Bivalve shells, a natural alkaline material, play a crucial role in coastal carbon cycles by influencing total alkalinity (TA) and dissolved inorganic carbon (DIC). This study investigated oyster shell dissolution in Narragansett Bay, Rhode Island, under varying pCO2 conditions, revealing TA regeneration rates of 4–56 μmol L-1 d-1, which could mitigate localized ocean acidification (OA). Notably, significant dissolution occurred even in oversaturated waters (Ωcalcite > 1) due to corrosive microenvironments created by microbial respiration. Although shell formation (calcification) emits CO2, TA regeneration (shell dissolution) buffers OA when the carbonate chemistry of the water is corrosive, offsetting the initial CO2 emissions. Therefore, recycling shells enhances ecosystem resilience by buffering acidification stress for OA-sensitive organisms. This research highlights the need to revisit shell management policies to promote sustainable aquaculture and sheds light on the potential of incorporating this nature-based alkaline material into ocean alkalinity enhancement strategies for improved coastal carbon management.
Continue reading ‘Harnessing nature’s buffer: assessing the role of bivalve shells in coastal alkalinity regeneration’Posts Tagged 'North Atlantic'
Harnessing nature’s buffer: assessing the role of bivalve shells in coastal alkalinity regeneration
Published 15 July 2025 Science ClosedTags: chemistry, field, mitigation, North Atlantic
Observations of Sargassum carbon influx and biogeochemical impact in La Parguera Marine Reserve
Published 15 July 2025 Science ClosedTags: algae, biogeochemistry, biological response, chemistry, field, North Atlantic
The massive influx of pelagic Sargassum spp. species, also known as Sargassum inundation events (SIEs), first arrived at the Caribbean’s coastal waters in 2011. These events have been linked to hypoxia, among other ecological disturbances. Here, we report data from 2022 on (1) an assessment of the relative magnitude of particulate organic carbon (POC) load arising from SIEs into the La Parguera Marine Reserve (LPMR) basin off the southwest coast of Puerto Rico and (2) the biogeochemical impact of SIE in a nearshore mangrove key within the reserve, Monsio Jose Key Bay (MJKB). Our analysis yields that the carbon influx increased by 20% in the LPMR basin and by 103% in MJKB. Weekly observations of Sargassum input, along with the collection and analysis of water samples in MJKB, evidenced a cause-effect relation between Sargassum carbon loading and frequency of hypoxic (DO < 2 mg·L-1) and critically acidic conditions (Aragonite saturation, Ω < 2.0). During the 2022 Sargassum season, hypoxic conditions were detected in 43% of samples collected in MJKB. Considering the modulation of biogeochemical parameters by changes in tide height (Δh) and wind speed (m·s-1), stepwise multiple regression analyses (RDA-AIC model selection) showed that significant parameters influencing DO, pH, and Ω include the Sargassum carbon influx and Δh (p < 0.05). These findings strongly support the hypothesis that the additional input of POC influx enhances microbial mineralization rates responsible for depressed oxygen concentrations and acidic conditions, which could be detrimental to coastal ecosystems. This is particularly concerning in areas prone to SIEs where geomorphological features facilitate the entrainment of floating materials. Proper management requires the identification of vulnerable sites and Sargassum removal. Ongoing efforts towards that goal are underway for LPMR.
Continue reading ‘Observations of Sargassum carbon influx and biogeochemical impact in La Parguera Marine Reserve’Temporal trends of ocean acidification in the Gulf of Guinea and the potential impact on socio economic development
Published 15 July 2025 Science ClosedTags: chemistry, modeling, North Atlantic, regionalmodeling, review
Ocean acidification, primarily driven by increased atmospheric CO₂, poses significant environmental and socioeconomic threats, particularly in vulnerable regions like the Gulf of Guinea. This study analyses historical pH trends, spatial variations, and projected acidification scenarios using data from CMIP6 models and NOAA observational records, focusing on the Gulf of Guinea’s unique ecological and economic challenges. Findings indicate a steady decline in pH from 8.20 to 8.08 between 1750 and 2010, with pronounced deviations linked to industrial activities and rising atmospheric CO₂ concentrations. Seasonal fluctuations and upwelling events exacerbate acidification in this high-productivity region, intensifying the vulnerability of marine biodiversity and fisheries. Projections for 2050–2100 under SSP2 4.5 and SSP5-8.5 scenarios reveal further pH declines, with potential hotspots emerging in coastal areas. These changes threaten critical ecosystems, such as shellfish habitats, and threaten food security and economic stability for communities dependent on marine resources. The study underscores the necessity of regional monitoring programs, international collaboration, and mitigation strategies, including carbon emission reductions, ecosystem-based adaptation, and sustainable aquaculture practices. This research highlights the Gulf of Guinea’s heightened sensitivity to acidification due to its unique biogeochemical processes and socioeconomic dependencies. It advocates for integrating science, policy, and local initiatives to address these challenges. Targeted interventions, such as mangrove restoration and regional partnerships, can strengthen resilience and provide valuable insights for global ocean acidification management efforts.
