Ocean acidification (OA) is a major climate-related threat to fish that can disrupt the regulation of the reproductive axis of fish, impacting reproductive success. However, previous studies have only focused on a single reproductive cycle and reported increased fecundity in some species exposed to OA. Since acclimation over several reproductive cycles can occur, it is necessary to evaluate successive reproductive cycles for predicting the actual resilience of species to OA. In this study we assessed the impact of lifetime exposure to different ocean pH/pCO2 levels (Current condition, Moderate OA and High OA) on the sexual maturation and spawning phenology of the European sea bass, over its two first reproductive periods. We tested the hypothesis that OA would exert its greatest impact at the onset of puberty (first reproduction). Accordingly, High OA exposure induced an earlier onset of puberty in both sexes, resulting in a longer spawning period and an increased fecundity. These effects were reduced during the second reproductive season. However, OA affected egg quality and sperm motility profile during the second reproductive season, leading to a total mortality at hatching of embryos spontaneously produced. This mortality was not observed in embryos produced through hormone-induced oocyte maturation and in vitro fertilisation. These results suggest that OA affects the regulation of oocyte maturation and/or the synchronisation of eggs and sperm release. The OA-driven shift in spawning may misalign with optimal environmental conditions for offspring survival. This increases the population’s vulnerability and could favour species whose reproduction is more resilient to OA.
Continue reading ‘Ocean acidification affects the timing of puberty and the reproductive output in a marine temperate fish’Posts Tagged 'North Atlantic'
Ocean acidification affects the timing of puberty and the reproductive output in a marine temperate fish
Published 2 April 2026 Science ClosedTags: adaptation, biological response, fish, laboratory, morphology, mortality, North Atlantic, otherprocess, reproduction
Skeletal growth and loss of the cold-water coral Lophelia pertusa from multiple environmental drivers in a year-long experiment
Published 27 March 2026 Science ClosedTags: biological response, corals, dissolution, growth, laboratory, morphology, mortality, multiple factors, North Atlantic, oxygen, physiology, respiration, temperature
Colony-forming scleractinian cold-water corals (CWCs) are important ecosystem engineers, forming complex 3-dimensional habitats in the deep sea, which in turn sustain high biodiversity. They are threatened by future environmental changes such as ocean acidification, warming, deoxygenation, and food limitation, but little is known about the effect of these drivers in combination or on the long-term. We conducted a year-long aquarium experiment with Lophelia pertusa (syn. Desmophyllum pertusum) under projected end-of-century conditions, investigating the combined effect of differences in pH (8.1 and 7.7), temperature (9°C and 12°C), oxygen concentration (100% and 90%) and food supply (100% and 60%) on coral survival, growth, respiration rates, skeletal dissolution and energetic reserves. Growth rates of L. pertusa decreased significantly in both multiple driver treatments, resulting in negative and more variable growth rates. However, growth rates only started to decrease after 4.5 months, clearly showing a delayed response. In addition, survival rates and energetic reserves were slightly lower in multiple driver treatments, whereas L. pertusa was not affected by reduced oxygen concentration examined as a single factor. Negative growth rates in multiple driver treatments were driven by dissolution of bare skeletal parts due to reduced seawater pH and temporary aragonite undersaturation, visualised here through micro-computed tomography images. While live CWCs may be able to cope with projected future environmental changes over the timescale of 1 year, ocean acidification will lead to dissolution of the dead skeletal framework of CWC reefs and net loss, reducing the complexity and associated biodiversity of these reefs. However, the challenge remains in closing the gap between long-term experiments and the much longer-term chronic exposure of CWCs to projected environmental changes.
Continue reading ‘Skeletal growth and loss of the cold-water coral Lophelia pertusa from multiple environmental drivers in a year-long experiment’Ocean acidification disrupts the biomineralization process in the oyster Crassostrea virginica via intracellular calcium signaling dysregulation
Published 20 March 2026 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, morphology, North Atlantic, physiology, reproduction
Calcium is a key component in the shell and skeleton structure, serving as a second messenger for regulating biomineralization across many species. Ocean acidification (OA) is well-studied for causing shell dissolution in marine bivalve species by disordering calcium deposition. However, the regulatory pathway of calcification affected by OA remains unclear. This study assessed eastern oyster (Crassostrea virginica) to determine how calcium signaling responds to elevated pCO2 and influences shell formation. Under elevated pCO2, increased calcium influx was found in mantle epithelial cells, followed by the upregulation of calmodulin, a primary sensor of intracellular calcium. Expression levels of shell matrix proteins (SMPs), representing shell construction conditions, were significantly upregulated in the CO2-induced mantle cells. Larval C. virginica exhibited developmental stage-dependent alterations in calcium signaling and SMPs disarrangement stimulated by pCO2. Pharmaceutical blockage of the calcium binding on calmodulin induced abnormal expression of downstream genes and shell matrix changes consistent with those caused by elevated pCO2. Restored SMPs expressions in CO2-treated mantle cells were achieved by rescuing the level of calcineurin, a downstream effector of calmodulin. These findings suggest that shell deformities under OA are primarily caused by the disruption of the calcium-calmodulin signaling pathway in mantle epithelial cells.
