Previous studies in the Beibu Gulf have documented the distributions and controlling factors of carbonate system parameters in surface waters; however, their dynamics in subsurface and bottom waters remain poorly constrained. Here, we present the first observations of pH and the aragonite saturation state (Ωarag) in subsurface and bottom waters of the Beibu Gulf during spring and fall 2024. In spring, pH and Ωarag in subsurface and bottom waters off Ledong were predominantly governed by physical mixing. In contrast, their variability off Dongfang was driven jointly by biological respiration occurring outside the Dongfang oil/gas field and by respiration within the field itself. Quantitative analysis revealed that respiration outside the field increased dissolved inorganic carbon (DIC) concentrations by ~18 ± 3 µmol kg−1, a magnitude comparable to that attributable to in-field respiration (~18 ± 7 µmol kg−1). Collectively, these two respiration sources induced only slightly declines in pH (0.03 ± 0.01 and 0.04 ± 0.01) but statistically significant reductions in Ωarag (0.18 ± 0.03 and 0.21 ± 0.08, respectively). During fall, carbonate system dynamics in subsurface and bottom waters off both Dongfang and Ledong were dominated by physical mixing. The differential influence of North Pacific Tropical Water (NPTW) resulted in a decline in Ωarag from 2.99 ± 0.10 off Dongfang to 2.75 ± 0.32 off Ledong. All observed Ωarag values remained well above the thermodynamic saturation threshold (Ωarag = 1), indicating no immediate risk of ocean acidification to calcifying organisms in the study area under current conditions. This study helps bridge a critical observational gap in the regional inorganic carbonate system. However, due to sampling constraints, carbonate system parameters are reported here for spring and fall only. Observations for summer and winter, as well as multi-year time-series measurements, are planned for the near future.
Continue reading ‘Acidification states and controlling factors in subsurface and bottom water of the Beibu Gulf, China’Acidification states and controlling factors in subsurface and bottom water of the Beibu Gulf, China
Published 10 November 2026 Science Leave a CommentTags: chemistry, field, North Pacific
Amazon river plume control on carbonate chemistry in the western tropical Atlantic
Published 10 November 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, South Atlantic
The Amazon River Plume (ARP) modulates the carbonate system of the western Tropical Atlantic (WTA) through physical and biological processes, including freshwater dilution, biological carbon uptake, and circulation-driven transport; however, its basin-scale impact has not been quantitatively assessed. Here we combine climatological spatial anomalies of sea surface salinity (SSS), carbonate system variables, and biogeochemical indicators to determine the percentage contribution of offshore ARP waters to regulate carbonate chemistry during wet and dry seasons. We show that ARP-derived freshwater and nutrients drive ∼8%–10% reductions in sea surface fugacity (fCO2), total alkalinity, dissolved inorganic carbon and carbonate ion concentrations across the WTA during the wet season, closely matching a ∼9% decrease in SSS. These reductions represent a substantial perturbation to carbonate chemistry across the offshore plume-influenced WTA, strengthening the role of the ARP in modulating carbon cycling and atmospheric CO2 uptake. These findings identify physical dilution, enhanced photosynthesis and nitrogen cycle transformations, as strong first-order controls on carbonate system drawdown, supporting CO2 uptake in low-SSS waters. ARP-driven reductions in fCO2 extend far beyond the plume through offshore export by the North Brazil Current and North Equatorial Countercurrent, decreasing fCO2 by up to 20 μatm near 10°N and modulating carbonate chemistry across the equatorial Atlantic. Together, these results demonstrate that the ARP is a major regulator of sea surface carbonate chemistry in the WTA, enhancing atmospheric CO2 uptake through coupled physical–biological processes. The spatial anomaly approach provides a robust framework for quantifying river-plume impacts on basin-scale carbon cycling.