Continue reading ‘Temporal trends of ocean acidification in the Gulf of Guinea and the potential impact on socio economic development’Mollusc epifaunal assemblages are simplified due to habitat shifts under ocean acidification
Published 14 July 2025 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, mollusks, North Atlantic, otherprocess, vents
Highlights
- Ocean acidification can modify the structure of marine communities.
- The macroalga Halopteris sp. supports a rich community of associated molluscs.
- Halopteris sp. from an acidified site support fewer and less diverse assemblages.
- Most abundant species were present both at the acidified and reference sites.
- Biodiversity of molluscs will be simplified under acidified conditions.
Abstract
Ocean acidification can have profound effects on marine organisms, particularly those that rely on calcium carbonate for shell and skeleton formation, resulting in structural changes to marine ecosystems. Here, we contrast the structure of marine mollusc communities (epifauna) associated with an abundant shallow-water macroalga, Halopteris scoparia, in an area with seawater carbonated by natural CO2 seeps and three reference sites, off the Azores archipelago. Epifaunal mollusc abundance and diversity were significantly lower at the CO2 seep compared to reference sites whilst species accumulation curves and Jaccard multivariate analyses showed that the mollusc assemblage was consistently less diverse at the CO2 seep. Most of the abundant epifaunal species that were present at the CO2 seep were also found at reference sites, but less common or rare species were generally absent from the former. We conclude that while some molluscs are likely to cope with ocean acidification, the overall biodiversity of epifaunal molluscs will be simplified under these conditions in a future ocean.
Continue reading ‘Mollusc epifaunal assemblages are simplified due to habitat shifts under ocean acidification’Chemical and biological oceanographic conditions in the Labrador Sea from 2019 to 2023
Published 10 July 2025 Newsletters and reports ClosedTags: chemistry, field, North Atlantic
The Atlantic Zone Off-Shelf Monitoring Program samples the AR7W line annually. This report summarises trends from 2019-2023 for three regions: AR7W-W (Labrador shelf and slope), AR7W-C (central Labrador Sea), and AR7W-E (Greenland shelf and slope). Samples revealed a continued increase in dissolved inorganic carbon and a decrease in pH from 2019 to 2023. Mean concentration of CFC-12 decreased in 2020, and SF6 continued its steady increase. Mean temperature from 0-100 m in the Labrador Sea was above normal in 2019, below normal on the next mission (2022), and near or above normal in 2023. Surface (0-100 m) nutrients were mainly below normal from 2019-2023, which could be attributed to mission timing. However, below-average deep nutrients (>100 m, less impacted by sampling timing) suggests a profound change in the biogeochemistry of the Labrador Sea. Integrated (0-100 m) chlorophyll-a was below normal in 2019 and in AR7W-E in 2022-2023, but above normal elsewhere, with a record high value in AR7W-C in 2022 caused by an unusually large bloom of Phaeocystis spp.. Satellite data revealed high variability in the timing of the spring and fall blooms and surface average chlorophyll-a concentration. Mesozooplankton abundances showed high interannual variability since 2019.
Continue reading ‘Chemical and biological oceanographic conditions in the Labrador Sea from 2019 to 2023’Climate vulnerability assessment of fish and invertebrates in the U.S. South Atlantic large marine ecosystem
Published 9 July 2025 Science ClosedTags: biological response, crustaceans, fish, mollusks, North Atlantic, review
Trait-based climate vulnerability assessment (CVA) is a rapid and repeatable approach to simultaneously assess the vulnerability of a large number of species to projected regional changes in climate. We conducted the first CVA in the U.S. South Atlantic Large Marine Ecosystem for 71 ecologically, economically, and culturally important fish and invertebrate species. The CVA was conducted by a 16-member panel based on scoring 12 biological sensitivity attributes and seven climate exposure factors. About two-thirds of the species were considered highly vulnerability to future climate projected under the RCP 8.5 emissions scenario, with diadromous species, invertebrates, and deepwater reef fishes the most vulnerable functional groups. Ocean acidification, sea surface temperature, and salinity were the exposure factors with the greatest influence on climate vulnerability, while population growth rate, population status, and early life history traits were the most important biological sensitivity attributes. More than two-thirds of the species had high potential for shifts in geographic distribution, due mostly to the prevalence of broadcast spawning, extensive larval dispersal, and high adult mobility of many species, and the generalist habitat requirements of several estuary-dependent and hard-bottom reef species. Some shifts in distribution have already occurred though potential relationships to environmental conditions associated with climate are not well-understood. Uncertainty analyses confirmed the robustness of the climate vulnerability rankings, but comparison of alternative types of elicited informed judgement did not always agree, suggesting higher uncertainty in climate vulnerability for some species. In addition, several species may benefit under future climate conditions, and climate effects on some species considered to be highly vulnerable may be of relatively small magnitude. These results can be used to prioritize conservation, research, and management efforts, and identify key uncertainties related to the impacts of future climate on fishery resources in the U.S. South Atlantic region.
