Ocean acidification monitoring relies predominantly on field test and numerical modeling, while bioindicators are emerging as practical and economic approaches for seawater pH monitoring. Here, we report indoor dissolution experiments on the scale of red seabream (Pagrosomus major) under varied pH (from 7.1 to 7.9), showing that the mean aspect ratio of ventral ctenii and caudal/ventral lepidonts negatively correlated with pH. We propose to employ these ultrastructures of fish scale to be a novel bioindicator for marine pH reconstruction. This semiquantitative proxy would be applicable to both contemporary biomonitoring and paleo-oceanic pH reconstruction for the extensive occurrences of fish in modern oceans and fossil records.
Continue reading ‘Experimental observations on ultrastructure of scales of red seabream (Pagrosomus major) for seawater pH monitoring’Posts Tagged 'fish'
Experimental observations on ultrastructure of scales of red seabream (Pagrosomus major) for seawater pH monitoring
Published 18 February 2026 Science ClosedTags: biological response, dissolution, fish, laboratory, morphology, North Pacific
Photoaged microplastics disrupt the response of marine medaka (Oryzias melastigma) to ocean acidification: perspectives from energy metabolism and ammonia production
Published 2 February 2026 Science ClosedTags: biological response, fish, laboratory, molecular biology, multiple factors, North Pacific, physiology, plastics, respiration
Ocean acidification (OA) and microplastics (MPs, <5 mm) are co-occurring stressors that threaten marine ecosystems. Although the marine environment contains multiple pollutants, OA can alter the environmental behavior of MPs, influencing their toxicity and environmental fate. Therefore, investigating the interactive effects of OA and MPs is essential. Fish can activate physiological compensatory mechanisms to adapt to OA; however, it remains unclear how MPs affect these mechanisms. In this study, marine medaka were exposed to acidified seawater (pH 7.70) containing environmentally relevant concentrations of MPs (0.1 mg/L) for 90 days to investigate the disruptive effects of MPs on responses to OA. The results showed that while OA triggered compensatory energy metabolism reprogramming to enhance ammonia production, MPs disrupted this process, reducing the TCA cycle intermediate α-ketoglutarate. This α-ketoglutarate deficiency limited the glutamate supply for ammonia production. Simultaneous inhibition of glutamate dehydrogenase activity further limited glutamate availability. As a result, MPs reduced the level of ammonia production by 25.29%, compromising the ability to neutralize excess H+. Crucially, photoaging exacerbated this toxicity, leading to a 32.04% reduction in ammonia production. This study demonstrates that MPs interfere with fish responses to OA via α-ketoglutarate-mediated metabolic reprogramming, highlighting a vulnerability in marine organisms facing climate change scenarios.
Continue reading ‘Photoaged microplastics disrupt the response of marine medaka (Oryzias melastigma) to ocean acidification: perspectives from energy metabolism and ammonia production’Ocean acidification effects on growth, survival and physiological immunity of farmed Larimichthys crocea
Published 29 January 2026 Science ClosedTags: biological response, fish, fisheries, laboratory, morphology, mortality, North Pacific, physiology
Ocean acidification has become a significant global ecological issue, particularly in coastal regions with intensive aquaculture. Fish farming is a crucial component of global food security, yet research on the impact of acidification on the aquaculture performance of economically important teleosts remains limited. In this study, we reared the fast-growing large yellow croaker (Larimichthys crocea) for 30 days under three different pH conditions: severe acidification (LA, pH 7.4), moderate acidification (MA, pH 7.8), and control (HA, pH 8.1). We comprehensively evaluated growth performance, survival rate, tissue structure, antioxidant enzyme activity, and innate immunity. The results showed that the LA group exhibited suppressed growth (significantly lower than the MA group, p < 0.05), elevated cortisol and T4 levels (p < 0.05), and trends of reduced antioxidant enzyme and innate immune enzyme activities, along with organ-specific pathological changes (vacuolation, structural loosening) in gills, liver, kidneys, and intestines, though most indices showed no significant difference from the HA group. Notably, the MA group showed optimal growth performance, stable physiological and immune responses. In conclusion, while acidification did not markedly affect the survival rate of L. crocea, severe acidification (pH 7.4) induces stress responses and tissue damage. These findings suggest that L. crocea exhibits a certain degree of tolerance to the acidification conditions tested, as several physiological parameters were not significantly affected. However, when considering the overall set of observations, including histological alterations across multiple tissues and changes in plasma and tissue parameters, long-term exposure to severe acidification (pH 7.4) appears to induce tissue damage and stress-related physiological disturbances, indicating potential health risks. This study provides empirical evidence regarding the potential risk posed by projected ocean acidification on L. crocea aquaculture and supports the development of climate change adaptation strategies for coastal mariculture.