Continue reading ‘Amazon river plume control on carbonate chemistry in the western tropical Atlantic’Ocean acidification and mass extinctions: reconstructing CO2 from fluid inclusions
Published 10 November 2026 Science Leave a CommentTags: chemistry, globalmodeling, methods, modeling, paleo
The composition of Earth’s atmosphere and oceans have varied over the Phanerozoic and is tightly coupled with the planet’s climate and the extinction and evolution of life. Central to Earth’s climate and habitability is the concentration of CO2 in the atmosphere-ocean system, where rapid perturbations of CO2 correspond with hyperthermal and mass extinction events. These intervals of environmental catastrophes coincide with several periods of large-scale volcanic eruptions (million km3 of lava) called Large Igneous Provinces (LIPs), capable of releasing massive quantities of CO2. Among these events, the end-Triassic extinction (ETE; 201.564 Ma) represents one of the most severe biotic crises of the Phanerozoic and is temporally associated with the emplacement of the Central Atlantic Magmatic Province (CAMP). As one of the most voluminous large igneous provinces, CAMP is characterized by repeated disruptions to the global carbon cycle and intense ocean acidification events. However, understanding the relationship between the massive release of CO2, ocean chemistry, and extinction dynamics requires robust constraints on ancient CO2 concentrations. For time intervals prior to the ice core record, CO2 reconstructions rely on geochemical proxies derived from fossils and minerals. While these proxies often reproduce similar long-term trends, they commonly diverge in absolute CO2 estimates, limiting confidence in quantitative reconstructions of ancient atmospheric and oceanic carbon reservoirs. Direct constraints on CO2 in deep time can overcome this limitation, which can be achieved by using fluid inclusions hosted in minerals that precipitated in equilibrium with the environment. These fluid inclusions trap and preserve aliquots of ancient air and brine at the time of mineral formation in which the bulk gas compositions can be directly quantified using mass spectrometry and Raman spectroscopy. Fluid inclusions have increasingly been recognized to be excellent archives of past environmental conditions, including temperature, salinity, and atmospheric composition, though uncertainties remain about carbon speciation, the fidelity of preserved gas and brine compositions, and the broader applicability of using fluid inclusions to reconstruct major carbon cycle perturbations. This dissertation applies direct and quantitative methods to extract CO2 concentrations from fluid inclusions trapped in sedimentary minerals. Confocal Raman spectroscopy is used to quantify carbonate system parameters using fluid inclusions hosted in calcite, enabling reconstruction of pH and pCO2 conditions during mineral formation. Subsequently, fluid inclusions in halite are assessed for their reliability to trap gases during mineral precipitation and validate their use for ancient CO2 reconstructions. Fluid inclusion analyses were applied to deep ocean bedded cherts, showing repeated pulses of elevated CO2 and associated decreases in ocean pH and aragonite saturation state across the ETE and the Triassic-Jurassic transition. Integration of these records with carbon cycle modeling constrains the magnitude and pacing of the carbon release associated with CAMP volcanism and shows that large, repeated CO2 injections are sufficient to reproduce observed perturbations in ocean chemistry. By combining fluid inclusion analyses with carbon cycle modeling and independent geological and paleontological constraints, link large igneous province volcanism, repeated disruptions to the global carbon cycle, mass extinctions, and widespread ocean acidification during the end-Triassic.
Continue reading ‘Ocean acidification and mass extinctions: reconstructing CO2 from fluid inclusions’Quantifying coastal ocean anthropogenic carbon changes and their uncertainties
Published 10 November 2026 Science Leave a CommentTags: biogeochemistry, chemistry, methods
Despite recent progress in quantifying anthropogenic carbon (Canth) in global oceans, coastal regions remain understudied due to methodological and observational challenges. Here, we develop and generalize a Regional rEgression–based Coastal Anthropogenic carbon estimation algorithm (RECA) designed specifically for coastal environments. Regional rEgression–based Coastal Anthropogenic carbon estimation algorithm builds upon the extended multiple linear regression framework, incorporating adaptations such as improved regression construction strategies, optimized data selection, and reduced subjectivity in decision-making, creating a unified approach across diverse coastal settings. Using synthetic datasets with known ∆Canth from global ocean biogeochemical model simulations across multiple North American coastal regions, we estimate that the uncertainty of RECA is about 3.25 μmol kg−1. We also compare RECA with two other regression-based algorithms, originally developed for the open ocean, to evaluate their performance in coastal environments after some adaptations. All three approaches have similar biases but different strengths, underscoring the importance of using a consistent method. An ensemble approach combining these three algorithms modestly improves reconstruction fidelity, but at the cost of increased complexity. We also evaluate the contributions of non-steady-state variations of both natural and Canth components because uncertainty about these components has long challenged the interpretation of regression-based ∆Canth results. We find that the algorithms indeed remove most, but not all, of the natural variations and appear to capture some, but not all, of the non-steady-state Canth. This methodological framework provides a robust, broadly applicable, and easy-to-implement tool for estimating coastal ∆Canth with uncertainty quantification, allowing us to more confidently track Canth accumulation in a changing dynamic coastal ocean.
