Large-scale Euro-Atlantic variability, shaped by the polar jet stream, governs weather and climate in the Baltic Sea region, thereby impacting the physical and biogeochemical properties of the Baltic Sea ecosystem. This review synthesizes how key atmospheric circulation features and modes of climate variability, including the North Atlantic Oscillation, atmospheric blocking and the Atlantic Multidecadal Variability, influence the Baltic Sea region. By integrating evidence from the published literature, observational datasets, and both global and regional climate model simulations, we assess established as well as potential linkages to key climatic variables, including temperature, precipitation, and storm activity, across temporal scales ranging from synoptic events to multidecadal variability. We then evaluate how these climate controls cascade into ecosystem-relevant processes, namely oxygen dynamics, primary productivity and ocean acidification. Although physical links are already established, the pathways connecting large-scale atmospheric patterns to biogeochemistry are still poorly constrained, partly because dedicated field studies and targeted model experiments are limited. We outline priority research needs to enhance near-term predictability and reduce uncertainty in future projections for the Baltic Sea.
Continue reading ‘Large-scale atmospheric circulation and its impact on the Baltic Sea region: controls, predictability and consequences’Large-scale atmospheric circulation and its impact on the Baltic Sea region: controls, predictability and consequences
Published 15 May 2026 Science Leave a CommentExtending planktic foraminiferal Mg/Ca palaeothermometry into polar temperature ranges: crust- and lamellae specific calibrations and non-thermal controls
Published 15 May 2026 Science Leave a CommentThe rapidity of climate change in the polar regions underscores the need for improved understanding of its impacts on ocean circulation at both regional and global scales. Reconstructions of past polar ocean-cryosphere interactions can provide this context, but large uncertainties in existing proxies limit the utility of such studies. For instance, there are currently no low-temperature (<9 °C) culture-based Mg/Ca-calibrations for planktic foraminifera, a key tool for reconstructing past changes in ocean temperatures. There is also limited understanding of non-thermal influences on Mg/Ca in Neogloboquadrina pachyderma, the only modern polar planktic foraminifera. Moreover, this species exhibits considerable levels of heterogeneity in composition precipitating a thick lower-Mg/Ca outer crust over higher Mg/Ca inner lamellae calcite; specimens with predominantly, albeit variable crust–lamellae proportions, are thus thought to introduce substantial uncertainty into high-latitude palaeotemperature reconstructions. Here, we used N. pachyderma cultured across a range of temperatures, salinities, and carbonate chemistry conditions including experiments in which pH and [CO32-] either covaried or were decoupled. By using a laser ablation approach to analyse crust and lamellae separately, we present new Mg/Ca-temperature calibrations for each component that extend culture-based calibrations in N. pachyderma down to the lower temperature-range (2–9 °C). The crust-specific calibration is of particular importance in high-latitude downcore records where N. pachyderma are commonly observed to preserve predominantly or only crust. Our results show significant carbonate chemistry influence on Mg/Ca with opposite influences from pH and carbonate ion concentration, when these variables changed in isolation. Additionally, we show that environmental conditions regulate crust-lamellar proportions, where increased salinity and temperature, and lower pH lead to less crust formation with implications for future ocean acidification and Arctic Atlantification, and for downcore reconstructions.
Continue reading ‘Extending planktic foraminiferal Mg/Ca palaeothermometry into polar temperature ranges: crust- and lamellae specific calibrations and non-thermal controls’Newly discovered microbial world helps protect developing lobsters
Published 15 May 2026 Press releases Leave a CommentAs ocean temperatures rise and marine ecosystems change, scientists are working to understand how valuable species like the American lobster will respond. New research from William & Mary’s Batten School of Coastal & Marine Sciences & VIMS suggests one source of resilience may come from the microscopic bacterial communities living on lobster embryos.
The study, published in Scientific Reports, found that lobster eggs host surprisingly diverse microbiomes that change as the embryos develop but otherwise remain remarkably stable even under conditions simulating future environmental conditions. The findings challenge decades of assumptions that lobster eggs contained only a few key bacterial species and could help scientists better understand disease risks in one of North America’s most valuable fisheries.
“We were hoping to discover one dominant microbe early on,” said study coauthor Jeffrey Shields, a professor at the Batten School & VIMS who collaborated with several of his students on the research, including lead author Sarah Koshak. “Instead, it was a mishmash, a rich community of different bacteria whose roles we don’t yet fully understand.”
The exterior surface of a late-stage lobster embryo covered by filamentous bacteria at 400x magnification.Credit: Jeffrey Shields.
A hidden ecosystem on lobster eggs
Using advanced genetic sequencing techniques, researchers analyzed microbial communities on lobster embryos and newly hatched larvae raised under varying temperatures and pH conditions designed to mimic present-day and future ocean conditions in the Gulf of Maine.