Continue reading ‘Ocean acidification disrupts the biomineralization process in the oyster Crassostrea virginica via intracellular calcium signaling dysregulation’UConn helps sea scallop communities adapt to ocean warming
Published 19 March 2026 Web sites and blogs ClosedTags: fisheries, modeling, mollusks, North Atlantic
UConn Marine Sciences Associate Professor Samantha Siedlecki co-leads a project to incorporate data on historic and projected ocean conditions to predict the growth of scallops across vast geographic regions and more than a century of time. The project uses a novel tool developed by UConn Ph.D. candidate Halle Berger. Photo by NOAA.
In the coastal waters stretching from Maine to Virginia, Atlantic sea scallops rival lobster as the top shellfish caught in the wild. This delectable mollusk supports one of the most valuable fisheries in the U.S., generating $360 million in revenue annually, and making the U.S. a global leader in wild scallop fishing.
A combination of conservation measures has helped the industry weather the effects of overfishing. Now, warming and acidifying oceans are posing new threats and prompting new solutions.
A team of researchers co-led by UConn Associate Professor of Marine Sciences Samantha Siedlecki, Shannon Meseck, of NOAA’s Northeast Fisheries Science Center, and Robert “Bobby” Murphy, a social scientist with NOAA’s Northeast Fisheries Science Center, is exploring how environmental data can be used to develop a new management approach adapted for and responsive to a changing ocean. With the support of a three-year grant of just over $1 million from NOAA’s Ocean Acidification Program (OAP), the project will integrate oceanographic modeling, industry engagement, and socioeconomic research to create actionable strategies for industry and management. The project is one of six announced by OAP in November aimed at helping U.S. coastal communities adapt to ocean acidification.
“This is one of the earliest attempts to forecast optimal regions for Atlantic sea scallop growth, based on both carbon content and ocean temperature,” says Siedlecki.
Continue reading ‘UConn helps sea scallop communities adapt to ocean warming’Novel in situ CO2 enrichment system reveals seagrass meadows are a refugium against coastal acidification for North Atlantic bivalves
Published 18 March 2026 Science ClosedTags: biological response, BRcommunity, chemistry, growth, laboratory, mollusks, mortality, North Atlantic, phanerogams
While the accumulation of anthropogenic CO2 in the atmosphere is causing a decline in global ocean pH, many eutrophic estuaries are already experiencing acidification due to accelerated respiration driving the consumption of dissolved oxygen (DO) and production of CO2, decreasing available carbonate ions (CO32-) and threatening marine calcifiers. Here, a novel in situCO2 enrichment system was constructed to examine the effects of coastal acidification on the growth and survival of two species of North Atlantic bivalves (Argopecten irradians and Crassostrea virginica) in two distinct estuarine habitats: a seagrass meadow and an unvegetated sandy bottom in an open water estuary. The in-situ system captured natural diel dynamics as ambient chambers displayed chemistry nearly identical to the surrounding water, while CO2-enriched, acidified chambers maintained a consistent ~Δ 0.3–0.5 pH offset. At the unvegetated sandy bottom site, A. irradians and C. virginica displayed significant reductions in growth and survival in the acidified chambers (pHT = 7.3–7.5; saturation state of aragonite, ΩAr = 0.6–0.9) relative to ambient conditions (pHT = 7.6–7.9; ΩAr = 1.6–2). At the seagrass site, while growth of A. irradians and C. virginica in the acidified treatments (pHT = 7.3–7.7; ΩAr = 0.7) receiving the same delivery of CO2 was, again, significantly slowed compared to the control (pHT = 7.5–8.1; ΩAr = 2 – 2.8), the growth reduction, mortality rates, and levels of acidification were attenuated compared to the sandy bottom experiment, evidencing the ability of seagrass to buffer seawater and serve as a potential acidification refuge for bivalves. Collectively, the novel experimental CO2 enrichment system constructed for this project demonstrates that coastal acidification can have deleterious effects on marine bivalve populations, and that future conditions as well as the habitat refuge offered by seagrasses must be considered when developing management and restoration plans for temperate estuaries.
