohai Sea)’Genomic responses of fishes to ocean acidification: insights from volcanic CO2 seeps
Published 20 October 2026 Science ClosedTags: biological response, field, fish, molecular biology, North Pacific, physiology, vents
Extreme and marginal reef environments provide valuable opportunities to examine the effects of altered seawater parameters that resemble predicted end-of-century ocean conditions under climate change. Volcanic CO2 seeps, in particular, have proven useful for studying the effects of ocean acidification (OA) in natural settings. In this chapter, we present a case study from a volcanic CO2 seep at Shikine Island, Japan, investigating the genomic response of the neon damselfish (Pomacentrus coelestis) to OA conditions. We examined transcriptomic profiles from brain and gill tissues collected across two seasons (July and November) and compared them to samples from multiple control sites to assess consistent patterns of gene expression under elevated CO2. Our results found that genes involved in blood oxygen regulation, immune response, and circadian rhythm were differentially expressed across seasons and tissues, suggesting their key role in the response to OA in P. coelestis. We also detected seasonal shifts in gene expression patterns, highlighting the complexity of the physiological responses to OA in natural environments. Many of the differentially expressed genes align with findings from previous laboratory and field studies, reinforcing the value of volcanic CO2 seeps for OA research. Finally, we discuss the challenges of working in natural seep environments, including variability across control sites and seasons, and emphasize the future potential of CO2 seeps for advancing our understanding of fish responses to ocean acidification.
Continue reading ‘Genomic responses of fishes to ocean acidification: insights from volcanic CO2 seeps’