Continue reading ‘Newly discovered microbial world helps protect developing lobsters’High-resolution temporal biogeochemical variations in a seagrass-coral cohabitate ecosystem: day-night, rain, and coral spawning
Published 14 May 2026 Science Leave a CommentHighlights
- Seagrass-coral habitats act as CO2 sources driven by intense nighttime respiration
- High-resolution data enable predictive modeling of DIC, DOC, and POC dynamics
- Metabolic cues govern DIC, while temperature and alkalinity regulate POC and DOC
- Episodic coral spawning and rainfall trigger rapid ocean acidification
- Short-term disturbances dramatically shift organic and inorganic nutrient loads
Abstract
Seagrass meadows and coral reefs are global hotspots for productivity, yet they are often studied in isolation despite their intense biogeochemical connectivity. Significant gaps remain in understanding how coupled inorganic and organic processes within the water column drive blue carbon services in such mixed habitats, particularly during rapid environmental disturbances. Here, we investigated a unique, intertwined ecosystem in the Dongsha Atoll, where massive Porites corals are distributed on seagrass meadows, creating a natural laboratory for studying water column carbon biogeochemistry. During a 10-day sampling period, we collected continuous hydrological and discrete biogeochemical data at two- to four-hour intervals. Our results reveal that the dissolved inorganic carbon (DIC) covaried with dissolved oxygen and pH in strong diurnal patterns, which were governed by photosynthesis and respiration. As an outcome, variable but mostly high pCO2 values (141–2070 μatm) indicate the seagrass meadow was a source of CO2 to the atmosphere due to strong night-time respiration. Particulate organic carbon (POC) increased with temperature but showed no diurnal pattern. Dissolved organic carbon (DOC) showed a weak diurnal pattern and was linked to variations in POC and total alkalinity, highlighting the tight coupling between the organic production of the meadow and the inorganic chemistry of the calcification framework. Additionally, coral spawning led to a surge in organic content and changed inorganic nutrient levels. Rainfall events significantly acidified the ocean and enhanced submarine groundwater discharge to the seagrass-coral habitat. The distinctive contributions of this study are the extremely high temporal resolution of discrete samples, allowing the simultaneous tracking of multiple organic and inorganic pools during natural disturbances. The high-resolution data provide fundamental information for parametrizing models that explain DIC, POC, and DOC, which yield insights into organic carbon cycling in seagrass meadow-coral habitats.
Continue reading ‘High-resolution temporal biogeochemical variations in a seagrass-coral cohabitate ecosystem: day-night, rain, and coral spawning’Mechanistic drivers of climate-induced reproductive collapse in African catfish: multi-stressor interactions under IPCC scenarios
Published 14 May 2026 Science Leave a CommentClimate change is increasingly disrupting freshwater ecosystems in sub-Saharan Africa, posing severe threats to the reproductive success and population viability of key fish species. This study investigated the mechanistic effects of elevated temperature across a gradient and the combined impact of elevated temperature, acidification and hypoxia under a simulated future climate scenario (IPCC SSP5-8.5) on the reproductive physiology and early life stages of Clarias gariepinus in the Cross River Estuary. Single-stressor trials examined the effect of temperature (28–38°C) on oestrogen synthesis, cortisol levels and gonadosomatic index (GSI). A combined-stressor scenario (35°C, pH 6.2, dissolved oxygen 2 mg/L) was used to simulate predicted climate conditions. Each treatment was replicated across triplicate tanks, with 10 broodstock per tank, over an 8-week period. Environmental parameters were tightly controlled using aquarium heaters, aerators and pH regulators. Combined stressors markedly disrupted reproductive function. Oestrogen synthesis ceased at 34°C, coinciding with a sharp decline in GSI (r2 = 0.81, p < 0.001). Cortisol concentrations increased fourfold under concurrent heat and hypoxia. Cortisol concentrations increased fourfold under heat and hypoxia co-stress. Larval performance also declined sharply, with prey capture efficiency reduced by 33% at pH 6.0 and cumulative mortality reaching 82% by day 5 under combined-stressor conditions. Habitat suitability models projected a 71% reduction in spawning habitat availability in the estuary by 2070 under the SSP5-8.5 scenario. Genetic screening revealed a significant correlation (r2 = 0.63, p = 0.004) between heat shock protein 70 (HSP70) allele frequency and larval survival, indicating potential for adaptive resilience. These findings suggest a compounded vulnerability of C. gariepinus to climate-related stressors and highlight the potential need for targeted conservation efforts. Recommended interventions include habitat restoration, enhancement of dissolved oxygen regimes and selective breeding programmes to support thermal and hypoxic tolerance in vulnerable populations.
Continue reading ‘Mechanistic drivers of climate-induced reproductive collapse in African catfish: multi-stressor interactions under IPCC scenarios’Understanding natural ecosystems: biogeochemical modelling
Published 14 May 2026 Web sites and blogs Leave a Comment
Why do we study ocean biogeochemistry?
The ocean has a huge and diverse range of ecosystems, from shallow coastal waters to the vast open sea and the deep seafloor. Each one supports life that’s adapted to its own specific environment and food webs. Ultimately, at the base of almost all marine ecosystems are tiny, microscopic organisms: the phytoplankton.