Continue reading ‘Novel in situ CO2 enrichment system reveals seagrass meadows are a refugium against coastal acidification for North Atlantic bivalves’Physiological responses of Swedish maerl to ocean acidification and warming
Published 17 March 2026 Science ClosedTags: algae, biological response, calcification, laboratory, multiple factors, North Atlantic, photosynthesis, respiration, temperature
Maerl, (Corallinales, Rhodophyta), are free-living calcareous algae found in coastal ecosystems. They form biogenic beds with complex structures in which other species can find refuge or on which other species can settle, which highlights their importance as an ecosystem. While many species have been investigated worldwide, maerl from the Swedish west coast are poorly studied. This report investigated both acidification and warming impacts on different physiological functions of Swedish maerl, including photosynthesis, respiration and calcification. The maerl were exposed to different pH levels and temperatures in both light and dark conditions to determine their physiological thresholds, where photosynthesis and respiration were measured via oxygen fluctuations, photosynthetic efficiency via PAM fluorometry and calcification via alkalinity titrations. It was found that neither photosynthetic nor respiratory oxygen exchange showed positive or negative trends when exposed to changes in pH. On the contrary, photosynthesis peaked at the natural ambient temperature of 16°C and respiration increased with increasing temperature. Photosynthetic efficiency also did not show any trends to pH changes. However, calcification showed a significant (p < 0.05) negative response to pH in both light and dark conditions, with the response more severe in dark conditions. This suggests that decreasing pH may induce skeletal dissolution, and that photosynthesis could help buffer internal responses to external conditions. Carbonate production at ambient conditions in the light was calculated to be 556 ± 54 g CaCO3 m-2 yr-1, showing that Swedish maerl are just as, if not more, productive than maerl found elsewhere. Overall, this report showed that photosynthetic and respiratory thresholds may not be reached with acidification and that temperature increases could instead have much more severe consequences. It also showed that calcification thresholds will be met sooner rather than later, depending on acidification rates, in darker conditions for maerl found in temperate and possibly polar regions.
Continue reading ‘Physiological responses of Swedish maerl to ocean acidification and warming’An invisible threat in Long Island’s waters
Published 16 March 2026 Media coverage ClosedTags: fisheries, North Atlantic
For generations, the waters surrounding Long Island have defined its identity — from the wide-open waterfronts of the South Shore to the shellfish beds of the North Shore. But beneath the surface, a quieter transformation is underway.
Ocean acidification is often called climate change’s “evil twin,” and refers to the lowering of the water’s pH, the scale used to measure the concentration of hydrogen ions in the water. While global warming refers to rising temperatures, acidification describes a shift in seawater chemistry.
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On Long Island, acidification is not driven by global carbon emissions alone. Local factors intensify the problem. Nitrogen discharged from wastewater, septic systems and fertilizer runoff flows into bays and harbors, fueling harmful algal blooms. When those blooms die and decompose, the process consumes oxygen and releases additional carbon dioxide in the water, further lowering pH.
The result is a compounding effect: global atmospheric carbon dioxide combined with local nitrogen pollution accelerates acidification in shallow, enclosed estuaries.
Warming waters add another layer of stress. As temperatures rise, marine organisms’ metabolic demands increase, but warmer water holds less dissolved oxygen. Together, warming and acidification can weaken shellfish during their most vulnerable larval stages, making it harder for them to survive and build shells.
For Long Island’s oyster and clam farmers — industries that have experienced both revival and setbacks in recent decades — these chemical changes aren’t just theoretical. They are measurable, seasonal and, increasingly, part of daily operations.
Continue reading ‘An invisible threat in Long Island’s waters’Temperature and pH-dependent potassium currents of muscles of the stomatogastric nervous system of the crab, Cancer borealis
Published 13 March 2026 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, multiple factors, North Atlantic, physiology, temperature
HIGHLIGHTS
- Cancer borealis stomach muscles are sensitive to temperature and pH.
- Warming or alkalizing hyperpolarizes fibers and reduces synaptic response amplitude.
- qRT-PCR detects K2P gene transcripts CbKCNK1 and CbKCNK2 in muscles.
- CbKCNK1 and CbKCNK2 are candidates for the temperature and pH-dependent conductances.
SUMMARY
Marine crustaceans such as the crab Cancer borealis experience fluctuations in temperature and pH, yet their stomatogastric neuromuscular system must remain functional for feeding. We examined 16 of ∼40 stomach muscle pairs and found that warming consistently hyperpolarized muscle fibers (∼10 mV per 10°C) and reduced excitatory junctional potentials and currents. Muscle responses were also strongly influenced by extracellular pH, with an optimal range between pH 6.7 and 8.8; outside this window, abnormal activity emerged. Voltage-clamp analysis of gastric muscle gm5b revealed a temperature- and pH-sensitive conductance with a reversal potential near the potassium equilibrium potential and insensitivity to tetraethylammonium and barium, arguing against classical voltage-gated potassium channels. Quantitative RT-PCR detected expression of two putative two-pore domain potassium (K2P) channels in these muscles. Together, these results suggest that muscle excitability in C. borealis is shaped by temperature- and pH-sensitive potassium currents consistent with contributions from K2P channels.
