Posts Tagged 'North Atlantic'

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Strength and duration of diel pH and dissolved oxygen cycles control the survival and performance of early life stage North Atlantic bivalves (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians and Mytilus edulis)

Published 9 January 2026 Science Closed
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Highlights

  • Cycling from nocturnal hypoxia – acidification to mild hyperoxia- hypocapnia reduced larval survival in all experiments.
  • Cycling from nocturnal hypoxia – acidification to normoxia- normocapnia reduced survival of larvae in 50 % of experiments.
  • Nocturnal hypoxia and acidification caused increased clearance and respiration rates in juvenile mussels.
  • The impacts of diel DO and pH cycles on early life stage bivalves depend on cycle duration, cycle intensity, and species.

Abstract

Many economically important bivalves spawn during the summer months when diel cycles of dissolved oxygen (DO) and pH occur in estuaries. Little is known, however, regarding how cycles of differing durations and magnitudes affect these organisms. Here, larval bivalves (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians) and juvenile mussels (Mytilus edulis) were exposed to cycles of low DO and pH of varying duration (4-, 6-, 8-, and 12-h) and strength (moderate: DO range ∼ 6 mg L−1, pH range ∼ 0.6 and severe: DO range ∼ 10 mg L−1, pH range ∼ 0.9) compared to positive (normoxic and normocapnic) and negative (hypoxic and acidified) static controls. Growth, survival, respiration and clearance rates were measured. During experiments, 12 h of nocturnal hypoxia and acidification coupled with mildly hyperoxic (∼11.3 mg L−1 DO) and hypocapnic (∼8.13 pH) conditions by day significantly reduced survival in larval C. virginica, M. mercenaria, and A. irradians in all experiments (p < 0.05), while 12 h of nocturnal hypoxia and acidification without hyperoxic and hypocapnic conditions did so in only half of experiments indicating that hyperoxia and hypocapnia were additional and significant stressors. Six hours of low DO/pH significantly reduced survival in only 16 % of experiments, indicating that larval bivalves are more impacted by longer duration and greater magnitude cycles of DO and pH compared to cycles of shorter duration or lower magnitude. Across species, M. mercenaria larvae were more resilient to nocturnal hypoxia and acidification than A. irradians and C. virginica. The growth and survival of juvenile M. edulis were unaffected by nocturnal hypoxia and acidification but mussels experienced significantly increased clearance and respiration rates under these conditions (p < 0.01) evidencing physiological mechanisms for coping with these stressors. Collectively, this study demonstrates that the impacts of diel DO and pH cycles on early life stage bivalves are dependent upon cycle duration, cycle intensity, bivalve life stage, and bivalve species.

Continue reading ‘Strength and duration of diel pH and dissolved oxygen cycles control the survival and performance of early life stage North Atlantic bivalves (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians and Mytilus edulis)’

Ocean acidification in Massachusetts bay and Boston harbor: insights from a 1-D modeling approach

Published 8 January 2026 Science Closed
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Highlights

  • NeBEM, an ERSEM-based biogeochemical and ecosystem model, is established for the U.S. Northeast.
  • NeBEM provides process-based insights into carbonate system variability beyond the capability of empirical data-fitting methods.
  • Biological processes strongly influence TA and DIC variability in outer Massachusetts Bay.

Abstract

Massachusetts Bay (MB)/Boston Harbor (BH) in the northeastern United States has reduced buffering capability, making it highly vulnerable to ocean acidification (OA). We applied the U.S. Northeast Biogeochemistry and Ecosystem Model (NeBEM), integrating the unstructured grid, Finite Volume Community Ocean Model with a modified European Regional Seas Ecosystem Model (ERSEM), to investigate seasonal and interannual OA variability through one-dimensional (1-D) experiments. Objectives were to (a) evaluate model skill in reproducing observed seasonal cycles of OA-related variables, particularly pCO2 and pH, in shallow and deep regions, and (b) assess sensitivity to parameterizations and algorithms for calculating dissolved inorganic carbon (DIC), total alkalinity (TA), pCO2, and pH. The 1-D NeBEM reproduced variability of nutrients, dissolved oxygen, chlorophyll-a, pCO2, and pH at the deep outer bay site, where air-sea interactions dominate, but failed at the shallow inner bay site due to the absence of river discharge-driven advection. Of TA algorithms tested, the semi-diagnostic method best captured observed seasonal pCO2 variation, achieving the highest correlation and lowest root mean square error, although all methods performed similarly for pH. Comparisons with multi-linear regression methods showed that empirical models are highly sensitive to calibration set. Mechanistic analysis indicated that TA variability is mainly regulated by nitrification and net community production (NCP), while DIC variability is driven primarily by NCP. Atmospheric CO₂ loading was the first-order contributor to DIC change in magnitude. However, it has decreased in MB over the past two decades, in contrast to regional and global trends. Therefore, it is not a major driver of OA progression in this system.