Why Does the Ocean’s Carbon Cycle Matter?
The ocean plays a dominant role in the Earth’s carbon cycle. It holds more than 90% of the planet’s carbon and absorbs around 25% of our carbon dioxide (CO₂) emissions. This uptake reduces the amount of CO₂ left in the atmosphere to cause climate warming. Understanding how the ocean’s carbon cycle works is a critically important area of research.
Marine ecosystems play a significant part in the ocean’s natural carbon cycle by transporting carbon from the surface to the deep ocean. This process is known as the “biological carbon pump” (BCP). However, climate-driven changes in ocean temperature, circulation, and mixing are expected to reduce the supply of deep nutrients that fuel the BCP. This may disrupt its vital role in storing carbon.”
How Does Ocean Biogeochemistry Affect Human Communities?
Focusing more directly on human concerns, marine productivity is ultimately what provides us with resources like fisheries. Marine ecosystems support global fisheries, which collectively employ 62 million people and feed about 3.2 billion, sustaining regional economies.
In coastal areas, seaweeds provide ecosystem services like pollution remediation and have a natural value we can all appreciate. On top of that, the wider ocean carbon cycle could potentially be leveraged by marine carbon dioxide removal (mCDR) technologies. These aim to remove CO₂ from the atmosphere and eventually help reduce the extent of climate warming.
So, studying how marine ecosystems operate, and how they might change, is a major goal for our ecosystems modelling group.
What is MEDUSA?
MEDUSA (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) describes the surface ocean ecosystem with a simple, size-based model (nutrient-phytoplankton-zooplankton-detritus). It simulates the linked biogeochemical cycles of carbon, nitrogen, silicon, iron, and oxygen. We use MEDUSA in detailed, high-resolution simulations to help understand how human systems, including fisheries, may change in the future.
MEDUSA is typically run inside physical models of the ocean. This means its components respond to properties like temperature and salinity, and are transported around the ocean by currents. We can then compare the geographical and seasonal output from our models with observational data from ships, autonomous platforms, or satellites. This helps us work out how good a job the model is doing and how we can improve it.
How Does MEDUSA Contribute to Climate Research?
An important part of our work comes from MEDUSA serving as the marine biogeochemistry component of the UK’s state-of-the-art Earth system model, UKESM. Through UKESM, MEDUSA contributes to the international climate simulations that inform the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports. This helps improve our global understanding of how the ocean influences climate.
Using UKESM also allows our group to better study the links between marine ecosystems and the wider atmosphere and land systems. This integrated approach lets us examine how changes in one part of the Earth system cascade through to affect others.
Why is the Research Important for the Future?
Ocean biogeochemistry is important for understanding the ocean’s carbon cycle and its ecosystems, so crucial for both tackling global-scale challenges such as climate change and knowing how we can mitigate these or adapt to them.
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Continue reading ‘Understanding natural ecosystems: biogeochemical modelling’Anti-predatory responses of Mytilus coruscus to the combined effects of ocean acidification and microplastics
Published 13 May 2026 Science Leave a CommentTags: biological response, chemistry, crustaceans, laboratory, mollusks, multiple factors, North Pacific, performance, physiology, plastics
Highlights
- 1.Predator cues can significantly induce byssal secretion in Mytilus coruscus.
- 2.Ocean acidification inhibits the anti-predatory responses of Mytilus coruscus.
- 3.Microplastics exerts sublethal effects on the byssus of Mytilus coruscus.
- 4.The presence of predators amplifies the mild disturbances caused by ocean acidification and microplastics.
- 5.The combined stress shows a synergistic inhibitory trend on the anti-predatory capability of Mytilus coruscus.
Abstract
Ocean acidification (OA) and microplastics (MPs) pollution are major abiotic stressors in coastal ecosystems. Byssus is the core structural trait for Mytilus coruscus to defend against predators, and it is vulnerable to environmental stress, which in turn impairs its anti-predator function. However, the anti-predator response characteristics of M. coruscus byssus and the interaction mechanisms among OA, MPs and predation pressure from Charybdis japonica remain unclear under their combined stress. The study conducted acute exposure experiments, measuring five key byssus indicators: secretion frequency, quantity, diameter, volume and tensile strength, to explore the variation characteristics of the byssus-based anti-predator function of M. coruscus under multi-stressor conditions. Results showed that predators served as a key biological signal to trigger the anti-predator responses and significantly promoted byssus secretion; OA had the most prominent inhibitory effect on byssus function; MPs exposure only induced sublethal disturbances with no significant effects on core anti-predator indicators. Furthermore, the combined stress of ocean acidification and microplastics exhibited a synergistic trend, impairing the byssus-centered anti-predatory defense capacity of M. coruscus. This study provides experimental evidence for analyzing the variation patterns of mussel byssus under multiple stressors and suggests that future marine ecological risk assessments should focus on the interactions between biotic and abiotic stressors to more accurately predict the dynamic changes of coastal ecosystems.
