Posts Tagged 'North Pacific'

California’s 2026 Coast and Ocean Assessment

Published 1 April 2026 Science Leave a Comment
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Key Messages

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.

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pCO2-induced seawater acidification influencing cadmium toxicity on antioxidant defenses responses in juvenile Manila clam Ruditapes philippinarum

Published 30 March 2026 Science Leave a Comment
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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.

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Tolerance to future elevated CO2 conditions in sablefish (Anoplopoma fimbria), a deep-water benthic dwelling fish species

Published 26 March 2026 Science Leave a Comment
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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.

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Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification

Published 26 March 2026 Science Leave a Comment
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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.

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Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea

Published 25 March 2026 Science Leave a Comment
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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.

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Tolerance of egg and yolk-sac larval yellowfin sole (Limanda aspera) to ocean warming and acidification

Published 23 March 2026 Science Leave a Comment
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Yellowfin sole (Limanda aspera) support the largest flatfish fishery in the world and contribute substantially to the eastern Bering Sea (EBS) flatfish catch. The EBS has been warming and acidifying, trends that are expected to intensify into the future. Sustainable management of yellowfin sole requires an understanding of how yellowfin sole respond to environmental change, which can be assessed through controlled laboratory investigations. Across four independent trials, yellowfin sole embryos and larvae were incubated at one of six experimental treatments spanning three temperatures (9°C, 12°C, and 15°C) and two pCO2 target levels (low and high), and a range of organismal and physiological responses were measured. Embryonic daily mortality rates and metabolic rates increased with increasing temperature but were not affected by ocean acidification. At- hatch and at- yolk absorption, morphometric measurements (length, dry weight, myotome height, and yolk area) were temperature- sensitive, but the response differed across the four trials. There was a consistent increase in length- based growth and yolk absorption rates with increasing temperature across trials. All morphometric and rate- based measurements were not affected by ocean acidification. Yellowfin sole metabolic enzyme activities were measured at- yolk absorption. Lactate dehydrogenase (anaerobic metabolism) and β- hydroxyacyl CoA dehydrogenase (fatty acid metabolism) both increased with increasing temperature, indicating elevated energy demand. Citrate synthase (aerobic metabolism) declined with increasing pCO2 levels, indicating potential metabolic suppression. Overall, embryonic and larval yellowfin sole demonstrated relatively high tolerance to ocean warming and acidification. We hypothesize the variation in temperature responses across the trials may be driven by maternal effects, which could support tolerance to future ocean conditions.

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Influence of ocean warming and acidification on juveniles of the true giant clam, Tridacna gigas, and its microalgal symbionts

Published 19 March 2026 Science Closed
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Uncontrolled carbon dioxide emissions from human activities contribute to ocean warming and acidification. These alterations in ocean chemistry threaten marine organisms, such as the true giant clam, Tridacna gigas, which is already imperiled due to overharvesting and habitat destruction. To gain an understanding of the physiological and molecular responses of T. gigas and its symbiotic dinoflagellates to ocean warming and acidification, we subjected juvenile individuals to different treatments simulating predicted seawater pH (7.6 and 8.0) and temperature (28°C, 30°C, 32°C and 34°C) levels for the next century. Juvenile giant clams were able to tolerate sustained exposure to temperatures of up to 32°C and pH as low as 7.6, while exposure to higher temperature (34°C), regardless of pH level, resulted in total mortality after a week. However, symbiosis was compromised even in the sublethal treatments, as indicated by the decrease in Symbiodiniaceae density and changes in symbiont gene expression. Symbionts significantly upregulated genes involved in splicing, translation, fatty acid metabolism, and DNA repair, which may constitute an adaptive response, while downregulating genes involved in photosynthesis and transmembrane transport, suggests impaired transfer of photosynthates to the host. These findings demonstrate the vulnerability of the juvenile T. gigas holobiont to heat stress, highlighting the critical importance of continued conservation and management alongside efforts to mitigate global changes in ocean conditions to safeguard this iconic marine bivalve.