Continue reading ‘Ocean acidification in Massachusetts bay and Boston harbor: insights from a 1-D modeling approach’

Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management

Published 7 January 2026 Science Closed
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Highlights

  • We spatially couple a scallop bioenergetic model to a regional oceanographic model.
  • Our model reproduces observed growth patterns using temperature, food, and pCO2.
  • Mid-century warming enhances scallop growth except in the south.
  • By 2100, scallops grow faster but reach smaller sizes under warming and acidification.
  • This tool can inform adaptive fisheries management under climate change.

Abstract

Climate-ready fisheries management requires reliable predictions of species responses to changing conditions across large-scale environmental gradients. Bioenergetic frameworks, such as Dynamic Energy Budget (DEB) models, relate physiological processes to environmental conditions, enabling predictions of organismal growth under projected climate change conditions. Here, we provide the first large-scale coupling of a DEB model to downscaled regional oceanographic simulations to resolve spatiotemporal changes and reveal how climate stressors emerge at relevant biogeographic, economic, and oceanographic scales. We calibrated our DEB model for the Atlantic sea scallop (Placopecten magellanicus) with forcing from a realistic oceanographic and biogeochemical model for the Northeast U.S. continental shelf to predict the effects of ocean acidification (OA) and warming on individual growth historically and over the next century. Our model reproduced observed historical patterns in scallop age at harvest size and maximum size. At mid-century (2035–2050), scallop growth was projected to increase in most areas except the southern Mid-Atlantic, and OA effects were limited to the deep Gulf of Maine. By the end of the century (2080–2095) under a high emissions scenario, scallops were predicted to grow faster but attain smaller maximum sizes. Our results highlight that warming stress is more acute than previously accounted for, particularly in the southern Mid-Atlantic. While warming stress emerges in the south first, OA stress emerges before warming in the north. Together, these emerging stressors compress the spatial range for optimal growth. Altogether, our findings demonstrate the utility of the spatially coupled DEB model as a tool to inform adaptive fisheries management.

Continue reading ‘Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management’

The role of heterotrophy in the response of Oculina arbuscula to ocean acidification

Published 31 December 2025 Science Closed
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On both tropical and temperate reefs, the calcium carbonate skeletons produced by scleractinian corals provide habitat that supports a high biodiversity of fishes and invertebrates. Ocean acidification (OA), driven by excess anthropogenic CO2 uptake, causes declines in seawater pH and carbonate ion concentration and can compromise coral calcification by causing increased energetic demands. Deciphering how corals meet this increased energetic demand is critical to predicting their future persistence. Oculina arbuscula is a facultatively symbiotic temperate coral common on subtropical reefs of the South Atlantic Bight. This coral has demonstrated calcification resilience to reduced pH conditions in both symbiotic and aposymbiotic forms, despite aposymbiotic colonies lacking access to photosynthetically-derived energy. I hypothesized that energy acquired through heterotrophy is a mechanism by which O. arbuscula obtains the resources necessary to overcome the heightened energy demand created by ocean acidification. To investigate the role of heterotrophy, a 90-day laboratory experiment was conducted exposing aposymbiotic O. arbuscula fragments to a pH of either 7.7 or 8.0 under three different feeding levels of Artemia spp. nauplii. Although fragments with greater food consumption showed significantly higher calcification rates, this effect was independent of pH. Similarly, biochemical analyses indicated that total protein and total carbohydrate stores increased with higher food consumption but were unaffected by pH exposure. In contrast, total lipid stores decreased during the experiment, regardless of pH exposure or food level, suggesting the heterotrophic contribution to lipid stores was deficient. Together, these results indicate that while heterotrophically-derived energy may not be a primary mechanism underlying the ability of O. arbuscula to sustain calcification rates under OA stress, this coral species should continue to thrive in an increasingly acidifying ocean as long as heterotrophic food resources are in abundance.

