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’Posts Tagged 'field'
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
Acidification in coastal waters of Adélie Land, Antarctica (1985–2025)
Published 29 April 2026 Science Leave a CommentTags: Antarctic, chemistry, field, modeling, regionalmodeling, sensor
Ocean acidification is expected to be particularly severe in Antarctic continental shelves due to enhanced anthropogenic carbon uptake in cold waters in response to rising atmospheric CO2, sea-ice retreat, freshening and climate-change feedbacks. Models suggest that undersaturated conditions with respect to aragonite (Ωar), a major form of calcium carbonate formed by marine species, could be reached as soon as 2052 for austral winter. Here we present new ocean carbonate system observations from cruises conducted since 2010 in the Adélie Land coastal region in East Antarctica, along with data from a BCG-Argo float and results from a neural network model for the period 1985–2025. The region is a permanent CO2 sink and was most pronounced since 2006. The CO2 sink leads to a positive increase of surface water total CO2 concentrations (CT) (+0.44 ± 0.01 µmol.kg-1.yr-1) and to a progressive decrease of pH (-0.013 per decade) and Ωar (-0.035 per decade) for the winter season. The lowest surface Ωar of 1.2 was observed in winter 2024 from the float data, a critical limit for some marine species such as pteropod. A projection of the CT concentrations in the future, based on observed anthropogenic CO2 concentrations and emissions scenarios, suggests that aragonite saturation state (Ωar = 1) will occur in surface waters as soon as 2055 in the Adélie Land region, which is part of a larger area of East Antarctica proposed as a Marine Protected Area by the Commission for the Conservation of Antarctic Marine Living Resources since the early 2010s.
Continue reading ‘Acidification in coastal waters of Adélie Land, Antarctica (1985–2025)’Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters
Published 27 April 2026 Science Leave a CommentTags: abundance, biogeochemistry, biological response, chemistry, field, molecular biology, morphology, North Pacific, phytoplankton
Coccolithophores, as calcifying phytoplankton, play a critical role in the global carbon cycle by producing calcium carbonate (CaCO 3 ) in the ocean through their calcitic coccoliths. Here we examine Gephyrocapsa huxleyi (formerly Emiliania huxleyi) and related species abundance and genetic diversity along the West Coast of North America from samples taken on the 2021 NOAA West Coast Ocean Acidification (WCOA21) cruise, along the margin from British Columbia, Canada, to San Diego, California, USA. Significant carbonate chemistry gradients were observed across 17 transects, mostly in the onshore-offshore and north-to-south direction. Abundance and morphometrics of Gephyrocapsa spp. was evaluated using real-time PCR of mitochondrial cytochrome c oxidase subunit 3 ( cox3 ) gene and by microscopy. Variation in PIC concentrations, G. huxleyi and related species abundance, and coccosphere thickness were found to be associated with the gradients in carbonate chemistry and nutrient concentrations (phosphate, nitrate, nitrite, ammonium) across stations sampled during the cruise. We identified 5 unique amplicon sequence variants (ASVs) of Gephyrocapsa spp. cox3 that systematically varied in relative abundance across the California Current System. Southern California locations had greater diversity in cox3 sequences than northerly locations. These analyses represent baselines for evaluation of the impacts of future environmental changes in coastal waters along this productive upwelling regime.
Continue reading ‘Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters’Real-time acidification monitoring through Sofar buoy and SAMI-pH integration
Published 23 April 2026 Science ClosedTags: chemistry, field, methods
Ocean acidification (OA) impairs the ability of corals to build and maintain reef structures by reducing calcium carbonate deposition and accelerating the dissolution of existing frameworks. OA conditions can result from both natural pH fluctuations, driven by diel and seasonal variability in biological activity and water quality, and long-term increases in atmospheric CO2 absorption. Accurate characterization of OA requires precise, high-frequency time-series data, particularly in nearshore ecosystems where benthic community metabolism can cause rapid, localized shifts in carbonate chemistry. However, continuous, high-resolution pH monitoring remains challenging, and most existing technologies lack real-time feedback capabilities. Here, we present a real-time acidification monitoring system that integrates a Sofar Spotter buoy with a Sunburst SAMI-pH sensor. The system delivers continuous environmental data (benthic pH and temperature, surface temperature, wind, wave height, and barometric pressure) and sensor health diagnostics (battery levels and cellular connectivity status) to a public-facing dashboard. This system enables real-time access to high-frequency pH data and provides a modular and cost-effective alternative to larger, more complex platforms such as MAPCO2 buoys. Increased accessibility supports broader and more scalable monitoring efforts, supporting scientists, resource managers, and policymakers in tracking diel, seasonal, and long-term OA dynamics.