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Differential impacts of ocean acidification and alkalinization on shell microstructure and molecular responses in Mytilus edulis

Published 18 March 2026 Science Closed
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Anthropogenic CO2 emissions are intensifying ocean acidification (OA), disrupting carbonate chemistry and threatening marine calcifiers such as mussels. Ocean alkalinity enhancement (OAE) has been proposed as a marine carbon dioxide removal (mCDR) strategy that can also mitigate OA, but its ecological safety for aquaculture species remains poorly understood. Here, we examined the short-term (21 days) responses of the blue mussel Mytilus edulis to OA (pH 7.3) and NaOH-based OAE (pH 9.0) using integrated shell microstructure analysis and transcriptomics. The results showed that while survival rates were unaffected, OA caused marked shell degradation and activated stress-related molecular pathways, whereas OAE enhanced shell integrity and stimulated growth-associated processes. Across treatments, a core set of biomineralization-related genes (e.g., VWA7, CA14, ALPL) exhibited expression shifts, suggesting central roles in carbonate homeostasis. In contrast, differential regulations of genes such as CA10 and VWDE revealed pH-specific responses. Notably, OAE induced minimal disruption of biomineralization and alleviated OA-related damage, highlighting its potential to support mussel aquaculture under future ocean conditions. While model simulations and plankton-scale experiments suggest global benefits of OAE, this study provides direct organism-level experimental evidence linking shell ultrastructure and transcriptomic responses under OA and OAE conditions. These findings offer mechanistic insights into mussel resilience and provide a critical empirical basis for evaluating the ecological safety of OAE as both a carbon sequestration strategy and a tool for sustainable aquaculture.

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Groundwater-derived carbon promotes hypoxia and acidification in a large tropical estuary

Published 18 March 2026 Science Closed
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Abstract

Submarine groundwater discharge (SGD) derived nutrient inputs have been extensively documented. However, SGD-derived carbon fluxes remain largely unconstrained, representing a critical gap in most coastal carbon budgets. Here, we resolve SGD and dissolved carbon budgets in the Pearl River Estuary (PRE), the largest estuary in Southern China surrounded by the world’s largest urban conglomerate. Broadly-defined SGD contributes 89%–96% of the dissolved inorganic carbon (DIC) pool (2–4 times riverine inputs) and 20%–70% of the dissolved organic carbon (DOC) fluxes of the PRE. SGD transports DIC exceeding total alkalinity (TAlk) by 2.7–7 times, potentially driving pH decline and acidification of nearshore waters. Groundwater pCO2 values are 10–36 times higher than estuarine waters. SGD-derived DOC mineralization can decrease estuary water pH by 0.04–0.16 units and increase CO2 by 6.0–90.0 μmol L−1, affecting local coral populations and benthic organisms. SGD also reduces seawater dissolved oxygen (DO) by 12–150 μmol L−1 and fuels the development of hypoxic zones. Overall, SGD regionally intensifies seawater hypoxia and acidification, creating challenging conditions for coral reef survival in an already stressed ecosystem. Our findings demonstrate that SGD should be integrated into carbon budgets and ecological assessments of the land-ocean continuum.

Plain Language Summary

Submarine groundwater discharge can transport large amounts of dissolved carbon into the coastal ocean, but it is often overlooked due to challenges in quantification. Here, we investigate the contribution of groundwater to the dissolved carbon pool in a large tropical estuary using radium isotopes and carbon data. We found that groundwater is a significant source of estuarine dissolved carbon and has the potential to acidify seawater oxygen-depleted waters. These findings emphasize the importance of considering groundwater when evaluating carbon budgets and the ecological health of coastal ecosystems.

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The economic impact of climate change on coral reef in the Main Hawaiian Islands

Published 18 March 2026 Science Closed
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Coral reefs are highly diverse and productive ecosystems that provide a wide range of ecosystem services, including recreation, coastal protection, and marine biodiversity. Climate change impacts, including ocean warming and acidification, pose a significant threat to coral reefs and the ecosystem services they provide. The variability of these impacts underlines the need to develop more spatially explicit tools in coastal ecosystem management that integrate and assess potential ecological and socio-economic outcomes. To address this, a spatially explicit predictive ecological model is applied to project changes in coral reef cover, using downscaled data from Shared Socioeconomic Pathway (SSP) climate scenarios. Based on these projections, welfare impacts of changes in recreational value are estimated across different populations and landscapes. Cumulative welfare losses for Hawaiʻi residents range from $1.5 to $3.3 billion in 2024$ by 2100. Counterintuitively, cumulative welfare losses are higher under optimistic emissions scenarios, where coral reef degradation is less severe than higher emission scenarios, because more people will experience smaller ecological losses. The approach incorporates site-specific characteristics, income distribution, and projected regional population growth to connect ecological change with welfare outcomes. EJScreen is used to assess variation in welfare impacts, identifying disadvantaged communities based on demographic and environmental indicators such as poverty, minority status, and exposure to environmental risks. These findings can inform policy and resource allocation by supporting ecosystem management strategies that account for both ecological dynamics and community-level socio-economic conditions.