Continue reading ‘The role of heterotrophy in the response of Oculina arbuscula to ocean acidification’

Aquaculture of seaweeds (Saccharina latissima, Ulva spp., Gracilaria spp.) significantly improves the growth of co-cultivated bivalves in mesotrophic, but not eutrophic, estuaries

Published 29 December 2025 Science Closed
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The co-cultivation of seaweeds with bivalve shellfish is a potential strategy for protecting bivalve crops against anthropogenic coastal acidification and hypoxia. We co-cultivated seaweeds and bivalves using a succession of seaweed species according to season (winter, Saccharina latissima → spring, Ulva spp. → summer, Gracilaria spp.) together with eastern oysters (Crassostrea virginica) and blue mussels (Mytilus edulis). Bivalves and seaweeds were deployed in two estuaries that contrasted in trophic state, one mesotrophic and one eutrophic. In all five experiments in the mesotrophic system, cocultivation with seaweeds significantly increased weight- and/or shell-based growth of bivalves (p < 0.05). Growth rate increases for C. virginica were modest, with weight-based growth improving by 17–21% and shell-based growth improving by 3–27% with seaweed co-culture of all macroalgal species. For M. edulis, the effect was large; co-culture with S. latissima caused 47% and 114% increases in shell- and weight-based growth rates, respectively. In the four experiments in the eutrophic estuary, co-culture with seaweeds did not significantly improve bivalve growth. Seaweed cultivation significantly improved water quality metrics (increased pH and dissolved oxygen (DO); p < 0.05 in all cases) in and around the seaweed sites at both locations, although increases in pH and DO were modest, and even in control treatments, there were no prolonged periods of harmful pH or DO levels. An abundance of macroalgal detritus may have bolstered the diets of co-cultivated bivalves in the mesotrophic estuary, a hypothesis supported by lower chlorophyll a concentration, and therefore lower planktonic food levels, at that site. Given that seaweeds display species-specific allelopathic effects against phytoplankton, it is also possible that the presence of seaweeds altered the phytoplankton community to the benefit of the bivalves. Regardless, the findings here demonstrate that co-cultivation with seaweeds can accelerate the growth of bivalves.

Continue reading ‘Aquaculture of seaweeds (Saccharina latissima, Ulva spp., Gracilaria spp.) significantly improves the growth of co-cultivated bivalves in mesotrophic, but not eutrophic, estuaries’

Ecological stability of late Maastrichtian benthic foraminifera amidst Deccan volcanism

Published 29 December 2025 Science Closed
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Highlights

  • Benthic foraminifera assemblage at Bidart reveal a stable, mesotrophic late Maastrichtian seafloor.
  • K/Pg boundary at Bidart shows signs of ecological stress and taphonomic dissolution.
  • Deccan-induced calcification stress was restricted to surface ocean and had minimal impact on benthic foraminifera.
  • Robust test ratio and fragmentation index together serve as effective taphonomic proxies.

Abstract

The late Maastrichtian witnessed profound disruptions in biogeochemical cycles, leading to the fifth mass extinction at the Cretaceous–Paleogene (K/Pg) boundary. At Bidart section (France), the final ∼60 kyr of the Maastrichtian coincide with mercury (Hg) peaks, low magnetic susceptibility, evidence of biological stress and taphonomic alteration in planktic foraminifera, indicative of an ocean acidification event. While this event primarily appears to be a surface-ocean phenomenon, previous studies also documented a minor rise in benthic foraminiferal test fragmentation beginning 0.5 m below the K/Pg boundary, with a pronounced spike at the boundary itself.

A detailed investigation of benthic foraminifera in biozone CF1 at Bidart section (France) reveals a diverse and balanced assemblage preceding the K/Pg boundary, with minimal taphonomic alterations. At the K/Pg boundary, infaunal populations diminished, diversity declined sharply, test fragmentation intensified, yet paradoxically, the absolute abundance of genera rose markedly. Preferential preservation is evident in the dominance of robust taxa (Cibicidoides spp., Coryphostoma spp.), while a high fragmentation index reflects strong taphonomic dissolution and time-averaging. A plausible explanation for this could be CO2-rich waters mixing into the ocean interior over 100–1,000 years, driving dissolution during the ∼10,000-year deposition of the K/Pg boundary red clay. The stark contrast between the planktic and benthic census and morphometric data at Bidart section clearly constrains any Deccan-related calcification stress to the surface mixed layer. Lastly, the integrated planktic and benthic considerations re-emphasize a need to carefully separate taphonomic signals from true ecological stress.

