Posts Tagged 'physiology'

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Climate change and fish reproduction: a meta-analysis of global laboratory-based experimental evidence across species and ecosystems

Published 22 October 2026 Science Closed
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Climate change is altering fish reproduction by disrupting spawning cycles, reducing egg viability, and altering reproductive behaviours essential for population sustainability, to our knowledge, this is the first synthesis to integrate laboratory-based evidence for temperature, hypoxia, ocean acidification, and their combined exposure across reproductive performance, physiological, developmental, and molecular endpoints, and across freshwater, brackish, and marine habitats. Following PICOS and PRISMA criteria, we synthesised 779 effect sizes (740 retained after outlier exclusion) from 80 controlled laboratory studies (38,500 observations; 54 species; 28 countries). A three-level multilevel model accounting for non-independence among effect sizes drawn from the same study showed a significant overall negative effect of climate stressors on fish reproduction (Hedges’ g = −0.421, 95% CI: −0.631 to −0.210, p < 0.001; I² = 94.9%, decomposed into 36.3% between-study and 58.6% within-study heterogeneity). Hypoxia was the dominant and statistically distinct driver (g = −1.145, 95% CI: −1.648 to −0.643, p < 0.0001), most severely impairing gonadal development and sperm quality. The overall warming effect did not reach significance once non-independence was accounted for (g = −0.221, 95% CI: −0.448–0.006, p = 0.057), an uncertain negative trend rather than confirmed impairment, although tropical freshwater species showed significant subgroup-specific declines in reproductive physiology and genetic parameters. Ocean acidification showed a small positive effect (g = 0.199, 95% CI: 0.056–0.343, p = 0.006) that was not robust under robust variance estimation (p = 0.133) and is interpreted with caution. Combined multi-stressor exposure showed a negative trend (g = −0.901, 95% CI: −1.992–0.190, p = 0.106) that did not reach significance, based on only three studies. A formal omnibus test confirmed that stressor categories differ significantly in their effects (QM = 18.61,df = 3, p = 0.0003), with hypoxia statistically distinct from both temperature and ocean acidification. Leave-one-out and cumulative meta-analyses confirmed the robustness of the overall finding.

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Carry-over effects of low salinity during embryonic development modulate larval responses to combined salinity-pH stress in an estuarine crab

Published 21 October 2026 Science Closed
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Early life stages of estuarine organisms are exposed to concurrent environmental stressors, but the extent to which embryonic conditions shape larval responses to multiple stressors remains largely unexplored. We evaluated whether salinity during embryogenesis modulates larval responses to combined salinity and pH stress in the estuarine crab Neohelice granulata. Embryos were reared at two salinities (15 and 33), and larvae were subsequently exposed to combinations of pH (8 and 6.9) and salinity (15 and 33). Salinity during embryogenesis did not affect development duration or eye size, but altered other embryonic traits: embryos at low salinity showed higher heart rate, larger egg volume, and increased egg mass at late stages. In larvae, salinity was the main driver, strongly affecting development, survival, and metabolic performance, whereas pH alone had limited or stage-dependent effects. However, their interaction intensified responses, particularly increasing mortality. Low salinity during the larval stage increased intermolt duration and mortality, effects further exacerbated under low pH. The strongest negative responses occurred under combined low salinity and low pH, with delayed development, higher mortality, and reduced oxygen consumption rates. Although low salinity during embryogenesis influenced larval performance under low pH, larval responses were primarily driven by current environmental conditions. These results highlight that co-occurring stressors can outweigh early-life conditioning. Given that low salinity events and acidification frequently co-occur in estuarine systems, their interaction is critical for understanding organismal responses.

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Present but overlooked: biogenic acidification in aquaculture waters and its implication for mollusc mariculture

Published 21 October 2026 Science Closed
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Mollusc mariculture, a critical global source of high-quality protein, is increasingly threatened by seawater acidification. While climate-driven ocean acidification (OA) has been widely studied, intensive aquaculture systems face an additional, locally exacerbated phenomenon: biogenic acidification. In this review, we comprehensively compare biogenic acidification with OA and other seawater acidification types, highlighting its occurrence across various aquaculture systems and its capacity to induce conditions more corrosive than end-of-century OA projections under densely stocked settings. Driven by the respiration and calcification of high-density mollusc populations, biogenic acidification leads to distinct alterations in the carbonate chemistry of mollusc farming systems—notably a reduction in total alkalinity (TA)—that are mechanistically different from OA. We further discuss how biogenic acidification imposes stronger physiological stresses on molluscs, impairing calcification, growth, and energy allocation, and how it synergistically interacts with climate change. Finally, we propose practical mitigation strategies, including TA supplementation and integrated multi-trophic aquaculture, to enhance the resilience and sustainability of mollusc farming. This review underscores the necessity to address biogenic acidification as a distinct and ongoing challenge in global mariculture.