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Seasonal variations and key controls on seawater aragonite saturation state in the Northern Yellow Sea, China

Published 17 March 2026 Science Closed
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Based on four field surveys conducted from August 2022 to May 2023, seasonal distribution and dynamics of the seawater aragonite saturation state (Ωarag) were investigated in the northern coastal zone of the Northern Yellow Sea, an important fishery region, to assess impacts of ocean acidification especially in river-dominated coastal systems. Results revealed seawater Ωarag had significant spatiotemporal variability with surface values ranging from 1.42 to 3.76 in summer, 1.22 to 2.34 in autumn, 1.71 to 2.48 in winter, and 2.03 to 3.56 in spring. Subsurface seawater Ωarag was generally lower than surface values, while seawater with Ωarag < 1.5—a critical threshold for severe biological stress—were predominantly found in the nearshore areas and in the southwestern offshore bottom waters. Persistent seasonal acidification was observed across the study area. While seawater temperature played an important role in seasonal Ωarag variation, its effect was masked in the nearshore zones by river-diluted water inputs, especially in summer, and in offshore bottom waters by community respiration during summer and autumn. These mechanistic insights clarify key drivers of coastal acidification and provide a scientific basis for developing targeted strategies to detect acidification trends and ecosystem responses in anthropogenically impacted coastal regions.

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Multi-level holobiont dysregulation increases the ecological risk of combined ocean acidification and benzo[a]pyrene pollution to the reef-building coral Porites lutea

Published 17 March 2026 Science Closed
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Highlights

  • Combined ocean acidification and BaP induce holobiont dysregulation, evidencing by a decoupled Symbiodiniaceae proliferation and a collapse of the archaeal Nanoarchaeota-Halobacterota symbiosis.
  • The coral host shifts its defense strategy from antioxidant capacity to cellular homeostasis, while the bacterial community increases functional redundancy, revealing a costly acclimation mechanism.
  • The multi-level dysregulation demonstrates an underestimated ecological risk, highlighting that current single-stressor risk assessments are inadequate for protecting corals under complex pollution scenarios.

Abstract

Reef-building corals are increasingly threatened by the combined effects of global climate change and localized organic pollutants. However, the holistic impacts of co-exposure to ocean acidification (OA) and benzo[a]pyrene (BaP) on coral holobionts remain poorly understood. Here, we investigated the multi-level responses of the reef-building coral Porites lutea to short-term (7-day) exposure to OA (pH 7.80), BaP (10 µg/L), and their combination, by integrating physiological measurements with microbiome profiling (ITS2 and 16S rRNA). We found that combined stress was associated with a dysregulated response in Symbiodiniaceae, characterized by a significant increase in cell density without a parallel rise in chlorophyll content, suggesting a possible compensatory but inefficient proliferation response. Despite this, the dominant symbiont Cladocopium C15 remained stable. The bacterial diversity increased (e.g., enrichment of Ruegeria and Acanthopleuribacter, decline of Endozoicomonas), which may suggest enhanced functional redundancy, while the archaeal community was significantly restructured, most notably a marked decline of the putative obligate Nanoarchaeota–Halobacterota symbiosis. At the host level, combined stress was associated with suppressed antioxidant enzyme activities (SOD/POD) but upregulated genes related to protein folding (Hsp90) and calcium homeostasis (NCX1, VAMP4). These findings suggest a complex holobiont reconfiguration under combined stress, involving a stabilized core symbiont, altered microbiomes, and a shifted host defense strategy. Our study suggests that the ecological risk of combined OA and organic pollution may not be extrapolated from single-stressor responses, indicating the need to incorporate multi-stressor frameworks into coral reef risk assessments.

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Marine heatwaves, ocean warming and acidification reshape reef fish gut microbiomes