Continue reading ‘Ecological stability of late Maastrichtian benthic foraminifera amidst Deccan volcanism’

Compound hypoxia with heat or acidification stress induces synergistic and additive effects on coral physiology

Published 26 December 2025 Science Closed
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As climate change accelerates, coastal marine ecosystems are increasingly exposed to co-occurring stressors whose combined effects are nonlinear and difficult to predict. Deoxygenation is a rapidly intensifying yet underrecognized threat to coral reefs that interacts with heat and acidification to alter coral physiology and stress resilience. However, the effects of hypoxia-related compound events on corals are largely unknown, underscoring the need for multi-stressor studies. Here, we conducted two extended-exposure experiments (12–17 days) across the coral species Porites furcata, Porites astreoides and Siderastrea siderea, to disentangle the individual and combined effects of low dissolved oxygen (hypoxia) with either heat or acidification. We measured eight phenotypic traits related to growth, metabolism, and symbiosis health to test whether hypoxia imposes energetic constraints or other physiological stress that amplify the effects of heat or acidification. Standardized effect size analysis across 24 stressor–trait combinations revealed 13 additive, 10 synergistic, and only one antagonistic response. Hypoxia consistently suppressed dark respiration by 37–49% across species and altered photophysiology in the two Porites species, whereas acidification alone had minimal effects, particularly in S. siderea. Heat stress caused the most pronounced declines across nearly all traits, and when combined with hypoxia, it produced the highest number of synergistic interactions. In contrast, the combination of hypoxia and acidification largely resulted in additive responses, suggesting that independent physiological mechanisms underlie these effects. All corals showed strong metabolic depression under hypoxia which is likely beneficial as a short-term adaptive response but may impose energetic constraints in the long-term. These findings highlight deoxygenation as critical yet often overlooked drivers of coral reef vulnerability. More multi-stressor experiments across a range of species are urgently needed to improve predictions of reef resilience under future ocean conditions, where compound stress events are expected to become more frequent and severe.

Continue reading ‘Compound hypoxia with heat or acidification stress induces synergistic and additive effects on coral physiology’

Interactive effects of ocean acidification and benthic biofilm composition on the early development of the European abalone Haliotis tuberculata

Published 23 December 2025 Science Closed
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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 individual and interactive effects of OA and algal density, acting through biofilm composition, on post-larval and juvenile abalone (Haliotis tuberculata). In a three-month 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 throughout the experiment. Biofilm biomass and composition 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 units) and highlight indirect macroalgal effects through changes in diatom communities. In natural environments, 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 benthic biofilm composition on the early development of the European abalone Haliotis tuberculata’

Genotype and symbiont composition rather than environment influence susceptibility to stony coral tissue loss disease in coral restoration broodstock

Published 19 December 2025 Science Closed
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Over the last several decades, Florida’s Coral Reef has been impacted by global and local stressors causing significant declines in living coral with no signs of natural recovery. Ocean warming, ocean acidification, and infectious diseases are major contributors to the precipitous loss of corals within this region. Since 2014, the stony coral tissue loss disease (SCTLD) outbreak has been particularly devastating, causing unprecedented mortality in over 20 massive coral species. As SCTLD is now endemic in the region, and threats from climate change are likely to persist, studying the disease susceptibility of different coral genotypes under future environmental scenarios is vital for effective restoration. Here, we exposed Orbicella faveolata and Pseudodiploria clivosa genotypes to wild colonies showing signs consistent with SCTLD immediately following a 2-month long exposure to ocean warming (OW) and ocean acidification (OA) scenarios. Corals were exposed to SCTLD for 3 weeks while maintaining the environmental treatments. For both species, pre-exposure to OW and OA scenarios did not make corals more susceptible to SCTLD. However, three genotypes hosting higher levels of Breviolum were at increased risk for showing SCTLD signs under these conditions. One O. faveolata genotype was consistently resistant to SCTLD under the different scenarios, suggesting that natural levels of resistance exist in coral restoration broodstock. Understanding why this genotype could withstand exposure to these stressors may be critical for ensuring survival of restored populations into the future.

Continue reading ‘Genotype and symbiont composition rather than environment influence susceptibility to stony coral tissue loss disease in coral restoration broodstock’

Multifactorial neural disruption in the brain of the Senegalese Sole (Solea senegalensis) under ocean acidification