Continue reading ‘Real-time acidification monitoring through Sofar buoy and SAMI-pH integration’Decadal shifts in hypoxia and acidification reveal changing anthropogenic pressures on bottom waters of a coastal shelf
Published 20 April 2026 Science ClosedTags: chemistry, field, North Atlantic
Coastal systems provide habitat that sustains valuable shellfisheries but are subject to dissolved oxygen (DO) and/or carbonate chemistry impairment from anthropogenic pressures such as eutrophication and increasingly, climate change. Although extreme events can have disproportional negative ecological impacts, their ephemeral nature and a lack of baseline monitoring data make them challenging to characterize. Through assessments of historical records and a series of modern-day cruises, this study documented the magnitude and extent of summer hypoxia and acidification in the coastal shelf bottom waters of an urban shelf ecosystem, the New York Bight, before and during a devastating hypoxic event in 1976 and at present. In 1974, the most severe DO (2.39 mg L−1) and carbonate chemistry [pHN: 7.47; aragonite saturation state (ΩAr): 0.45] conditions occurred as a halo around a now derelict sewage disposal site, while averaging 4.43 mg L−1 (DO), 7.84 (pH), and 1.25 (ΩAr) across the region that August. During the mass mortality event of 1976, extremely low DO (< 1 mg L−1), pHN (< 7.5), and ΩAr (< 0.5) levels were observed across bottom waters during summer. Comparisons of modern subsurface chemistry to that of 1974—a year with ocean dumping but no mass mortality—indicated increases in bottom water DO, with evidence to suggest that ocean acidification has dampened the concomitant increases in ΩAr over the intervening half-century. This study highlights the impacts of ocean dumping and the threat of ocean acidification to systems that are experiencing or recovering from coastal hypoxia.
Continue reading ‘Decadal shifts in hypoxia and acidification reveal changing anthropogenic pressures on bottom waters of a coastal shelf’Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea
Published 20 April 2026 Science ClosedTags: biological response, community composition, field, morphology, North Pacific, otherprocess, physiology, phytoplankton
Highlights
- Miniaturization coincides with reduced species diversity and elevated chlorophyll a.
- Declining pH and reduced dissolved inorganic nitrogen are key drivers for smaller cells.
- Salinity, dissolved oxygen and cooling jointly reshape phytoplankton community structure.
Abstract
Phytoplankton are tiny drifting photosynthetic organisms that support marine food webs and help control the global carbon cycle. However, it remains unclear how ongoing environmental changes are altering their cell size, species diversity, and chlorophyll a concentration in coastal seas. In this study, we investigated changes in phytoplankton cell size, species diversity, and chlorophyll a concentration along the Yellow Sea coast of China from 2021 to 2024, based on fourteen research cruises conducted at twenty-six coastal stations. We then employed statistical models to explore how individual and combined environmental factors were related to those biological features. We observed a clear shift to predominance of smaller cells, a reduction in species diversity, and an increase in chlorophyll a concentration. pH and reduced dissolved inorganic nitrogen were strongly associated with smaller cell size, while higher salinity and higher oxygen were associated with lower diversity. Lower surface water temperature and higher dissolved oxygen were associated with higher chlorophyll a concentrations. Overall, our findings suggest that interacting changes in pH, nutrient supply, temperature, salinity, and oxygen are associated with a simpler phytoplankton community structure, smaller mean cell size, and higher biomass levels in the Yellow Sea coastal region, with potential consequences for local food webs and carbon cycling.
Continue reading ‘Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea’Synergistic effects of ocean acidification and thermal stress on shell biomineralization and parasitism in the white clam Leukoma asperrima (Bivalvia: Veneridae)
Published 17 April 2026 Science ClosedTags: biological response, BRcommunity, crustaceans, field, mollusks, morphology, North Pacific
Ocean acidification (OA) and global warming are fundamentally altering the biomineralization processes of calcifying marine organisms. This study evaluates shell malformations and parasitism in the white clam Leukoma asperrima at Bique Beach, Panama, from December 2024 to November 2025. Environmental parameters (pH, temperature) were monitored monthly across two sampling stations (n=1100). Results indicate that 13.6% of the population exhibited shell malformations, and 6.3% were parasitized by the pea crab Pinnotheres pisum. A strong positive correlation was found between pH and healthy individuals (r=0.97, p<0.001), whereas critical pH levels (min. 5.75) were associated with increased shell fragility and dissolution. Despite thermal tolerance observed up to 35.7°C, the synergistic effect of OA and local stressors compromises the structural integrity of L. asperrima, threatening the sustainability of this socio-economic resource in the Tropical Eastern Pacific.
Continue reading ‘Synergistic effects of ocean acidification and thermal stress on shell biomineralization and parasitism in the white clam Leukoma asperrima (Bivalvia: Veneridae)’Unravelling marine benthic functioning shifts under ocean acidification
Published 10 April 2026 Science ClosedTags: algae, biological response, BRcommunity, calcification, community composition, crustaceans, field, Mediterranean, mollusks, morphology, otherprocess, photosynthesis, physiology, porifera, respiration, vents
Ocean acidification (OA) driven by increasing atmospheric CO2 is altering marine biodiversity. However, impacts of OA on ecosystem functioning at the community level, including calcification, primary production and nutrient uptake, remain largely unknown. Here, we conducted community transplant experiments at natural CO2 vents to assess how declining pH affects marine community species composition, biomass, and key ecosystem processes over time. Our results indicate that community shifts caused by declining pH lead to decreased biomass and calcification rates, while photosynthesis and nutrient uptake rates increased. By leveraging OA field model systems and in situ measurements of ecosystem functioning, this study provides critical insights into how OA-induced biodiversity loss reshapes the structure and functioning of temperate marine coastal ecosystems.
