Reef-building corals form the calcium-carbonate frameworks that underpin tropical coral reefs, yet global coral cover has declined by ~50% in recent decades, due to marine heatwaves and other stressors. Identifying refugia environments, such as upwelling systems, that buffer stress, promote recovery, and enhance resilience by promoting physiological plasticity that supports thermotolerance is therefore critical. Here, we compared benthic community composition, coral percent cover, and photo-physiology between an upwelling location in the Gulf of Papagayo and a non-upwelling location in Sámara on the Pacific coast of Costa Rica. Waters in Papagayo were cooler, more acidic, and richer in chlorophyll a. Reefs at this location exhibited higher crustose coralline algae, higher sea urchin cover, and lower macroalgae cover, compared to Sámara. Papagayo also showed higher stony coral cover, driven by Pocillopora spp., while Sámara was dominated by massive, heat-tolerant Porites spp.. When significant, photophysiological measurements showed 9.7 – 44.5% higher photosynthetic efficiency (Fv’/Fm’) in Papagayo corals and 19.94 – 42.75 % higher maximum photosynthetic rates (Pmax) in Sámara corals. These results highlight how contrasting environmental regimes within a relatively small geographic area can shape distinct coral community compositions and photophysiological strategies, with implications for identifying areas of reef persistence or refugia.
Continue reading ‘Seasonal upwelling shapes coral reef community structure and photophysiology on the Pacific Coast of Costa Rica’Posts Tagged 'North Pacific'
Seasonal upwelling shapes coral reef community structure and photophysiology on the Pacific Coast of Costa Rica
Published 3 June 2026 Science Leave a CommentTags: algae, biological response, community composition, corals, echinoderms, field, modeling, North Pacific, otherprocess, photosynthesis, physiology, regionalmodeling
Upper-ocean variability of the marine carbonate system in the Northeast Pacific
Published 2 June 2026 Science Leave a CommentTags: chemistry, field, globalmodeling, modeling, North Pacific, regionalmodeling
In the Northeast Pacific, the marine carbonate system’s variability across timescales is not well constrained. Here, we quantify observed seasonal and non-seasonal variability in Dissolved Inorganic Carbon (DIC), partial pressure of carbon dioxide () and aragonite saturation state and discuss potential drivers. We used three decades of observations from four Line P time series stations, the longest marine carbonate system time series in the Northeast Pacific (1990–2019). To gauge the spatial extent of the variability patterns, we used output from a global ocean model representing the observed period. In the Northeast Pacific, seasonal and non-seasonal variability at 10 m was minimal, mostly damped by the opposing influence of DIC and temperature changes at both seasonal and interannual timescales. For DIC and , the seasonal cycle dominated total variability in the top 60–70 m, with mean-transect 10 m seasonal amplitudes of 35 3 μmol and 0.31 0.04, respectively. In the upper 60–70 m, the magnitude of non-seasonal variability was at least half that of the seasonal variability for most variables. From five climate indices examined, we focused on the basin-scale Pacific Decadal Oscillation index (PDO) to investigate potential drivers of non-seasonal variability, with 20%–40% of the non-seasonal variability in DIC and associated to this index. In the Northeast Pacific, positive PDO periods were linked to a mean reduction in 10 m DIC of 5 μmol and an increase in 10 m of 0.04 for each PDO unit increase, which could potentially reduce the occurrence and severity of ocean acidification events. The opposite could be expected during negative PDO periods.
Plain Language Summary
Using 30 years of observations from the Northeast Pacific, we characterized sources of variability for three marine carbonate system variables: , dissolved inorganic carbon (DIC) and the saturation state of aragonite (an common indicator of ocean acidification). The seasonal and non-seasonal variability was minimal in the top 10 m. The seasonal cycle of DIC and aragonite saturation state was the major contributor to total variability in the top 60–70 m, and not detectable below. Also, in the top 70 m of the water column, up to 20%–40% of the DIC and aragonite saturation state non-seasonal variability was associated to the Pacific Decadal Oscillation index (PDO). The PDO is a statistics-derived index that captures variability patterns influencing the whole Pacific basin and has a positive and negative phase. We found that a warmer than usual upper water column in the Northeast Pacific during a positive PDO phase, potentially driven by reduced mixing, was linked to a lower DIC and higher values of aragonite saturation state. The opposite could be expected during negative PDO periods. Knowing the magnitude of natural variability in the marine carbonate system is important to identify the emergence of ocean acidification and other human-driven changes in the ocean.