Continue reading ‘Anti-predatory responses of Mytilus coruscus to the combined effects of ocean acidification and microplastics’An updated version of the OA-ICC bibliographic database is available online.
The database currently contains 9,838 references and includes citations, abstracts and assigned keywords. Updates are made every month.
The database is available as a group on Zotero. Subscribe online or, for a better user experience, download the Zotero desktop application and sync with the group OA-ICC in Zotero. Please see the “User instructions” for further details.
Continue reading ‘OA-ICC bibliographic database updated’Leveraging AI-driven predictors of enzyme pH optima to unravel microbial adaptation to environmental pH
Published 12 May 2026 Science Leave a CommentTags: chemistry, modeling
It is well-known that pH (potential of hydrogen) influences enzyme catalytic activity (Schomburg and Salzmann, 1991; Nelson et al., 2021). The pH optimum (pHopt), at which an enzyme displays maximal catalytic activity, is therefore critical for enzyme design and applications (Zhang et al., 2025). To identify suitable enzymes for target pH environments or optimize enzymatic performance in biotechnology, enzyme engineering requires efficient characterization of kinetic properties across large numbers of amino acid sequences. However, experimental determination of pHopt for numerous sequences is time-consuming, labor-intensive, and costly. To address these limitations, computational approaches based on machine learning have been developed for rapid prediction of enzyme pHopt, supporting applications in protein engineering.
Recent advances, exemplified by EpHod (enzyme pH optimum prediction with deep learning) (Gado et al., 2025), enable prediction of the enzyme pHopt directly from protein sequences. The EpHod model leverages embeddings from the protein language model (PLM) ESM-1v and achieves a root mean squared error (RMSE) of 1.25 pH units on the held-out test data (Gado et al., 2025). To further improve predictive performance, an increasing number of AI-driven tools have been developed. For instance, (Zhang et al. 2025) introduced the model VENUS-DREAM, which employs the PLM ESM-2 and reduces the RMSE to 0.809. These AI-powered tools are revolutionizing enzyme discovery and design by enabling high-throughput prediction of pHopt.
Similarly, studies of microbial adaptation to environmental pH frequently require knowledge of enzyme pHopt. This information can be used to investigate the underlying adaptive mechanisms. However, experimental determination of pHopt for large-scale enzyme sequences remains impractical due to high costs and low throughput. Fortunately, the high-throughput predictive capacity of these AI-driven tools offers a powerful alternative for obtaining enzyme pHopt values, which can facilitate investigations into the mechanisms by which microorganisms adapt to environmental pH. The potential applications are illustrated with examples below.
Continue reading ‘Leveraging AI-driven predictors of enzyme pH optima to unravel microbial adaptation to environmental pH’Scientists collaborate with aquaculture industry on ocean acidification resiliency
Published 12 May 2026 Web sites and blogs Leave a CommentAn innovative new research project led by William & Mary’s Batten School & VIMS is bringing together scientists, shellfish farmers and community planners to prepare for emerging environmental challenges related to ocean and coastal acidification (OCA) in the Chesapeake Bay.
“It isn’t something that we’re thinking about on a daily basis, but that doesn’t mean that we shouldn’t begin planning for it now,” said Marcia Berman, co-founder of Cappahosic Oyster Company. “Aquaculture is a vulnerable industry, and more science is always welcome in helping us prepare.”
Supported by a $1.2 million grant from the National Oceanic and Atmospheric Administration’s Ocean Acidification Program, the Regional Vulnerability Assessment (NOAA RVA) study combines traditional coastal and marine science with community research to develop adaptation resources and strategies for the aquaculture industry.
With an advisory committee comprised of Batten School & VIMS experts, members of the region’s shellfish industry and community planners, work is now underway to develop a dynamic, web-based dashboard featuring user-friendly tools that will support businesses and municipalities through complex decision-making processes in the decades ahead.
An invisible shellfish stressor approaches from both land and sea
OCA is the result of both global and local processes. On a global scale, acidification occurs when the ocean absorbs excess carbon dioxide from the atmosphere, reducing the water’s pH and making it more acidic. In coastal regions like the Chesapeake Bay, freshwater runoff introduces nutrients to coastal waters, inducing processes that can lead to further acidification.
“It’s this hidden stressor sneaking up on us and on the shellfish,” said Rivest, an associate professor at the Batten School of Coastal & Marine Sciences & VIMS and the project’s primary investigator (PI). “Animals like oysters and clams that build their shells out of calcium carbonate provide valuable environmental services and are particularly vulnerable to acidification. Understanding the impact of [OCA] on shellfish, and on shellfish farmers, is critical if we want to support the ecosystems and communities that depend on them.”