Continue reading ‘Temperature and pH-dependent potassium currents of muscles of the stomatogastric nervous system of the crab, Cancer borealis’Trophic status and climatic stressors in the shallow coral reefs of the Cuban marine shelf
Published 12 March 2026 Science ClosedTags: chemistry, field, North Atlantic
The “Bojeo a Cuba” expedition (summer 2023) provided a synoptic, national-scale snapshot of oceanographic conditions around Cuba’s shallow coral reefs during a regional marine heatwave. At 66 sites across six regions, we evaluated key climatic stressors (sea surface temperature, pH, alkalinity) and trophic status indicators. Satellite-derived SST during each site’s sampling week revealed significantly warmer waters on the southern shelf (mean = 30.93 °C) than the northern shelf (mean = 29.21 °C, P < 0.01). In situ SST was consistently high (mean = 30.52 °C), documenting the heatwave’s intensity. pH (mean = 8.12) and total alkalinity (mean = 2343 µmol kg⁻¹) indicated a currently balanced carbonate system. Concentrations of dissolved inorganic nitrogen and phosphorus were below our methods’ quantification limits (1.61 µmol L⁻¹ for P-PO₄³⁻), while chlorophyll-a (mean = 0.04 µg L⁻¹) consistently classified waters as oligotrophic. This study establishes a critical summer baseline, confirming oligotrophic conditions while documenting the severity of thermal stress during the 2023 heatwave—the most immediate and uniform threat to Cuban reefs. Our findings underscore the vulnerability of these ecosystems to extreme warming events within the context of long-term Caribbean warming trends.
Continue reading ‘Trophic status and climatic stressors in the shallow coral reefs of the Cuban marine shelf’Glacial meltwater impacts marine carbonate chemistry on Iceland’s continental shelf
Published 6 March 2026 Science ClosedTags: chemistry, field, North Atlantic
Increased meltwater runoff from glaciers may drive localized ocean acidification and impact carbon dioxide (CO2) uptake in the coastal ocean. However, the paucity of carbonate system observations from continental shelves receiving inputs from glaciers limits our understanding of cryosphere‐ocean connectivity. Here, we contrast meltwater impacts on seawater carbonate chemistry and stable isotopes (δ13C‐DIC) off marine‐ and land‐terminating glacier outflows off Iceland. On the shelf outside a marine‐terminating glacier, glacial meltwater reduced the seawater buffer capacity of receiving surface waters through dilution of total alkalinity, and increased CO2 uptake through salinity‐driven drawdown of pCO2. Primary production acted as a counterbalance to the lowered [TA‐DIC]. On the shelf area receiving meltwater from large glacial river deltas, CO2 uptake was almost halved and the saturation state of aragonite was 0.2 units lower than on the marine‐terminating glacier shelf. Reduced net autotrophy due to higher turbidity and upwelling of low‐pH deep waters off the delta‐dominated shelf likely explain those differences. The diverging carbonate dynamics on the two shelves build on previous observations that land‐terminating glaciers can reduce the buffer capacity as well as CO2 uptake potential of nearshore surface waters in comparison to marine‐terminating glaciers. The future retreat of many marine‐terminating glaciers onto land is likely to modify how meltwater will impact coastal seawater carbonate chemistry.
Continue reading ‘Glacial meltwater impacts marine carbonate chemistry on Iceland’s continental shelf’Applying omics techniques to examine microscopic life fueling Gulf region ecosystems
Published 6 March 2026 Press releases ClosedTags: biological response, chemistry, field, North Atlantic
Scientists at NOAA’s Atlantic Oceanographic & Meteorological Lab and the Northern Gulf Institute applied omics techniques to provide the first basin-scale assessment of the microbial communities at the base of marine ecosystems across the Gulf region. The new study from Dr. Luke Thompson’s group, conducted by Dr. Sean Anderson and co-authors, is the largest environmental DNA (eDNA) or microbiome survey of the Gulf of America ever performed.
Scientists collected environmental DNA (eDNA) – genetic material from whole microbes or shed by marine life into the environment – during the 2021 Gulf and Ocean Monitoring Ecosystems and Carbon Cruise (GOMECC). These samples unlock crucial new insights into the microscopic life across an entire basin – from nearshore coastal ecosystems out to the open Gulf. By analyzing the microbial communities throughout the water column, we can better understand how they are being impacted by changing environmental conditions.