Published 16 March 2026 Science Closed
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Extreme climatic events and gradual climate change are increasingly anticipated to interact and reshape ecological communities. However, the combined effects of ocean warming, acidification and marine heatwaves on host‐associated microbial communities and their potential role in host adaptation remain poorly understood. Here, we assessed shifts in gut microbiome communities and their associations with physiological performance in one tropical ( Abudefduf vaigiensis ) and one subtropical ( Microcanthus strigatus ) reef fish species, across three temperate reefs representing natural analogues of climate change: a present‐day baseline (‘cool reef’), a chronically warmed reef (‘warm reef’) and a reef experiencing combined warming and extreme acidification (‘extreme reef’). We also examined gut microbiome changes in A. vaigiensis before and during a severe marine heatwave. A. vaigiensis had lower gut microbiome evenness and diversity at the warm (43% and 44% decrease, respectively) and extreme (38% and 31% decrease) reefs compared to the cool reef, and its gut microbiome community shifted at the extreme reef with a 122% increase in abundance of opportunistic bacteria Vibrio. A. vaigiensis also had lower gut microbiome richness at the warm (42% decrease) and extreme (52% decrease) reefs during the heatwave compared to pre‐heatwave individuals. In contrast, M. strigatus showed higher microbiome evenness (99% increase) and diversity (98% increase) at the warm reef compared to the cool reef; however, these gains were lost at the extreme reef, with microbiome diversity and evenness returning to cool reef levels. Microbiome changes in both species were generally not associated with their physiological performance (protein content, oxidative stress, antioxidant capacity or body condition). Our findings suggest that marine heatwaves, ocean warming and acidification can reshape reef fish gut microbiomes, driving simplification in Abudefduf vaigiensis but distinct restructuring in Microcanthus strigatus . We conclude that climate‐driven microbiome reshuffling may alter host–microbiome relationships and functions in fishes in a future ocean.

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Stony coral symbioses show variable responses to future ocean conditions

Published 16 March 2026 Science Closed
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Coral reefs support over a quarter of marine species and nearly a billion people worldwide but are also among the ecosystems most threatened by anthropogenic impacts. There is long-standing debate about whether coral symbioses will be disrupted or respond adaptively under future ocean conditions. Using a factorial 2.5-year future-ocean mesocosm experiment across eight coral species representing the major coral lineages, we tracked symbiont community shifts within replicate fragments from the same individual coral. Some corals exhibited stochastic divergence consistent with dysbiosis, whereas others showed deterministic, thermally adaptive shifts. Heat stress generally reduced symbiont diversity and promoted predictable restructuring, supporting deterministic processes under moderate stress but stochastic dysbiosis under extreme conditions. We propose that adaptive and stochastic responses represent endpoints along a continuum of host-orchestrated symbiont sorting. This study bridges coral reef ecology with broader host–microbiome theory, offering an integrated perspective on how symbiotic systems may respond to environmental change.

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Environmental controls and nonlinear responses of the diatom-dinoflagellate ratio in Jiaozhou Bay

Published 13 March 2026 Science Closed
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Highlights

  • Dia/dino abundance, biomass, and diversity ratios exhibited similar temporal patterns;
  • All ratios showed considerable heterogeneity without a consistent distributional trend;
  • Dia/dino ratios responded distinctly to DO, nutrients, and their interactions;
  • Shifting seawater properties exerted large influence on diatom-dinoflagellate dynamics.

Abstract

Diatoms and dinoflagellates are widely recognized as key indicators of marine ecosystem status and play central roles in ecosystem functioning and biogeochemical cycling. Yet how these two major phytoplankton groups adjust to changing coastal environments, and whether such adjustments occur coherently in different ecological dimensions, remains poorly constrained. Hence, we studied the temporal and spatial dynamics of diatom-dinoflagellate (dia/dino) ratios in Jiaozhou Bay during 2021 and 2024, integrating abundance-, carbon biomass-, diversity-, and richness-based metrics. Although abundance, biomass, and diversity ratios exhibited broadly similar temporal trajectories, the richness ratio displayed an opposite pattern, highlighting a decoupling between numerical dominance and species composition. Spatially, all four ratios exhibited significant heterogeneity, without a consistent nearshore-offshore gradient, reflecting complex local regulation. Correlation analyses revealed distinct controls on dia/dino ratios. The abundance ratio increased under conditions of elevated dissolved inorganic nitrogen (DIN) and reduced dissolved oxygen (DO), whereas the diversity ratio was associated with high DIN and low dissolved inorganic phosphorus (DIP). In contrast, the carbon biomass ratio was primarily linked to reduced DO and lower pH, while the richness ratio responded most strongly to the combined influence of low DO and elevated DIP. These contrasting responses indicated that dia/dino ratios captured different facets of phytoplankton community reorganization rather than reflecting a single environmental driver. Overall, our results suggested that the balance between diatoms and dinoflagellates in Jiaozhou Bay emerged from the coupled and nonlinear interactions among nutrient availability and oxygen dynamics. This study highlighted the dia/dino balance as an integrative indicator of coastal ecosystem condition and implied the importance of considering multiple ecological dimensions when assessing phytoplankton responses to ongoing eutrophication and environmental change.