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Continue reading ‘Scientists collaborate with aquaculture industry on ocean acidification resiliency’Divergent responses of the diatom Thalassiosira weissflogii to ocean acidification during light and dark periods
Published 11 May 2026 Science Leave a CommentTags: biological response, laboratory, light, multiple factors, physiology, phytoplankton, temperature
Given the limited understanding of discrepancies in responses of diatoms to ocean acidification (OA), we comparatively investigated the physiological and transcriptional performances of a diatom Thalassiosira weissflogii acclimated to OA (pHt drop of 0.35–0.41) between day and night periods. We found that OA enhanced its specific growth rate (up to 10%) in the light period by upregulating light reaction, Calvin cycle and H+ pumps to cope with the decreased pH. On the other hand, OA reduced its apparent specific growth rate (14%) in the dark period due to additive pH drop caused by OA-enhanced respiratory CO2 release. In the dark period, the cells could not effectively cope with the decreased pH since H+ pumps were downregulated. Consequently, OA did not affect cell growth during a 24 h diel cycle. These findings suggest that daytime positive and night negative effects of OA on diatoms could be responsible for differential results observed under different conditions, with implications for possible seasonal and latitudinal effects of OA.
Scientific Significance Statement
Progressive ocean acidification (OA) due to continuous dissolution of anthropogenic CO2 into seawater is known to affect diatoms that contribute to approximately 20% of the Earth’s primary production. However, impacts of OA on diatoms through a daily cycle remain poorly understood. Our data provide compelling evidence from both physiological and molecular aspects that OA enhances growth of a diatom during the light period by upregulating its photosynthetic CO2 fixation against the stress of decreased pH, but decreases its apparent specific growth rate during the night period due to the aggravated stress of pH drop from respiratory CO2 release overlaid with OA. These findings align well with transcriptional imprints, suggesting the essential role of light in modulating the effects of OA on diatoms, with implications for possible seasonal and latitudinal effects of OA given the changing lengths of daytime.
Continue reading ‘Divergent responses of the diatom Thalassiosira weissflogii to ocean acidification during light and dark periods’Aragonite saturation state and coral reefs health assessment in Sri Lanka
Published 11 May 2026 Science Leave a CommentTags: biogeochemistry, biological response, chemistry, corals, field, Indian
Ocean acidification (OA) and nutrient enrichment can separately or together threaten coral reefs by reducing calcification efficiency and increasing physiological stress, ultimately weakening reef resilience. Therefore, the study evaluates the prevailing OA level over the Sri Lankan coral reef areas using the aragonite saturation state (ΩAr) and assesses the nitrate (NO3−), and phosphate (PO43−) concentrations over the coral sites. The study was conducted on coral reefs on the eastern coast (EC), southern coast (SC), northern coast (NC), and west coast (WC) of Sri Lanka from April to June 2024. A total of 63 seawater samples were collected around each coastal site for analysis. The ΩAr were supersaturated (ΩAr > 1) and ranged from 2.98 ± 0.04 to 4.92 ± 0.12. Throughout the study period, the study sites had ΩAr values exceeding 2.92 ± 0.16, indicating that the nation’s corals were resilient to deterioration, and the comparative analysis demonstrates that these sites were not vulnerable to OA. However, the NC exhibited significantly (P < 0.05) the lowest ΩAr values (3.2 ± 0.64), positioning the regions near the lower bound of optimal calcification conditions. While ΩAr values indicate low OA stress during sampling, elevated NO3− concentrations (2 – 5 μmol L−1) in SC (2.19 ± 1.28 µmol L−1) and WC (3.52 ± 1.48 µmol L−1) may exacerbate coral bleaching during thermal stress events, representing a co-stressor rather than OA effect. Coral bleaching HotSpot (HS) identification emphasizes how spatially distributed HS are from January to June. The OA risk assessment confirmed that climate change will bring high risk to the coral calcification, reproduction, and damage to the breeding ground, which impact on the ecology and economy of Sri Lanka.