Continue reading ‘Unravelling marine benthic functioning shifts under ocean acidification’Responses of reef fish populations to similar environmental changes across distant oceanic islands
Published 9 April 2026 Science ClosedTags: abundance, adaptation, biological response, chemistry, field, fish, otherprocess, South Atlantic
Oceanic islands are among the most remote and understudied regions of the planet, yet they harbour unique reef fish communities that are increasingly vulnerable to global environmental change. Because these islands are geographically isolated, their populations are often assumed to respond mainly to local environmental conditions. However, by analysing temporal patterns in oceanographic variables across two distant systems (3204 km apart) in the South Mid-Atlantic Ridge (both encompassed by marine protected areas—MPAs), we found that temporal alignment in environmental conditions was associated with coordinated shifts in counts of nine reef fish populations in each study area. Among the evaluated variables, pH emerged as the most influential factor. Despite the divergent responses among reef fishes, possibly reflecting differences in physiological plasticity, shared temporal patterns in pH appeared central to parallel population patterns observed across assemblages. Increases in sea surface height and chlorophyll-a played secondary roles, potentially benefiting some populations, although such effects may be transient. These results suggest that climate-driven convergence in environmental conditions can override geographic isolation, promoting similar biological responses that may reduce resilience and increase extinction risk. Given that both islands are legally protected, our findings highlight that even MPAs are not insulated from large-scale oceanographic stressors, underscoring the need for long-term monitoring and adaptative conservation strategies for remote reef systems.
Continue reading ‘Responses of reef fish populations to similar environmental changes across distant oceanic islands’Climate change influence on salinity, temperature, dissolved oxygen and pH in Biscayne Bay (Florida): two decades of observations (2001–2021)
Published 8 April 2026 Science ClosedTags: chemistry, field, North Atlantic
Highlights
- Research Highlight 1: Biscayne Bay is transitioning from an estuarine to a more marine regime due to sea level rise.
- Research Highlight 2: Salinity is increasing at canal mouths, with saltwater intrusion detected in bottom layers.
- Research Highlight 3: Global warming has raised Bay water temperature, and the past decade has been the warmest on record.
- Research Highlight 4: Ocean acidification is influencing the Bay.
Abstract
An evaluation of 20 years (2001-2021) of monthly data from a long-term monitoring program was performed to determine the temporal, seasonal and spatial changes in the distribution of salinity, temperature, dissolved oxygen, and pH, to identify the potential impacts of climate change on Biscayne Bay, the largest estuary on the Atlantic coast of Florida. Data were evaluated by decade, season, and zone. Decade 2 showed higher salinity in four of eight zones, along with saltwater intrusion in the bottom layer of some canals. The zones most influenced by the Atlantic Ocean did not show decadal salinity changes. In decade 2, the overall median temperature in-creased (+0.5◦C), with North Bay exhibiting the highest increase (+0.8◦C). In decade 2, dissolved oxygen was higher in four zones, while pH decreased in six zones, suggesting that ocean acidification is also influencing the Bay. Temperature, dissolved oxygen, and pH displayed pronounced seasonal patterns across zones. Collectively, these results suggest that sea level rise and climate change are gradually transforming Biscayne Bay from an estuarine system to one that is more marine in nature.
Continue reading ‘Climate change influence on salinity, temperature, dissolved oxygen and pH in Biscayne Bay (Florida): two decades of observations (2001–2021)’Effects of upwelling-driven acidification and deoxygenation on the dissolved inorganic carbon system over the southeastern Arabian Sea shelf
Published 8 April 2026 Science ClosedTags: chemistry, field, Indian
Highlights
- Summer monsoon upwelling drives strong acidification and deoxygenation over the EAS shelf.
- Non-upwelling DIC and TAlk variability is largely governed by conservative water-mass mixing.
- Elevated nDIC35 during upwelling confirms DIC enrichment beyond salinity stratification alone.
- AOU-nDIC35 coupling indicates respiratory amplification of upwelled CO2-rich source waters.
- Reduced buffering and lower ΩCa–ΩAr increase seasonal chemical stress on shelf ecosystems.