Continue reading ‘Ocean acidification effects on growth, survival and physiological immunity of farmed Larimichthys crocea’Core transcriptional plasticity pave the way for fish to succeed in a high-CO2 world
Published 26 January 2026 Science ClosedTags: biological response, BRcommunity, field, fish, molecular biology, performance, South Pacific, vents
Ocean acidification (OA) can alter the physiological and behavioural traits of marine fishes, raising concerns about how wild species will adapt to rising pCO2. Using natural volcanic CO2 vents at White Island, New Zealand, as analogues for future OA conditions, we quantified behaviours in situ and sequenced the brain transcriptomes of four highly site-attached fish species from two vents and a nearby control site with ambient pCO2, of which two species exhibit increased population densities at the vent. We found that two species showed changes in habitat preferences, and all four species with significant changes in gene expression related to circadian rhythm, visual perception, and energy metabolism at the vents. Strikingly, three differentially expressed genes, a heat shock protein (HS90A) and two immediate early genes (IEGs: JUN and FOS), were central regulators for transcriptional changes across all species at the vents. Within the circadian entrainment pathway, expression changes in opsins may act as a trigger, while core clock genes and IEGs function as downstream effectors, suggesting that elevated pCO2 may reset the circadian clock in these fishes. Notably, the two species with increased populations at the vents exhibited distinct transcriptional responses in genes involved in calcium signalling, reproduction, intracellular pH regulation and energy metabolism. Together with convergent evolution in a calcium signalling gene and an HS90 facilitator, these molecular features may confer their reproduction advantages and ability to cope with elevated pCO2. Our study provides novel insights into the molecular mechanisms underlying fish responses to OA and highlights key pathways that may support survival and ecological success under a naturally high-CO2 world.
Continue reading ‘Core transcriptional plasticity pave the way for fish to succeed in a high-CO2 world’Acute CO2 toxicity and the effects of seawater acidification on health status, histopathology, immunity and disease resistance in Asian Seabass (Lates calcarifer)
Published 12 January 2026 Science ClosedTags: biological response, fish, laboratory, molecular biology, mortality, physiology, reproduction
Carbon dioxide capture and storage (CCS) is a technology that can be used to reduce carbon dioxide (CO2) emissions generated by both natural and anthropogenic industrial processes, particularly petroleum production. To mimic and investigate the effects of CO2 leakage that may result from CCS, the acute toxicity of seawater acidification induced by continuous CO2 injection was studied in Asian seabass (Lates calcarifer) fry under static bioassay conditions. Fry (0.828 ± 0.22 g) were exposed to seawater with different pH levels (5.5, 6.0, 6.5, 7.5, and 8.3). Rapid and 100% mortality within 15 min was observed in the pH 5.5 exposure group, while mortality rates ranging from 10.00–41.67% were recorded at 6–96 h in the pH 6.0 exposure group; no mortality was noted in the other pH exposure groups. According to these mortality data, the median lethal concentration at 96 h (96 h LC50) was determined to be a pH of 5.884. Interestingly, after exposure to seawater with pH levels of 5.5 and 6.0, histopathological alterations in the skin, gills, trunk kidney and liver were evident. Additionally, some water quality parameters, especially dissolved oxygen (DO) levels, alkalinity, ammonia levels, and nitrite levels, vary depending on the pH. To further investigate the effects of seawater with pH levels of 8.3 and 5.884 (96 h LC50) and 6.5 (10% safety level) on health status, immune responses and disease susceptibility, fingerling fish (21.25 ± 3.89 g) were studied. Unexpectedly, fish exposed to seawater with a pH of 5.884 rapidly lost muscle control and gradually died, reaching 100% mortality within 24 h, and all response analyses were aborted. Interestingly, with the exception of hematocrit and some immune parameters, various serum innate immune indices, blood biochemistry parameters and immune-related gene expression patterns were similar in fish exposed to seawater with pH levels of 8.3 and 6.5. Additionally, fish were challenged with 0 (control), 1 × 107 and 1 × 109 CFU/mL Vibrio vulnificus, and fish in seawater with a pH level of 6.5 showed a higher sensitivity to 1 × 109 CFU/mL Vibrio vulnificus than fish in seawater with a pH level of 8.3, with mortality rates of 71.24% and 25.44%, respectively (p < 0.05). These findings enhance the understanding of the toxicity effects of seawater acidification caused by CO2, which will be useful for further assessing the site-specific effects of CCS projects.