Continue reading ‘Aragonite saturation state and coral reefs health assessment in Sri Lanka’Controls on boron isotope ratios in marine bivalve shells: insights from a controlled experiment across pH and temperature gradients
Published 8 May 2026 Science Leave a CommentTags: biological response, BRcommunity, calcification, chemistry, growth, mollusks, multiple factors, reproduction, temperature
Documenting spatial and temporal patterns of ocean acidification and understanding the way marine organisms build carbonate skeletons is critical to assessing their potential vulnerability to present and future stressors. The boron isotopic composition (δ11Bc) of many marine carbonates provides insight into the pH at the site of calcification within biocalcifiers and, by extension, the pH of ambient seawater when the carbonate formed. The modification of seawater carbonate chemistry at the site of calcification by marine calcifiers and the utility of different taxa as paleo-pH proxy archives remains an area of active research. Despite the significance of marine bivalves to ecosystem function, high-resolution paleoclimatic studies, and the shellfish industry, their biocalcification mechanisms, controls on internal pH, and potential for reconstructing records of past seawater pH remain unclear. To address these gaps, a 20.5-week flowthrough tank experiment was conducted in which four species of commercially important bivalves from the northwest Atlantic Ocean were grown in tanks with controlled pHT (pH 7.4 to 8.0) and temperature conditions (6 to 12 °C). A total of 106 shell samples from 99 individuals of adult and juvenile Arctica islandica (ocean quahog), juvenile Mercenaria mercenaria (northern quahog or hard clam), juvenile Mya arenaria (soft-shell clam) and juvenile Placopecten magellanicus (Atlantic sea scallop) were analyzed from this controlled experiment to assess the seawater pH, temperature, and growth rate controls on shell δ11Bc.These four bivalve species, grown under identical, controlled conditions, showed differential responses to the same seawater temperature and pH, likely due to differences in how they regulate the pH of their internal fluids. Juvenile P. magellanicus and juvenile M. mercenaria demonstrated significant relationships (R≥0.60; p-value <0.006) between tank pHT and δ11Bc, suggesting potential utility as proxies for past ambient seawater pH. Conversely, the δ11Bc of juvenile A. islandica and juvenile M. arenaria did not yield a strong relationship with seawater pHT but instead yielded significant relationships with shell growth rate (linear extension), with a positive relationship for M. arenaria and a negative relationship for juvenile A. islandica. The δ11B results from the few (n=9) adult A. islandica shells measured show the most variability across the range of pH and temperatures (range of 16‰) and no significant relationship was found with seawater pH or growth rate. Despite rigorous oxidative cleaning of samples, the data suggest that adult A. islandica shells contain boron-rich organic phases resistant to traditional cleaning techniques. This suggests that the next step in the development of boron-based pH proxies in A. islandica requires additional research into robust cleaning and sampling methods of periostracum and other organics. Despite the need for further investigations to constrain growth rate effects and cleaning techniques in A. islandica and M. arenaria, there is potential for developing paleo-pH proxies from P. magellanicus and M. mercenaria to better understand spatial and temporal patterns of past, present and future ocean acidification.
Continue reading ‘Controls on boron isotope ratios in marine bivalve shells: insights from a controlled experiment across pH and temperature gradients’Projected future of African marine ecosystems under climate change and stratospheric aerosol injection
Published 8 May 2026 Science Leave a CommentTags: biological response, modeling, multiple factors, North Atlantic, phytoplankton, regionalmodeling, salinity, temperature
Stratospheric Aerosol Injection (SAI) has been proposed as a potential strategy to cool the planet. The ARISE-SAI-1.5 approach, which employes a moderate emission scenario, is simulated to limit future global warming to 1.5°C by injecting aerosols into the stratosphere in the year 2035. However, the climate response to this SAI scenario, particularly along the African coast, remains unclear. In this study, we investigate the potential impacts of climate change under the SSP2-4.5 scenario and ARISE-SAI-1.5 on regional African marine ecosystems through key biological (chlorophyll), physical (salinity, temperature), and chemical (nitrate, acidification, and dissolved oxygen) parameters. Our results indicate that climate change may reduce productivity in African coastal ecosystems, with chlorophyll concentrations decreasing between 10% and 62%. Sea surface temperatures are projected to rise by 1.5°C along the entire coast by 2069, while surface salinity increases up to 0.3 g/kg, except for a slight decrease of up to 0.1 g/kg along the Congolese-Angolan coast. This salinity dipole in the Gulf of Guinea results from enhanced precipitation and river discharge, reinforced by stratification that traps freshwater at the surface. Additionally, climate change drives ocean acidification and may expand the oxygen minimum zone in the Gulf of Guinea, with oxygen levels decreasing by 10%–30% at depths of 100–200 m. Although ARISE-SAI-1.5 may help reduce surface oxygen depletion, it may not significantly mitigate subsurface oxygen loss or continued acidification. Nevertheless, it may reduce some negative climate change impacts on marine ecosystems by stabilizing chlorophyll levels, sea surface temperatures, and salinity.
Plain Language Summary
Stratospheric Aerosol Injection is being explored as a way to cool the planet and limit future global warming, for instance, to 1.5°C in the scenario we explore here (ARISE-SAI-1.5). However, its effects on the ocean, especially along the African coast, are not fully understood. This study examines key factors such as chlorophyll, water temperature, salinity, and oxygen levels to assess changes in marine ecosystems. Our findings show that climate change could reduce productivity, with chlorophyll levels dropping by 10%–62%. Sea surface temperatures are expected to rise by 1.5°C by 2069, and salinity will increase along most coastal areas. The low-oxygen zone in the Gulf of Guinea may expand, making deep waters less habitable for marine life. While the SAI we study here helps slow oxygen loss near the surface, it does not prevent deeper waters from losing oxygen or the ocean from becoming more acidic. However, it can still reduce some harmful effects of climate change by stabilizing chlorophyll levels, temperatures, and salinity.