Abstract
Repeated measurements of inorganic carbon system parameters over one year along two coastal transects (Kochi in the southern EAS and Mangalore in the central EAS) in the eastern Arabian Sea (EAS) reveal strong seasonal coupling between upwelling, deoxygenation, acidification, and inorganic carbon accumulation on the shelf. During the non-upwelling (oxic) period, the variability of dissolved inorganic carbon (DIC) concentrations and total alkalinity (TAlk) was governed predominantly by conservative water-mass mixing, particularly between low-salinity Bay of Bengal-derived waters and more saline Arabian Sea shelf waters, as demonstrated by the marked reduction in salinity normalised DIC (nDIC35) and TAlk (nTAlk35). In contrast, during the summer monsoon (June–September), coastal upwelling transported oxygen-poor, DIC-rich subsurface waters onto the shelf, leading to pronounced subsurface inorganic carbon enrichment, hypoxia, and acidification. Vertical profiles of nDIC35 showed that elevated inorganic carbon concentrations persisted even after removing salinity effects, increasing from ∼1950–2000 μmol kg−1 at the surface to >2100–2200 μmol kg−1 below ∼40 m. Nearshore surface waters during peak upwelling exhibited a strong offset between measured DIC and nDIC35, indicating localized freshwater dilution, but salinity-normalised values confirmed that the underlying carbon inventory remained high. Apparent oxygen utilisation (AOU) and nDIC35 were positively correlated, indicating that a substantial fraction of the residual DIC enrichment was associated with oxygen consumption, although this relationship reflects the combined imprint of DIC-rich upwelled source waters and subsequent microbial remineralisation within the stratified shelf system. Thus, carbon accumulation during the summer monsoon is best explained by a two-stage mechanism: (i) physical advection of CO2-rich, oxygen-deficient upwelled waters, followed by (ii) secondary amplification through local respiration. In contrast, TAlk exhibited much weaker non-conservative modification, and the elevated alkalinity generated under low-oxygen conditions was insufficient to counteract the strong DIC-driven reduction in carbonate-system buffering capacity, thereby increasing the system’s vulnerability to pCO2 build-up and acidification. Consequently, calcite and aragonite saturation states declined sharply during upwelling, with ΩCa and ΩAr falling to ∼2.5 and ∼ 1.5, respectively, when pCO2 exceeded 1000 μatm under severe oxygen depletion. The co-occurrence of hypoxia, acidification, and weakened carbonate buffering characterises the eastern Arabian Sea shelf as a highly dynamic natural laboratory for understanding multi-stressor impacts on coastal biogeochemistry and ecosystem vulnerability.
Continue reading ‘Effects of upwelling-driven acidification and deoxygenation on the dissolved inorganic carbon system over the southeastern Arabian Sea shelf’Investigation of the adaptive mechanisms to ocean acidification in Patella species from CO2 vent systems of the Mediterranean Sea
Published 7 April 2026 Science ClosedTags: adaptation, biological response, field, Mediterranean, molecular biology, mollusks, morphology, otherprocess, physiology, respiration, vents
The continuous increase in anthropogenic carbon dioxide (CO2) emissions into the atmosphere is one of the main factors contributing to ocean acidification (OA). In fact, CO2 is partially absorbed by the oceans, where it alters carbonate chemistry and seawater pH, which is expected to decrease from the current level of 8.1 to 7.7 by 2100. OA exerts harmful impacts primarily on calcifying organisms, as it affects the availability of carbonates, which makes their calcareous structures thinner and more fragile. Moreover, several studies have described the detrimental effects of OA across many marine taxa, affecting important physiological and metabolic mechanisms. On the other hand, research conducted at CO2 vent systems, which are volcanic naturally acidified sites, showed that several organisms can survive under acidified conditions through specific tolerance and/or adaptive strategies. Among these organisms, the gastropod Patella spp. is one of the few calcifiers capable of inhabiting naturally acidified sites, such as the Castello Aragonese vent systems at Ischia Island and the San Giorgio vent systems at Sicily Island. Nonetheless, the complex mechanisms that allow survival and potential adaptation of these organisms to natural OA conditions need to be understood. Therefore, this PhD study aimed at investigating the potential molecular, physiological, metabolic, genetic, and epigenetic mechanisms that enable these organisms to tolerate and survive under OA conditions through a stepwise approach. Specifically, this PhD research attempted to answer the following questions: • Does OA entail a stressful condition in resident populations of Patella spp. living at reduced pH conditions, thereby affecting their overall well-being and health status? • Are there specific physiological, metabolic, and biochemical mechanisms that contribute in defining tolerance to OA? • Are limpets genetically adapted to OA? • Is DNA methylation contributing to promote tolerance to OA in limpets? • What is the role of environmental conditions in shaping the response to OA? The first chapter of this thesis considered three Patella species (P. caerulea, P. rustica, and P. ulyssiponensis) collected from the CO2 vent systems of the Castello Aragonese (Ischia Island). This vent system exhibits a natural acidification gradient ranging from ambient pH (N1: pH = 8.1), to intermediate pH (N2: pH = 7.7), and to extremely low pH (N3: pH < 7.4). Resident populations were collected along the gradient and at San Pietro, an additional ambient pH site (pH = 8.1), located at a distance of 4 km from the Castello vent. In addition, a 30-day in situ transplant experiment was conducted using P. caerulea, in order to evaluate the short-term responses induced by