Continue reading ‘Upper-ocean variability of the marine carbonate system in the Northeast Pacific’Present and future seawater CO2 chemistry across multiple coral reef habitats and scales at Dongsha Atoll and Taiping Island in the South China Sea
Published 22 May 2026 Science ClosedTags: biogeochemistry, chemistry, corals, field, laboratory, North Pacific, sensor
Coral reefs consist of diverse benthic habitats that influence seawater CO2 chemistry variability on multiple spatial and temporal scales. Understanding the present-day seawater CO2 chemistry variability across both habitat-specific and reef-wide scales is critical to accurately predict the effects of future environmental change. Here, we utilize autonomous sensors and discrete seawater samples across diverse habitats at multiple scales ranging from habitat-specific (inner lagoon, patch reefs and seagrass beds; 0.02–0.72km2) to reef-wide scales at Dongsha Atoll (250km2) and Taiping Island (20km2) to characterize seawater chemistry. Across all habitats, daily mean pH ranged from 7.79–8.60 with mean diel variability ranging from 0.19–0.91. Spatially, pH variability ranged from 0.08 (patch reef) to 1.29 (inner lagoon). Biogeochemical modification of seawater chemistry was dominated by organic carbon cycling at individual habitat scales, whereas inorganic carbon cycling dominated at the scale of Dongsha Atoll. The largest alkalinity depletion (net calcification) was associated with patch reef habitats, whereas the highest alkalinity repletion was associated with a semi-enclosed lagoon. Under two climate change scenarios (linear dissolved inorganic carbon increase derived from historical observations and the CMIP6 SSP5-8.5 pathway), pH and/or aragonite saturation state (ΩAr) observations across all habitats in this study are projected to be below proposed thresholds for net reef accretion (pH < 7.7: inner lagoon ~ 10–13%; seagrass beds ~ 21–44%; patch reefs ~ 0–100%; atoll-wide ~ 4–98% of observations) or net dissolution (ΩAr < 2.92: inner lagoon ~ 10–18%; seagrass beds ~ 44–75%; patch reefs ~ 77–100%; atoll-wide ~ 94–100% of observations) by the year 2100. The results highlight the importance of habitat-specific and scale-conscious assessments of future coral reef environmental conditions.
Continue reading ‘Present and future seawater CO2 chemistry across multiple coral reef habitats and scales at Dongsha Atoll and Taiping Island in the South China Sea’Impacts of coinciding ocean acidification and warming on the fatty acid profile of the pteropod Limacina helicina within the Northeast Pacific coastal region
Published 19 May 2026 Science ClosedTags: biological response, laboratory, mollusks, mortality, North Pacific, physiology
Under global climate change, co-occurrence of ocean acidification (OA) and warming poses a substantial threat to marine ecosystems. The present study focused on the Strait of Georgia within the Northeast Pacific region, where conditions of aragonite undersaturation exist year-round across the majority of the water column, with further intensification expected under OA. These conditions coincide with persistent rises in mean seasonal seawater temperatures and increased prevalence of acute stressor events, such as marine heatwaves and low-pH upwelling events. Limacina helicina, a pteropod species well-represented within the region’s zooplankton communities, is susceptible to OA and warming, with documented impacts including altered shell development, growth, and survival. To date, however, there has been minimal investigation into the effects of OA and warming on the species’ fatty acid profile under regionally-relevant conditions, thereby contributing to a lack of understanding of how impacts at lower trophic levels may relay across ecosystems. To address this knowledge gap, we examined the survival and fatty acid profile of L. helicina under future conditions via a laboratory experiment during which pteropods were exposed to singular and coinciding warming (mean summer seawater temperature + 4 °C) and OA (Ωarag < 1) conditions, with fatty acid analyses carried out via gas chromatography at 48-h and 5-d timepoints. OA conditions significantly altered fatty acid proportions at 48 h, and there was an additional interactive effect of OA and warming. Temperature significantly affected survival at 5 d, although experimental starvation conditions likely confounded this result. Additionally, fatty acid analyses of L. helicina picked from historical plankton samples collected in the region over 2014–2023 were carried out to examine time-series changes in fatty acid profiles in relation to temperature records. Results indicated no significant differences in fatty acid fractions among years, though there was suggestion of a changing proportion of myristic acid over a number of year groups. Overall, findings suggest that short-term OA conditions may result in altered fatty acid composition in pteropods, potentially leading to shifts in nutritional quality and associated impacts on trophic energy transfer.
Continue reading ‘Impacts of coinciding ocean acidification and warming on the fatty acid profile of the pteropod Limacina helicina within the Northeast Pacific coastal region’Changes in salinity impact nitrogen removal and carbon preservation in coastal wetlands sediment
Published 18 May 2026 Science ClosedTags: biological response, chemistry, laboratory, multiple factors, North Pacific, salinity, sediment
Highlights
- Coastal freshening suppressed N removal via denitrification while accelerating net organic carbon mineralization.
- Salinity shaped N removal vs. N retention and carbonate vs. alkalinity balance through sulfate availability.
- Salinity changes had concurrent implications for coastal eutrophication and ocean acidification.