Continue reading ‘Quantifying coastal ocean anthropogenic carbon changes and their uncertainties’Ocean acidification pushes Mediterranean marine calcifiers toward a tipping point
Published 10 November 2026 Science Leave a CommentTags: biological response, community composition, dissolution, field, Mediterranean, modeling, molecular biology, morphology, otherprocess, protists, regionalmodeling, vents
The increasing emission of carbon dioxide (CO2) is altering seawater chemistry, lowering ocean pH and threatening marine biodiversity. Predicting how marine biota will be adversely affected by ocean acidification (OA) remains a key challenge. Here, we document that functional morphological traits offer a more robust metric of calcifier sensitivity to OA than taxonomic diversity alone. Using benthic foraminifera from a Mediterranean CO2 vent system, we identify an empirically derived pH threshold beyond which community structure and function shift markedly. Applying this threshold to end-of-century projections under Shared Socioeconomic Pathway SSP5-8.5 reveals that most western Mediterranean coastal zones will exceed critical acidification levels by 2090–2100. These results highlight the susceptibility of the Mediterranean coastal ecosystems to OA under high-emission scenarios, underscoring the risk of widespread biodiversity loss and impaired ecosystem functioning. Our approach provides a trait-based framework for forecasting ecosystem responses to OA and informing adaptation strategies in climate-sensitive marine regions.
Continue reading ‘Ocean acidification pushes Mediterranean marine calcifiers toward a tipping point’Southern Ocean productivity and carbonate chemistry imprinted on coccolith morphology across the last Glacial-Holocene transition
Published 10 November 2026 Science Leave a CommentTags: abundance, biogeochemistry, chemistry, morphology, otherprocess, paleo, phytoplankton, protists
Highlights
- Glacial C. pelagicus coccoliths were larger, with broader distal shields.
- Coccolith size variability tracked glacial-Holocene STF productivity changes.
- Dust-driven Fe fertilisation enhanced glacial nutrient utilisation along the STF.
- Coccolith distal shield thinning linked to deglacial Southern Ocean CO₂ outgassing.
- C. pelagicus morphometry records Southern Ocean carbonate chemistry variability.
Abstract
The Southern Ocean plays a key role in regulating atmospheric CO₂ through changes in overturning circulation and is projected to undergo major warming and ocean acidification under future climate scenarios. Coccolithophores, a dominant calcifying phytoplankton group in the northern Southern Ocean, are expected to be particularly sensitive to such changes. Here, we evaluate glacial–Holocene coccolith size variability using morphometric analyses of Coccolithus pelagicus from sediment core ABP S4 located at the Subtropical Front (STF) in the western Indian sector of the Southern Ocean. Mean coccolith size was calculated from statistically robust populations to minimise intra-coccosphere variability. Glacial intervals are characterized by larger coccoliths with broader distal shields (coccolith rim), whereas deglacial and Holocene intervals exhibit smaller coccoliths with thinner distal shield. Coccolith size variability closely corresponds with regional paleoproductivity records, indicating enhanced glacial carbonate production along the STF, while previous studies report increased opal production at the Subantarctic Front (SAF). Together, these findings suggest elevated glacial productivity across the Subantarctic Zone (SAZ) driven by more efficient nutrient utilisation under dust-induced Fe fertilisation. While overall coccolith size reflects changes in productivity and nutrient availability, the distal shield area appears more sensitive to deglacial carbonate chemistry changes. Deglacial reductions in the distal shield area paralleled enhanced Southern Ocean CO₂ outgassing and reinvigorated overturning circulation, indicating strong carbonate chemistry control on coccolith calcification. These findings highlight the potential of coccolith morphometry for tracking Southern Ocean productivity, carbon cycling, and the sensitivity of calcifying phytoplankton to future environmental change.
