Posts Tagged 'fish'

Fish trait-based indicators of mercury bioaccumulation under natural ocean acidification: Insights from a mediterranean CO₂ vent system

Published 22 July 2026 Science Leave a Comment
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Highlights

  • Low pH conditions at CO₂ vents increase THg bioavailability and fish exposure.
  • Functional traits explain THg patterns better than species identity.
  • Under low pH, less-mobile benthic fish accumulate more THg than highly-mobile fish.
  • Trophic position drives stronger THg biomagnification at low pH sites.

Abstract

Ocean acidification is not an isolated climate-related threat to marine organisms, as it may act in combination with other stressors such as trace element contamination. Here, we took advantage of naturally acidified conditions and mercury spill-out from the shallow CO2 vent of Vulcano Island (Italy) to test whether fish functional traits explain contaminant dynamics better than species identity under ocean acidification scenarios. Specifically, we investigated if trophic group and mobility influence total mercury (THg) bioaccumulation and trophic transfer in fish inhabiting Cymodocea nodosa seagrass meadows under low and ambient pH conditions. Low-mobility benthic fish, mainly represented by invertebrate feeders and small piscivores, exhibited higher THg concentration at the vent site than at reference sites, while highly mobile zooplanktivorous fish showed no significant differences, highlighting the importance of fish mobility and local trophic benthic pathways in shaping contaminant exposure and bioaccumulation. Moreover, the relationship between trophic position and THg concentration in fish was stronger in the low pH site, indicating enhanced trophic transfer and biomagnification when Hg availability is higher. In contrast, weak or absent biomagnification in the reference sites suggests that Hg transfer depends more on contaminant availability and food web structure than trophic position alone. Overall, these findings indicate that functional traits better predict Hg bioaccumulation patterns than species identity, supporting trait-based approach to assess contaminant dynamics in future ocean acidification scenarios.

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Impacts of ocean acidification on reproduction and early life development in marine teleost fish—a synthesis

Published 17 July 2026 Science Leave a Comment
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Ocean acidification (OA) remains a major and underexplored threat to marine fishes, particularly regarding reproductive physiology and early life stages (ELS). Although research over the past 15 years has documented diverse OA effects, substantial knowledge gaps persist. Most studies focussed on a limited set of species from North America and Europe, leaving broad uncertainty across phylogenetic groups, geographic regions and multi-stressor conditions. In adult fish, especially females, elevated pCO2 can shift energy allocation to prioritise reproductive output at the expense of egg or clutch size. While adult and juvenile fish have well-developed acid–base balancing systems, embryos and larvae possess only rudimentary mechanisms, making them more vulnerable to OA. This article stresses the importance of understanding these physiological and mechanistic responses to predict the future of fish stocks and ecosystem health as OA intensifies due to ongoing CO2 emissions. Our results highlight that OA responses in fish are highly variable and often specific to life stage and species, with acute and sometimes stage-specific effects not fully documented. Lastly, our recommendations on targeted research and funding are necessary to address the remaining knowledge gaps, including broadening taxonomic and geographic sampling, exploring multi-stressor scenarios and improving understanding of the downstream effects of OA on fish reproduction and development. Maintaining robust fish populations is vital for food security, employment and ecosystem functioning, making continued investigation into OA’s impacts a scientific and societal priority.

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Impacts of warming, acidification, and deoxygenation on embryos and larvae of gilthead seabream (Sparus aurata)

Published 13 July 2026 Science Closed
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Simple Summary

This study evaluated how the combination of ocean warming, acidification, and deoxygenation (“deadly trio”) affects the early development of the fish Sparus aurata. Embryos and recently hatched larvae were exposed to increased temperature (Δ + 4 °C; 22 °C), elevated CO2 levels (pCO2 ~1000 μatm, Δ − 0.4 units; pH 7.7), and reduced oxygen (Δ − 60% O2 saturation; 3 mg O2 L −1). Deoxygenation emerged as the primary stressor, significantly reducing hatching rates, larval survival, and heart rates. These effects were further intensified when combined with warming and acidification. Acidification alone also reduced larval phototactic behavior by 50%, while exposure to all three stressors eliminated phototactic responses entirely. Overall, the results demonstrate that multiple climate-related stressors together severely harm fish early life stages, emphasizing the need to study combined environmental changes to better predict future impacts of climate change on marine fish populations and ecosystem functioning.