Continue reading ‘Acute CO2 toxicity and the effects of seawater acidification on health status, histopathology, immunity and disease resistance in Asian Seabass (Lates calcarifer)’Multifactorial neural disruption in the brain of the Senegalese Sole (Solea senegalensis) under ocean acidification
Published 9 December 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, North Atlantic, physiology
Global ocean acidification, driven by rising atmospheric CO2, is threatening marine ecosystems and biodiversity, with increasing evidence of its disruptive effects on fish neurobiology and behaviour, yet the mechanisms underpinning its impact on fish neurobiology remain unresolved. Here, we reveal how chronic exposure to future-predicted CO2 levels disrupts brain function in the marine teleost Solea senegalensis, a species with functionally distinct olfactory organs. Using an integrative approach combining electrophysiology, immunohistochemistry, and transcriptomics, we demonstrate that elevated CO2 conditions induce a complex multifaceted disruption in brain physiology. Notably, our findings conflict with the widely held GABAA receptor reversal hypothesis; we observed increased Cl- and CO2 in cerebrospinal fluid and suppressed neural excitability, rather than the predicted loss of Cl- and heightened excitatory signalling. Immunohistochemistry further revealed reduced expression of glial fibrillary acidic protein across multiple brain regions, suggesting glial impairment. Furthermore, transcriptomic profiling of the olfactory bulb uncovered immune modulation, downregulation of neural excitability genes, and upregulation of neuroplasticity, ciliary, and anti-inflammatory pathways, hallmarks of cellular stress adaptation. Notably, genes involved in circadian regulation and thyroid signalling were also dysregulated, pointing to broader neuroendocrine disruption. These findings challenge current relatively simple models of ocean acidification impact and unveil a complex cascade of central and peripheral alterations, including enhanced GABAergic inhibition, immune shifts, glial dysfunction, and disrupted timekeeping mechanisms, likely contributing to the behavioural impairments observed under high CO₂. Challenging current models, our work highlights the need for integrative neurophysiological frameworks to predict marine fish resilience and vulnerability in a changing ocean.
Continue reading ‘Multifactorial neural disruption in the brain of the Senegalese Sole (Solea senegalensis) under ocean acidification’Impact of climate change driven freshening, warming, and ocean acidification on the cellular metabolism of Atlantic cod (Gadus morhua)
Published 27 October 2025 Science ClosedTags: biological response, fish, laboratory, multiple factors, North Atlantic, physiology, salinity, temperature
Climate change is causing increasing sea surface temperature, ocean acidification and, in near shore waters, freshening. We investigated the metabolic effects of all three and their combination in Atlantic cod from the Skagerrak (eastern North Sea) by measuring concentration changes of a wide range of metabolites involved in energy production in the liver and muscles. Liver metabolism was more strongly affected than muscle, reflecting its central regulatory role. Most amino acid concentrations declined in both tissues across all treatments, and metabolomic pathway analysis revealed significant enrichment in ten metabolic pathways. This suggests enhanced amino acid metabolism in a climate change future. Warming and ocean acidification induced increased liver concentrations of lactate, glucose and fructose 1,6-bisphosphate indicating that gluconeogenesis will increase to meet increased production of enzymes to counter future stress. The molar contribution of glutamine to the total change in liver amino acids constituted 49%, 16% and 29% under warming, ocean acidification and their combination accentuating its importance in energy production also under future climate change. We observed contrasting responses in AMP, ADP, and NAD+ concentrations between warming and acidification suggesting possible antagonistic effects. Our findings demonstrate significant and complex metabolic responses to future climate stress in Atlantic cod in northern European waters.