OA. Morphometric traits, such as shell length, height, width, and soft-tissue weight, were measured, and a set of biomarkers related to antioxidant system, energy metabolism, neurotoxicity, and biomineralization was applied. For resident populations, P. caerulea showed increased size and energy reserves at the extremely acidified site, likely related to a shift from erect calcified algae to biofilm, or to reduced competition and/or predatory pressure under acidified conditions. Biochemical endpoints measured in both P. caerulea and P. ulyssiponensis were not modified by OA. Conversely, P. rustica exhibited significant modulation of nearly all biochemical parameters, likely due to its different position on the rocky shore, which makes this species more exposed to tidal fluctuations and therefore to an additional source of disturbance, besides OA. Short-term exposure of P. caerulea to OA resulted in a decrease in protein content and an increase in glycogen content at the extremely acidified site, with the induction of superoxide dismutase and glutathione-S-transferase activities at intermediate pH, suggesting the activation of compensatory mechanisms to cope with reduced pH conditions. Overall, results revealed a distinct response to OA of the three species of Patella. Moreover, the increased size and energy-related endpoints observed in P. caerulea and P. rustica highlighted the need to further investigate energy metabolism aspects, in order to better understand the trade-offs between compensatory mechanisms and the energetic cost underlying tolerance to OA. Based on these evidences, the second chapter focused exclusively on P. caerulea, with the aim of deeply investigating metabolic and physiological stress-responses, comparing resident populations of the Castello Aragonese vent systems and transplanted organisms, similarly to the first chapter. Respiration and ammonia excretion rates were measured four times across the year. Additionally, untargeted metabolomics analyses were performed to investigate metabolic pathways potentially involved in response to OA. Only during summer, OA increased respiration rate in limpets from the most acidified site, while simultaneously reduced excretion rates, likely to allocate more energy resources to face the increasing temperature, besides OA. Furthermore, both resident and transplanted populations up-regulated carnitine metabolism, suggesting that OA induced an increase of energy production through β-oxidation and subsequent Krebs cycles. Moreover, several metabolites involved in osmoregulation, oxidative stress, and nucleic acid mechanisms were increased. Overall, results seem to confirm the presence of negative effects and of an energetic cost underpinning tolerance to OA. The third and final chapter investigated the potential influence of phenotypic plasticity, genetic adaptation, and DNA methylation in tolerance to OA in adult and juvenile populations of P. caerulea collected from two CO2 vent systems of the Mediterranean Sea. Adult and juvenile specimens were sampled along the acidification gradient of the Castello Aragonese vent systems of Ischia Island (San Pietro/N1: pH = 8.1; N2: pH = 7.7; N3: pH < 7.4) and from the San Giorgio vent systems of Sicily Island (Patti: pH = 8.1; San Giorgio: pH = 7.8). Following genomic DNA extractions from foot tissue and individual libraries preparation with the NEB Next® Enzymatic Methyl-seq Kit, samples were sequenced on the Illumina NovaSeq 6000 sequencer. Data processing and analyses were conducted on Euler platform mainly using biscuit tool, which enabled to simultaneously extract genomic and epigenomic information from DNA methylation sequencing. Population genomics and epigenomics analyses revealed divergent patterns between the Ischia and Sicily populations. Populations from the Ischia vent revealed marked signs of genomic differentiation, particularly in adults from the intermediate and extremely low pH sites, while reduced differences in DNA methylation levels were detected, especially in adults. These findings suggest a strong signature of purifying selection acting on standing genetic variation, through a within-generation response, likely driven by the more pronounced pH fluctuations occurring at these sites. Conversely, no genomic differentiation was observed between the Sicily populations, but greater differences in DNA methylation were detected between acidified and non-acidified sites at both adult and juvenile stages. These results revealed that this epigenetic mechanism, rather than genomic changes, may play a key role in the response to the milder pH variations of this vent and potentially enhance organisms’ tolerance to OA. In conclusion, this PhD project investigated tolerance to OA in limpets through a holistic approach that, for the first time, integrated morphological, physiological, metabolic, biochemical, genetic, and epigenetic analyses. Overall, findings revealed that Patella spp. has the ability to survive under acidified conditions even though with a physiological and metabolic cost, which could be partially compensated by more favorable environmental conditions. This study further highlights the importance of conducting research in naturally acidified environments, since it allows to formulate more realistic hypotheses about the ability of marine organisms to persist in future changing oceans.
Continue reading ‘Investigation of the adaptive mechanisms to ocean acidification in Patella species from CO2 vent systems of the Mediterranean Sea’Millennial-scale changes in marine lithofacies during the Paleocene-Eocene Thermal Maximum: a deep-time analog for Anthropocene hydrologic and acidification impacts
Published 30 March 2026 Science ClosedTags: chemistry, field, paleo
Highlights
- Global marine sediment changes during the PETM were quantitatively reconstructed.
- Sediment changes controlled by sea level and latitudinal hydrology.
- Acidification influenced pelagic sediment composition, especially in the Atlantic.