Continue reading ‘Climate vulnerability assessment of fish and invertebrates in the U.S. South Atlantic large marine ecosystem’Something in the water: how kelp is helping Maine’s mussels boom
Published 8 July 2025 Media coverage ClosedTags: mitigation, North Atlantic
On a glimmering May morning, Tom Briggs pilots a 45ft aluminium barge through the waters of Casco Bay for one of the final days of the annual kelp harvest. Motoring past Clapboard Island, he points to a floating wooden platform where mussels have been seeded alongside ribbons of edible seaweed.
“This is our most productive mussel site,” says Briggs, the farm manager for Bangs Island Mussels, a Portland sea farm that grows, harvests and sells hundreds of thousands of pounds of shellfish and seaweed each year. “When we come here, we get the biggest, fastest-growing mussels with the thickest shells and the best quality. To my mind, unscientifically, it’s because of the kelp.”
A growing body of science supports Briggs’s intuition. The Gulf of Maine is uniquely vulnerable to ocean acidification, which can impede shell development in mussels, clams, oysters and lobster, threatening an industry that employs hundreds of people and generates $85m to $100m (£63m to £74m) annually.
Atmospheric carbon dioxide from fossil fuels is the main driver of declining ocean pH, increasing the acidity of the world’s oceans by more than 40% since the preindustrial era and by more than 15% since 1985. Add carbon runoff from growing coastal communities, regular inflows of colder, more acidic water from Canada, and intense thermal stress – the Gulf of Maine is warming three times faster than the global average – and you’re left with a delicate marine ecosystem and key economic resource under threat.
Enter kelp. The streams of glistening, brownish-green seaweed that Bangs Island seeds on lines under frigid November skies and harvests in late spring are a natural answer to ocean acidification because they devour carbon dioxide. Sensors placed near kelp lines in Casco Bay over the past decade have shown that growing seaweed changes water chemistry enough to lower the levels of carbon dioxide in the immediate vicinity, nourishing nearby molluscs.
Continue reading ‘Something in the water: how kelp is helping Maine’s mussels boom’The coupled oxygen and carbon dynamics in the subsurface waters of the Gulf and Lower St. Lawrence Estuary and implications for artificial oxygenation
Published 7 July 2025 Science ClosedTags: biogeochemistry, chemistry, mitigation, modeling, North Atlantic, regionalmodeling
The Gulf and Lower St. Lawrence Estuary have experienced major environmental change over the past century, including the development of hypoxic bottom waters and their simultaneous warming and acidification. Here, we use biogeochemical observations collected during the 2021–2023 TReX project as well as historical data, combined with a tracer-calibrated 1D Advection-Diffusion model with variable boundary conditions to represent dissolved oxygen (DO) and dissolved inorganic carbon (DIC) dynamics within the core of the oxygen minimum zone (27.15–27.3 kg m-3 isopycnals) of the Laurentian Channel. The rate of in-channel oxygen utilization in the deep layer was nearly invariant from 2003 to 2023 at 21.1 ± 2.5 µmol kg-1 yr-1 and the DIC accumulation rate was estimated to be 18.3 ± 2.5 μmol kg-1 yr-1. Using δ13CDIC data, we assess the effect of microbial organic matter remineralization processes and dilution of the 13CDIC pool (−6.6×10-3 ‰ per μmol of added metabolic DIC). These data and the use of a tracer-calibrated model to resolve advection and mixing dynamics reconcile differences in prior estimates of biogeochemical transformation rates. Finally, we apply the model to the mitigation scenario proposed by Wallace et al. (2023) for artificial re-oxygenation of the Laurentian Channel bottom waters using pure oxygen. We estimate that the injection of ~8.3 × 105 tonnes yr-1 of oxygen, equivalent to an additional 55 μmol kg-1 relative to the 2023 boundary concentration proximal to the Cabot Strait, would be required to achieve and maintain above hypoxic levels (>62.5 μmol kg-1) at the head of the Laurentian Channel. Using the model, we estimate the time required to re-establish steady-state along-channel distributions of DO and DIC following a change in offshore boundary conditions to be about 10 years, or twice the along-channel transit time.