Continue reading ‘Projected future of African marine ecosystems under climate change and stratospheric aerosol injection’Coupled ocean warming and acidification reduce shell integrity and bioenergetics in juvenile Mytilus coruscus
Published 7 May 2026 Science Leave a CommentTags: biological response, laboratory, molecular biology, mollusks, morphology, multiple factors, physiology, temperature
Under realistic climate change scenarios, marine bivalves face compounding stressors from concurrent ocean warming and acidification. Research has established the separate effects of these factors; however, the synergy driving physiological adaptation in mollusks has yet to be fully elucidated. We assessed the physiological responses of an ecologically significant mussel, Mytilus coruscus, to 2 mo exposure under varying environmental conditions (25°C/28°C and pH 7.7/8.1). Key metrics included shell properties, flesh weight, antioxidant defenses, bioenergetics, and gene expression. Compared to control groups, experimental groups showed reductions in shell hardness and compressive strength, >10% decrease in flesh weight, and 40-52% suppression of carbonic anhydrase and Ca2+-ATPase activities. Molecular analyses of the mantle tissue demonstrated compromised mitochondrial energy transduction (>40% reduction in ATP6 expression) alongside upregulated stress response markers (>2.1-fold COX3 increase). Notably, cellular energy allocation declined, accompanied by depletion of energy reserves (proteins, lipids, carbohydrates), indicating metabolic prioritization toward stress compensation. These findings elucidate how coupled stressors disrupt homeostasis through multilevel interactions, forcing energy trade-offs between defense mechanisms and growth processes, and confirm the tissue-specific vulnerability of the mantle and individual resilience of bivalves under multifactorial climate change.
Continue reading ‘Coupled ocean warming and acidification reduce shell integrity and bioenergetics in juvenile Mytilus coruscus’Ordovician sedimentary processes and related driving forces: Jordan, Arabian Plate
Published 7 May 2026 Science Leave a CommentTags: paleo, sediment
The Ordovician-Lower Silurian siliciclastics deposited on the Jordanian Platform represent a transitional sedimentary system between their granitoid Gondwana source area and the Paleo-Tethys. While fluvial fining upward cycles (FUCs) of quartz arenite dominate braid plain deltas/upper shore face environments of the Lower Ordovician, arkosic tempestite and oxygen-deficient bituminous pelite/tuffite cycles cover upper/lower shore face environments of the Sandbian and Katian. The mineral deficit (feldspar, unstable heavy minerals) relates to acid sturz-rain events during volcanic degassing (SO2, HCl, HF, NOx) sourced in an Infracambrian/Cambrian Large Igneous Province (LIP) around S Sinai/Wadi Araba Rift-Zone. The change of sedimentary architectural elements/lithofacies types during the Upper Darriwilian took place after an L-chondrite of the Main Asteroid Belt (MAB) crossed the Earth’s orbit (~470 Ma), which resulted in some small meteorite craters (i.e., Lockne). Through the Sandbian and Katian, this insignificant impact series was accompanied by massive tephra production during worldwide explosive subduction-related volcanic arc magmatism. During the Upper Ordovician High Stand-System Tract (HST), the glass-bearing tephras were transformed under marine conditions into montmorillonite (K-bentonite), contributing to green tuffitic pelite interbedded with storm-generated arkosic clastics. Transtensional tectonics (pull-apart type) caused the main Ordovician-Silurian unconformity (“paleovalleys”) in SE Jordan and Saudi Arabia. Their sedimentary fills expose arkosic FUCs originated by shallow-water turbidites during the Hirnantian. The intensive explosive volcanism generated almost continuously negative climate forcing (“cosmic winter”) by tephra, aerosols, smog, and clouding that led to regional glaciation in the S Hemisphere. The abrupt 87Sr/86Sr-ratio decrease accompanies, at the Sandbian base, the onset of magmatism, while δ13C excursions follow a Transgressive System Tract (TST) and three T-maxima indicating increasing phytoplankton growth. The undulation—0% mirrors a cyclicity of volcanic events, climate forcing, Eh, and pH conditions. The δ18O rise shows a continuous CO2 assimilation until its stop (~1200 ppm CO2) and the following formation of black-shale facies.
Continue reading ‘Ordovician sedimentary processes and related driving forces: Jordan, Arabian Plate’Effects of ocean acidification on radular tooth material properties in Littorina littorea (Gastropoda, Mollusca)
Published 6 May 2026 Science Leave a CommentTags: biological response, laboratory, mollusks, mortality, philosophy
Ocean acidification is known to affect calcified structures in marine organisms, yet its impact on non-calcified but functionally essential feeding tools remains poorly understood. The radula is a defining molluscan apomorphy, whose mechanical performance is critical for feeding and survival. Here we investigated the effects of reduced seawater pH on the radular teeth of the intertidal gastropod Littorina littorea. Individuals were maintained for seven weeks under acidified conditions (pH 7.5) or near-present-day conditions (pH 8.1) and compared with a field-collected control group. Radulae were analysed using scanning electron microscopy, confocal laser scanning microscopy, energy-dispersive X-ray spectroscopy, and nanoindentation.