Continue reading ‘Impact of climate change driven freshening, warming, and ocean acidification on the cellular metabolism of Atlantic cod (Gadus morhua)’Ocean acidification enhances TiO2 nanoparticle toxicity in Oryzias melastigma: dominant role of size effects in driving bioaccumulation and hepatotoxicity
Published 21 October 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, multiple factors, physiology, toxicants
Highlights
- OA reduces TiO₂ NPs aggregation/sedimentation, increasing NP bioaccumulation
- NPs preferentially accumulate in liver, inducing hepatotoxicity via oxidative stress
- Size effect outweighs biological resistance as primary NP toxicity driver under OA
- Combined OA-NPs suppress hepatic genes, activate senescence and cell death pathways
- First evidence quantifying hydrodynamic size dominance in OA-enhanced NP toxicity
ABSTRACT
Ocean acidification (OA) and engineered nanoparticles (NPs) pollution represent two critical global environmental challenges. Marine organisms are suffering from their combined stress. However, few studies address their combined effects, and the toxicity mechanisms of NPs under OA are largely unresolved. In this study, we investigated the responses of the marine medaka Oryzias melastigma to environmentally relevant concentration of TiO2 NPs (1.0 mg/L) under OA (pH 7.40). We found that OA alleviated the aggregation and sedimentation of NPs, and decreased the resistance ability of the marine medaka to NPs stress, leading to elevated bioaccumulation of TiO2 NPs. Notably, NPs preferentially accumulated in the liver, inducing hepatotoxicity through oxidative stress and histopathological and ultrastructural damage. Critically, an integrated biomarker approach quantified the relative contributions of size effects (58%) and biological resistance (42%) to NP toxicity under OA, demonstrating that hydrodynamic size dominates toxicity outcomes. Transcriptomic analysis further revealed suppressed hepatic gene transcription and translation, alongside activated cellular senescence and programmed cell death pathways under combined exposure. These findings provide critical insight into the combined toxicity mechanisms of NPs and OA, significantly advancing our understanding of the profound risks that NPs pose to marine ecosystems under OA conditions.
Continue reading ‘Ocean acidification enhances TiO2 nanoparticle toxicity in Oryzias melastigma: dominant role of size effects in driving bioaccumulation and hepatotoxicity’Warming, but not acidification, increases metabolism and reduces growth of redfish (Sebastes fasciatus) in the Gulf of St. Lawrence
Published 16 October 2025 Science ClosedTags: biological response, fish, fisheries, growth, laboratory, multiple factors, performance, physiology, temperature
Understanding the effects of global change, including temperature, pH, and oxygen availability, on commercially important species is crucial for anticipating consequences for these resources and their ecosystems. In the Gulf of St. Lawrence (GSL), redfish (Sebastes spp.) were under moratorium from 1995 to 2023, but the fishery has reopened in 2024 following massive recruitment observed in 2011–2013. Despite current high abundance, little is known about their metabolic and thermal physiology. To address this, we quantified the effects of four acclimation temperatures (2.5, 5.0, 7.5, and 10.0 °C) and two ocean acidification scenarios (current and future) on standard and maximum metabolic rates (SMR and MMR), aerobic scope (AS), factorial aerobic scope, hypoxia tolerance (O2crit), food consumption, growth and food conversion efficiency (FCE) in redfish (Sebastes fasciatus Storer, 1854). SMR, MMR, and AS increased with temperature, but growth and FCE decreased with temperature, likely due to increased cost of maintenance. Food consumption was lower at 2.5 °C, but similar at higher temperatures. Redfish were less hypoxia-tolerant at higher temperatures. Except for SMR, no significant effect of pH was observed. These results suggest that future changes in the GSL will challenge redfish, with potential long-term effects on growth due to increased energy requirements.