Published 9 December 2025 Science Closed
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Global ocean acidification, driven by rising atmospheric CO2, is threatening marine ecosystems and biodiversity, with increasing evidence of its disruptive effects on fish neurobiology and behaviour, yet the mechanisms underpinning its impact on fish neurobiology remain unresolved. Here, we reveal how chronic exposure to future-predicted CO2 levels disrupts brain function in the marine teleost Solea senegalensis, a species with functionally distinct olfactory organs. Using an integrative approach combining electrophysiology, immunohistochemistry, and transcriptomics, we demonstrate that elevated CO2 conditions induce a complex multifaceted disruption in brain physiology. Notably, our findings conflict with the widely held GABAA receptor reversal hypothesis; we observed increased Cl- and CO2 in cerebrospinal fluid and suppressed neural excitability, rather than the predicted loss of Cl- and heightened excitatory signalling. Immunohistochemistry further revealed reduced expression of glial fibrillary acidic protein across multiple brain regions, suggesting glial impairment. Furthermore, transcriptomic profiling of the olfactory bulb uncovered immune modulation, downregulation of neural excitability genes, and upregulation of neuroplasticity, ciliary, and anti-inflammatory pathways, hallmarks of cellular stress adaptation. Notably, genes involved in circadian regulation and thyroid signalling were also dysregulated, pointing to broader neuroendocrine disruption. These findings challenge current relatively simple models of ocean acidification impact and unveil a complex cascade of central and peripheral alterations, including enhanced GABAergic inhibition, immune shifts, glial dysfunction, and disrupted timekeeping mechanisms, likely contributing to the behavioural impairments observed under high CO₂. Challenging current models, our work highlights the need for integrative neurophysiological frameworks to predict marine fish resilience and vulnerability in a changing ocean.

Continue reading ‘Multifactorial neural disruption in the brain of the Senegalese Sole (Solea senegalensis) under ocean acidification’

Resistance of the cold-water coral Dendrophyllia cornigera to single and combined global change stressors

Published 28 November 2025 Science Closed
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Current knowledge of the consequences on global change in deep marine ecosystems is still limited, especially since environmental pressures do not act separately, and their potential interactions are mostly unknown. Cold-water corals (CWC) play a significant role in the deep sea, being ecosystem engineers supporting high biodiversity. However, global change may impact CWCs, compromising their integrity and survival. In this study, a nine-month aquaria experiment was conducted on the CWC Dendrophyllia cornigera from the NW Iberian Shelf (NE Atlantic Ocean). The aim was to assess the individual and combined effects of elevated temperature (12 vs. 15 °C), low pH (~ 7.99 vs. 7.69 pHT) and low oxygen (~ 6.4 vs. 4.7 mL L−1), based on the IPCC RCP 8.5 scenario. During the experiment, coral survival, skeletal growth, tissue cover and respiration were monitored as response variables. No significant effects were found on any of the response variables for either individual or combined stressors, pointing to the resistance of D. cornigera to different global change scenarios. Such a physiological resistance may support D. cornigera persistence under future conditions where other CWCs with narrower tolerance ranges may face greater limitations. However, further research is needed to assess potential trade-offs to cope with environmental change, which might impact the long-term survival capacity of this species.

Continue reading ‘Resistance of the cold-water coral Dendrophyllia cornigera to single and combined global change stressors’

Ocean acidification in the Bay of Biscay: two decades of data reveal a silent shift

Published 26 November 2025 Press releases Closed
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The sea along the Basque coast is changing quietly. An analysis of more than 21,700 measurements collected between 2002 and 2022 shows that the pH of seawater is steadily decreasing—clear evidence of ocean acidification driven by rising atmospheric carbon dioxide.

According to the study, published in Continental Shelf Research, the pH of waters from the surface down to 100 meters is declining by 0.022 to 0.041 units per decade. “If this trend continues at the same pace, the impacts on the health of marine ecosystems could be significant,” explains Ernesto Villarino, AZTI researcher and lead author of the study.

Conducted by AZTI with the support of the Naturklima Foundation, as part of the Gipuzkoa Marine Climate Change Observatory, and in collaboration with the Institute of Marine Sciences of Andalusia (ICMAN-CSIC), this research analyzes the longest continuous pH monitoring series ever recorded along the Basque coast. The data, provided by the Basque Water Agency (URA), confirm that the Bay of Biscay is also affected by ocean acidification, underlining the need to strengthen mitigation and climate-adaptation strategies.