Graphical abstract
Global change reshapes marine microbial communities, functions and One Health outcomes
Published 10 November 2026 Science Leave a CommentTags: biogeochemistry, biological response, community composition, corals, nitrogen fixation, otherprocess, photosynthesis, physiology, phytoplankton, policy, porifera, primary production, prokaryotes, respiration, review, socio-economy
Marine microorganisms underpin primary production, biogeochemical cycling and host-associated symbioses, supporting climate regulation, coastal protection, fisheries and other ecosystem services. Rapid global change, including ocean warming and marine heatwaves, acidification, deoxygenation, eutrophication, pollution and overuse reshape microbial communities and their functions across marine habitats. These changes can alter carbon, nitrogen and sulfur cycles, promote microbialization and harmful algal blooms, disrupt host–microbiome associations and modify pathogen and antimicrobial resistance dynamics, collectively amplifying the ecological and societal impacts of global change. This Review frames marine microbiomes as cross-scale mediators that translate external pressures, including climate change, pollution, eutrophication and habitat degradation, into altered microbial metabolism, biogeochemical fluxes, host-associated health outcomes, ecosystem service consequences and broader One Health risks. We synthesize shared mechanisms and cross-habitat patterns, highlight cases in which microbiome interventions and stewardship could mitigate impacts and/or accelerate recovery, and outline management options ranging from the reduction of local stressors to emerging microbiome stewardship approaches in ecosystem restoration. Building upon this, we outline pathways for embedding marine microbiome science into globally coordinated One Health strategies, operational management protocols and financing frameworks that align economic incentives with long-term ecosystem and public health outcomes.
Continue reading ‘Global change reshapes marine microbial communities, functions and One Health outcomes’Ocean Seminar – Facing the unknown: modern planktonic foraminifera migration is not enough, by Sonia Chaabane
Published 10 November 2026 Events , Science Leave a CommentThe Ocean’s Challenge groups are organizing a new seminar by Sonia Chaabane, from the IRD CEREGE, Aix-en-Provence, France.
Seminar: “Facing the unknown: modern planktonic foraminifera migration is not enough”
Speaker: Sonia Chaabane, IRD CEREGE, Aix-en-Provence, France
- Date: Thursday, 12th of November 2026
- Time: from 13 to 14h
- Venue: Room Z/033, ICTA-UAB and online https://zoom.us/j/92074418017?pwd=NZKbGoHsC3FiLEPn3I1SbZm5ALD6ab.1
Rising atmospheric CO₂ concentrations are driving ocean warming and acidification, reshaping marine habitats and threatening calcifying organisms such as planktonic foraminifera. These microorganisms play an important role in marine biogeochemical cycles, while their fossil record provides valuable archives of past environmental and climatic changes. However, their responses to ongoing climate change, particularly their capacity to adapt through geographical and vertical migration, remain poorly understood at the global scale.
To address this knowledge gap, the FORCIS (Foraminifera in a Changing Ocean) project has compiled the most comprehensive database to date of living planktonic foraminifera distributions, encompassing over 180,000 samples collected since 1910 across different ocean basins, depths, and sampling techniques. This extensive dataset provides a unique opportunity to investigate long-term changes in species abundance, diversity, and ecological niches in response to changing ocean conditions.
Our century-scale analyses reveal substantial poleward shifts in planktonic foraminifera distributions, accompanied by increasing diversity at mid- and high latitudes. Several species have also shifted their vertical habitats towards deeper, cooler waters, potentially as a response to warming surface conditions. Despite these movements, global planktonic foraminifera abundance has declined by 24.2 ± 0.1% over the last eight decades.
Looking ahead, projections for 2050 and 2100 suggest that tropical species will increasingly experience environmental conditions beyond their currently observed ecological niches, particularly in terms of temperature and carbonate chemistry. Ecological niche models further predict habitat contractions, continued poleward redistribution, and potential biodiversity losses in tropical oceans.
Together, these findings suggest that although geographical and vertical migration represent important responses to climate change, they may not be sufficient to compensate for the accelerating pace of ocean warming and acidification. These changes also have important implications for marine biodiversity, ocean carbon cycling, and the reliability of planktonic foraminifera as paleoceanographic proxies.