Continue reading ‘The coupled oxygen and carbon dynamics in the subsurface waters of the Gulf and Lower St. Lawrence Estuary and implications for artificial oxygenation’Data-driven modeling of 4D ocean and coastal acidification in the Massachusetts and Cape Cod Bays from surface measurements
Published 7 July 2025 Science ClosedTags: chemistry, modeling, North Atlantic, regionalmodeling
Abstract
A significant portion of atmospheric emissions is absorbed by the ocean, resulting in acidified seawater and altered carbonate composition that is harmful to marine life. Despite detrimental effects, assessing ocean and coastal acidification (OCA) is difficult due to the scarcity of in situ measurements and the high costs of computational modeling. We develop a parsimonious data-driven framework to model indicators of OCA and test it in the Massachusetts Bay and Stellwagen Bank, a region with fishing and tourism industries affected by OCA. First, we trained a neural network to predict in-depth fields for temperature and salinity using surface quantities from satellites and in situ measurements . The relationship between 2D surface and 3D properties is captured through the in-depth modes and coefficients obtained from principal component analysis applied to a high-resolution historical reanalysis data set. Next, we used Bayesian regression methods to estimate region-specific relationships for in-depth total alkalinity (TA), dissolved inorganic carbon (DIC), and aragonite saturation state as functions of temperature, salinity, and chlorophyll. Lastly, 4D daily field predictions are generated from surface measurements with a spatial resolution of 4 km horizontally and 45 sigma levels vertically. The model’s performance is evaluated using withheld measurements across depths, locations, and seasons with RMSEs of 1.59°C, 0.31 PSU, 37.54 mol, 39.40 mol, and 0.42 for temperature, salinity, TA, DIC, and , respectively, at one withheld location. The framework is useful for understanding OCA and includes uncertainty quantification for future planning and optimal sensor placement.
Plain Language Summary
About a quarter of carbon dioxide emissions in the atmosphere is absorbed by the oceans. When this carbon dioxide dissolves in seawater, it results in ocean acidification (OA). A useful indicator of OA is the saturation state of aragonite, a type of calcium carbonate used by organisms that form shells. However, understanding the effects of OA is difficult due to the lack of observations and the high cost and complexity of modeling. We present a data-driven approach to model carbonate chemistry using readily available observations from satellites and low-cost sensors. Given surface measurements of temperature, salinity, and chlorophyll, our machine learning model produces temperature, salinity, total alkalinity, dissolved inorganic carbon, and aragonite saturation state covering spatial (latitude, longitude, and depth) and temporal domains for these variables. Compared to withheld observations, our model achieved reasonable accuracy across many seasons and depths, a level of resolution not matched by other models for the same set of inputs. Our model is useful for monitoring, decision-making, and future planning.
Key Points
- We present a data-driven approach to rapidly model 4D carbonate chemistry fields given readily available surface observations
- By using training data from both physics simulations and field observations, the model achieves very high resolution with minimal inputs
- The step-by-step method can be reproduced in other regions or for new data, and includes uncertainty quantification for decision-making
Increased temperature and acidification elevate the risk of starvation in American lobster larvae
Published 4 July 2025 Science ClosedTags: biological response, crustaceans, laboratory, morphology, multiple factors, North Atlantic, physiology, reproduction, temperature
The geographic range of the American lobster, Homarus americanus, spans a steep thermal gradient along the coastal Northwest Atlantic. As CO2 emissions increase globally, this range is rapidly warming and acidifying. Larval H. americanus hatch with a finite amount of maternally sourced lipid stores in their yolk sac, which provide an energetic buffer during the intermediate period between hatch and first feed. This study examines the response of newly-hatched, unfed H. americanus larvae to the combined effects of elevated pCO2 and temperature. Using a space-for-time approach, we compared larvae of two distinct sub-populations from thermally contrasting regions: Rhode Island, at the warmer, southern limit of the species range, and Midcoast, Maine, a cooler northern region. Average larval initial post-hatch weight was similar across regions and variability therein could be explained by maternal effects. Under 6 days of starvation, larvae from the two regions lost ∼14% of their initial dry weight and 25% of their Carbon weight. Still, end-century elevated temperature or acidification did not substantially alter those rates for larvae from either region. However, under an identical range of conditions over the 6-day experiment, larvae from the warmer regime maintained relatively stable oxygen consumption rates, while those from the cooler regime started 50% higher, then dropped by 80% within 2 days. If depressed metabolic functioning translates to reduced feeding efficiency for cool regime larvae, our findings suggest that subpopulations in the southern edge of the species range have a relative advantage in food-scarce environments under these conditions, adding to previous evidence for countergradient variation in this species. Further analysis of total fatty acid losses conducted on Midcoast larvae suggested starved larvae exposed to elevated temperature (19°C) experienced considerably greater losses of key lipid groups than larvae under ambient conditions (16°C, 400 ppm), particularly within the first 2 days of exposure. Our results highlight the short time frames over which ocean warming can accelerate the depletion of energy stores and make larvae more vulnerable to starvation.