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Changes in the composition of these microbial communities in any given region has cascading effects, influencing the biodiversity and feasibility of commercially viable species to survive and flourish in a specific region. Understanding how microbial diversity throughout the water column varies with changing conditions – changes in salinity, temperature, nutrient levels – could unlock key insights and provide early indicators of how entire ecosystems will be impacted by exacerbated environmental stressors, including ocean acidification.
Continue reading ‘Applying omics techniques to examine microscopic life fueling Gulf region ecosystems ‘Modelling seawater pCO2 and pH in the Canary Islands region based on satellite measurements and machine learning techniques
Published 4 March 2026 Science ClosedTags: chemistry, modeling, North Atlantic, regionalmodeling
Recent advancements in remote sensing systems, combined with new machine-learning model-fitting algorithms, have enabled the estimation of seawater carbon dioxide partial pressure (pCO2,sw) and pH (pHT,is) in the waters around the Canary Islands (13–19° W; 27–30° N). Continuous time-series data collected from moored buoys and Voluntary Observing Ships (VOS) between 2019 and 2024 were used to train and validate the models, providing a robust observational basis for satellite-derived estimates.
Among all models tested, bootstrap aggregation (bagging) performed best, achieving an RMSE of 2.0 µatm (R2>0.99) for pCO2,sw and 0.002 for pHT,is. Multilinear regression (MLR), neural networks (NN) and categorical boosting (CatBoost) also showed good predictive skill, with RMSE values between 5.4 and 10 µatm for pCO2,sw (360–481 µatm) and 0.004–0.008 for pHT,is (7.97–8.07). Using the most reliable model, we identified an increasing trend in pCO2,sw of 3.51±0.31 µatm yr−1, exceeding the atmospheric CO2 growth rate (2.3 µatm yr−1), alongside an acidification trend of −0.003 ± 0.001 yr−1.
Over the 2019–2024 period, rising atmospheric CO2 and increasing sea surface temperatures (reaching up to 0.2 °C yr−1 during the unprecedented 2023 marine heatwave) likely contributed to these trends. The Canary Islands region shifted from a weak CO2 source (0.90 Tg CO2 yr−1) in 2019 to 4.5 Tg CO2 yr−1 in 2024. After 2022, eastern sites that previously acted as annual CO2 sinks became net sources.
Continue reading ‘Modelling seawater pCO2 and pH in the Canary Islands region based on satellite measurements and machine learning techniques’Interactive effects of ocean acidification and settlement biofilm on the early development of the European abalone Haliotis tuberculata
Published 3 March 2026 Science ClosedTags: biological response, communityMF, laboratory, mollusks, morphology, multiple factors, North Atlantic, performance, phytoplankton, reproduction, respiration
Highlights
- Interactive effects of OA and settlement biofilm were investigated on juvenile abalone.
- Post-larval density and total length decreased significantly under lower pH.
- Biofilm composition induced indirect effects through changes in diatom biomass.
- (pH × Ulvella) interaction affected abalone shell resistance and colouration.
Abstract
Ocean acidification (OA) and associated shifts in carbonate chemistry represent major threats to marine organisms, particularly calcifiers. OA effects can be influenced by other environmental variables, including the biotic environment. This study investigated the effects of OA and algal density, acting through an Ulvella-conditioned settlement biofilm, on post-larval and juvenile abalone (Haliotis tuberculata). In a three-month full factorial experiment, abalone were exposed from metamorphosis onward to two pH conditions (ambient 8.0 and reduced 7.7) and two initial densities of the green alga Ulvella lens on settlement plates. Biofilm biomass and composition were characterised using spectral reflectance and HPLC pigment analysis. Biological (density, length), physiological (respiration rate), behavioural (hiding response) and shell parameters (colour, surface corrosion, strength) of abalone were measured. Biofilm biomass and composition assessed with pigment proxies remained relatively stable under both pH conditions, though greater variability in algal biomass occurred at low initial Ulvella density. Post-larval density and total length decreased significantly under low pH, while high Ulvella density reduced juvenile length at 80 days, likely due to competition between algal groups. A pH × Ulvella interaction affected shell fracture resistance and colouration, but not metabolism or behaviour, indicating that juvenile abalone maintained vital functions. Overall, the results confirm the sensitivity of early H. tuberculata stages to moderate OA (−0.3 pH unit) and highlight indirect macroalgal effects through changes in diatom cover. In natural environment, the capacity of abalone to cope with future OA will depend on complex trade-offs between direct acidification effects and food-related biotic interactions.