- Carbonate “overshoot” occurred during the PETM recovery.
Abstract
Extreme climatic events can significantly alter marine lithofacies. However, global oceanic sediment patterns during deep-time hyperthermal events, which are potential analogues for the hydrologic and climatic impacts of modern anthropogenic warming, remain poorly constrained. Here, we compile 162 marine stratigraphic records to track millennial-scale sediment dynamics during the Paleocene–Eocene Thermal Maximum (PETM). We find that sedimentation was primarily controlled by hydrologic intensification (resulting in ∼36% carbonate platform demise), eustatic fluctuations (resulting in ∼52% siliciclastic shelf retrogradation), and ocean acidification (resulting in ∼41% deep-sea calcareous sediment replacement). Lithofacies changes along continental margins show distinct latitudinal zonation, reflecting variations in hydrologic intensity and carbonate productivity. The impact of eustatic sea-level change is strongest in region where hydrologic effects are muted. Deep-sea acidification was widespread, with the strongest expression in the Atlantic, and weaker effects in the Pacific and Indian oceans. Widespread carbonate “overshoot” following PETM recovery suggests enhanced continental weathering. This study implies that ongoing anthropogenic warming could rapidly reorganize marine sedimentation through intensified hydrological cycle, accelerated sea-level rise, and ocean acidification on centennial timescales, much faster than during the PETM and potentially with greater magnitude.
Continue reading ‘Millennial-scale changes in marine lithofacies during the Paleocene-Eocene Thermal Maximum: a deep-time analog for Anthropocene hydrologic and acidification impacts’Individual foraminiferal analysis: a promising tool for high-resolution temperature and pH reconstruction
Published 27 March 2026 Science ClosedTags: biogeochemistry, biological response, chemistry, field, methods, paleo, protists
Compared with traditional bulk foraminiferal analysis methods, in situ analysis of individual foraminiferal tests (individual foraminiferal analysis or IFA) offers several advantages over traditional bulk methods, including enhanced temporal resolution where fossiliferous sample material is limited as well as potentially resolving seasonal-scale climate variability in deep time. Despite these advantages, applications of element-to‑calcium (El/Ca) ratios and δ11B in benthic foraminifera using IFA remain limited, and the biogeochemical drivers of intra-test and inter-test geochemical variability are poorly constrained. In this study, we systematically evaluate El/Ca ratios and δ11B in individual benthic foraminifera. By analysing Holocene epifaunal benthic foraminiferal species Cibicidoides wuellerstorfi from a deep ocean core site (ODP Site 999), we conclude that intra- and inter-test variabilities are regulated by ontogenetic effects resulting in inter-test variabilities of ±0.14 mmol/mol Mg/Ca, ± 14 μmol/mol B/Ca, and ± 0.18 ‰ δ11B. Application of the IFA method to epifaunal benthic foraminifera species Cibicides lobatulus from a box core in the English Channel, UK reveals ~0.1 pH units acidification and ~ 1 °C warming since the mid-19th century. By demonstrating that individual-level variability in reconstructed temperature and pH tracks seasonal trends in the available contemporaneous water-column instrumental measurements at the same site, we provide a ground-truthing to our multi-proxy IFA methodology, and also demonstrate the potential for benthic IFA to provide seasonal-scale reconstructions of ocean climate over hundreds to millions of years.
Continue reading ‘Individual foraminiferal analysis: a promising tool for high-resolution temperature and pH reconstruction’Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification
Published 26 March 2026 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, field, laboratory, mollusks, morphology, mortality, North Pacific, otherprocess, phytoplankton, reproduction, vents
Highlights
- Natural CO₂ seep systems showed reduced intertidal chiton abundance.
- Adult chitons showed resilience to acidification in field and lab experiments.
- Larval survival and recruitment were strongly impaired under acidified seawater.
- Population declines are linked to early life-stage vulnerability.
- Loss of chitons may reduce grazing and bulldozing, reshaping intertidal communities.
Abstract
Ocean acidification (OA) is a major threat to marine calcifiers; however, the sensitivity across taxa and life stages remains elusive. In this study, we combined field surveys of natural CO₂ seeps with laboratory exposure, transplantation, and larval settlement experiments to assess the effect of OA on chitons, a group of calcifying grazers and bulldozers that play critical roles in the structure of rocky intertidal ecosystems. Field surveys revealed approximately 98.6% reduction in chiton (Acanthopleura loochooana, Liolophura japonica, and Acanthochitona rubrolineata) abundance at acidified habitats (pH 7.6), despite greater microalgal food availability and no detectable increase in predator abundance. Laboratory CO₂-exposure experiments showed no direct effect of OA on adult A. loochooana survival, which is consistent with the presence of protective structural features in the valves that confer resistance to dissolution. Transplant experiments revealed no evidence of increased adult A. loochooana mortality in the acidified habitats (pH 7.6). In contrast, larvae showed pronounced sensitivity to OA, with acidified seawater (pH 7.6) reducing larval settlement by approximately 81.5% compared to control conditions (pH 8.1); early life stages were the most vulnerable. These findings suggest that OA-associated decline in chiton abundance is mainly mediated by impaired recruitment rather than by direct adult mortality, predation, or food limitation. Given the role of chitons as grazers and bulldozers, their loss could substantially change intertidal community dynamics by decreasing grazing pressure and disturbing algal and microbial assemblages. Our findings underscore the criticality of considering life-stage vulnerability and ecological function when evaluating the ecosystem-level consequences of OA.