Continue reading ‘Increased temperature and acidification elevate the risk of starvation in American lobster larvae ‘First study of seawater carbonate chemistry variability in a portion of the southern Atlantic coast of Cameroon: impact of organic pollution
Published 2 July 2025 Science ClosedTags: biogeochemistry, chemistry, field, North Atlantic
The carbonate system variability and acidification process remain little understood in the coastal ocean of Cameroon. The aim of this study was to assess the variability of the carbonate system in a portion of the southern coast of Cameroon, and the influence of local seawater physicochemical and biological properties on keys parameters of this system. The study was carried out at three fixed sampling stations (Bp, Kb, and Eb), from September 2021 to August 2022 involving all the seasons encountered in the study area. The carbonate system was determined from Total alkalinity (TA), pH, temperature and salinity, using the CO2SYS_xls program. In addition, nutrients (nitrate, nitrite, phosphate and nitrogen ammonia) and chlorophyll-a data were collected simultaneously at each station. The results showed a high variability of the carbonate system parameters on both temporal and spatial scale. TA and bicarbonate ions (HCO3− ) were significantly different between the large rainy season (LRS) and small rainy season (SRS), while CO2 and CO2 partial pressure (pCO2) were significantly different between Kb and Eb sampling stations (p-value < 0.05). The critical thresholds for ocean acidification (OA) seems to not been reached in the southern coastal ocean of Cameroon, given the means values of pH (8.14 ± 0.17), aragonite (3.31 ± 1.3 Ω) and calcite (5.3 ± 2.05 Ω) saturation states obtained. Salinity appears as the main driver of the variability of TA in the study area, while, nitrogen ammonia and the dissolved carbon dioxide from the degradation of organic matter, respiration and atmospheric absorption, appears as the drivers of pH variation. The large rainy season (LRS) seems to be the most critical period for OA sensitive organisms, while the Bp station looks most vulnerable.
Continue reading ‘First study of seawater carbonate chemistry variability in a portion of the southern Atlantic coast of Cameroon: impact of organic pollution’Non-additive phospholipidomic responses to ocean warming and acidification drive intraspecific variation in cell membrane vulnerability in a marine ectotherm
Published 1 July 2025 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, multiple factors, North Atlantic, otherprocess, physiology, temperature
Highlights
- Shrimp show non-additive phospholipidome responses to combined OW and OA.
- Synergistic and antagonistic responses are origin- and scenario-dependent.
- Physiological shifts emerge when OA occurs near shrimp’s thermal limits.
- Shrimp show potential local adaptation/acclimatisation of cell membrane phenotypes.
- Shrimp cell membrane vulnerability to combined OW and OA is origin-dependent.
Abstract
The lipidome is fundamental to the good functioning of cells and organisms. However, its role in species acclimatisation and adaptation to global changes remains overlooked. Investigating intraspecific variation in lipidome responses to combined global change drivers is therefore paramount to predict species’ vulnerability in future oceans. Here, we profiled the phospholipidome of the Northern shrimp, Pandalus borealis, from four different origins in the Northwest Atlantic, within an orthogonal design of ocean warming (OW) and acidification (OA) scenarios. We report complex origin-dependent non-additive responses under combined global changes. Shrimp display a high degree of intraspecific variation with distinct profiles of synergism, antagonism or temperature-driven phospholipidome responses when OA is superimposed on OW. Shrimp from the southernmost origin are only sensitive to OW, whilst those from the other three origins respond to combined OW and OA. These patterns involve changes in cellular membranes’ unsaturation, fluidity, curvature and thickness, underlying differential intraspecific cellular vulnerability to global changes. The isolated effects of OA are subtler, visible only in shrimp from the St. Lawrence Estuary (SLE). Shrimp from SLE also show the most pronounced phospholipidome remodelling, allowing them to acclimate to combined OW and OA. Whilst SLE shrimp seem most sensitive to global changes, those from the northernmost origins (Newfoundland and Esquiman Channel) display the greatest cellular vulnerability under combined OW and OA. Our findings evidence the highly complex interplay of OW and OA in remodelling marine ectotherms’ phospholipidomes, with direct implications for prioritising conservation efforts on populations most vulnerable to global changes.