Continue reading ‘Interactive effects of ocean acidification and settlement biofilm on the early development of the European abalone Haliotis tuberculata’Decadal biogeochemical predictions for the bottom marine environment of the Northeast U.S. Continental Shelf
Published 27 February 2026 Science ClosedTags: chemistry, modeling, North Atlantic, regionalmodeling
The Gulf of Maine and the surrounding Northeast U.S. Continental Shelf are experiencing rapid marine environmental change arising from complex regional dynamics that challenge near-term (1–10 years) predictive capabilities for valuable living marine resources. Here, using a high-resolution regional ocean model, we demonstrate skilful decadal forecasts of ocean bottom habitat characteristics including bottom temperature, dissolved oxygen (O2), pH and aragonite saturation state (Ωar). Bottom temperature and pH predictions show substantial skill driven primarily by radiatively forced warming and carbon uptake trends, while bottom O2 and Ωar predictions benefit more from initialization due to stronger internal variability. Retrospective forecasts successfully predicted observed historical changes in water masses and environmental properties, including recent cooling/freshening transitions driven by replacement of Warm Slope Water with Labrador Slope Water. This water mass variability also modulates biogeochemical conditions and ocean acidification buffering capacity, with our recent forecasts indicating that benefits from the expected respite from rapid warming might be tempered by challenges posed by rapid acidification. The demonstrated predictability of coupled physical-biogeochemical processes supports developing integrated prediction systems for climate-informed marine resource management.
Continue reading ‘Decadal biogeochemical predictions for the bottom marine environment of the Northeast U.S. Continental Shelf’Wind control of the interannual ocean‐biogeochemical variability in the South Atlantic Bight
Published 23 February 2026 Science ClosedTags: biogeochemistry, chemistry, modeling, North Atlantic, regionalmodeling
Abstract
In the South Atlantic Bight (SAB), changes in the Gulf Stream (GS), particularly its strength and proximity to the coast, are thought to be primary factors determining the shelf-break upwelling rate. However, it is still not entirely clear if and to what extent those factors influence cross-shelf nutrient fluxes and shape the ocean biogeochemistry at interannual and longer timescales. Here, we use a high-resolution regional ocean-biogeochemical model and an ocean reanalysis product (1993–2022), along with a satellite-derived chlorophyll data set (1997–2022), to investigate the interannual ocean-biogeochemical variability in the SAB. Regional model outputs suggest that year-to-year changes in phytoplankton production are indeed largely driven by upwelling of cold and nutrient-rich water to the shelf-break. The upwelling variability, reflected in bottom temperature and vertically integrated production patterns, is strongly linked to surface velocity changes in the GS near the shelf break, but weakly related to the depth-integrated GS transport. The GS’s velocity changes, and the temperature and production anomalies, are well correlated to the alongshore wind stress, suggesting that local wind is the leading driver of the shelf-break upwelling variability at interannual timescales. Those relationships are also supported by circulation patterns from ocean reanalysis and satellite chlorophyll anomalies. Finally, examining the simulated shelf-slope interchanges in the carbonate system, we find that shelf-break upwelling significantly increases bottom acidification, a pattern linked to the low carbonate concentration in the slope waters. This study thus provides new insight for understanding and predicting GS and winds impacts on biogeochemical patterns from the SAB.
Plain Language Summary
The ocean current known as the Gulf Stream (GS) can induce upwelling of subsurface cold and nutrient-rich waters into the coastal margin of the South Atlantic Bight, influencing coastal temperature and phytoplankton growth. Previous studies suggested that the GS strength and its proximity to the coast are key factors determining the intensity of upwelling events. However, the degree to which these factors impact the year-to-year changes in phytoplankton production and other ocean properties remains unclear. Here we use numerical models of ocean currents and seawater biogeochemistry, as well as chlorophyll records derived from satellite measurements, to investigate that impact. The patterns showed that interannual changes in coastal temperature, phytoplankton production, water acidity, and dissolved oxygen are strongly modulated by upwelling changes in the outer edge of the continental margin (about 70 m depth in this region). This interannual upwelling variability is tightly coupled to variations in the surface alongshore GS velocity close to that outer edge, which is modulated by alongshore wind variability. Our study characterizes GS patterns associated with high and low productivity years, and highlights the role of surface wind as ultimate driver of the interannual upwelling variability in the South Atlantic Bight.