Continue reading ‘Ocean Seminar – Facing the unknown: modern planktonic foraminifera migration is not enough, by Sonia Chaabane’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
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’Ocean acidification impairs the chiton shadow defensive response via degradation of aragonitic lenses
Published 9 November 2026 Science Leave a CommentTags: biological response, dissolution, laboratory, mollusks, morphology, North Pacific, performance, physiology
Ocean acidification (OA) has the potential to disrupt the behavior of marine organisms by altering the function of γ-aminobutyric acid type A (GABAA) receptors. In addition, OA can impair sensory performance by reducing the calcification of mineralized sensory structures. Some species of polyplacophoran mollusks (chitons) possess calcified visual organs (aragonitic lenses) that contribute to shadow defense responses triggered by sudden decreases in overhead illumination. Therefore, we hypothesized that OA affects this response by impairing GABAA-mediated signaling or lens calcification. To test this hypothesis, we exposed chitons to “control” or acidified seawater and examined their shadow defensive behavior with and without gabazine, a GABAA antagonist known to restore OA-induced GABAergic dysfunction. Although gabazine did not eliminate behavioral differences between the control and acidified groups, acidification reduced the response strength, suggesting that factors other than GABAA-mediated signaling may contribute to the observed behavioral impairment. Microscopic observations revealed clouding of aragonitic lenses under acidic conditions, suggesting reduced optical performance. Overall, our results indicate that OA-induced degradation of calcified lens structures is associated with impaired shadow defense responses and may contribute to behavioral dysfunction. To the best of our knowledge, this study provides the first evidence that acidification-induced physical and optical changes in the visual anatomy can alter behavioral performance in animals.
Continue reading ‘Ocean acidification impairs the chiton shadow defensive response via degradation of aragonitic lenses’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
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’Spectroscopic transduction in miniaturized lab-on-a-chip devices: functional nanomaterials and edge AI integration for real-time in situ environmental monitoring of heavy metals, pesticides, and marine pollutants
Published 9 November 2026 Science Leave a CommentTags: chemistry, methods, review
The rising demand for real-time, in situ monitoring of heavy metals, pesticides, marine pollutants, and ocean acidification proxies has exposed the limitations of conventional laboratory-based spectroscopic methods, which suffer from slow turnaround, high costs, and poor adaptability to remote environments. This critical review surveys advances from 2023–2026 in microfluidic lab-on-a-chip (LOC) platforms that integrate functional nanomaterials with spectroscopic transduction (primarily fluorescence, absorbance, surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), and quantum dot-based optical detection) and edge-deployable AI. Emphasis is placed on how nanomaterials enhance spectroscopic signals within microfluidic channels while addressing laminar flow control, passive mixing, antifouling, and stability in high-salinity and high-pressure marine matrices. The convergence with lightweight, hardware-aware AI/ML for on-chip denoising, drift compensation, multiplexing, and anomaly detection is examined under strict power and memory constraints. Ocean acidification monitoring requiring high-precision spectrophotometric pH and total alkalinity (TA) measurements serves as a rigorous benchmark for Arctic, open-ocean, and buoy deployments. Performance metrics, matrix interferences, autonomy limitations, and scalability barriers of these spectroscopic LOC systems are critically evaluated, with a forward-looking roadmap toward autonomous, IoT-enabled, and biodegradable spectroscopic microfluidic platforms for sustainable environmental monitoring.
Continue reading ‘Spectroscopic transduction in miniaturized lab-on-a-chip devices: functional nanomaterials and edge AI integration for real-time in situ environmental monitoring of heavy metals, pesticides, and marine pollutants’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, zooplankton
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’Phenotypic plasticity supports green tide persistence before bioenergetic failure underlies terminal decline
Published 9 November 2026 Science Leave a CommentTags: adaptation, algae, biological response, molecular biology, North Pacific, otherprocess, photosynthesis, physiology
Trans-regional green tides dominated by Ulva prolifera exert significant impacts on coastal ecosystems. While the mechanisms of early-stage proliferation are well documented, the specific physiological and molecular drivers governing the transition from bloom persistence to terminal decline during this trans-regional drift remain unresolved. Using in situ physiological and transcriptomic data collected across a 300-km latitudinal gradient in the Yellow Sea, we found that a dominant molecular type (5S-II) within the sampled 2021 U. prolifera population showed phenotypic plasticity, with its physiological and transcriptional traits varying across environmental conditions. Physiological observations showed declines in photosynthetic performance (Fv/Fm and rETR) and pigment content along the northward drift path, marking a transition from active growth to physiological decline. Transcriptomic and physiological evidence further indicated that the intermediate drifting phase was characterized by a compensatory photoprotective state, potentially involving cyclic electron flow. By contrast, terminal-phase stress was associated with reduced expression of G-protein-signaling-related genes and patterns suggesting that PSII repair could no longer compensate for photodamage as energy metabolism declined. This bioenergetic failure coincided with a shift toward endogenous catabolism and a transition from vegetative growth toward sporulation. Together, these findings provide insight into bloom termination and suggest that ocean warming may accelerate late-stage senescence, whereas acidification may intensify photosynthetic inhibition under multiple stressors, potentially increasing coastal hypoxia risk.