Abstract

The interaction between increased dissolved carbon dioxide, rising temperatures, and oxygen loss—the so-called “deadly trio”—is expected to strongly affect marine biota over the coming years, undermining ocean services and uses. Nonetheless, no study has so far scrutinized the cumulative impact of these three stressors on fish embryos and larvae. To fill this knowledge gap, we conducted a fully multi-factorial experiment to investigate the effects of warming (+4 °C: 22 °C), acidification (Δ − 0.4 pH units: 7.7 pH, pCO2 ~1000 μatm), and deoxygenation (Δ − 60% O2 saturation: 3 mg O2 L−1) on physiological and behavioral responses of the commercially important species Sparus aurata. Deoxygenation was the primary factor reducing hatching rates (64.25%), survival (46.71%), and heart rates (31.99%) of recently hatched larvae, being generally further exacerbated when combined with warming and acidification. No larvae exposed to the interaction of the three treatments reacted to the phototactic behavior test. However, acidification alone caused a 50% reduction in phototactic behavior. Our findings demonstrate that the deadly trio is detrimental to early fish development, impacting several key features at this critical life stage, and the need to assess the impacts of stressors’ interaction on marine taxa to better predict future ecosystem responses to ocean changes.

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Climate assessment report for the Central Arctic Ocean (CAO) [Suppl. to ICES Scientific Reports 8(25)]

Published 9 July 2026 Science Closed
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Climate change is transforming the Central Arctic Ocean (CAO) at an unprecedented pace. Sea ice is rapidly declining in extent, thickness, and age, with projections indicating an ice-free summer Arctic by mid-century, possibly earlier. This loss of ice amplifies warming, alters stratification and circulation, and accelerates ocean acidification—occurring up to four times faster than the global average—threatening calcifying organisms and ecosystem stability.

Biological impacts are profound: shifts in microbial and primary producer communities, reduced ice-associated biodiversity, and boreal species moving northward disrupt food webs. Benthic ecosystems show signs of long-term decline in biodiversity and organic carbon supply, while fish, seabirds, and marine mammals face habitat loss, changing prey availability, and new stressors such as increased predation and contaminants. Some species may benefit from enhanced productivity, but cumulative effects of warming, acidification, and ice loss remain uncertain. These changes interact with other pressures—pollution, invasive species, and human activities—creating complex, compounding stress on the CAO ecosystem. Knowledge gaps on tipping points and resilience underscore the urgent need for research on circulation, carbon dynamics, and species adaptation to inform conservation and management strategies.

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Marine invertebrates and fishes exhibit inconsistent body size responses to ocean acidification

Published 18 June 2026 Science Closed
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Body size is a fundamental characteristic of all living organisms that determines physiological functions and life-history traits. Ecological theory predicts that ocean acidification can cause body size reductions, confirmed by several studies reporting miniaturization in ectotherms. Based on this prediction, we would expect a broad suite of species to show similar plastic body-size responses to elevated CO2. Using four natural climate change analogues of ocean acidification across the northern and southern hemispheres, we quantified body size alterations across 18 marine invertebrate and fish taxa to test for climate-driven miniaturization. Only three species consistently showed body-size reductions under ocean acidification: one urchin and two fish species. In contrast, 15 other species, ranging from highly calcified to non-calcified, displayed unchanged or increased body sizes or inconsistent miniaturization. If body-size miniaturization responses were consistently reproducible across taxa we would have observed it more frequently, suggesting that species responses to ocean acidification are more variable than previously thought and likely vary depending on a species’ physiology and life history. Thus, rather than entire communities undergoing miniaturization, species are likely to display a spectrum of responses, with some exhibiting size reductions, others demonstrating physiological resistance to elevated CO2, and others potentially benefiting from the indirect effects of ocean acidification.

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Temperature, but not acidification, influences the growth and lipid profile of juvenile sand whiting, Sillago ciliata (Cuvier 1829)