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Two decades of skeletal density decline in Pocillopora spp. corals in the Mexican Pacific Ocean: insight into a tropical eastern Pacific acidification scenario?

Published 10 March 2026 Science Closed
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Corals demonstrate vulnerability to environmental changes, exhibiting the capacity to substantially modify coral calcification. In this study, we estimated declines in the density of Pocillopora coral species in the Mexican Pacific. The samples utilized in this study encompass both recently collected corals and those stored in Mexican repositories collected in the northeastern and southern Mexican Pacific regions. Density estimates indicate a 28.6% decline in coral density over the past 23 years (−0.0227 g CaCO3 cm-3 y-1) in the southern Mexican Pacific, while at the entrance to the Gulf of California, density has decreased by 15.4% over the past 20 years (−0.017 g CaCO3 cm-3 y-1). A comprehensive evaluation of environmental data reveals that the observed decline in Pocillopora skeletal density in Mexican Pacific reefs is concomitant with decreases in Ωar and pH, and an increase in ocean temperature on a substantial regional scale. When considered in conjunction with the previously documented reductions in coral growth of Pocillopora spp. skeletons in the eastern Tropical Pacific, our findings indicate a potential decline in CaCO3 production within the region’s reef systems. The results of this study underscore the significance of generating long-term series of coral growth parameters for relevant reef-building species and the carbonate system in key and representative coastal areas, particularly those that are already challenging for coral survival and reef maintenance.

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Sex-specific physiological-biochemical and multi-omics responses of Sargassum thunbergii to ocean acidification

Published 10 March 2026 Science Closed
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Highlights

  • A multi-omics study on sexual dimorphism of macroalgae under OA.
  • Male S. thunbergii adopted a growth-oriented strategy under OA.
  • Female S. thunbergii showed a defense-oriented survival strategy under OA.
  • Fundamental trade-off between growth and defense underlay sex-specific responses.

Abstract

Ocean acidification (OA), driven by increasing atmospheric CO2 concentrations, poses significant threats to the ecologically important intertidal macroalgae. Multiple previous studies have indicated species-specific responses to OA, the sex-specific physiological-biochemical responses and underlying molecular mechanisms in dioecious macroalgae remain poorly understood. In this study, we investigated the responses of male and female Sargassum thunbergii to acidification treatment (2000 ppm CO2) by integrating physiological-biochemical, transcriptomic, and metabolomic analyses. Both sexes maintained photosynthetic performance, with increased maximum relative electron transport rates (rETRmax). Males exhibited a growth-oriented strategy, characterized by higher accumulation of storage compounds like triglycerides and up-regulation of genes related to the photosynthesis and biosynthesis pathways. In contrast, females displayed a survival-oriented strategy, with reduced carbon storage, increased soluble protein and phenolic substance contents, and up-regulation of genes related to defense- and stress-response pathways. These findings provided physiological-biochemical and molecular evidence for a growth and defense trade-off between male and female S. thunbergii under acidification treatment. Our study provided the mechanistic insights into the sex-specific responses of marine macroalgae to global climate change and highlighted the importance of accounting for sexual dimorphism in predicting the ecological resilience of intertidal macroalgae populations under future ocean conditions.

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Ocean acidification and changes in biological production in the western subarctic region of the North Pacific over the quarter century, 1999–2023

Published 2 March 2026 Science Closed
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Changes in the physical and biogeochemical conditions of the ocean over time can affect marine ecosystems. In this study, we use biogeochemical observational data for the past 25 years (1999–2023) to investigate ocean acidification and changes in biological production at site K2 (47˚ N, 160˚ E) in the western subarctic region of the North Pacific Ocean. During this period, satellite-derived sea surface temperatures increased at a rate of 0.056 °C yr–1, while the surface mixed-layer salinity decreased by 0.004 yr−1. As a result of the oceanic uptake of anthropogenic CO2 from the atmosphere, the deseasonalized annual mean surface mixed-layer pH and saturation states of calcium carbonate minerals of calcite and aragonite decreased at rates of 0.0013 ± 0.0004, 0.007 ± 0.003, and 0.004 ± 0.002 yr−1, respectively. These rates are consistent with those calculated for winter. Under these acidification conditions, no significant trends were observed in either the annual mean or winter concentrations of nutrients (phosphate, nitrate, and silicate), or in total alkalinity in the surface mixed layer. However, the decadal trends in nutrient concentrations show a significant increase in May and decrease in July. Net community production (NCP), which is an index of biological production, was estimated from differences in nutrient concentrations between winter and May or July. This analysis revealed significant decreasing trends in NCP from winter to May, followed by increasing trends from winter to July. The stoichiometric molar ratio of Si associated with the July NCP increase (P:N:Si = 1:15:55) is higher than the previously reported ratio (1:16:40). A significant decreasing trend in satellite-derived photosynthetically active radiation (PAR) was observed in May (0.20 ± 0.08 yr−1), which may be linked to reduced biological production during that month. This decrease may be offset by increased production in summer that is likely due to a shift in the timing of the diatom bloom. These findings highlight the effects of long-term changes of potential drivers of both atmospheric and deep oceanic origin on oceanic biological production.