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The impact of the CO2 fertilization effect in seagrasses: a comparative perspective with terrestrial plants

Published 20 October 2026 Science Closed
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This article comments on:

Pazzaglia J, Marín-Guirao L, Ambrosino L, Pes K, Costa M, Barrote I, Silva J, Procaccini G. 2025. Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings. Journal of Experimental Botany 76, 6958–6973. https://doi.org/10.1093/jxb/eraf276.

Seagrass meadows are among the world’s most ecologically and economically important marine ecosystems. Although they cover only 0.1% of the seafloor, they sequester carbon at rates rivalling tropical rainforests, protect coastlines, and support marine biodiversity (do Amaral Camara Lima et al., 2023). Yet they are declining globally due to anthropogenic pressures including coastal development, pollution, and climate change (Waycott et al., 2009; Dunic et al., 2021). While ocean acidification and ocean warming are pervasive stressors under accelerating global change, Pazzaglia et al. (2025) have demonstrated that elevated dissolved CO2 may enhance seagrass resilience by increasing thermal tolerance in Posidonia oceanica seedlings through the CO2 fertilization effect.

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Long-term coral responses to high CO2: insights from volcanic vents and semi-enclosed bays

Published 20 October 2026 Science Closed
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This chapter provides a comprehensive review of natural laboratories used to study the effects of ocean acidification (OA) on coral reefs, emphasizing volcanic CO2 vents and semi-enclosed bays. It examines key environmental conditions at these study sites and their implications for coral physiology, biodiversity, and reef resilience. Two prominent natural analogues are highlighted: the Shikine Island warm-temperate shallow CO2 vent system in Japan and the semi-enclosed lagoon of Bouraké in New Caledonia.

Shikine Island represents a unique high-latitude coral environment influenced by the Kuroshio Current. The island’s CO2 vents provide a natural setting to investigate the community level effects of ocean acidification and how elevated CO2 levels interact with ocean warming and influence coral tropicalization. Findings suggest that while some corals persist at high CO2 levels, biodiversity declines significantly, with sensitive species unable to establish stable populations. Corals growing in these conditions exhibit reduced calcification, and the community structure shifts toward simpler, lower-complexity ecosystems dominated by turf algae. These results indicate that ocean acidification may act as a constraint on the poleward expansion of tropical corals, counteracting warming-induced range shifts.

In contrast, the semi-enclosed lagoon of Bouraké experiences extreme environmental fluctuations in pH, oxygen, and temperature, providing a window into the multifactorial stressors coral reefs may face in the future. Despite prolonged exposure to acidified, hypoxic, and thermally variable waters, corals in Bouraké demonstrate remarkable resilience. The system harbors diverse coral assemblages, with species exhibiting metabolic adjustments, increased heterotrophy, and shifts in symbiotic algae communities. This site suggests that coral ecosystems can develop physiological adaptations that enhance their survival in extreme conditions, offering valuable insights into the potential for long-term acclimatization.

By comparing these two contrasting natural analogues, this chapter highlights the complex interplay between acidification, warming, and other environmental stressors on coral reefs. While both sites provide critical insights into the future of coral ecosystems, they also underscore the urgent need for continued research and conservation efforts to mitigate the effects of climate change on marine biodiversity.

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Genomic responses of fishes to ocean acidification: insights from volcanic CO2 seeps

Published 20 October 2026 Science Closed
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Extreme and marginal reef environments provide valuable opportunities to examine the effects of altered seawater parameters that resemble predicted end-of-century ocean conditions under climate change. Volcanic CO2 seeps, in particular, have proven useful for studying the effects of ocean acidification (OA) in natural settings. In this chapter, we present a case study from a volcanic CO2 seep at Shikine Island, Japan, investigating the genomic response of the neon damselfish (Pomacentrus coelestis) to OA conditions. We examined transcriptomic profiles from brain and gill tissues collected across two seasons (July and November) and compared them to samples from multiple control sites to assess consistent patterns of gene expression under elevated CO2. Our results found that genes involved in blood oxygen regulation, immune response, and circadian rhythm were differentially expressed across seasons and tissues, suggesting their key role in the response to OA in P. coelestis. We also detected seasonal shifts in gene expression patterns, highlighting the complexity of the physiological responses to OA in natural environments. Many of the differentially expressed genes align with findings from previous laboratory and field studies, reinforcing the value of volcanic CO2 seeps for OA research. Finally, we discuss the challenges of working in natural seep environments, including variability across control sites and seasons, and emphasize the future potential of CO2 seeps for advancing our understanding of fish responses to ocean acidification.