Published 18 June 2026 Science Closed
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Seafood provides an essential source of macro- and micronutrients for coastal communities worldwide. Climate change is a key threat to seafood security, altering the sizes, abundances, distributions, physiology and ecological interactions of fisheries species, and increasingly, there is evidence of impacts to seafood nutritional quality. In a 12-week mesocosm experiment, we tested the influence of projected ocean warming and acidification scenarios on the growth and lipid quality of juvenile sand whiting (Sillago ciliata), a popular fisheries species in eastern Australia. The growth of S. ciliata significantly increased (by 61% body weight) under elevated temperature (+3°C) but was not affected by acidification treatment levels. Lipidomic analysis revealed no influence of temperature or acidification on total lipid content or the composition and total proportions of lipid classes and subclasses. However, elevated temperatures significantly impacted the overall composition of fatty acids, including a shift toward higher saturation and a decline in important omega-3 fatty acids. Fish exposed to elevated temperature treatments had more saturated fatty acids than those at control temperatures, along with reduced levels of the valuable omega-3 eicosapentaenoic (C20:5) and docosahexaenoic (C22:6) fatty acids. Despite impacting fatty acid composition in S. ciliata, the increased growth of the juvenile whiting, if sustained into adulthood, under elevated temperatures, may help compensate for the overall availability of essential polyunsaturated fatty acids to support consumer nutritional requirements. These findings contribute to the growing body of evidence on variable climate resilience in nearshore species to future environmental conditions and the implications for the trophic transfer of nutrients in estuarine ecosystems.

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Climate change is redefining tetrodotoxin accumulation and ecological dynamics in pufferfishes

Published 16 June 2026 Science Closed
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Marine pufferfishes are globally distributed and ecologically important organism notable for accumulating tetrodotoxin [TTX], a potent neurotoxin with wide ecological ramifica-tions. Unlike many endogenous defences, TTX in pufferfishes is acquired indirectly via microbial and trophic pathways, linking pufferfish toxicity to the dynamics of marine mi-crobial assemblages and food webs. Anthropogenic climate change principally ocean warming, deoxygenation, and acidification is rapidly reshaping marine environments in ways that are likely to intensify and redistribute TTX exposure. Observational and experimental studies indicate that elevated seawater temperatures favour the proliferation of thermophilic, toxin-producing bacteria [e.g., Vibrio spp.], increase the abundance of toxic prey, and raise TTX burdens in pufferfish tissues seasonally and spatially. Concurrently, warming-driven range shifts have promoted poleward expansions of several tropical and subtropical puffer species, producing novel sympatric assemblages, hybridization events, and “cryptic” toxic phenotypes that complicate species identification and risk assess-ment. These biogeographic rearrangements, together with altered prey communities and microbial composition, reconfigure the trophic pathways by which TTX is transferred and concentrated in higher trophic levels. Early evidence also links multistressor conditions elevated temperature combined with hypoxia or acidification to altered developmental success and changes in toxin allocation during reproduction, suggesting potential popu-lation-level consequences. This review synthesizes current global evidence on cli-mate-linked changes in pufferfish TTX dynamics, integrating microbial ecology, trophic transfer, life-history shifts, and biogeography. We highlight [i] mechanistic pathways by which warming and associated ocean changes increase environmental TTX availability, [ii] how shifting species ranges and hybridization alter toxicity patterns across regions, and [iii] key methodological advances [e.g., high-resolution LC-MS/MS, metagenomics] needed to resolve open questions. We identify critical research gaps long-term field moni-toring, integrated microbial–trophic mapping, and multistressor population studies and recommend synthesis strategies that link environmental monitoring to toxin surveillance. Understanding pufferfish toxification as a climate-sensitive ecological process [not a static species trait] is essential to anticipate how marine toxin landscapes will change in the Anthropocene and to develop timely, science-based monitoring frameworks.

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Short communication: skin melatonin and cortisol responses to water acidification and basification within the optimal pH range in three-spined sticklebacks

Published 15 June 2026 Science Closed
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Highlights

  • Cutaneous Mel, unlike cortisol, shows high sensitivity to slight shifts in water pH.
  • Water pH was regulated by a custom-designed system controlling dissolved CO2 levels.
  • High skin Mel levels and distinct pH-dependent responses indicate local Mel synthesis.

Abstract

Fish skin functions not only as a passive protective barrier but also as an active site of key physiological processes, including a local stress response system. In fish, this system involves the hormones cortisol and melatonin (Mel), which contribute to counteracting environmental stressors and maintaining homeostasis. In this study, we examined the sensitivity of both components of the cutaneous stress response system (CSRS) in three-spined sticklebacks (Gasterosteus aculeatus) exposed to acidic (pH = 6.54) and basic (pH = 8.70) water conditions, representing the boundary values of the species’ optimal pH range, under either rapid or gradual pH change regimes. Water pH in the aquaria was precisely controlled using a custom-designed gas-exchange system regulating dissolved CO2 levels. Mel concentrations were measured in the skin, brain and eyeball, while cortisol was determined in the skin. Samples were collected during the day. Skin Mel levels were significantly higher under acidification than under basification (P = 0.036; rapid change regime), whereas cortisol remained stable across all conditions. Ocular Mel levels were not affected by treatments. Brain Mel concentrations were generally very low but tended to be slightly higher under basification than under acidification in both regimes (P = 0.05, borderline significance). The marked differences in skin Mel levels between acidic and basic pH water conditions, accompanied by stable cortisol concentrations, indicates that cutaneous Mel, but not cortisol, is highly sensitive to subtle water pH fluctuations even within the species’ optimal range.