Continue reading ‘Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification’The role of seagrass in modifying dissolved oxygen and pH in coastal systems: a meta-analysis
Published 26 March 2026 Science ClosedTags: biological response, chemistry, field, phanerogams, review
Highlights
- Seagrass productivity drives diel pH–DO variation, enhancing local buffering capacity
- Oxygen–pH coupling highlights seagrass role in mitigating acidification during photosynthesis
- Studies should integrate temperature, salinity, and light to parse biological drivers
- Expanded geographic scope, especially tropics and Global South, is urgently needed
- Standardized pH scales and advanced sensors to improve comparability and monitoring
Abstract
Seagrass meadows, highly productive ecosystems, can influence local water chemistry by increasing dissolved oxygen in the water column and removing dissolved CO2 thus raising pH. This study provides the first quantitative synthesis of literature comparing pH and dissolved oxygen (DO) between systems with and without seagrasses. Through a systematic literature review and meta-analysis, we collated and analysed data from 63 studies reporting pH values and 70 studies reporting DO. Across studies, seagrass habitats were associated with slightly higher mean pH relative to non-seagrass habitats. Seagrass habitats showed the highest mean pH (8.11 ± 0.30) and the greatest diel variability (0.47 ± 0.65) of all habitats investigated with unvegetated areas exhibiting lower mean pH and reduced variability. The diel pH range was also significantly higher in seagrass habitats (p = 0.024). The pooled standardized mean difference was small (0.15), indicating a modest overall effect of seagrass presence on pH across studies. Although mean DO concentrations were slightly lower in seagrass habitats compared to other vegetated systems, they experienced fewer hypoxic events (12% of values < 2 mg/L) compared to other vegetated systems (55%). Generalized additive models identified DO as the strongest predictor of pH, with minor contributions from temperature and salinity. Overall, seagrass habitats are associated with increasing average pH and reducing hypoxia across multiple sites and regions. However, the magnitude and direction of effects vary widely among studies (I2 = 97%). These findings indicate that seagrass influences on water chemistry are context-dependent and likely driven by interactions among biological processes and local environmental conditions. Key knowledge gaps were identified; including the need for a greater focus on H+ concentration and the need for more research on seagrass ecosystems in underrepresented geographical regions.
Continue reading ‘The role of seagrass in modifying dissolved oxygen and pH in coastal systems: a meta-analysis’Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea
Published 25 March 2026 Science ClosedTags: abundance, biological response, chemistry, community composition, crustaceans, field, nematodes, North Pacific, otherprocess, zooplankton
This study aimed to investigate the meiofauna community characteristics in coastal waters affected by ocean acidification. Therefore, the meiofauna communities in the coastal waters of Hupo in Uljin-gun, which showed a high ocean acidification trend in the integrated data on the coastal areas of South Korea for the previous ten years, were monitored over five years. During the study period, the mean abundance of total meiofauna communities expressed in population density was 614 individuals (Inds.)/10 cm2. The most dominant taxa were nematodes (65–70%) and harpacticoids (7–20%); these two taxa accounted for approximately 80% of the total meiofauna abundance. Station (St.) 5 and 10, which had the lowest seawater pH values, showed the lowest average abundance values for harpacticoids (average 46 Inds./10 cm2) and nauplius (average 4 Inds./10 cm2) among the major meiofaunal groups over the 5-year period. In addition, St. 5 indicated the lowest meiofaunal diversity index of 0.54. To examine the effect of ocean acidification on meiofauna communities at the species level, species of nematodes, the most dominant taxon, were analyzed. The results indicated that the number of nematode species at St. 10, one of the two stations with the lowest pH, was the lowest compared to those at other stations. Analysis of c-p values for nematode species showed that both species sensitive to environmental disturbance and species resistant to environmental pollution appeared at high rates. According to the feeding type of nematodes, epistrate feeders accounted for a remarkably high proportion at St. 10. This study provides various data on meiofauna community characteristics to understand the effects of ocean acidification on coastal ecosystems.