Continue reading ‘Non-additive phospholipidomic responses to ocean warming and acidification drive intraspecific variation in cell membrane vulnerability in a marine ectotherm’Effects of acidification and habitat loss on coastal nitrogen cycling dynamics
Published 29 May 2025 Science ClosedTags: biogeochemistry, chemistry, field, North Atlantic
Excess nitrogen (N) in urbanized coastal waterways from wastewater or agricultural inputs causes widespread habitat decline due to harmful algal blooms, poor water quality, and changes to seawater chemistry. For example, during an algal bloom, nocturnal respiration and seasonal decomposition of algal biomass release carbon dioxide (CO2) into the water column, which lowers seawater pH in a process known as coastal acidification. Additionally, high N loading leads to the death of salt marsh vegetation communities, in turn leading to salt marsh erosion and loss, with implications for coastal stability. Estuarine habitats such as seagrass beds and salt marshes are known as hotspots of microbially-mediated nutrient cycling, but it has been unclear how stressors caused by N loading (i.e., coastal acidification, macroalgal blooms, and salt marsh erosion/loss) impact vital biogeochemical processes in these habitats. This dissertation explored the effects of acidification on nutrient cycling in eelgrass beds and salt marshes (in Shinnecock Bay, Long Island and Jamaica Bay, New York City, respectively), as well as the impacts of salt marsh loss on N dynamics in eutrophic urban estuaries. Results show that lower seawater pH shifted sediments in eelgrass beds from net sources of reactive N to net N sinks, with implications for water quality mitigation. In salt marshes, acidification appeared to have no effect on nutrient cycles. Instead, N cycling in salt marshes is likely to respond to erosion and increasing inundation. De-vegetated marsh sediments showed net N release compared to still-intact vegetated marsh areas, suggesting that losses in salt marsh habitat may contribute to water quality decline and algal bloom conditions, as well as perpetuate further habitat loss. This body of research addressed critical gaps in understanding the processes that underpin coastal habitat function under various N loading-related stressors, such as acidification-induced impacts on nitrification and denitrification in eelgrass beds and changes to sediment N cycling as marshes erode. The former finding may suggest that N loading may be at least partially mitigated during a coastal acidification event, while the latter finding suggests that marsh restoration may prevent loss of N removal services. The applications of this research are likely to become increasingly critical, as these habitats serve as vital natural infrastructure against sea level rise, storm surges, and coastal change.
Continue reading ‘Effects of acidification and habitat loss on coastal nitrogen cycling dynamics’Exploring the land-ocean biogeochemical and microbial connectivity in the Ría de Vigo (NW Iberian Peninsula) through submarine groundwater discharge
Published 20 May 2025 Science ClosedTags: biogeochemistry, BRcommunity, chemistry, community composition, field, molecular biology, North Atlantic, otherprocess, prokaryotes
Highlights
- SGD affects the carbonate system, methane and nitrous oxide content of the embayment
- Solute composition of SGD largely impacted by subterranean estuary reactivity
- Contrasting poor microbial connectivity across the different aquatic environments
- Subterranean estuaries may act as microbial boundaries in the aquatic continuum
Abstract
Increasing evidence demonstrates the widespread occurrence of submarine groundwater discharge (SGD) in coastal zones, where it may influence biogeochemistry and microbial ecology. Here, we analyze the biogeochemical composition and microbial communities across diverse aquatic environments in a highly productive coastal system (Ría de Vigo, NW Iberian Peninsula), influenced by significant fresh SGD, to assess the extent of microbial and biogeochemical connectivity—i.e., mass transfer—among them. Samples were collected from surface and deep porewaters from two subterranean estuaries (STEs), surface seawater, riverine water, and continental groundwater. These samples were analyzed for a comprehensive set of microbial and biogeochemical variables, including radioisotopes used as SGD tracers. A significant correlation between SGD tracers and carbonate system parameters, N2O, and CH4 concentrations in surface seawater indicates SGD influences biogeochemistry of the embayment. However, some of these solutes do not originate from continental groundwater but are produced in the local STEs, which act as biogeochemical reactors modifying fresh SGD. The findings also reveal highly diverse microbial communities, with higher diversity in STEs due to the variety of niches present. Indicator taxa included the phyla Euryarchaeota, Chloroflexi, Omnitrophicaeota, and the family Nitrosopumilaceae in STEs; the phylum Cyanobacteria and the family Burkholderiaceae in freshwater endmembers; and the Flavobacteriaceae and Cryomorphaceae families in seawater. Most operational taxonomic units (∼87%) were unique to a single environment (river, continental groundwater, coastal water, or STE), showing STEs limit subterranean microbial transfer between groundwater and marine ecosystems. Our results highlight STEs as reservoirs of diversity and zones of intense biogeochemical reactivity.
Continue reading ‘Exploring the land-ocean biogeochemical and microbial connectivity in the Ría de Vigo (NW Iberian Peninsula) through submarine groundwater discharge’A widely distributed clam, Chama macerophylla, exhibits mixed responses to single and combined warming and acidification stress
Published 7 May 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, physiology, temperature
Bivalves enhance microhabitat complexity and improve water clarity in coastal ecosystems. Ocean warming (OW) and acidification (OA), pose a significant threat to bivalves in shallow continental shelf environments where stressors can be amplified and uncoupled. This study investigated global change effects on Chama macerophylla, a widespread clam in the Gulf of Mexico. Laboratory experiments assessed physiology and shell mineralogy of C. macerophylla exposed to different levels of OW, OA, and combined stressors (OWA). Temperature and carbonate chemistry from collection sites confirm ambient (control) treatments used in experiments were commonly observed in the field. Clam oxygen consumption increased with OW and, initially, with OA. After 30 days, clams within moderate and extreme OA lowered consumption. In contrast, clam oxygen consumption declined in OWA treatments. Net calcification was only affected by OA with higher calcification in the extreme treatment than in moderate. Meat weight relative to shell weight (condition) was negatively affected by OW in the extreme treatment. Shell accretion, clearance rates, and mineralogy were unaffected by OW, OA, and OWA. This is the first report of a bimineralic shell for this species. Results highlight resilience of clam survivorship to stressors. OW appears to increase metabolism and drive declines in clam condition (meat: shell weight). OWA may have a greater impact on C. macerophylla than single stressors, particularly if reduced oxygen consumption is sustained. This research underscores the need to understand long-term stress on bivalves. Future research should examine both size-age relationships with global stressors and the role of acclimation to prolonged stress.