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A synthesis of Eastern oyster (Crassostrea virginica) growth and calcification responses under changing environmental conditions

Published 21 November 2025 Science Closed
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Eastern oysters (Crassostrea virginica) are foundational reef builders and ecosystem engineers that provide habitat complexity, enhance biodiversity, and influence biogeochemical cycles by shifting local carbonate chemistry in estuaries along the U.S. Atlantic coast and Gulf of Mexico. However, the environmental ranges governing oyster shell growth and calcification rates remain poorly constrained because available studies vary in the metrics quantified, experimental settings, and spatial coverage. We synthesized existing literature on C. virginica growth and calcification, assessing directional responses to changing environmental conditions. Variability in ecological, spatial, and temporal scales among studies and disparities between laboratory and field-based measurements complicate direct comparisons. Despite heterogeneity in the synthesized data, consistent patterns emerged; shell growth limitations were common at salinities below ~ 12 in U.S. Gulf of Mexico populations, and calcification declines were frequently observed under acidified conditions (pH < 7.7) in U.S. Atlantic populations. By summarizing patterns across life stages, regions, and study types, we highlight environmental stressors likely to impair oyster reef resilience and function. A more integrative research approach, incorporating both individual- and reef-scale processes across experimental and natural settings, is critical for refining predictions of oyster reef resilience. Standardized methodologies and interdisciplinary frameworks will enhance our ability to quantify the role of oyster reefs in carbon cycling and assess their response to future environmental stressors.

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Coastal ocean acidification in our local waters

Published 19 November 2025 Media coverage Closed
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Off the coast of Long Island, climate change and pollution are making local waters more acidic.

This is from a process known as Coastal Ocean Acidification where carbon dioxide and land-based pollution lower the water’s ph. The problem can also worsen when algal blooms or fast-growing algae feed on that pollution. With lower pH levels, species like clams and phytoplankton have trouble forming their shells.

Christopher Gobler, a professor at Stony Brook’s School of Marine and Atmospheric Sciences explains. “That carbonate that they use to make their shell, becomes less abundant. And so almost like a linear relationship. So it goes down and the carbonate concentrations go down with it. And that makes calcifying a challenge,” he said.

The process or synergy shows how climate change, algal blooms, and local pollution, when combined, can affect our waters to this level. “That’s one of the . . . unintended or unanticipated outcome sometimes, of all these processes. And . . . it’s one of the things that makes climate change less predictable than we would like,” Gobler said.

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A century of change in the California Current: upwelling system amplifies acidification

Published 19 November 2025 Science Closed
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Predicting the pace of acidification in the California Current System (CCS), a productive upwelling system that borders the west coast of North America, is complex because the anthropogenic contribution is intertwined with other natural sources. A central question is whether acidification in the CCS will follow the pace of increasing atmospheric CO2, or if climate effects and other biogeochemical processes will either amplify or attenuate acidification. Here, we apply the boron isotope pH proxy to cold-water orange cup corals to establish a historic level of acidification in the CCS and the Salish Sea, an associated marginal sea. Through a combination of complementary modeling and geochemical approaches, we show that the CCS and Salish Sea have experienced amplified acidification over the industrial era, driven by the interaction between anthropogenic CO2 and a thermodynamic buffering effect. From this foundation, we project future acidification in the CCS under elevated CO2 emissions. The projected change in pCO2 over the 21st century will continue to outpace atmospheric CO2, posing challenges to marine ecosystems of biological, cultural, and economic importance.

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Consequences of climate change for foraminifera and foraminifera communities

Published 11 November 2025 Science Closed
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Single-celled protists called foraminifera perform critical ecosystem functions across the world’s oceans, including cycling of biogeochemically relevant compounds, sequestering carbon, and serving as biological monitoring tools of ecosystem health. However, anthropogenic climate change increases risks for these species in the oceans of the future. As ocean conditions change due to increased carbon dioxide in the atmosphere from anthropogenic sources, dire consequences to the world’s oceans are emerging such as oceanic deoxygenation, or the reduction of dissolved oxygen in water due to increased heat; coastal acidification, or decreases in coastal water pH due to increased dissolved carbon dioxide; and sea-level rise, which is cause by rising temperatures and melting icecaps. Currently, the responses of foraminifera to these important climate change risk-factors have not been well-studied. This study examines the responses of this group to the threats of climate change to predict their ecological success and capacity to serve as bioindicators as oceans continue to change.

In Manuscript I, transcriptomes were collected from two species of foraminifera collected from the Santa Barbara Basin off the coast of California: Nonionella stella and Bolivina argentea. These two species thrive in anoxic to euxinic and hypoxic sediments, respectively. However, the metabolic processes that enable these species to achieve high ecological success in extreme conditions are unclear. This study presented detailed metabolic reconstructions and differential gene expression that illustrated the cellular processes localized to the peroxisome and mitochondria. This metabolism enables survival in oxygen-depleted sediments and suggested that these species are likely to experience range expansion as deoxygenated regions get larger with climate change.