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Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification

Published 8 June 2026 Science Closed
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  1. 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.
  2. 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).
  3. 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.
  4. 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.
  5. 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.
  6. We conclude that climate change can indirectly modify behavioural expression in shoal-forming fishes through habitat-driven erosion of social structure.
Continue reading ‘Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification’

A screening approach for aquaculture breeders based on sperm performance under climate change-related stress

Published 4 June 2026 Science Closed
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Highlights

  • Temperature rise reduced European sea bass and Senegalese sole sperm motility.
  • Gilthead seabream sperm showed lower variation under acidification and warming.
  • Challenge tests allowed differentiation among males based on sperm performance.
  • Approach provides a screening framework for sperm performance.

Abstract

We aimed to develop a screening approach to differentiate among males of European sea bass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), and Senegalese sole (Solea senegalensis) based on sperm performance under environmental acidification and temperature increase. Sperm samples were selected using a CASA system, and three challenge tests were applied. The first one consisted of sperm activation with artificial seawater (ASW) across a pH range (7.6–8.2). The second assessed activation at species-specific temperatures. The third test evaluated the combined effect of ASW pH (7.8 and 8.2) and different temperatures. Results from the third challenge test revealed differences in sperm performance under environmental variations, allowing differentiation among males. For this purpose, sperm motility values obtained for each sample under species-specific natural environmental conditions were used as references, and variations in motility were compared across challenge conditions. Different levels in the criteria (regarding the different percentages of motility variation) were applied to differentiate among males. The temperature increase affected the sperm kinetic parameters of European sea bass and Senegalese sole, while gilthead seabream sperm showed lower variation under seawater acidification and rising temperatures. The challenge test allowed differentiation among males based on sperm performance under environmental variations and represents a preliminary screening approach. However, these results are based on in vitro conditions and should be interpreted as a first proxy, requiring further validation to establish links with reproductive performance in vivo.

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Chemical cues and molecular mechanisms suspected in abiotic stress communication

Published 1 June 2026 Science Closed
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For nearly a century, scientists have tried to resolve the sensory physiology of chemical communication caused by predation stress. Only recently have we evidenced that abiotic stressors from a changing world, such as heat and ocean acidification, also trigger chemical communication between aquatic organisms – which we dubbed abiotic stress communication. Generally, the behavioural and physiological response to stress-induced cues are well understood, whereas the molecular mechanisms – cue identities, pathways of release, and perception – of this stress communication remain unresolved. Here, we propose a framework to organize the existing evidence for candidate mechanisms involved in abiotic stress-induced chemical communication, focusing on heat and acidification as two major abiotic stressors with environmental relevance. Drawing on transcriptomic, metabolomic and behavioural evidence, we propose that stressor-specific communication likely involves multiple cues and parallel routes rather than a single mechanism, such as membrane-related processes. We call for integrative work that links -omics with chemical profiling and ecological function assays to uncover the mechanisms of abiotic stress communication.

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Effects of acidified seawater on growth, nutritional condition, and olfactory sensory of the Asian seabass (Lates calcarifer) larvae

Published 28 May 2026 Science Closed
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Marine ecosystems are increasingly vulnerable to multiple stressors associated with climate change, resulting in significant ecological impact including ocean acidification. A 30-day experiment was conducted to investigate the effect of acidified seawater on the growth performance, nutritional status and free neuromast of olfactory organ condition of early larval stage of Asian seabass (Lates calcarifer) larvae. In this experiment, carbon dioxide (CO2) gas was introduced to lower seawater pH, and a timer system was installed to maintain the pH within specific ranges (5.5, 6.0, 6.5, and 7.0) while, a control treatment (pH fluctuating from 7.8 to 8.5) was also set, mimicking the current pH value of the seawater. Asian seabass larvae (initial total length: 2.13 ± 0.23 mm) were stocked at 30 individual/L in a 7L experimental aquarium in triplicate. The highest survival rate was obtained by Asian seabass larvae reared in control treatment 30.9±8.6% %, while total mortality was observed in pH 5.5 as early as day 1, followed by pH 6.0 and 6.5 at day 2 and 7.0 at day 5, respectively. The larvae in control group showed significantly better growth (14.25±1.02 mm) with excellent nutritional condition. Meanwhile, exposure to acidified seawater significantly reduced the length and density of larval olfactory neuromast hair cells compared to the control. It was concluded that acidified seawater induced mortality at early stage and triggered poor morphological development, resulting from inadequate nutritional condition and impaired sensory function.