Continue reading ‘A widely distributed clam, Chama macerophylla, exhibits mixed responses to single and combined warming and acidification stress’Aragonite saturation state as an indicator for oyster habitat health in the Delaware Inland Bays
Published 28 April 2025 Science ClosedTags: chemistry, field, North Atlantic
Aragonite and calcite are important nutrients for bivalves who biomineralize calcium carbonate in the water to form their outer shells. Ocean acidification can lead to a decrease in carbonate ions making forming these shells difficult. When the saturation state falls below a certain threshold (Ω < 1), it can cause oyster shells to dissolve. Therefore, measuring the Aragonite Saturation State yields crucial insight into the suitability of habitats to support oyster growth and productivity. Physiochemical water quality parameters were monitored from May to October 2020-2023. Using Seacarb, the aragonite-calcite saturation state was calculated using the following water quality parameters: temperature, salinity, alkalinity, and pH as inputs. Calcium hardness and dissolved oxygen was also measured to determine whether values were at a recommended threshold for shellfish hatcheries. There were fluctuations in the saturation states at each site, and oftentimes the values were undersaturated, especially during the cooling months. Spearman heatmaps demonstrate significant positive correlations between temperature and salinity (p = 0.46); pH and aragonite (p = 0.72); and alkalinity and aragonite (p = 0.51). This project aimed to determine the feasibility of different sites in supporting the establishment of oyster farms and oyster restoration efforts based on water quality conditions.
Continue reading ‘Aragonite saturation state as an indicator for oyster habitat health in the Delaware Inland Bays’Cold spells, fresh waves, and the biogeochemical response in the North Atlantic cold anomaly region
Published 22 April 2025 Science ClosedTags: biogeochemistry, chemistry, field, North Atlantic
Regional effects of marine cold spells (MCS, periods of anomalous cooling), their impact on ecosystem biogeochemistry, and link to salinity extremes remain underexplored. A case in point is North Atlantic’s Cold Anomaly (CA) region (known as the “cold blob”), which hits record low temperatures during 2014–16 while most of the global ocean warmed. Using up to 42 years of observations, we characterize the CA as a manifestation of both MCS and Fresh Waves (FW, low salinity extremes) and analyze the surface biogeochemical response. We observe a quasiperiodic pattern of MCS from the 1980s and FW (at least) from the 1990s to early 2020s in the CA region with alternations from cool and freshwater to warm and saline conditions. Since 1990s, the CA region appears to be potentially undergoing MCS and FW compound events that are more frequent and prolonged but less intense than other North Atlantic areas. The 2014‐16 CA was among the most widespread and prolonged MCS and FW events associated with a deeper mixed layer and distinct biogeochemical signature, including elevated nutrients and oxygen, an overall increased chlorophyll‐a and intensified ocean acidification. These resultssuggest that MCS could mitigate certain climate change effects through cooling and enhanced productivity, while exacerbating others such as ocean acidification. We compare 2014–16 CA region effects with those of Pacific’s warm blob, identifying contrasting behaviors from physical processes to biogeochemical impacts and discussing a common atmospheric driver. Our findings emphasize the need to further study ecological responses to MCS in the North Atlantic.
Continue reading ‘Cold spells, fresh waves, and the biogeochemical response in the North Atlantic cold anomaly region’The Piver’s Island coastal observatory – a decade of weekly+ observations reveal the press and pulse of a changing temperate coastal marine system
Published 16 April 2025 Science ClosedTags: chemistry, field, North Atlantic
Historically, oceanographic time-series have focused on long-term measurements of large open ocean gyres; yet, the coastal oceans, with their high productivity, tidal impacts, human feedbacks, and land-sea coupling, represent critical regions for predicting ocean dynamics and biogeochemistry under global change. The Piver’s Island Coastal Observatory (PICO) time-series, located in the second largest estuarine system on the US East Coast (Albemarle-Pamlico Sound), comprises more than a decade of weekly (or more frequent) measurements of core physical, chemical, and biological oceanographic variables. PICO provides insight into a coastal, mesotrophic ecosystem in an ecologically-diverse and biochemically-active region impacted by global change. Here, we report on a decade of observations focusing on pulse and press ecosystem changes. We observe strong mean annual cycles in environmental variables including temperature (10.1-28.9°C), pH (7.89-8.12), dissolved inorganic carbon (DIC: 1965 – 2088 µM), chlorophyll (2.54-5.77 mg Chl m-3), upon which are layered episodic disturbances (e.g., tropical cyclones) that dramatically and persistently (>1 month) impact this ecosystem. Among other variables, long term trends in pH (-0.004 ± 0.001 y-1; p<0.01), DIC (-9.8 ± 1.5 µM y -1; p<0.01) and chlorophyll (-0.17 ± 0.02 µg L-1 y-1; p<0.01) are exceeding those observed in the open ocean, suggesting an ecosystem in flux. These analyses provide a benchmark for future studies of the impact of changing climate and oceanographic climatology; further research will use this long-term research to developed targeted sampling and experimental manipulations to better understand ecosystem structure and function.