Abstract
Coastal wetlands naturally remediate nitrogen (N) pollution through microbial pathways that either remove reactive N via denitrification and anammox, or retain it via dissimilatory nitrate reduction to ammonium (DNRA). The balance among three processes is closely linked to the carbon (C) cycle, as both heterotrophic denitrification and DNRA consume organic C and release alkalinity. While salinity fluctuations can disrupt these processes through direct ionic stress or sulfur (S) cycling, their net impact on N removal and C preservation services remains unclear. Here, we deployed microcosm experiments using mangrove sediments under a large salinity gradient (0-30 psu). We quantified N transformation rates using 15N isotope tracing technique, combined with geochemical analysis, and functional genes quantification. Freshening from ambient 30 psu to 10 psμ decreased N removal efficiency by ∼20%. This decline was caused by reduced denitrification, whereas anammox and DNRA were unaffected. Meanwhile, lower salinity appears to have stimulated C decomposition via reduced ionic stress. The reduced sulfate input diminished total alkalinity (TA) generation relative to dissolved inorganic carbon (DIC). The stoichiometric shift of TA:DIC ratio could further contribute to acidification in adjacent coastal waters. Additionally, the S-mediated regulation of N partitioning appears to be nitrate-dependent: under nitrate limitation, higher sulfate favored N retention; conversely, with enriched nitrate, it potentially favored N removal. Integrating the coupling effect of salinity on interaction between N, C and S cycles, our study demonstrates that coastal water freshening may weaken wetlands’ ability to remove N and preserve C.
Continue reading ‘Changes in salinity impact nitrogen removal and carbon preservation in coastal wetlands sediment’Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification
Published 18 May 2026 Science ClosedTags: biological response, corals, field, fish, North Pacific, performance
- Social context is a critical yet underexplored determinant of behavioural resilience to climate change. Group living can buffer individuals against environmental stress through enhanced vigilance, reduced predation risk and improved foraging efficiency.
- However, whether these behavioural expressions persist under chronic (warming, acidification) and acute (marine heatwaves) climate stressors remains unclear. Using natural climate analogues spanning present-day, ocean warming and combined warming–acidification reefs, we quantified how shoal size influences behavioural expression in a range-extending reef fish (Pomacentrus coelestis).
- Across all climate conditions, fish in larger shoals consistently exhibited higher foraging and activity levels and reduced risk-avoidance behaviours, whereas direct effects of warming, acidification and heatwaves on behaviour were negligible.
- In contrast, ocean acidification most likely constrained collective behaviour indirectly by simplifying benthic habitats, where fish densities were 84% lower than at the warming reef, resulting in shoals that were up to 79% smaller than the Warming and Control reefs.
- Combined, our data suggest that shoal size mediates behavioural expression between foraging and predator avoidance and that acidification-driven habitat simplification can alter behavioural expression indirectly by reducing fish densities and the formation of large shoals.
- We conclude that climate change can indirectly modify behavioural expression in shoal-forming fishes through habitat-driven erosion of social structure.
High-resolution temporal biogeochemical variations in a seagrass-coral cohabitate ecosystem: day-night, rain, and coral spawning
Published 14 May 2026 Science ClosedTags: biogeochemistry, biological response, chemistry, community composition, corals, field, laboratory, North Pacific, otherprocess, phanerogams, physiology, reproduction
Highlights
- Seagrass-coral habitats act as CO2 sources driven by intense nighttime respiration
- High-resolution data enable predictive modeling of DIC, DOC, and POC dynamics
- Metabolic cues govern DIC, while temperature and alkalinity regulate POC and DOC
- Episodic coral spawning and rainfall trigger rapid ocean acidification
- Short-term disturbances dramatically shift organic and inorganic nutrient loads
Abstract
Seagrass meadows and coral reefs are global hotspots for productivity, yet they are often studied in isolation despite their intense biogeochemical connectivity. Significant gaps remain in understanding how coupled inorganic and organic processes within the water column drive blue carbon services in such mixed habitats, particularly during rapid environmental disturbances. Here, we investigated a unique, intertwined ecosystem in the Dongsha Atoll, where massive Porites corals are distributed on seagrass meadows, creating a natural laboratory for studying water column carbon biogeochemistry. During a 10-day sampling period, we collected continuous hydrological and discrete biogeochemical data at two- to four-hour intervals. Our results reveal that the dissolved inorganic carbon (DIC) covaried with dissolved oxygen and pH in strong diurnal patterns, which were governed by photosynthesis and respiration. As an outcome, variable but mostly high pCO2 values (141–2070 μatm) indicate the seagrass meadow was a source of CO2 to the atmosphere due to strong night-time respiration. Particulate organic carbon (POC) increased with temperature but showed no diurnal pattern. Dissolved organic carbon (DOC) showed a weak diurnal pattern and was linked to variations in POC and total alkalinity, highlighting the tight coupling between the organic production of the meadow and the inorganic chemistry of the calcification framework. Additionally, coral spawning led to a surge in organic content and changed inorganic nutrient levels. Rainfall events significantly acidified the ocean and enhanced submarine groundwater discharge to the seagrass-coral habitat. The distinctive contributions of this study are the extremely high temporal resolution of discrete samples, allowing the simultaneous tracking of multiple organic and inorganic pools during natural disturbances. The high-resolution data provide fundamental information for parametrizing models that explain DIC, POC, and DOC, which yield insights into organic carbon cycling in seagrass meadow-coral habitats.