Continue reading ‘Ocean acidification and changes in biological production in the western subarctic region of the North Pacific over the quarter century, 1999–2023’

Pathways to adaptation for shellfish aquaculture on the U.S. West Coast

Published 2 March 2026 Science Closed
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Understanding how shellfish growers adapt to environmental and socioeconomic stressors is critical for food security, especially with growing impacts from climate change. However, we know relatively little about the supporting factors that lead shellfish growers who experience stressors to make adaptive choices. Through interviews conducted with US West Coast (California and Oregon) shellfish farm owners and managers (growers), we document environmental and socioeconomic stressors that growers experience and investigate whether they can adapt, react, or cope (ARC response) to these stressors. We further identify growers’ strategies for adaptation and link these strategies to theoretical adaptive capacity domains (ie, assets, flexibility, social organization, learning, agency, and governance) using qualitative comparative analysis (QCA). We found regulatory stressors were the most impactful to growers overall. These stressors caused financial burdens and time delays to operations for growers in both states. Ocean acidification and/or hypoxia (OAH) was the most frequently reported environmental stressor. Ocean acidification and/or hypoxia impacts include increased mortality and shellfish die-off events. Out of 125 responses to stressors, growers were able to adapt in just over half of stressor responses (54.4%). Agency, flexibility, learning, and social organization supported adaptation most frequently, while governance was employed the least. Growers responded with cope responses (35.2%) more frequently than react responses (10.4%). Growers combined adaptive capacity domains in various ways to adapt. For example, the adaptive capacity domain of agency was frequently employed, but almost always in combination with other adaptive capacity domains (eg, assets, governance, flexibility, and learning). This study demonstrates that US West Coast shellfish growers combine adaptive capacity domains in creative ways to form adaptive pathways and illuminates pathways to better support adaptive capacity in shellfish aquaculture.

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Range-extending fish become competitive dominants under ocean warming but not heatwaves or acidification

Published 27 February 2026 Science Closed
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Ocean warming is driving species range extensions into cooler regions. The direct physiological influence of warming on species performance can accelerate such extensions into novel ecosystems; however, indirect effects of invader–resident interactions in cooler regions may counter these positive effects. Here, we examined the foraging performance and densities of competing warm‐water and cool‐water fishes across a latitudinal temperature gradient spanning 1500 km from tropical to temperate reefs subjected to rapid ocean warming in the southern hemisphere, and across natural analogs of temperate, tropicalized, and acidified reef localities in the northern hemisphere, and during a severe marine heatwave at a temperate reef. While current levels of ocean warming have allowed the warm‐water fish to extend their ranges into temperate ecosystems at both hemispheres, their foraging performance was reduced at both the cold‐ and warm‐temperate reefs compared to the (sub)tropical reefs. However, at the (warmer) tropicalized reef, the warm‐water fish had higher foraging performance and maintained densities, even under extreme pH reduction, compared to the temperate reef. In contrast, the cool‐water species struggled at the warmer tropicalized and extreme reefs with reduced foraging performance and lower population densities compared to the temperate reef. Contrastingly, the severe heatwave experienced at the temperate reef did not alter the foraging behaviors of either species. We suggest that ocean warming boosts the foraging performance of the range‐extending warm‐water fish and impairs that of their cool‐water competitor at temperate reefs, irrespective of acidification and heatwaves, leading to a shift in dominance hierarchies on temperate reefs. We conclude that warming‐driven increases in foraging performance of the warm‐water species may alleviate foraging limitations and enhance its establishment at its leading range edges under climate change, to the detriment of its cool‐water competitors.

Continue reading ‘Range-extending fish become competitive dominants under ocean warming but not heatwaves or acidification’

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