Continue reading ‘The Piver’s Island coastal observatory – a decade of weekly+ observations reveal the press and pulse of a changing temperate coastal marine system’Benthic biogeochemical processes and fluxes in the hypoxic and acidified northern Gulf of Mexico (nGoM), part I: carbonate dissolution from in situ microprofiles
Published 14 April 2025 Science ClosedTags: biogeochemistry, chemistry, field, North Atlantic
Highlights
- High resolution in situ pH and O₂ microprofiles at the sediment-water interface.
- Benthic measurements of carbonate system parameters, including pH, DIC, TA, Ca2+.
- Large decrease in oxygen concentrations in overlying water, accompanied by DIC accumulation and a pH drop.
- Undersaturation with respect to aragonite and occasionally calcite.
- No significant dissolution of calcium carbonate minerals detected.
Abstract
The northern Gulf of Mexico (nGoM) experiences seasonal coastal hypoxia due to nutrient enrichment from the Mississippi-Atchafalaya River basin, leading to one of the world’s largest hypoxic zones. In these shallow zones, benthic processes play an essential role in driving/maintaining deoxygenation and acidification of bottom waters. In this regard, this paper investigates carbonate dissolution processes in surface sediment of the nGoM during hypoxic conditions in summer 2022, as the main acidification feedback mechanism, with a specific focus on the effects of bottom water acidification. A strong linear relationship is observed between oxygen and pH, with a pH difference of 0.37 between the most oxygenated and the nearly anoxic station, reaching a value of 7.63. Using high-resolution techniques, this study combines pH and O₂ microprofiling (200 μm) with benthic measurements of carbonate system parameters (pH, DIC, TA, Ca2+) to assess carbonate dissolution at millimeter-scale resolution. The pH microprofiles reveal a significant decrease in the first 3 cm, with pore water pH reaching values of 6.90 at the most hypoxic station. Despite undersaturation with respect to aragonite and occasionally calcite, Ca2+ profiles indicate no significant carbonate dissolution, suggesting stability of calcium carbonate in these sediments during the summer. This lack of dissolution, likely influenced by the absence of aragonite, and possible inhibitory effects of dissolved organic carbon and orthophosphate, points to a limited buffering capacity in these sediments. These insights are essential for refining models predicting coastal acidification and hypoxia responses to environmental stressors in the nGoM and similar eutrophic systems.
Continue reading ‘Benthic biogeochemical processes and fluxes in the hypoxic and acidified northern Gulf of Mexico (nGoM), part I: carbonate dissolution from in situ microprofiles’New capability in autonomous ocean carbon observations using the autosub long-range AUV equipped with novel pH and total alkalinity sensors
Published 11 April 2025 Science ClosedTags: chemistry, methods, North Atlantic
The development of marine autonomous platforms has improved our capability to gather ocean observations at fine spatial scales and high temporal frequency, which can be used to better measure, characterize, and model ocean carbon. As part of the OCEANIDS program, novel carbonate sensors were integrated into the Autosub Long-Range (ALR) autonomous underwater vehicle (AUV) and deployed in the Celtic Sea. Autonomous Lab-On-Chip (LOC) sensors measured pH and total alkalinity (TA) while onboard the ALR. Using interpolation, the ALR-sensor data set is compared against CTD co-samples. The average differences between the LOC sensor and co-sample pH range from −0.011 to −0.015. The TA sensor data agrees with co-samples within 1–2 μmol kg–1 on average. Biogeochemical water properties differing between CTD and ALR observations reveal correlations to carbonate parameter variations. The LOC sensors enabled the characterization of the marine carbonate system from autonomous subsurface measurements for the first time. Sensor pH and TA data were used to calculate dissolved inorganic carbon (DIC), partial pressure of CO2 (pCO2), and aragonite saturation state (ΩAr) and are compared with CTD co-samples with mean residuals of 4–7 μmol kg–1, 10–17 μatm, and −0.03 to −0.06, respectively. Future perspectives on sensor deployment and analysis are discussed.
Continue reading ‘New capability in autonomous ocean carbon observations using the autosub long-range AUV equipped with novel pH and total alkalinity sensors’