Continue reading ‘High-resolution temporal biogeochemical variations in a seagrass-coral cohabitate ecosystem: day-night, rain, and coral spawning’Anti-predatory responses of Mytilus coruscus to the combined effects of ocean acidification and microplastics
Published 13 May 2026 Science ClosedTags: biological response, chemistry, crustaceans, laboratory, mollusks, multiple factors, North Pacific, performance, physiology, plastics
Highlights
1.Predator cues can significantly induce byssal secretion in Mytilus coruscus.
2.Ocean acidification inhibits the anti-predatory responses of Mytilus coruscus.
3.Microplastics exerts sublethal effects on the byssus of Mytilus coruscus.
4.The presence of predators amplifies the mild disturbances caused by ocean acidification and microplastics.
5.The combined stress shows a synergistic inhibitory trend on the anti-predatory capability of Mytilus coruscus.
Abstract
Ocean acidification (OA) and microplastics (MPs) pollution are major abiotic stressors in coastal ecosystems. Byssus is the core structural trait for Mytilus coruscus to defend against predators, and it is vulnerable to environmental stress, which in turn impairs its anti-predator function. However, the anti-predator response characteristics of M. coruscus byssus and the interaction mechanisms among OA, MPs and predation pressure from Charybdis japonica remain unclear under their combined stress. The study conducted acute exposure experiments, measuring five key byssus indicators: secretion frequency, quantity, diameter, volume and tensile strength, to explore the variation characteristics of the byssus-based anti-predator function of M. coruscus under multi-stressor conditions. Results showed that predators served as a key biological signal to trigger the anti-predator responses and significantly promoted byssus secretion; OA had the most prominent inhibitory effect on byssus function; MPs exposure only induced sublethal disturbances with no significant effects on core anti-predator indicators. Furthermore, the combined stress of ocean acidification and microplastics exhibited a synergistic trend, impairing the byssus-centered anti-predatory defense capacity of M. coruscus. This study provides experimental evidence for analyzing the variation patterns of mussel byssus under multiple stressors and suggests that future marine ecological risk assessments should focus on the interactions between biotic and abiotic stressors to more accurately predict the dynamic changes of coastal ecosystems.
Continue reading ‘Anti-predatory responses of Mytilus coruscus to the combined effects of ocean acidification and microplastics’Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters
Published 27 April 2026 Science ClosedTags: abundance, biogeochemistry, biological response, chemistry, field, molecular biology, morphology, North Pacific, phytoplankton
Coccolithophores, as calcifying phytoplankton, play a critical role in the global carbon cycle by producing calcium carbonate (CaCO3) in the ocean through their calcitic coccoliths. Here we examine Gephyrocapsa huxleyi (formerly Emiliania huxleyi) and related species abundance and genetic diversity along the West Coast of North America from samples taken on the 2021 NOAA West Coast Ocean Acidification (WCOA21) cruise, along the margin from British Columbia, Canada, to San Diego, California, USA. Significant carbonate chemistry gradients were observed across 17 transects, mostly in the onshore-offshore and north-to-south direction. Abundance and morphometrics of Gephyrocapsa spp. was evaluated using real-time PCR of mitochondrial cytochrome c oxidase subunit 3 ( cox3 ) gene and by microscopy. Variation in PIC concentrations, G. huxleyi and related species abundance, and coccosphere thickness were found to be associated with the gradients in carbonate chemistry and nutrient concentrations (phosphate, nitrate, nitrite, ammonium) across stations sampled during the cruise. We identified 5 unique amplicon sequence variants (ASVs) of Gephyrocapsa spp. cox3 that systematically varied in relative abundance across the California Current System. Southern California locations had greater diversity in cox3 sequences than northerly locations. These analyses represent baselines for evaluation of the impacts of future environmental changes in coastal waters along this productive upwelling regime.
Continue reading ‘Coccolithophore genetic diversity, morphology, and contribution to particulate inorganic carbon production in Western North American coastal waters’Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea
Published 20 April 2026 Science ClosedTags: biological response, community composition, field, morphology, North Pacific, otherprocess, physiology, phytoplankton
Highlights
- Miniaturization coincides with reduced species diversity and elevated chlorophyll a.
- Declining pH and reduced dissolved inorganic nitrogen are key drivers for smaller cells.
- Salinity, dissolved oxygen and cooling jointly reshape phytoplankton community structure.