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Bioturbation under stress: linking coastal environmental change to the physiology and function of marine bioturbators

Published 13 October 2026 Science Closed
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Coastal benthic habitats are increasingly exposed to human-driven environmental changes, resulting in multiple co-occurring stressors. Bioturbators, which provide vital ecosystem services, are particularly vulnerable due to their limited mobility and are directly exposed to these multiple stressors. However, the ecological impacts of these stressors on bioturbators, especially their activity levels, remain poorly understood. This review synthesizes current knowledge on how selected environmental stressors, including extreme weather events, eutrophication, and anthropogenic emissions, affect bioturbation, organismal physiology and survival. Reported impacts vary widely depending on the species and stressors’ intensity. The strongest negative effects were typically observed under high-intensity stressor scenarios, which sometimes exceeded environmentally relevant thresholds. However, only a few studies examined the combined effects of multiple stressors. Their effects on bioturbators can be neutral, antagonistic, synergistic or additive, highlighting the complexity of stressor interactions in natural systems. The summary of this review suggests that key ecosystem functions provided by bioturbators are threatened by constant exposure to multiple environmental stressors and that ongoing environmental changes are further exacerbating this situation. To better understand the risks faced by these organisms, it is important to explore the combined effects of multiple stressors, to support more accurate predictions and effective conservation and restoration efforts.

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Differential gene expression reveals molecular mechanisms for physiological resilience to ocean acidification stress in native and introduced oyster species

Published 9 October 2026 Science Closed
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Coastal-estuarine habitats are rapidly changing with respect to ocean acidification (OA). Along the West Coast of the United States, coastal upwelling regions are high in productivity and rich in nutrients, making them key areas for aquaculture oyster production. The native Olympia oyster Ostrea lurida has experienced population collapse due increased commercial harvest, habitat loss, and the introduction of the non-native Pacific oyster Magallana gigas. Despite intense focus on physiological responses of oysters to OA stress, molecular underpinnings of have yet to be fully described, particularly in niche species. Juvenile oysters of both M. gigas and O. lurida were exposed to a range of experimental OA conditions for six weeks to investigate transcriptomic and biomineralization responses under fluctuating and chronic low pH. Low pH had a significant effect on shell dissolution for both Pacific and Olympia oysters, with no statistical difference observed between the two species. Differential gene expression revealed distinct differences in responses of the Pacific and Olympia oysters to OA on the transcriptomic level, with M. gigas showing elevated molecular responses to OA stress. Our findings suggest that the two species may employ distinct adaptive strategies to mitigate low pH that are informative for species-specific management strategies.

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Behavioural responses of fishes to abiotic stressors: a comparative synthesis of shared physiological mechanisms and ecological consequences

Published 8 October 2026 Science Closed
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Highlights

  • Comparative review of behavioural responses to major abiotic stressors
  • Conserved physiological mechanisms underlie diverse behavioural responses
  • Cross-stressor synthesis identifies common and stressor-specific effects
  • Ecological consequences extend from individuals to populations
  • Research priorities for predicting fish responses to global environmental change