Continue reading ‘Warming, but not acidification, increases metabolism and reduces growth of redfish (Sebastes fasciatus) in the Gulf of St. Lawrence’The impact of an early exposure to 17α-ethynylestradiol on the physiology of the three-spined stickleback (Gasterosteus aculeatus) under current and future climatic scenarios
Published 9 October 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, morphology, mortality, multiple factors, reproduction, temperature, toxicants
Highlights
- RCP8.5 scenario modulated some of the long-lasting physiological responses to EE2.
- RCP8.5-EE2 group led to sex and tissue specific responses.
- RCP8.5-EE2 scenario resulted in lower body length at five months post-contamination.
- RCP8.5 reduced survival rate of embryo-larval but not juvenile stages.
- Early-life exposure to EE2 led to stickleback feminisation.
- Early-life exposure to EE2, led to long-lasting effect on stickleback physiological responses.
Abstract
Ocean warming and acidification are climate change related drivers that impact the physiology of marine organisms and their ability to cope with future environments. Marine ecosystems are also facing pollution from an ever-growing diversity of chemical contaminants, including endocrine disruptors. A common example is the 17α-ethynylestradiol (EE2), which can affect the endocrine regulation of fish and hence potentially impact their fitness. Thus, fish have to cope to multiple climatic and chemical stresses that can interact, influencing the overall impact on fish physiology. In this study, we investigated whether the direct and carry-over effect of early exposure to EE2 (15 ng.L−1; one month during embryo-larval development) are modulated by the RCP8.5 scenario (+3°C; -0.4 pH unit). Five months post-contamination, we measured survival, growth and reproductive axis of prepubertal sticklebacks. Our findings revealed that the survival of juveniles, when exposed to EE2 during early development, is reduced under Current but not RCP8.5 scenario. Furthermore, under RCP8.5-EE2, a significantly lower body length was observed. Sex and tissue specific responses in terms of the expression profiles of genes related to development and sexual maturation was reported. Interestingly, significant interaction between RCP8.5 and EE2 was observed for the expression of ovarian aromatase (cyp19a1a), suggesting a long-lasting estrogenic effect under RCP8.5 scenario. Additionally, the skewed sex ratios and the presence of intersex individuals in both scenarios early exposed to EE2 suggested a feminization due to EE2, which could potentially disrupt sexual maturation and future reproduction. Hence, the early EE2 exposure had carry-over physiological effects on sticklebacks, and these effects can be modulated by the climate scenario. This underscores the importance of conducting long-term multi-stress studies to comprehensively understand the vulnerability on fish populations in future environments.
Continue reading ‘The impact of an early exposure to 17α-ethynylestradiol on the physiology of the three-spined stickleback (Gasterosteus aculeatus) under current and future climatic scenarios’Climate change and its effects on fish growth and physiology
Published 8 October 2025 Science ClosedTags: biological response, fish, growth, physiology, reproduction, review
Climate change, driven by anthropogenic greenhouse gas emissions, poses significant threats to aquatic ecosystems, particularly impacting fish physiology, growth, reproduction, and distribution. This article explores how rising temperatures, ocean acidification, and declining oxygen levels affect fish by altering metabolic rates, reducing oxygen availability, and disrupting physiological and behavioral processes. Species-specific thermal tolerances and susceptibility to hypoxia and acidification influence growth rates, survival, and reproductive success, especially during early developmental stages. Additionally, shifts in habitat and migration patterns, the introduction of exotic species, and reduced breeding success threaten fish populations and ecosystem stability. The article also emphasizes the importance of adaptation and mitigation strategies, such as habitat conservation, sustainable fisheries management, marine protected areas, and emissions reduction. Understanding these multifaceted impacts is critical to developing resilient fisheries and aquaculture systems in the face of a rapidly changing climate.