Continue reading ‘Phenotypic plasticity supports green tide persistence before bioenergetic failure underlies terminal decline’Pacific scientists build a regional picture of a changing ocean
Published 9 November 2026 Web sites and blogs Leave a Comment
SUVA, Fiji, November 4 (IPS) – The Pacific Ocean connects thousands of islands, and understanding how ocean acidification is unfolding across the region requires more than individual research projects or monitoring stations.
Scientists need observations from different island environments, collected over time, to understand how seawater chemistry is changing and what those changes could mean for marine ecosystems and the communities that depend on them.
The work is being strengthened through regional collaboration, with Pacific scientists sharing data, technical knowledge and research experience to build a more complete picture of a changing ocean.
Dr Katy Soapi, Pacific Community (SPC) Coordinator for the Pacific Community Centre for Ocean Science and a Pacific scientist, says the broader scientific community is aware that ocean chemistry is changing. The priority is now building local evidence to understand how those changes may affect different island environments.
“What Pacific scientists are now doing is building the local evidence needed to understand how those changes may impact our different island environments,” Soapi said.
“At many of our monitoring sites, we are seeing considerable natural variability in pH over days, months and seasons, which is normal,” she said. “It is important to capture this data over time because coastal waters are influenced by temperature, rainfall, freshwater inputs, biological activity, land-based pollution and local oceanographic conditions.”
Monitoring programmes are at different stages across the region. Fiji has an established programme, with monitoring in the Suva area since 2023 and data that contribute to Sustainable Development Goal 14.3.1 reporting.
Samoa has received support through access to monitoring equipment, training and technical advice, while the Solomon Islands programme is newer, with scientists from Solomon Islands National University receiving regional and in-country training as they establish the technical capacity for long-term monitoring. Kiribati and Papua New Guinea also have their own monitoring histories and research priorities.
These differences matter when comparing observations across the Pacific.
“This variation is important; a harbour in Fiji, a lagoon in Kiribati, coastal waters in Samoa or reef environments in Solomon Islands and Papua New Guinea can experience very different combinations of temperature, rainfall, freshwater input, current, biological activity and human pressure,” Soapi said.
“The Pacific is connected, but it is not environmentally uniform.
“This is why local monitoring is important and why we cannot rely solely on regional or global averages.”
Continue reading ‘Pacific scientists build a regional picture of a changing ocean’
Global cycles of carbon and phosphorus decouple under intensifying ocean acidification as marine diatoms restructure their lipid membranes and downregulate organic phosphorus scavenging to adapt to the decreasing pH.
The global ocean absorbs roughly 25–30% of all anthropogenic carbon dioxide (CO2) emissions1, which drives acidification. Marine phytoplankton are a key component of this ocean carbon uptake, because they take in atmospheric CO2 via photosynthesis and ultimately sequester the carbon into the deep ocean through the biological carbon pump2. The efficiency of this pump is partially governed by the availability of phosphorus3, a key macronutrient required for fundamental components of cells, including nucleic acids, energy-transfer molecules and cellular membranes.
Now, writing in Nature Geoscience, Wang and colleagues4 show that ocean acidification intersects with intensifying phosphate limitation to reshape phytoplankton phosphorus metabolism in a fundamental way. The authors demonstrate that phytoplankton species adapt to elevated CO2 by adopting phosphorus-saving cellular strategies. The results indicate a decoupling between carbon and phosphorus, in which particulate organic biomass becomes progressively enriched in carbon relative to phosphorus, so that sinking material will carry less phosphorus per unit of carbon. This may reduce the long-term resupply of phosphorus to the surface ocean.