Manuscript II investigated responses of a Rhode Island salt marsh foraminifera, Haynesina sp., to coastal acidification. As carbon dioxide concentrations raise in the atmosphere, chemical equilibria dictate that carbon dioxide concentrations increase in the ocean as well. When carbon dioxide dissolves in seawater, several spontaneous chemical reactions occur that lead to decreased pH, which can have detrimental impacts on calcium carbonate-depositing organisms. These processes can be exacerbated in coastal systems, where conditions fluctuate to higher extremes than in the open ocean. Many foraminifera, including Haynesina sp., have calcium carbonate tests that could leave these species at high risk due to ocean acidification. This study detailed the morphological responses of Haynesina sp. to coastal acidification over biologically relevant timescales to determine that, although Haynesina sp. may be resistant to moderate elevated carbon dioxide, exposure to high elevated pCO2 leads to morphological defects in living cells. Altogether, this study demonstrated that Haynesina are susceptible to extreme coastal acidification and risk dissolution under those conditions.

In Manuscript III, the scope of foraminifera examined was expanded from individual species to whole communities by using DNA metabarcoding to examine how communities may shift in response to sea-level rise mitigation efforts. As global climate change proceeds, temperatures are expected to rise, which will result in increases in sea-level as water stored in ice and glaciers continues to melt. Due to increases in sea-level, it is expected that many coastal regions of the United States could be submerged in the next 100 years. To mitigate increases sea-level rise, conservation efforts are underway to raise the elevation of salt marshes through thin layer placement of sediment. This restoration technique involves adding large amounts of sediment to the surface of salt marshes and has been noted to have beneficial impacts for vegetation; however, impacts on other associated ecosystems, such as the subtidal and intertidal regions, are unknown. This study found that each of the three sites examined across the Rhode Island coast had distinct foraminiferal communities. Additionally, in the two restored marshes, TLP seemed to significantly impact foraminiferal alpha diversity. Across the two restored marshes, variable responses in alpha and beta diversity were observed. The results show that Rhode Island salt marshes have divergent responses to thin layer placement and need to be studied individually to determine the impacts of restoration. Despite this, our results suggest that TLP can have positive impacts on the health of some intertidal ecosystems.

In conclusion, these studies demonstrate that foraminifera have complex and varied responses to risk factors associated with climate change and climate change mitigation efforts. In some scenarios, such as oceanic deoxygenation, some taxa are poised to experience success and range expansion. However, other scenarios, such as ocean acidification, may lead to increased risk for species within this group under extreme scenarios. Further, foraminifera have the capacity to act as bioindicators, as is seen in the face of sea-level rise mitigation efforts, where foraminifera demonstrate a strong potential to act as an indicator species for ecosystem health.

Continue reading ‘Consequences of climate change for foraminifera and foraminifera communities’

Impact of climate change driven freshening, warming, and ocean acidification on the cellular metabolism of Atlantic cod (Gadus morhua)

Published 27 October 2025 Science Closed
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Climate change is causing increasing sea surface temperature, ocean acidification and, in near shore waters, freshening. We investigated the metabolic effects of all three and their combination in Atlantic cod from the Skagerrak (eastern North Sea) by measuring concentration changes of a wide range of metabolites involved in energy production in the liver and muscles. Liver metabolism was more strongly affected than muscle, reflecting its central regulatory role. Most amino acid concentrations declined in both tissues across all treatments, and metabolomic pathway analysis revealed significant enrichment in ten metabolic pathways. This suggests enhanced amino acid metabolism in a climate change future. Warming and ocean acidification induced increased liver concentrations of lactate, glucose and fructose 1,6-bisphosphate indicating that gluconeogenesis will increase to meet increased production of enzymes to counter future stress. The molar contribution of glutamine to the total change in liver amino acids constituted 49%, 16% and 29% under warming, ocean acidification and their combination accentuating its importance in energy production also under future climate change. We observed contrasting responses in AMP, ADP, and NAD+ concentrations between warming and acidification suggesting possible antagonistic effects. Our findings demonstrate significant and complex metabolic responses to future climate stress in Atlantic cod in northern European waters.