Abstract

Anthropogenic activities, including global warming, deforestation, urbanization, intensive agriculture, and aquaculture, are accelerating environmental change with consequences for aquatic ecosystems. As ectothermic vertebrates, fishes are sensitive to alterations in abiotic conditions, responding through behavioural changes that influence survival, reproduction, and species interactions. Although several studies have investigated the effects of abiotic stressors, comparative syntheses across stressors remain limited, constraining our understanding of how environmental drivers influence fish behaviour. In this review, we synthesize evidence on the impacts of six abiotic stressors, including temperature, hypoxia, acidification, turbidity, salinity, and ammonia, and examine the processes underlying responses. Across these stressors, behavioural alterations affect swimming performance, feeding, predator avoidance, social interactions, habitat selection, exploration, courtship, and anxiety-like behaviours. Despite differences in their primary modes of action, these stressors frequently converge on physiological disturbances involving oxidative stress, neurotransmitter regulation, sensory impairment, ion homeostasis, and energy metabolism, ultimately producing behavioural outcomes with ecological consequences. Most studies have been conducted under controlled laboratory settings, limiting ecological relevance. Furthermore, the combined effects of multiple abiotic stressors, together with long-term, multigenerational, and transgenerational responses, remain poorly understood despite their potential consequences for fish growth, reproduction, recruitment, and community structure. This review highlights the urgent need for integrative, multi-stressor, and multigenerational studies spanning diverse species, developmental stages, and ecosystems to improve predictions of fish responses under environmental change. By identifying shared and stressor-specific responses, this synthesis provides a conceptual framework for understanding how abiotic stressors affect fish through physiological pathways that ultimately converge on common behavioural outcomes with important ecological implications.

Graphical abstract

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Diversity and dynamics of sponge microbiomes under ocean acidification: insights from natural CO₂ vents and reciprocal transplant experiments

Published 8 October 2026 Science Closed
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Marine sponges are key benthic organisms whose ecological success is closely linked to their associated microbial communities. This thesis investigated the microbiome responses of three Mediterranean HMA demosponges, Chondrosia reniformis, Petrosia ficiformis, and Chondrilla nucula, inhabiting natural CO₂ vents off Ischia Island. By comparing wild populations under ambient and reduced pH with in situ transplants, this work explored long-term acclimatization and short-term responses. Species-specific transplantation protocols were optimized to ensure survival of the three sponges and experimental reliability. Then, 16S rRNA gene metabarcoding was used to characterize sponge-associated and seawater microbial communities. Results showed that sponge microbiomes were distinct from seawater and structured by host identity but each species displayed different degrees of stability and plasticity under acidified conditions. Chondrosia reniformis exhibited a highly stable microbiome, with acidification inducing only fine-scale shifts within a conserved core. Petrosia ficiformis showed greater flexibility, but short-term responses were strongly constrained by donor identity and source-associated signatures. In C. nucula, light availability emerged as the main driver of microbiome reorganization, while low pH modulated this response, promoting shifts from photosymbiosis-related taxa toward lineages potentially linked to nitrification and chemoautotrophy. Overall, sponge holobiont resilience appears to rely not on extensive microbial replacement, but on species-specific rearrangements of resident symbionts within persistent host-associated frameworks.

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Carbon dynamics and water quality regulation in Ruditapes philippinarum-Chlorella vulgaris co-culture with cardiac monitoring

Published 8 October 2026 Science Closed
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Highlights

  • Clam addition rapidly altered nitrogen, oxygen and dissolved-carbon dynamics.
  • All chamber treatments maintained negative CO₂ fluxes during incubation.
  • Algal monoculture showed stronger 6-h CO₂ uptake than co-culture.
  • Hydrochemical variables and cardiac activity were recorded concurrently.

Abstract

Global warming and ocean acidification threaten marine aquaculture. Bivalve-microalgae co-culture is considered a promising approach for low-carbon aquaculture, but its effects on water quality, carbon dynamics and bivalve physiology are not fully understood. This study tested Ruditapes philippinarum and Chlorella vulgaris in sealed static chambers with three treatments: sterile seawater (NP-C), Chlorella monoculture (WP-C) and clam-Chlorella co-culture (WP). Water-quality variables, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), air-water CO₂ flux and clam heart rate were measured in separate 3-h and 6-h incubations. At the end of incubation, WP had higher ammonium concentrations and lower dissolved oxygen than WP-C, indicating that clam addition changed nitrogen and oxygen conditions. DOC and DIC also changed differently in the two biological treatments. All treatments showed negative air-water CO₂ fluxes. In the 6-h experiment, CO₂ uptake was strongest in WP-C and intermediate in WP. Heartbeats were recorded continuously in four clams for 7.07 h. Overall, the co-culture rapidly altered water-quality and dissolved-carbon dynamics but did not result in greater short-term CO₂ uptake than the algal monoculture under the present chamber conditions.

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Response of spore or gamete release of Ulva australis Areschoug to the superimposition of nutrients, salinity and ocean acidification: implication for Ulva sp. green tide outbreak

Published 7 October 2026 Science Closed
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Highlights

  • Sporophytes and gametophytes differed in germ cell release.
  • Sporophytes and gametophytes differed in physiological responses.
  • The different responses lead to Ulva sp. green tide outbreak.