Abstract
Phytoplankton are tiny drifting photosynthetic organisms that support marine food webs and help control the global carbon cycle. However, it remains unclear how ongoing environmental changes are altering their cell size, species diversity, and chlorophyll a concentration in coastal seas. In this study, we investigated changes in phytoplankton cell size, species diversity, and chlorophyll a concentration along the Yellow Sea coast of China from 2021 to 2024, based on fourteen research cruises conducted at twenty-six coastal stations. We then employed statistical models to explore how individual and combined environmental factors were related to those biological features. We observed a clear shift to predominance of smaller cells, a reduction in species diversity, and an increase in chlorophyll a concentration. pH and reduced dissolved inorganic nitrogen were strongly associated with smaller cell size, while higher salinity and higher oxygen were associated with lower diversity. Lower surface water temperature and higher dissolved oxygen were associated with higher chlorophyll a concentrations. Overall, our findings suggest that interacting changes in pH, nutrient supply, temperature, salinity, and oxygen are associated with a simpler phytoplankton community structure, smaller mean cell size, and higher biomass levels in the Yellow Sea coastal region, with potential consequences for local food webs and carbon cycling.
Continue reading ‘Nonlinear responses of phytoplankton size, diversity, and chlorophyll a to environmental forcing along the Yellow Sea’Effects of ocean acidification on the growth, shell integrity, and vulnerability to thermal stress and predation in Pacific oysters (Magallana gigas), and bay mussels (Mytilus spp.)
Published 17 April 2026 Science ClosedTags: biological response, laboratory, mesocosms, mollusks, morphology, mortality, multiple factors, North Pacific, predation, temperature
The ocean is absorbing approximately one third of the anthropogenic carbon dioxide (CO₂) emissions to the atmosphere. As a result, the pH of the ocean is declining steadily, a phenomenon known as ocean acidification (OA). This decline in pH and the associated reductions in calcium carbonate saturation states of the water can have widespread consequences for marine life, particularly to calcifying organisms. In this thesis, I aim to understand the effects of OA on the growth, shell integrity, and susceptibility to secondary stressors like heatwaves or predation, of two important shellfish species in British Columbia, Pacific oysters (Magallana gigas) and bay mussels (Mytilus spp.). I also aim to identify potential tipping points beyond which the biological responses of these shellfish to OA rapidly become more pronounced. I reared oysters and mussels in experimental mesocosms, in four pCO₂ treatments for eight-weeks to determine growth. I subsequently exposed these OA-acclimated animals to a secondary stressor by simulating heatwave conditions to assess thermal tolerance, and by introducing a predatory sea star to assess vulnerability to predation. Finally, shell condition was visually assessed, and shells were mechanically crushed to determine integrity. I found that OA decreased the growth of both oysters and mussels. No tipping point was observed for oyster growth, but reduced growth only emerged at the highest levels of OA in mussels. Sensitivity to atmospheric warming was not increased after exposure to acidic conditions for either species, although oysters had a considerably higher thermal tolerance than mussels. Mussel vulnerability to predation did increase, although the relationship was complex and depended on predator size. OA negatively affected shell strength, and possible tipping points emerged for this response metric in both species. Overall, OA was shown to negatively affect both species, but patterns of effect and the presence of potential tipping points depended on the species and the response metric. Understanding how these ecologically and commercially important bivalves are responding to OA is important for understanding how changing ocean chemistry will affect marine ecosystems, and to inform aquaculture managers on mitigation strategies.
Continue reading ‘Effects of ocean acidification on the growth, shell integrity, and vulnerability to thermal stress and predation in Pacific oysters (Magallana gigas), and bay mussels (Mytilus spp.)’Synergistic effects of ocean acidification and thermal stress on shell biomineralization and parasitism in the white clam Leukoma asperrima (Bivalvia: Veneridae)
Published 17 April 2026 Science ClosedTags: biological response, BRcommunity, crustaceans, field, mollusks, morphology, North Pacific
Ocean acidification (OA) and global warming are fundamentally altering the biomineralization processes of calcifying marine organisms. This study evaluates shell malformations and parasitism in the white clam Leukoma asperrima at Bique Beach, Panama, from December 2024 to November 2025. Environmental parameters (pH, temperature) were monitored monthly across two sampling stations (n=1100). Results indicate that 13.6% of the population exhibited shell malformations, and 6.3% were parasitized by the pea crab Pinnotheres pisum. A strong positive correlation was found between pH and healthy individuals (r=0.97, p<0.001), whereas critical pH levels (min. 5.75) were associated with increased shell fragility and dissolution. Despite thermal tolerance observed up to 35.7°C, the synergistic effect of OA and local stressors compromises the structural integrity of L. asperrima, threatening the sustainability of this socio-economic resource in the Tropical Eastern Pacific.