Continue reading ‘Sparing use of phosphorus in an acidifying ocean’Tenure-track faculty position – Assistant/associate professor of marine biogeochemistry or fisheries
Published 9 November 2026 Jobs Leave a CommentThe University of Massachusetts Dartmouth invites applications for a tenure-track faculty position at the Assistant or Associate Professor level in the Department of Fisheries Oceanography (DFO) or the Department of Estuarine and Ocean Sciences (DEOS) at the School for Marine Science and Technology (SMAST), beginning September 2027.
Marine Biogeochemistry
We seek a marine biogeochemist whose research addresses emerging challenges and opportunities relative to understanding, observing, and modeling open ocean and coastal systems. Areas of interest include nutrient and carbon cycling, stable isotope and tracer geochemistry, carbon sequestration and ocean alkalinity enhancement, ocean acidification, deoxygenation, greenhouse gas dynamics, and ecosystem resilience as well as marine pollution, including the fate and transformation of nitrogen, plastics and/or other contaminants in coastal environments. We welcome candidates whose research advances these areas through field observations, laboratory and experimental approaches, numerical modeling, data-driven and machine learning methods, or emerging observing technologies such as autonomous and sensor-based platforms.
Marine Fisheries
We seek a scientist with research interests in marine policy, governance, ecosystems, ocean modeling and AI, and fisheries technology, with a geographic focus on, but not limited to, the Northwest Atlantic Ocean. Emphasis is placed on interdisciplinary research, advanced technology and quantitative analysis to better understand and predict the impact of a rapidly changing ocean and human activity on marine fisheries and seafood supply and translating that knowledge into sustainable management and adaptative strategies.
Minimum Qualifications:
Education:
- An earned Ph.D. in Marine Science, Oceanography, or a closely related field by the time of appointment.
Experience:
- A record of graduate- or undergraduate-level teaching.
- Research accomplishments commensurate with years since the Ph.D., including:
- Peer-reviewed publications
- Leading or participating in externally funded projects
- Experience working with academic, government, or industry partners (desirable).
- Appointment level (Assistant or Associate Professor) set at hiring, based on teaching experience and research record relative to SMAST’s tenure and promotion criteria.
Other:
- Candidates must demonstrate a commitment to excellence in teaching, mentorship, and scholarly accomplishments, as well as a capability to build a strong research program with extramural support.
Preferred Qualifications:
- A track record of successful grant proposal submission and funding as a principal investigator.
- A track record of graduate course development and student mentorship.
- Strong written and oral communication skills as demonstrated by a record of publications and presentations.
- A demonstrated ability to be a productive member of a research collaboration.
Knowledge, Skills and Abilities Required:
- Background and experience in a marine-related research area of strategic interest to SMAST.
Please check the link below for more information and apply: https://careers.umassd.edu/en-us/job/530309
Continue reading ‘Tenure-track faculty position – Assistant/associate professor of marine biogeochemistry or fisheries’An updated version of the OA-ICC bibliographic database is available online.
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OA-ICC, 6 November 2026.
Delay-induced Hopf bifurcation in a coral-macroalgae system under carbon-driven acidification stress
Published 6 November 2026 Science Leave a CommentTags: algae, biological response, BRcommunity, community composition, communitymodeling, corals, growth, modeling, mortality
Ocean acidification can reduce coral growth, alter coral-macroalgae interactions, and weaken reef resilience. This study develops a delayed coral-macroalgae-acidification-pressure model describing live coral cover, fleshy macroalgal cover, and a dimensionless effective acidification-pressure index. The model incorporates coral-macroalgae overgrowth, external stress input, natural relaxation, macroalgal-associated attenuation, coral-associated feedback, and a delayed coral response to acidification pressure. We establish positivity and boundedness of solutions, determine biologically feasible equilibria, derive local stability conditions, and analyze the effect of delay on the coexistence state. The analysis identifies a critical delay at which the stable coexistence equilibrium loses stability through a Hopf bifurcation. For the baseline parameter set, the bifurcation is supercritical and generates a local branch of orbitally asymptotically stable periodic orbits. Numerical simulations, sensitivity analysis, and robustness tests support the analytical findings and show how coral stress sensitivity, external forcing, and reef-scale feedbacks influence stability thresholds and coral persistence. These results provide a mechanistic framework for examining how delayed ecological responses to acidification may promote oscillatory reef dynamics.
Continue reading ‘Delay-induced Hopf bifurcation in a coral-macroalgae system under carbon-driven acidification stress’