Abstract

The Ulva sp. green tide is one global marine ecological disaster, and its prevention and control have drawn global attention. However, existing control strategies based on ecological mechanisms of Ulva sp. green tide without distinguishing sporophytes from gametophytes have yielded limited success, suggesting that the green tide outbreaks are driven by intrinsic biological mechanisms. Ulva australis Areschoug gametophytes and sporophytes differ in chromosome number; hence, it is inferred that their reproductive strategies respond differentially to environment factors, which explains the biological mechanism of Ulva sp. green tides from the perspective of the origin of germ cells. To verify this hypothesis and for effective control of green tides, the sporophytes and gametophytes of U. australis Areschoug were respectively cultivated and exposed to the conditions of nutrient salts, salinity and carbon dioxide (CO2) superimposed in a uniform design experiment for 48 h to observe the release of germ cells (spores or gametes). The spore release rate of sporophytes was positively correlated with salinity (p<0.05). The gamete release rate of gametophytes had a positive correlation with the interaction between NH4-N and PO4-P (p<0.05), and a negative correlation with CO2 concentration (p<0.05). The difference in responses of sporophytes and gametophytes to environmental factors ensures the availability of germ cells of U. australis Areschoug, which facilitates the green tide outbreak. Thus, the sporophyte and gametophyte respond differently to environmental factors, suggesting that they can adapt to different habitats, which implies that the green tide outbreak of the Ulva sp. has an inherent biological promoting mechanism. Moreover, it is understandable that the effect of a single control strategy in dealing with Ulva sp. green tides is not satisfactory.

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Long-term exposure to ocean acidification modifies the biochemical composition of the adductor muscle of the commercial scallop Zygochlamys patagonica

Published 7 October 2026 Science Closed
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The scallop Zygochlamys patagonica is an ecologically and economically important seafood species in the Southwest Atlantic Ocean that has been shown to be sensitive to ocean acidification (OA), a global process caused by anthropogenic carbon dioxide emissions. This study experimentally evaluated the effects of a long-term exposure to low pH, including an OA scenario on the scallop adductor muscle— the commercially valuable tissue. We tested three levels of pH, two pH values within the present range of natural variability (high pHT= 8.00 and medium pHT= 7.80) and a lower pH level representing a true OA scenario (low pHT: 7.52). We examined biochemical alterations induced by low pH and assessed the potential for reversibility following a depuration period. No significant effects were observed for medium pH exposure. However, after 14 and 28 weeks of exposure to low pH (OA), significant reductions in protein and total lipid content were observed, resulting in decreased overall energy reserves, while glycogen levels remained unchanged. The fatty acid profile shifted under OA with an increased PUFA/ SFA ratio and higher sums of EPA and DHA. No signs of recovery were detected after the 2-month depuration period. These results indicate that OA-driven changes in biochemical composition may reflect altered physiological status, with potential socio-ecological implications for the sustainable exploitation of this valuable resource.

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High CO2 at stable pH disrupts olfactory homeostasis and function in largemouth bass

Published 6 October 2026 Science Closed
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Elevated CO₂ is a common water-quality challenge in recirculating aquaculture systems. Although its effects are often accompanied by environmental acidification, the direct impact of elevated CO₂ under stable-pH conditions on fish olfactory function remains poorly understood. This study investigated the effects of elevated CO₂ on olfactory function and olfactory epithelial homeostasis in juvenile largemouth bass (Micropterus salmoides). Fish were exposed to approximately 5 mg L−1 (control), 10 mg L−1, and 15 mg L−1 CO₂ for 4 days while maintaining stable pH. Olfactory function and olfactory epithelial responses were evaluated using behavioral assays, calcium imaging, histological analyses, Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, immunofluorescence, and gene-expression analyses. Exposure to 10 and 15 mg L−1 CO₂ significantly reduced attraction to food odor without affecting swimming activity, indicating impaired olfactory sensitivity. Calcium imaging revealed attenuated olfactory responses to L-alanine, accompanied by altered expression of genes involved in olfactory signal transduction. Elevated CO₂ also increased the number and area of acidic mucous cells, reduced the abundance of mature olfactory sensory neurons, increased apoptosis in the olfactory epithelium, and altered the expression of genes associated with apoptosis, cell proliferation, and neurogenesis. These findings indicate that elevated CO₂ under stable-pH conditions impairs olfactory function and disrupts olfactory epithelial homeostasis in juvenile largemouth bass. The present study demonstrates that dissolved CO₂, independent of environmental acidification, adversely affects the fish olfactory system and highlights the importance of monitoring CO₂ as a key water-quality parameter in recirculating aquaculture systems.