Continue reading ‘Synergistic effects of ocean acidification and thermal stress on shell biomineralization and parasitism in the white clam Leukoma asperrima (Bivalvia: Veneridae)’Future projections of compound events around the Main Hawaiian Islands
Published 15 April 2026 Science ClosedTags: modeling, North Pacific, regionalmodeling
The consequences of overlapping environmental stressors — referred to as compound events — may be more harmful to marine ecosystems than as individual stressors. Using recently conducted submesoscale-permitting future projections for the Main Hawaiian Islands, we present the first assessment of future compound events for Hawaiian waters. Our analysis focuses on surface and sub-surface heat-stress, ocean acidification, and low-oxygen events and is based on three different greenhouse gas emission scenarios. We show that a large fraction of ocean around Hawai‘i will be subject to compound events in the near future. However, the projected event characteristics such as duration and intensity vary substantially across the region suggesting that potential ecosystem impacts may differ over short distances. Our results reveal that these spatial differences are mainly driven by considerably different magnitudes of natural variability in ocean physics and chemistry across the domain driven by mesoscale processes, while anthropogenic trends exhibit only minor spatial differences. Our analysis demonstrates that small-scale tidal variability can significantly mitigate compound events in near-shore regions including some designated Marine Protected Areas. Overall, our findings highlight the need for high-resolution numerical models as well as for an extended observation network for robust future projections of local extreme events.
Continue reading ‘Future projections of compound events around the Main Hawaiian Islands’NOAA PMEL scientists provide analysis and expertise for 2026 California Coast and Ocean Assessment report
Published 14 April 2026 Web sites and blogs ClosedTags: chemistry, North Pacific
California’s 2026 Coast and Ocean Assessment was released in March by the California Ocean Protection Council (OPC), in partnership with the California Ocean Science Trust. This coast and ocean assessment is the result of the work of more than 120 scientific experts from academic institutions, state and federal agencies including NOAA, NGOs, and Tribes.
The report features the OA (ocean acidification) indicators analysis from NOAA PMEL Carbon Program scientists Adrienne Sutton and Simone Alin (starting on page 85). NOAA OAP (Ocean Acidification Program) funded coastal time-series moorings provided the foundation for the annual “trend” analysis and indicator development, led by Adrienne Sutton. Simone Alin, a long-time co-lead of WCOA cruises, served as West Coast OA subject matter expert.
NOAA teams were key to the development of the assessment report. OAP provided long-term coastal monitoring and data management, with significant partnership and synergy from the Global Ocean Monitoring and Observing (GOMO) Program-funded observation and data analysis efforts throughout the global ocean. Pacific Marine Environmental Laboratory (PMEL) supports lead researchers/primary investigators to engage with diverse coastal ocean interest holders, including fishery and water quality managers like the consortium of West Coast managers who requested the assessments in this report.
The 2026 report was initiated three years ago to codevelop ocean health indicators that could be used by the multiple California State agencies, non-governmental organizations, and tribal groups. These indicators provide the state with unified, comparable status and trend information, enabling better cross-organization collaboration.
Continue reading ‘NOAA PMEL scientists provide analysis and expertise for 2026 California Coast and Ocean Assessment report’Intracellular acid-base regulation mediates a trade-off between shell and somatic growth in a clam under ocean acidification
Published 9 April 2026 Science ClosedTags: biological response, growth, individualmodeling, laboratory, mesocosms, modeling, molecular biology, mollusks, North Pacific, physiology
Highlights
- Clams actively regulate intracellular pH against ocean acidification via CAc
- RNAi confirms CAc’s essential role in H+ efflux, measured by in vivo SIET.
- A CAc-sAC-NKA network forms a conserved regulatory pathway for acid-base balance.
- DEB model shows this pH defense sustains shell linear growth despite metabolic costs.
SUMMARY
Ocean acidification (OA) is predicted to threaten marine bivalves, casting them as passive victims of changing carbonate chemistry. Contributing to a revised understanding, we identified a conserved mechanism for acid-base regulation that supports intracellular resilience. Using the Manila clam Ruditapes philippinarum as a model, this study demonstrated that intracellular pH (pHi) homeostasis under elevated pCO2 was maintained through cytosolic carbonic anhydrase (CAc)-mediated H+ efflux. A causal link was established by combining in vivo scanning ion-selective electrode technique (SIET) with RNA interference (RNAi), where RpCAc knockdown suppressed H+ efflux and compromised pHi. A coordinated regulatory network involving CAc, soluble adenylyl cyclase (sAC), and Na+/K+-ATPase (NKA) was synergistically upregulated, suggesting an evolved adaptive pathway. Dynamic Energy Budget (DEB) modeling, calibrated with experimental data, revealed that this cellular compensation carries a high energetic cost, leading to a significant reallocation of resources: shell growth was maintained, but somatic growth was severely suppressed. These results elucidate a conserved cytoprotective mechanism that enables short-term tolerance of OA at a substantial somatic cost, redefining resilience to include energetic trade-offs.
Continue reading ‘Intracellular acid-base regulation mediates a trade-off between shell and somatic growth in a clam under ocean acidification’California’s 2026 Coast and Ocean Assessment
Published 1 April 2026 Science ClosedTags: North Pacific, policy, review
Key Messages
- California’s coastal ocean moderates our climate, holds potential solutions to climate change, and is directly impacted by a changing climate. California’s coast and ocean are also critical natural resources and economic assets, generating $51.3 billion in gross domestic product and supporting more than 500,000 jobs.