Continue reading ‘Effects of acidified seawater on growth, nutritional condition, and olfactory sensory of the Asian seabass (Lates calcarifer) larvae’

Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification

Published 18 May 2026 Science Closed
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  1. 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.
  2. 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).
  3. 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.
  4. 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.
  5. 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.
  6. We conclude that climate change can indirectly modify behavioural expression in shoal-forming fishes through habitat-driven erosion of social structure.
Continue reading ‘Ocean acidification, more than warming or heatwaves, constrains shoaling behaviour in a range-extending fish through habitat simplification’

Mechanistic drivers of climate-induced reproductive collapse in African catfish: multi-stressor interactions under IPCC scenarios

Published 14 May 2026 Science Closed
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Climate change is increasingly disrupting freshwater ecosystems in sub-Saharan Africa, posing severe threats to the reproductive success and population viability of key fish species. This study investigated the mechanistic effects of elevated temperature across a gradient and the combined impact of elevated temperature, acidification and hypoxia under a simulated future climate scenario (IPCC SSP5-8.5) on the reproductive physiology and early life stages of Clarias gariepinus in the Cross River Estuary. Single-stressor trials examined the effect of temperature (28–38°C) on oestrogen synthesis, cortisol levels and gonadosomatic index (GSI). A combined-stressor scenario (35°C, pH 6.2, dissolved oxygen 2 mg/L) was used to simulate predicted climate conditions. Each treatment was replicated across triplicate tanks, with 10 broodstock per tank, over an 8-week period. Environmental parameters were tightly controlled using aquarium heaters, aerators and pH regulators. Combined stressors markedly disrupted reproductive function. Oestrogen synthesis ceased at 34°C, coinciding with a sharp decline in GSI (r2 = 0.81, p < 0.001). Cortisol concentrations increased fourfold under concurrent heat and hypoxia. Cortisol concentrations increased fourfold under heat and hypoxia co-stress. Larval performance also declined sharply, with prey capture efficiency reduced by 33% at pH 6.0 and cumulative mortality reaching 82% by day 5 under combined-stressor conditions. Habitat suitability models projected a 71% reduction in spawning habitat availability in the estuary by 2070 under the SSP5-8.5 scenario. Genetic screening revealed a significant correlation (r2 = 0.63, p = 0.004) between heat shock protein 70 (HSP70) allele frequency and larval survival, indicating potential for adaptive resilience. These findings suggest a compounded vulnerability of C. gariepinus to climate-related stressors and highlight the potential need for targeted conservation efforts. Recommended interventions include habitat restoration, enhancement of dissolved oxygen regimes and selective breeding programmes to support thermal and hypoxic tolerance in vulnerable populations.

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Research progress on the comprehensive response mechanisms of marine organisms to multiple environmental stressors

Published 28 April 2026 Science Closed
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The ocean constitutes a vital component of the Earth’s ecosystem, serving as the breeding and habitat ground for marine organisms. Currently, the global marine ecosystem is confronting combined threats from multiple environmental stressors, such as seawater warming, acidification, hypoxia, and microplastic pollution. Research focusing solely on individual stressors can hardly reveal the authentic response patterns of marine organisms accurately. This paper presents a comprehensive review. It systematically integrates cutting-edge research findings from recent years. The review centers on two core themes. These themes are the interactive effects of multiple environmental stressors and the response mechanisms of marine organisms. Studies indicate significant species-specific differences in organism responses to combined stress. These differences exist across various organism groups. Additionally, the interactive effects of multiple environmental stressors often induce biological responses. These responses deviate from the predictions derived from single-factor studies. The research results presented herein can provide crucial theoretical support for the conservation of marine biological resources, the restoration of biodiversity, and the protection of the marine ecological environment. Meanwhile, they lay a foundation for the establishment of predictable marine stress-response relationship models.