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Mitigation of biogenic acidification via increased total alkalinity in high stocking density culture waters of Strongylocentrotus intermedius: effects on growth and metabolism

Published 6 October 2026 Science Closed
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Highlights

  • Biogenic acidification increases with stocking density in sea urchin culture.
  • Total alkalinity mitigates acidification and promotes growth and gonadal development.
  • Higher alkalinity shifts metabolism toward biosynthesis and energy storage.

Abstract

Among cultured sea urchins in China, Strongylocentrotus intermedius has the highest annual production, with seed production and grow-out primarily conducted under high-density intensive conditions where biogenic acidification readily develops. To investigate its development, effects, and mitigation, we conducted a short-term incubation experiment (1 d) and a 20-day cultivation experiment. In the short-term incubation experiment, a control group with initial pH ≈ 8.1 and TA ≈ 2300 μmol/kg and a TA-elevated group with initial pH ≈ 8.1 and TA ≈ 3600 μmol/kg were established, and sea urchins were cultured across a density gradient of 20–80 g/3 L. In the 20-d experiment, stocking density was 88 g/3 L with the same initial pH and TA settings. The short-term experiment showed that seawater acidification occurred in the control group, and stocking density was significantly correlated to pCO2, ΔpH (pH reduction), TA–DIC, and Ωarag. With increasing stocking density, pCO2 increased significantly, whereas ΔpH and TA–DIC significantly decreased simultaneously. In the TA-elevated group, all parameters except pCO2 were higher than those in the control group across all stocking densities. At the lowest stocking density, ΔpH, TA–DIC, and Ωarag in the control group were −0.09 ± 0.01, 111.48 ± 1.73 μmol/kg, and 1.43 ± 0.00, respectively, whereas the corresponding values in the TA-elevated group were 0.11 ± 0.01, 252.26 ± 6.98 μmol/kg, and 3.23 ± 0.08. These results indicate that increasing TA mitigates biogenic acidification and works to strengthen the buffering capacity of the carbonate system. At the end of the 20-day cultivation experiment, urchins from the TA-elevated group showed significantly higher specific growth rate (1.60 ± 0.08% vs. 1.27 ± 0.06%), weight gain rate (37.72 ± 2.25% vs. 29.04 ± 1.48%), and gonad index (6.09 ± 1.58% vs. 3.54 ± 0.49%) than those from the control group. Metabolomics analysis revealed that TA elevation enriched pathways related to protein biosynthesis, glycerophospholipid metabolism, and sphingolipid signaling, with higher abundances of essential amino acids (L-methionine, DL-isoleucine), sphingomyelins, and the antioxidant indole-3-pyruvic acid. In contrast, the oxidative stress marker DL-2-aminoadipic acid was upregulated in the control group. Overall, increasing seawater TA mitigates biogenic acidification in high-density sea urchin culture, shifting metabolism from stress defense toward biosynthesis and reserve accumulation, thereby supporting growth and gonadal development in juvenile sea urchins.

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Single-larva transcriptomics resolve phenotype-anchored Na+ K+ ATPase expression during first shell formation in Pacific oyster larvae under ocean acidification conditions

Published 5 October 2026 Science Closed
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Bivalve larvae are highly sensitive to ocean acidification (OA) conditions, a global climate shift that applies selective pressure on calcareous marine organisms. Although a growing body of work exists on the effects of OA on bivalve larvae, most studies rely on pooled-larval sampling, which may obscure gene expression patterns by including larvae with severely underdeveloped or deformed phenotypes, which are common in OA conditions but are unlikely to survive to metamorphosis. Here, we tested a combination of single-larva transcriptomic techniques to investigate the expression of a candidate gene previously shown to be upregulated in OA conditions, Na+ K+ ATPase (NKA), in Pacific oyster larvae of known phenotypes. We found that upregulation of the NKA gene is detected primarily in larvae with a developed first shell (prodissoconch I), and was not pronounced in underdeveloped or deformed larvae, suggesting its expression reflects active shell formation under OA conditions, rather than a generalized stress response. Further, NKA mRNA was primarily localized along the dorsal shell hinge, the site of CaCO3 deposition, substantiating its role in early shell development. This study provides a methodological framework for phenotype-anchored sampling to investigate the expressional signatures underpinning successful shell development in OA conditions.