Radulae from acid-treated individuals exhibited markedly increased tooth wear in the working zone despite largely preserved gross morphology. Wear was most pronounced at the cusps of central and lateral teeth and showed rounded profiles indicative of progressive abrasive wear. Acidic conditions caused pronounced changes in the outer tooth coating, including reduced silicon enrichment and substantial decreases in stiffness and hardness, while the inner tooth structure was only weakly affected. Confocal microscopy revealed treatment-specific autofluorescence patterns, suggesting pH-dependent alterations of the organic matrix. Differences between laboratory-maintained and field-collected individuals further indicate that feeding conditions influence radular tooth properties.
These results demonstrate that ocean acidification can impair radular function through material-level degradation of composite feeding structures, potentially reducing grazing efficiency and imposing sublethal fitness costs.
Continue reading ‘Effects of ocean acidification on radular tooth material properties in Littorina littorea (Gastropoda, Mollusca)’The influence of localized water quality on Eastern oysters (Crassostrea virginica) and their internal microbiome under changing environmental conditions
Published 5 May 2026 Science Leave a CommentTags: biological response, laboratory, mollusks, morphology, North Atlantic, physiology, prokaryotes
Oysters are found ubiquitously in estuaries along the Georgia coast, where marsh morphology and large daily tidal fluctuations create dynamic and stressful conditions to which oysters may be locally adapted. Based on water quality data from the Sapelo Island National Estuarine Research Reserve, it is evident that changing climatic conditions are rapidly causing shifts in water quality that may be adversely affecting oyster health, especially as ocean acidification alters the carbonate buffering capacity, increasing the amplitude of daily pH variations. Importantly, the rate of change of conditions are not uniform within estuaries, varying on spatial and temporal scales. The symbiotic relationship between oysters and their internal microbiome has been increasingly analyzed as a metric for oyster health. As filter feeders, oysters continuously introduce microorganisms into their hemolymph. Core families of bacteria, including Mycoplasmataceae, have been identified to be associated with healthy oysters. The abundance of core groups, or of pathogenic genera like Vibrio, can be used as an indicator of oyster condition. Utilizing reciprocal transplant and common garden tank designs, we examined how changing variability in localized water quality conditions drive oyster health using physical and microbial indicators, including oyster growth, condition index, and shifts in microbial community dynamics. Our results suggest that low pH conditions are detrimental to oyster physiology, inducing stress, leading to a reduction in overall health and growth. Low pH causes a shift within the microbial composition, altering community dynamics, and increasing the abundance of stress-related bacteria, including Arcobacteraceae and Vibrionaceae. Drivers of oyster health and host-associated microbial dynamics are site- and scale-dependent and will need further research to fully understand which biotic or abiotic factors are most influential in oyster conditions amidst low pH conditions. Oysters are increasingly used in nature-based restoration efforts to support reef recovery and salt marsh expansion, making it critical to understand how relocation influences oyster health. Our results indicate that oyster condition is driven by destination rather than origin, with relocation success dependent on water quality at the transplant site.
Continue reading ‘The influence of localized water quality on Eastern oysters (Crassostrea virginica) and their internal microbiome under changing environmental conditions’Evaluating the role of seaweed farming in ocean acidification mitigation: insights from high-frequency observations
Published 5 May 2026 Science Leave a CommentTags: algae, biological response, field, mitigation, North Atlantic, phytoplankton
The oceanic uptake of anthropogenic CO2 has resulted in ocean acidification (OA). Macroalgae farming has the potential to mitigate OA by removing CO2 from the surface water via photosynthesis. However, continuous in-situ observations of marine carbonate chemistry related to macroalgae farming remain limited, leaving its effectiveness in addressing OA uncertain. To address these knowledge gaps, this study examined a 2-acre Saccharina latissima, sugar kelp, farm located at Point Judith, Rhode Island, as a case study to assess the potential of sugar kelp aquaculture in mitigating local OA. Over the full growing season from December 2022 to May 2023, high-temporal-resolution (every 30–60 minutes) measurements of surface temperature, salinity, dissolved oxygen and pH were taken inside and outside the kelp farm. The results demonstrate that sugar kelp farming does not significantly impact the carbonate system, thus providing negligible OA mitigation locally. Specifically, a temporary, local-scale CO2 reduction and higher pH occurred during very early kelp growth in early February, but was reversed by a higher surface CO2, exaggerating OA, starting in mid-February. Over the entire observation period, kelp growth resulted in a 5.1 ± 11.6 μatm increase of pCO2 per week compared to the control site in the surface, a signal which is small compared to the substantial natural variability. However, the minimal pCO2 difference at the kelp farm may be reflective of the relatively small cultivation area (2 acres) or depressed growth of phytoplankton, resulting from nutrient competition between the kelp and in-situ phytoplankton. This study underscores the need for future sustained observations to evaluate the impact of seaweed cultivation on OA mitigation and the carbon cycle at the ecosystem scale.
Continue reading ‘Evaluating the role of seaweed farming in ocean acidification mitigation: insights from high-frequency observations’