- The public and policymakers can get a broad, state-level understanding of the overall status of the coast and ocean through this synthesis of complex data into single statewide metrics and subsequent aggregation of those evaluations in this report. At the same time, some categories are better understood through downscaled or local evaluations.
- This coast and ocean assessment is the result of the work of more than 120 scientific experts from academic institutions, state and federal agencies, NGOs, and Tribes. The widespread support that it has garnered exemplifies the value of leveraging buy-in from a broad scientific community that stands poised to continue to support in delivering the best available science to policymakers.
- State-federal partnerships provide essential infrastructure: evaluations for 13 of the 19 categories leveraged federal data, and the evaluations of five categories were fully reliant on the specialized expertise and in-kind time of federal scientists.
- Distilling data into single metrics for each category enabled us to flexibly incorporate multiple data types, retain geographic information while providing statewide coverage, and present findings that are both accurate and easily understood. This approach also ensures forward compatibility to incorporate new data as they become available and repeat this
analysis in the future. - The 2014-2015 marine heatwave was a seminal event that disrupted California’s ocean ecosystems, including loss of species and ecosystem services, declining populations, and geographic range shifts. We can expect more warm years like this in the future.
- The state has a valuable role to play in strengthening the ocean monitoring and evaluation enterprise, such as expanding monitoring in Northern California, coordinating networks and standardizing methods, supporting innovative monitoring technologies to better track cryptic species, and identifying where strategic investments can fill data gaps.
See summary of ocean acidification findings.
Continue reading ‘California’s 2026 Coast and Ocean Assessment’pCO2-induced seawater acidification influencing cadmium toxicity on antioxidant defenses responses in juvenile Manila clam Ruditapes philippinarum
Published 30 March 2026 Science ClosedTags: biological response, laboratory, metals, mollusks, multiple factors, North Pacific, physiology
Highlights
- GSH system and SOD-CAT act as complementary lines of antioxidant defense
- SA alters Cd effects on antioxidants depending on metal concentration
- High SA overrides Cd effects on antioxidant defenses in Manila clams
- Combined high SA and Cd exposure overwhelms antioxidant capacity
- Candidate biomarkers for monitoring SA or Cd stress are proposed
Abstract
Ocean acidification is known to interact with heavy metals, impacting physiological processes of marine organisms. This study investigated antioxidant defenses of juvenile Manila clam Ruditapes philippinarum exposed to cadmium (Cd) across ambient-relevant to high concentrations, under pCO2-induced seawater acidification (SA) scenarios corresponding to IPCC ocean pH projections. Results revealed that clam’s antioxidant system, encompassing GSH defense system and SOD-CAT defense lines, collectively combated oxidative stress dependent on specific stressors and their stress levels. GSH system is vital for detoxification and maintaining redox balance, while SOD and CAT are essential for scavenging ROS. Cd exposure notably activated GSH redox cycle, and SA markedly inhibited the antioxidants associated with this cycle. SOD and CAT exhibited distinct regulatory pathways with asynchronous responses to SA and Cd co-exposure. SA conditions modulate Cd-induced antioxidant response dependent on metal concentrations. Antioxidant biomarkers responded more prominently to SA and Cd interactions than to individual exposure, particularly, high SA effects could override Cd effects on antioxidant responses. Although SA effects did not directly induce lipid peroxidation, elevated MDA levels under Cd exposure occurred only under SA conditions, indicating insufficient antioxidant defense against lipid peroxidation under excess co-exposure. GSH and SOD were more sensitive to SA exposure, whereas MDA and GST were sensitive to Cd exposure, suggesting their potential as biomarkers for assessing SA or Cd-induced oxidative stress, respectively. These findings provide insights into interplay between metal toxicity and ocean acidification on antioxidant defenses in bivalves, shedding light on their strategies to combat metal pollution amidst global ocean change.