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Two decades of pHT measurements along the GO-SHIP A25 section

Published 27 October 2025 Science Closed
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The North Atlantic (NA) GO-SHIP A25 OVIDE-BOCATS section is a long-term repeat hydrographic transect extending from Portugal to Greenland. Since 2002, physical and biogeochemical measurements have been carried out biennially along the OVIDE-BOCATS section, contributing to a better understanding of water mass properties, mixing, circulation, carbon storage, and climate change impacts such as ocean acidification (OA) in the NA. In particular, the high-precision pH measurements on the total hydrogen ion scale (pHT) from the OVIDE-BOCATS program represent a key milestone in monitoring OA in this particularly climate sensitive region. The method used for pHT determination relies on adding meta-cresol purple (mCP) dye to the seawater sample and spectrophotometrically measuring its absorbances at specific wavelengths. The OVIDE-BOCATS program has used unpurified mCP dye, which impurities have been proven to bias pHT values. Here we quantified the bias induced by these impurities in pHT measurements. We found that measurements carried out using the unpurified mCP dye tend to be, on average, 0.011 ± 0.002 pHT units higher than those obtained using the purified mCP dye, with this difference slightly decreasing at higher pHT values. Moreover, we tested independent methods to correct the effect of impurities in both the historical and recent OVIDE-BOCATS pHT data, demonstrating that the correction is consistent across methods. The long-term pHT dataset has been updated to include newly acquired data and absorbance measurements, and to standardize corrections for mCP dye impurities. This effort results in a twenty-year dataset of pHT corrected for mCP dye impurities, that demonstrates the possibility of a global effort to improve the reliability and coherency of spectrophotometric pHT measurements made with unpurified mCP dye. The corrections applied to our pHT dataset have negligible implications for the OA rates previously reported, but they do affect the depth of the aragonite saturation horizon, implying a shoaling of approximately 150 m.

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A tri-national initiative to advance understanding of coastal and ocean acidification in the Gulf of Mexico/Gulf of America

Published 23 October 2025 Science Closed
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The Gulf of Mexico’s (also recognized by the United States government as the Gulf of America; herein referred to as “the Gulf”) valuable and diverse marine, coastal, and estuarine environments sustain many habitats, species, and economically important fisheries that are vulnerable to open ocean and coastal acidification (OOCA), including shellfish, coral reefs, and other carbonate reefs and seafloor. OOCA poses an economic threat to the Gulf’s economy, which is estimated to have a combined value of $2.04 trillion (US) per year across Cuba, Mexico and the United States (U.S.). Scientists from Cuba, Mexico, and the U.S. co-organized and co-hosted the first Gulf International Ocean Acidification Summit on Oct. 18-19, 2022 in Mérida, Yucatan, Mexico to exchange information and begin development of a new tri-national network to address the socioeconomic and ecological impacts of OOCA in the Gulf based on common needs. The meeting included representatives from government agencies, universities, research institutes, non-governmental organizations, and was sponsored by the Furgason Fellowship of the Harte Research Institute at Texas A&M University-Corpus Christi. Discussions focused on each country’s challenges, including known and potential socioeconomic vulnerabilities and biological and ecosystem responses to OOCA. Shared priorities were identified for observational, biological, environmental needs, socioeconomic research, outreach, and communications. Priority geographic locations for the study and short and long-term monitoring of OOCA were identified based on the group’s knowledge of oceanographic conditions and vulnerable regions. Longer-term actions that will help support multinational collaborations include: identifying shared data and information platforms; standardizing chemical and biological sampling methodologies; coordinating communications with regulatory agencies and resource managers; and coordinating monitoring activities, collaborative research projects, and tri-national comparisons and synthesis of findings. We present guidance from this effort for an integrated, multinational approach to understanding the causes and consequences of OOCA in the Gulf.

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Ocean change in the northeastern Atlantic and adjacent seas: a multi-dimensional challenge for the environment, society, and economy

Published 17 October 2025 Newsletters and reports Closed
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An ocean narrative is a powerful tool for making complex ocean changes better accessible while informing decision-making and inspiring collective action. This ocean narrative reports on ocean change in the northeastern Atlantic and adjacent seas and discusses its broader implications for Europe’s environment, economy, and society. The region is experiencing warming and acidification at rates exceeding the global average, with rising sea levels and record severe marine heatwaves (MHWs). These changes threaten marine ecosystems, biodiversity, cultural heritage, and key economic sectors, such as aquaculture and coastal tourism, which rely heavily on the balance and the health of the ocean. This ocean narrative emphasizes the importance of regional ocean indicators for the northeastern Atlantic and adjacent seas and underscores the importance of localized responses, as ocean changes affect regions differently, particularly in semi-enclosed seas such as the Baltic Sea, the Black Sea, and the Mediterranean Sea. The findings stress the urgency of timely action and the need to strengthen evidence-based and strategic ocean knowledge transfer at the science and policy interface for informed decision-making that balances environmental sustainability, economic resilience, and social inclusivity to address the growing challenges of ocean change in the northeastern Atlantic and its adjacent seas.

Continue reading ‘Ocean change in the northeastern Atlantic and adjacent seas: a multi-dimensional challenge for the environment, society, and economy’

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