Key Points
- A regional ocean model is used to investigate interannual variability of ocean-biogeochemistry in the South Atlantic Bight
- Year-to-year changes in primary production, chlorophyll, and carbonate system patterns respond to shelf-break upwelling anomalies
- Shelf-break upwelling is closely linked to the Gulf Stream velocity near the shelf break, modulated by alongshore wind variability
A biogeochemical perspective on acidification and buffering capacity in the Piscataqua Estuary
Published 18 February 2026 Science ClosedTags: biogeochemistry, chemistry, field, laboratory, North Atlantic, sediment
Coastal acidification is influenced not only by rising atmospheric CO2 and river-ocean mixing, but also by metabolic processes that alter seawater carbonate chemistry and buffering capacity. This study examines how sedimentary biogeochemical processes contribute to carbonate system variability in the Piscataqua Estuary, a tidally dynamic channel connecting Great Bay to the Gulf of Maine. The biogeochemical processes considered include sedimentary aerobic respiration, denitrification, sulfate reduction, and carbonate dissolution or precipitation. Two incubation experiments were conducted in September and October of 2024 at the University of New Hampshire’s Coastal Marine Laboratory (CML) to quantify changes in pH, dissolved inorganic carbon (DIC), and total alkalinity (TA) in the overlying water arising from sediment-water biogeochemical exchange. Sediment cores were collected to be paired with overlying water from slack low and slack high tides during each month. Across both experiments, sediment cores consistently exhibited greater acidification and larger shifts in DIC and TA concentrations compared to water-only cores, indicating strong sedimentary biogeochemical influence. Among the processes considered, sulfate reduction is likely the most influential driver of carbonate system variability, contributing to increases in both DIC and TA. Linking experimental results to in-situ measurements at CML revealed that variability observed over individual ebb or flood tides primarily reflected processes associated with tidal advection (ie, river-ocean mixing and water-column biogeochemical activity). However, when evaluating net changes over both tidal transitions (ebb and flood), contributions from sedimentary biogeochemical processes were comparable in magnitude to those of the other processes during September and October. Sedimentary biogeochemical processes also appear to exert more consistent contributions to DIC and TA than water-column biogeochemical processes. Together, these findings demonstrate that sedimentary biogeochemical processes play a major role in regulating carbonate system variability in the Piscataqua Estuary. This study underscores the importance of examining carbonate system variability across multiple timescales to obtain a more comprehensive understanding of estuarine carbonate dynamics. Additional experimental work is needed to further resolve the influence of metabolic processes on coastal carbonate systems under changing environmental conditions.
Continue reading ‘A biogeochemical perspective on acidification and buffering capacity in the Piscataqua Estuary’Shrinking shellfish? Risk of acidic water in the Indian River Lagoon
Published 17 February 2026 Press releases ClosedTags: chemistry, North Atlantic
FAU researchers measured aragonite saturation – a key indicator of water’s ability to support calcifying organisms like clams and oysters – throughout the Indian River Lagoon.
Florida’s Indian River Lagoon (IRL), one of the state’s most ecologically productive estuaries, is facing a growing but invisible threat that could reshape its marine ecosystems. Over the past decade, the lagoon has suffered severe degradation caused by nutrient pollution, excessive freshwater runoff, harmful algal blooms (HABs), and declining water quality. These changes have led to the loss of tens of thousands of acres of seagrass and have negatively impacted shellfish, fish, dolphins, manatees and other key species.
A new study from Florida Atlantic University’s Harbor Branch Oceanographic Institute now reveals that these pressures are also contributing to coastal acidification, a chemical shift in the water that threatens the ability of shell-building marine organisms to grow and thrive.
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To understand these changes, FAU Harbor Branch researchers studied the IRL from 2016 to 2017, measuring Ωarag and other water chemistry factors. They examined how nutrients, freshwater inputs, and other environmental conditions affect the lagoon’s ability to support shell-building marine life.
The study used two approaches. First, researchers conducted a broad survey across the lagoon, from nutrient-rich northern areas to southern regions affected by freshwater inflows. Second, they did weekly sampling at three central sites with different salinity and land-use conditions: an urban-influenced canal, a river mouth affected by urban and agricultural runoff, and a relatively natural reference site with strong ocean exchange.
Results of the study, published in the journal Marine Pollution Bulletin, revealed clear patterns. Northern sites with high nutrient concentrations and frequent HABs had lower aragonite saturation. Southern sites, influenced by freshwater discharges, also had lower Ωarag, primarily due to reduced salinity and dilution of aragonite. In the weekly surveys, Ωarag was positively correlated with salinity and negatively correlated with nutrient levels, confirming that both freshwater input and nutrient pollution play a role in controlling water chemistry.