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Involvement of CgPGC-1α in regulating mitochondrial biogenesis in Pacific oyster Crassostrea gigas under ocean acidification

Published 5 October 2026 Science Closed
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Highlights

  • CgPGC-1α with classical RRM domain was identified from Crassostrea gigas.
  • CgPGC-1α mRNA was ubiquitously expressed with the highest level in gill.
  • CgPGC-1α could respond to acidification treatment, promote mitochondrial biogenesis.
  • Acidification enhanced mitochondrial biogenesis and ATP via AMPKα/PGC-1α.

Abstract

Ocean acidification poses a significant threat to calcifying marine organisms. The Pacific oyster Crassostrea gigas is an economically and ecologically important bivalve species. Understanding the molecular mechanisms underlying its physiological adaptation to acidification stress is therefore of great ecological and aquaculture relevance. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a central regulator of mitochondrial biogenesis and cellular energy metabolism, which plays important roles in response to various stressors. In this study, a PGC-1α homolog was identified from Crassostrea gigas (CgPGC-1α), which harbors an evolutionarily conserved RRM domain. The phylogenetic tree indicated that CgPGC-1α first clustered with PGC-1α from molluscs, then grouped with vertebrate PGC-1α, and finally joined with the PGC-1α of arthropods. During larval development, expression level of CgPGC-1α increased from the early embryonic stages, reached its highest level at blastula stage, and subsequently decreased during later development stages. In adult oysters, expression level of CgPGC-1α were detected in haemocytes and all examined tissues, with the highest level in gills. When the oysters were exposed to acidified seawater at pH 7.4, the expression level of CgPGC-1α in gonad was significantly upregulated at 7 and 21 days. Furthermore, at 7 days after acidification treatment, the mtDNA copy number, the expression level of CgMFN mRNA transcripts, the CgPGC-1α protein levels and the pAMPKα (Thr172) phosphorylation levels all significantly increased (p < 0.05), while the relative mRNA expression level of CgDRP1 significantly decreased (p < 0.05). Moreover, a significant increase in the number of mitochondria with morphology changing from elliptical to irregular and cristae becoming swollen was observed, and the ATP content was significantly elevated. After 28d days of acidification, mtDNA copy number and the expression level of CgMFN and CgNRF2 were significantly decreased, whereas the expression level of CgDRP1 was significantly increased. Collectively, these findings reveal a temporal response to acidification, characterized by an early compensatory activation of the AMPKα/PGC-1α axis and enhanced mitochondrial biogenesis, followed by impaired mitochondrial homeostasis under prolonged acidification stress. This study provides new insights into the molecular mechanisms underlying oyster resilience to ocean acidification and highlights the potential importance of mitochondrial adaptation in coping with future environmental changes.

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Ocean acidification remodels the mantle phosphoproteome and weakens shell mechanical resilience in Mytilus edulis

Published 2 October 2026 Science Closed
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Highlights

  • Ocean acidification causes pH- and time-dependent disruption of nacreous and prismatic microstructures.
  • Shell compressive strength declines progressively with decreasing pH and exposure duration.
  • Quantitative mantle phosphoproteomics identified 3720 phosphoproteins and 10,780 phosphosites.
  • Differential phosphorylation is associated with signaling, vesicular trafficking, autophagy, and metabolic pathways.
  • Molecular and shell-level responses support a proof-of-concept dual-indicator framework.