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Ocean acidification induces neuronal hyperexcitation and anxiety-like behaviour in marine medaka via ASIC activation

Published 21 April 2026 Science Closed
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Ocean acidification presents a significant threat to marine life, yet its neurobiological mechanisms remain poorly understood. This study examined how acid-sensing ion channels (ASICs) mediate neuronal excitability and anxiety-like behaviour in marine medaka (Oryzias melastigma) under elevated CO2 concentrations (1000 and 1900 ppm). Transcriptomics revealed early upregulation of asic1a (4 days), while RT-qPCR demonstrated increased asic1a, asic1b, asic2 and asic4a (7 days), with only asic1a sustained at 30 days. Immunofluorescence confirmed heightened Asic2 in emotion-processing brain regions following acidification. Transmission electron microscopy unveiled distinct ultrastructural alterations: widened synaptic clefts, thinned postsynaptic densities, and decreased mitochondrial aspect ratios. Mitochondrial membrane potential assays revealed a reduction in membrane potential in response to acidification. Electrophysiological recordings showed increased neuronal firing count in the dorsolateral telencephalon under acidification, behavioural assessments revealed significant anxiety-like phenotypes, effects that were fully rescued by ASIC inhibition. These results indicated that temporal specificity in ASIC subtype expression in acidification response. The interplay of synaptic and mitochondrial dysfunction, neuronal hyperexcitability, and behavioural alterations suggested acidification impaired both synaptic transmission efficiency and mitochondrial function, destabilizing neural circuits. This study systematically elucidates the neurotoxic effects of ocean acidification on marine fish, providing critical scientific evidence for predicting the ecological impacts of climate change on marine organisms.

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Responses of reef fish populations to similar environmental changes across distant oceanic islands

Published 9 April 2026 Science Closed
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Oceanic islands are among the most remote and understudied regions of the planet, yet they harbour unique reef fish communities that are increasingly vulnerable to global environmental change. Because these islands are geographically isolated, their populations are often assumed to respond mainly to local environmental conditions. However, by analysing temporal patterns in oceanographic variables across two distant systems (3204 km apart) in the South Mid-Atlantic Ridge (both encompassed by marine protected areas—MPAs), we found that temporal alignment in environmental conditions was associated with coordinated shifts in counts of nine reef fish populations in each study area. Among the evaluated variables, pH emerged as the most influential factor. Despite the divergent responses among reef fishes, possibly reflecting differences in physiological plasticity, shared temporal patterns in pH appeared central to parallel population patterns observed across assemblages. Increases in sea surface height and chlorophyll-a played secondary roles, potentially benefiting some populations, although such effects may be transient. These results suggest that climate-driven convergence in environmental conditions can override geographic isolation, promoting similar biological responses that may reduce resilience and increase extinction risk. Given that both islands are legally protected, our findings highlight that even MPAs are not insulated from large-scale oceanographic stressors, underscoring the need for long-term monitoring and adaptative conservation strategies for remote reef systems.

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Ocean acidification affects the timing of puberty and the reproductive output in a marine temperate fish

Published 2 April 2026 Science Closed
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Ocean acidification (OA) is a major climate-related threat to fish that can disrupt the regulation of the reproductive axis of fish, impacting reproductive success. However, previous studies have only focused on a single reproductive cycle and reported increased fecundity in some species exposed to OA. Since acclimation over several reproductive cycles can occur, it is necessary to evaluate successive reproductive cycles for predicting the actual resilience of species to OA. In this study we assessed the impact of lifetime exposure to different ocean pH/pCO2 levels (Current condition, Moderate OA and High OA) on the sexual maturation and spawning phenology of the European sea bass, over its two first reproductive periods. We tested the hypothesis that OA would exert its greatest impact at the onset of puberty (first reproduction). Accordingly, High OA exposure induced an earlier onset of puberty in both sexes, resulting in a longer spawning period and an increased fecundity. These effects were reduced during the second reproductive season. However, OA affected egg quality and sperm motility profile during the second reproductive season, leading to a total mortality at hatching of embryos spontaneously produced. This mortality was not observed in embryos produced through hormone-induced oocyte maturation and in vitro fertilisation. These results suggest that OA affects the regulation of oocyte maturation and/or the synchronisation of eggs and sperm release. The OA-driven shift in spawning may misalign with optimal environmental conditions for offspring survival. This increases the population’s vulnerability and could favour species whose reproduction is more resilient to OA.

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

Published 23 March 2026 Science Closed
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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.

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

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