Continue reading ‘Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea’Long-term pH trends and spatiotemporal variability of the carbonate system in Jakarta Bay
Published 20 March 2026 Science ClosedTags: biogeochemistry, chemistry, field, South Pacific
Jakarta Bay, an industrialized and densely inhabited coastal area, presents considerable environmental issues as a result of excessive organic pollution and nutrient inflow. Understanding the spatiotemporal variability of the carbonate system in such an affected bay is critical for assessing marine ecosystem health. The spatiotemporal variability of the carbonate system, pH, partial pressure of carbon dioxide (pCO2), total alkalinity (TAlk), and dissolved inorganic carbon (DIC) was investigated in Jakarta Bay during the rainy and dry seasons of 2023. pH datasets from 2011 to 2023 were also collected from the Environmental Agency of DKI Jakarta (DLH DKI Jakarta) for trend analysis. The temporal analysis shows that during the SE monsoon, the lowest pH (mean: 8.06 ± 0.43); lowest TAlk (mean: 2099 ± 340 µmol kg-1); highest pCO2 (mean: 879 ± 1177 µatm); and highest DIC (mean: 2068 ± 806 µmol kg-1) were observed. The pH distribution gradually increased from the river outlet to the outer bay; inversely, pCO2, TAlk, and DIC gradually decreased. Furthermore, from 2011 to 2023, pH in Jakarta Bay showed a slight upward tendency that was statistically insignificant, reflecting high variability and the influence of local biogeochemical processes. The carbonate system variability reflects changes in biogeochemical (Chl-a, DO and nutrients) and physical (SST and Sal) parameters. In addition, the semi-enclosed hydrodynamic properties, together with the influence of human activities, including a continuous supply of nutrients and organic materials from the mainland through the incoming rivers, further affected the balance of the carbonate system in the bay.
Continue reading ‘Long-term pH trends and spatiotemporal variability of the carbonate system in Jakarta Bay’Groundwater-derived carbon promotes hypoxia and acidification in a large tropical estuary
Published 18 March 2026 Science ClosedTags: biogeochemistry, chemistry, field, North Pacific
Abstract
Submarine groundwater discharge (SGD) derived nutrient inputs have been extensively documented. However, SGD-derived carbon fluxes remain largely unconstrained, representing a critical gap in most coastal carbon budgets. Here, we resolve SGD and dissolved carbon budgets in the Pearl River Estuary (PRE), the largest estuary in Southern China surrounded by the world’s largest urban conglomerate. Broadly-defined SGD contributes 89%–96% of the dissolved inorganic carbon (DIC) pool (2–4 times riverine inputs) and 20%–70% of the dissolved organic carbon (DOC) fluxes of the PRE. SGD transports DIC exceeding total alkalinity (TAlk) by 2.7–7 times, potentially driving pH decline and acidification of nearshore waters. Groundwater pCO2 values are 10–36 times higher than estuarine waters. SGD-derived DOC mineralization can decrease estuary water pH by 0.04–0.16 units and increase CO2 by 6.0–90.0 μmol L−1, affecting local coral populations and benthic organisms. SGD also reduces seawater dissolved oxygen (DO) by 12–150 μmol L−1 and fuels the development of hypoxic zones. Overall, SGD regionally intensifies seawater hypoxia and acidification, creating challenging conditions for coral reef survival in an already stressed ecosystem. Our findings demonstrate that SGD should be integrated into carbon budgets and ecological assessments of the land-ocean continuum.
Plain Language Summary
Submarine groundwater discharge can transport large amounts of dissolved carbon into the coastal ocean, but it is often overlooked due to challenges in quantification. Here, we investigate the contribution of groundwater to the dissolved carbon pool in a large tropical estuary using radium isotopes and carbon data. We found that groundwater is a significant source of estuarine dissolved carbon and has the potential to acidify seawater oxygen-depleted waters. These findings emphasize the importance of considering groundwater when evaluating carbon budgets and the ecological health of coastal ecosystems.
Continue reading ‘Groundwater-derived carbon promotes hypoxia and acidification in a large tropical estuary’Seasonal variations and key controls on seawater aragonite saturation state in the Northern Yellow Sea, China
Published 17 March 2026 Science ClosedTags: chemistry, field, North Pacific
Based on four field surveys conducted from August 2022 to May 2023, seasonal distribution and dynamics of the seawater aragonite saturation state (Ωarag) were investigated in the northern coastal zone of the Northern Yellow Sea, an important fishery region, to assess impacts of ocean acidification especially in river-dominated coastal systems. Results revealed seawater Ωarag had significant spatiotemporal variability with surface values ranging from 1.42 to 3.76 in summer, 1.22 to 2.34 in autumn, 1.71 to 2.48 in winter, and 2.03 to 3.56 in spring. Subsurface seawater Ωarag was generally lower than surface values, while seawater with Ωarag < 1.5—a critical threshold for severe biological stress—were predominantly found in the nearshore areas and in the southwestern offshore bottom waters. Persistent seasonal acidification was observed across the study area. While seawater temperature played an important role in seasonal Ωarag variation, its effect was masked in the nearshore zones by river-diluted water inputs, especially in summer, and in offshore bottom waters by community respiration during summer and autumn. These mechanistic insights clarify key drivers of coastal acidification and provide a scientific basis for developing targeted strategies to detect acidification trends and ecosystem responses in anthropogenically impacted coastal regions.
Continue reading ‘Seasonal variations and key controls on seawater aragonite saturation state in the Northern Yellow Sea, China’