Abstract

Ocean acidification (OA), driven by rising atmospheric CO2, threatens the structural integrity and ecological performance of calcifying marine organisms, yet the mechanistic links between environmental acidification and compromised shell mechanical resilience remain insufficiently understood. Here, we integrate microstructural imaging, mechanical testing, and quantitative phosphoproteomics to characterize the structural, mechanical, and phosphorylation responses of Mytilus edulis to OA and examine their relationships. Adult mussels were exposed to near-future pH conditions (8.1, 7.9, 7.7) for up to 40 days. OA produced progressive disorganization of nacreous tablets and prismatic columns without altering aragonite–calcite polymorphs, indicating that acidification drives structural degradation rather than mineralogical shifts. Correspondingly, shell compressive strength declined in a pH- and time-dependent manner, with an approximately 60% reduction at pH 7.7 after 40 days. Phosphoproteomic profiling identified 3720 phosphoproteins (10,780 sites), revealing extensive acidification-induced remodeling of phosphorylation networks. Proteins corresponding to differentially phosphorylated peptides were predominantly nuclear and were enriched in kinase-, PH-, PDZ-, and RNA-recognition-domain-containing proteins. Functional analyses implicated MAPK signaling, vesicular trafficking, ion transport, glycolysis/gluconeogenesis, autophagy, and calcium-associated processes. Phosphoproteomic remodeling was associated with the deterioration of shell microstructure and compressive strength, supporting an association between mantle phosphorylation responses and compromised biomineralization under acidification. The enriched pathways and protein domains were functionally related to calcium-dependent signaling, vesicular trafficking, cytoskeletal organization, and cellular metabolism, providing testable candidates for future mechanistic validation. Together, these findings support a working model in which ocean acidification is accompanied by coordinated phosphorylation remodeling and progressive loss of shell mechanical resilience. We further propose a proof-of-concept dual-indicator framework that integrates candidate molecular sentinels with organismal metrics, providing a conceptual basis for future assessment of aquaculture resilience and ecosystem vulnerability under progressive ocean acidification.

Graphical abstract

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Survival costs flavor: microplastics reprogram metabolic resource allocation and compromise oyster quality under ocean acidification

Published 30 September 2026 Science Closed
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Ocean acidification (OA) and microplastic (MP) pollution are widespread marine stressors, yet their interactive effects on seafood quality and molecular metabolism remain unclear. This study investigated the combined effects of OA (pH 7.7) and MPs (2 and 200 μg/L) on the Pacific oyster (Magallana gigas). OA was the primary driver of textural deterioration, significantly reducing springiness and chewiness, while combined stress synergistically depleted protein and lipid reserves. Distinct lipid remodeling strategies were identified: OA induced DHA accumulation potentially associated with membrane stabilization, whereas MPs triggered EPA and ARA upregulation associated with stress and immune responses. The flavor profile was severely compromised, characterized by depletion of umami amino acids, nucleotide redistribution, and altered succinate contribution. Transcriptomic analysis revealed that high MP exposure activated genome maintenance and DNA repair-associated pathways, including the Fanconi anemia pathway, superimposed on OA-associated metabolic suppression. Concurrent upregulation of nucleotide salvage (APRT, HPRT) and amino acid catabolic genes (GLS, GDH) suggests increased utilization of flavor metabolites for energetic demands. These findings support a bioenergetic trade-off in which oysters exposed to OA and MPs reallocate resources from nutritional and sensory quality toward cellular maintenance and stress adaptation, highlighting underrecognized consequences of climate change and plastic pollution for seafood quality.

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The future of aquatic food systems: climate change adaptation and resilience strategies – a narrative review

Published 30 September 2026 Science Closed
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Across the world’s oceans, lakes, and rivers, climate change is reshaping fisheries and aquaculture systems on which billions of people depend for food and millions rely for their livelihoods. This narrative review summarizes peer-reviewed and selected literature published between 2008 and 2026 on climate impacts, adaptation options, and critical knowledge gaps in marine and freshwater fisheries, with a particular focus on tropical and African inland fisheries. This review shows that warming, acidification, deoxygenation, and altered hydrology are disrupting fish physiology; shifting the distribution of marine species poleward by over 70 km per decade, at rates that vary greatly by taxon, depth, and area; and destroying critical habitats. Although this rapid poleward shift is well documented in open marine environments, it contrasts sharply with landlocked or fragmented freshwater systems, where horizontal migration is physically constrained, a contrast central to the concept of climate entrapment developed in this review. In scenarios characterized by high emissions, tropical fisheries may see a reduction of up to 40% in their maximum catch potential, a statistic relevant to specific tropical Exclusive Economic Zones based on bioclimate-envelope forecasts, which should not be interpreted as a global or universal result. This figure is a model-derived projection under a bioclimate-envelope framework rather than an observed trend, and the realized outcome will depend on future emission pathways. These biophysical changes compound already serious pressures, overfishing, habitat loss, and pollution, and the burden falls heaviest on those least responsible: small-scale fishers, women, and indigenous communities. We introduce the concept of climate entrapment to describe the distinct vulnerability of freshwater fisheries: trapped by fragmented habitats and hydrological barriers, fish stocks cannot migrate to more secure waters as conditions deteriorate. While there are promising adaptation strategies, major gaps remain in understanding what works, for whom, and under what conditions. We conclude with priority recommendations for research, policy, and practice.

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