Continue reading ‘pCO2-induced seawater acidification influencing cadmium toxicity on antioxidant defenses responses in juvenile Manila clam Ruditapes philippinarum’Tolerance to future elevated CO2 conditions in sablefish (Anoplopoma fimbria), a deep-water benthic dwelling fish species
Published 26 March 2026 Science ClosedTags: biological response, fish, laboratory, molecular biology, North Pacific, performance, physiology
Numerous studies have found that elevated CO2 levels in marine waters induced significant physiological and behavioral effects in fish. In an earlier study of coho salmon (Oncorhynchus kisutch), we observed that elevated CO2 exposure impaired signaling in the olfactory bulb, through a mechanism likely involving interference of gamma-aminobutyric acid (GABA) signaling. However, the effects of elevated CO2 may be species-specific, and there have been few studies addressing the effects of elevated CO2 on benthic fish. In the current study, we investigated the effects of elevated CO2 exposures on the deep-water benthic species, sablefish (Anoplopoma fimbria). Sablefish were exposed to three different levels of CO2 (700, 1600 and 2700 µatm) for two weeks, followed by behavioral, neurophysiological and gene expression analysis of the olfactory system. Analysis of behaviors mediated by food odors, including swimming activity and food strikes did not differ between fish maintained under elevated or control CO2 conditions. Similarly, electro-olfactogram recordings of odorant signaling did not differ among treatment and controls. mRNA expression patterns of olfactory bulb genes that were altered in coho salmon exposed to elevated CO2 levels, were similarly examined in sablefish. Sablefish mRNAs encoding genes involved in GABA-mediated olfactory bulb signaling were generally unaffected by high CO2, but aldh9a1, an enzyme involved in the synthesis of GABA, was elevated by high CO2. The results of our study contrast other studies demonstrating adverse effects of elevated CO2 in pelagic fish, but support differences among fish species to susceptibility to elevated CO2, potentially associated with life history traits.
Continue reading ‘Tolerance to future elevated CO2 conditions in sablefish (Anoplopoma fimbria), a deep-water benthic dwelling fish species’Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification
Published 26 March 2026 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, field, laboratory, mollusks, morphology, mortality, North Pacific, otherprocess, phytoplankton, reproduction, vents
Highlights
- Natural CO₂ seep systems showed reduced intertidal chiton abundance.
- Adult chitons showed resilience to acidification in field and lab experiments.
- Larval survival and recruitment were strongly impaired under acidified seawater.
- Population declines are linked to early life-stage vulnerability.
- Loss of chitons may reduce grazing and bulldozing, reshaping intertidal communities.
Abstract
Ocean acidification (OA) is a major threat to marine calcifiers; however, the sensitivity across taxa and life stages remains elusive. In this study, we combined field surveys of natural CO₂ seeps with laboratory exposure, transplantation, and larval settlement experiments to assess the effect of OA on chitons, a group of calcifying grazers and bulldozers that play critical roles in the structure of rocky intertidal ecosystems. Field surveys revealed approximately 98.6% reduction in chiton (Acanthopleura loochooana, Liolophura japonica, and Acanthochitona rubrolineata) abundance at acidified habitats (pH 7.6), despite greater microalgal food availability and no detectable increase in predator abundance. Laboratory CO₂-exposure experiments showed no direct effect of OA on adult A. loochooana survival, which is consistent with the presence of protective structural features in the valves that confer resistance to dissolution. Transplant experiments revealed no evidence of increased adult A. loochooana mortality in the acidified habitats (pH 7.6). In contrast, larvae showed pronounced sensitivity to OA, with acidified seawater (pH 7.6) reducing larval settlement by approximately 81.5% compared to control conditions (pH 8.1); early life stages were the most vulnerable. These findings suggest that OA-associated decline in chiton abundance is mainly mediated by impaired recruitment rather than by direct adult mortality, predation, or food limitation. Given the role of chitons as grazers and bulldozers, their loss could substantially change intertidal community dynamics by decreasing grazing pressure and disturbing algal and microbial assemblages. Our findings underscore the criticality of considering life-stage vulnerability and ecological function when evaluating the ecosystem-level consequences of OA.
Continue reading ‘Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification’Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea
Published 25 March 2026 Science ClosedTags: abundance, biological response, chemistry, community composition, crustaceans, field, nematodes, North Pacific, otherprocess, zooplankton
This study aimed to investigate the meiofauna community characteristics in coastal waters affected by ocean acidification. Therefore, the meiofauna communities in the coastal waters of Hupo in Uljin-gun, which showed a high ocean acidification trend in the integrated data on the coastal areas of South Korea for the previous ten years, were monitored over five years. During the study period, the mean abundance of total meiofauna communities expressed in population density was 614 individuals (Inds.)/10 cm2. The most dominant taxa were nematodes (65–70%) and harpacticoids (7–20%); these two taxa accounted for approximately 80% of the total meiofauna abundance. Station (St.) 5 and 10, which had the lowest seawater pH values, showed the lowest average abundance values for harpacticoids (average 46 Inds./10 cm2) and nauplius (average 4 Inds./10 cm2) among the major meiofaunal groups over the 5-year period. In addition, St. 5 indicated the lowest meiofaunal diversity index of 0.54. To examine the effect of ocean acidification on meiofauna communities at the species level, species of nematodes, the most dominant taxon, were analyzed. The results indicated that the number of nematode species at St. 10, one of the two stations with the lowest pH, was the lowest compared to those at other stations. Analysis of c-p values for nematode species showed that both species sensitive to environmental disturbance and species resistant to environmental pollution appeared at high rates. According to the feeding type of nematodes, epistrate feeders accounted for a remarkably high proportion at St. 10. This study provides various data on meiofauna community characteristics to understand the effects of ocean acidification on coastal ecosystems.
Continue reading ‘Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea’