Continue reading ‘Shrinking shellfish? Risk of acidic water in the Indian River Lagoon’Acute microbial and nutrient responses to elevated temperature and pCO2: a coastal UK microcosm study
Published 13 February 2026 Science ClosedTags: abundance, biogeochemistry, community composition, laboratory, multiple factors, North Atlantic, nutrients, otherprocess, phytoplankton, temperature
The coastal ocean’s ecosystem resilience is consistently hampered by the compounding impacts of projected climate change and anthropogenic perturbation. In this microcosm study, we investigated how elevated temperature and pCO2, together with episodic nutrient pollution and a short-term marine heatwave, affect the nano- and picoplanktonic community of primary producers and subsequent changes in coastal biogeochemistry. Our study demonstrates that future elevated temperature and pCO2 conditions impact the planktonic community, first by a ∼ 50 % decreased autotrophic abundance, and second by a shift from larger eukaryotic to smaller cells. When combined with a heatwave, total primary producers experienced an additional 37–38 % decrease, indicative of a negative synergistic effect beyond either stressor alone. Picoeukaryotes were particularly sensitive, declining by 44–50 %. Short-term nutrient pollution under ambient conditions induced a 41 % increase in cell abundance, but failed to stimulate biomass under elevated temperature and pCO2, and instead led to altered organic matter dynamics, including significantly lower carbon fixation. These findings emphasize the need for further evaluation of multi-stressor interactions to better understand biogeochemical vulnerability, nutrient retention, and ecological functioning in coastal ecosystems undergoing rapid climatic and anthropogenic change.
Continue reading ‘Acute microbial and nutrient responses to elevated temperature and pCO2: a coastal UK microcosm study’Carbon concentration mechanisms in Canary Islands macroalgae and their implications for future benthic community structure under ocean acidification
Published 12 February 2026 Science ClosedTags: algae, biological response, BRcommunity, community composition, laboratory, North Atlantic, otherprocess, physiology, primary production, respiration, vents
In recent decades, due to the anthropogenic CO2 concentration increase in the atmosphere, the chemistry of seawater has been seriously altered, producing the phenomenon known as Ocean Acidification (OA). Of all the dissolved inorganic carbon (DIC) present in seawater, only 1% is in the form of CO2. However, if anthropogenic CO2 emissions to the atmosphere continue, it will no longer be a limiting resource. Part of the response of marine photosynthetic organisms to these changes depends on their carbon physiology. The presence and effectiveness of carbon concentration mechanisms (CCM) can define the production and growth of macroalgae under OA conditions. Although CCMs are not essential when the seawater concentration of inorganic carbon is high, species that do not use them can see their performance improved. Our goal was to determine the presence or absence of CCMs in a total of 19 species of common macroalgae in the Canary Islands through a pH drift experiment and to establish their primary production rates through incubations and measurements of the O2 variation. Samples of each species were incubated during 8, 24 and 32 h in isolated containers and under controlled lighting and temperature conditions. Of the 19 species studied, 11 presented CCM and 8 did not present CCM. Five of the eight species that did not show the presence of CCMs in the present study are present in the CO2 seeps of Fuencaliente and one of them, H. scoparia is a dominant species.
Continue reading ‘Carbon concentration mechanisms in Canary Islands macroalgae and their implications for future benthic community structure under ocean acidification’Microbial community dynamics over large spatial and environmental gradients in a subtropical ocean basin
Published 9 February 2026 Science ClosedTags: abundance, biogeochemistry, biological response, chemistry, community composition, field, molecular biology, North Atlantic, otherprocess, prokaryotes, protists
Microbes are fundamental to ocean ecosystem function, yet they remain understudied across broad spatial and environmental scales in dynamic regions like the Gulf of America/Gulf of Mexico (GOM). We employed DNA metabarcoding to characterize prokaryotes (16S V4–V5) and protists (18S V9) across 51 stations, spanning 16 inshore–offshore transects and three depths. Cluster analysis revealed three clusters corresponding to depth zones that integrated vertical and horizontal sampling: photic zone (inshore near surface–bottom and offshore surface), deep chlorophyll maximum (offshore), and aphotic zone (offshore near bottom). We applied group-specific generalized additive models (GAMs) to log-transformed abundance data of major taxa in the photic zone, identifying key environmental factors that explained 42%–82% of the variation in abundance. SAR11 and SAR86 were positively associated with temperature and dissolved inorganic carbon, while cyanobacterial genera (Prochlorococcus and Synechococcus) were differently impacted by nutrients, salinity, and pH in ways that often followed their expected ecological niches. Representatives of protist parasites (Syndiniales) and grazers (Sagenista) showed group-specific nonlinear associations with salinity, oxygen, nutrients, and temperature. Using GAMs, we expanded the spatial resolution of DNA sampling and predicted surface log abundances at 84 cruise sites lacking amplicon data. Indicator analysis was performed with sequence-level data, revealing several protists that were indicative of more acidic waters and the absence of any significant prokaryote indicators. Our results provide the first basin-scale survey of microbes in the GOM and highlight the need for coordinated omics and environmental sampling to improve predictions of microbial responses to changing conditions.
Continue reading ‘Microbial community dynamics over large spatial and environmental gradients in a subtropical ocean basin’