Continue reading ‘Climate change and its effects on fish growth and physiology’Effects of simulated ocean acidification on the activity, escape response, and muscle physiology of marine threespine stickleback (Gasterosteus aculeatus)
Published 19 September 2025 Science ClosedTags: biological response, fish, laboratory, North Pacific, performance, physiology
Rapidly increasing anthropogenic CO2 can impose physiological challenges for fish species that are thought to be tolerant. We tested the hypothesis that elevated pCO2 will affect the routine activity and escape response by affecting energy metabolism and/or the muscle physiology of coastal fish. We exposed threespine stickleback (Gasterosteus aculeatus) to pCO2 of ~ 700 µatm (pH 7.9 representing current levels), ~ 1400 µatm (pH 7.6 representing upwelling events) and ~ 3500 µatm (pH 7.3 representing a future predicted scenario for coastal areas) for 2 weeks. Baseline activity was significantly higher in fish exposed to 1400 µatm compared to the control at both sampling points, while the escape response was lower (p < 0.05). Metabolic rate was not different (p > 0.05), but lactate dehydrogenase activity was significantly higher at 3500 µatm compared to control fish after the first week (p < 0.05), while no difference was found in muscle histology between treatments or time points. Our study demonstrates that the baseline activity and escape responses of adult marine coastal fish were temporarily affected by the current level of ocean acidification, but this was not due to changes in metabolism or muscle function, but potentially neuronal effects of high pCO2. Our study shows that ocean acidification might affect predator‐prey interactions during current upwelling events and in the future.
Continue reading ‘Effects of simulated ocean acidification on the activity, escape response, and muscle physiology of marine threespine stickleback (Gasterosteus aculeatus)’No effect of ocean acidification on individual-level variation in behaviour and susceptibility to predation in a Great Barrier Reef damselfish
Published 9 September 2025 Science ClosedTags: biological response, fish, laboratory, mortality, performance, South Pacific
1) Ocean acidification, caused by rising carbon dioxide (CO2) in the atmosphere, has been reported to negatively impact a wide variety of behaviours in fishes, including activity, exploration, and predator avoidance.
2) These effects have been documented at the population level, but many animal species naturally show large and repeatable individual-level differences in behaviour. How environmental stressors, such as ocean acidification, affect behavioural variation at the individual level remains largely unknown but is critically important to understand adaptation given natural selection operates on variation at the individual rather than population level.
3) Using a statistical approach allowing variation in means and variation in variance to be modeled within a single framework, we quantified individual-level differences across five behaviours in the coral reef damselfish Pomacentrus amboinensis (emergence time, activity level, time spent sheltering, thigmotaxis, novel object inspection). We measured behaviour in a novel environment assay, twice before (CO2 ~450 µatm) and twice following acclimation to predicted end-of-century ocean acidification conditions (~1,100 µatm).
4) Following behavioural assays, we tested individual survival in a live predation experiment. We used predatory rock cod, Cephalopholis microprion, acclimated to the same CO2 treatments as Ambon damsel and examined predictors of survival probability.
5) All behaviours in damselfish were moderately and significantly repeatable, with no marked differences in repeatability estimates between the ambient CO2 and elevated CO2 treatment groups. Exposure to end-of-century ocean acidification conditions had no effect on any of the five behaviours measured, both in terms of group means and residual (within-individual) variance.
6) The probability of survival in the predation trials was similar for damselfish in the elevated and ambient CO2 treatment groups. Smaller damselfish as well as those that spent a greater amount of time inspecting a novel object (i.e., bolder individuals) had a lower probability of survival regardless of their CO2 treatment.
7) Our results challenge assumptions about the impacts of ocean acidification on coral reef fish behaviour and susceptibility to predation, both at the population and individual level. They also provide support for a trade-off between boldness and predation risk in fish.
Continue reading ‘No effect of ocean acidification on individual-level variation in behaviour and susceptibility to predation in a Great Barrier Reef damselfish’The swimming performance of mollies and their interaction with tiger barb fish when exposed to concurrent low pH and elevated temperature
Published 2 September 2025 Science ClosedTags: biological response, BRcommunity, fish, laboratory, multiple factors, performance, temperature
The global climate change and ocean acidification brought about by the anthropogenic release of carbon dioxide gas into the air is considered one of the greatest problems facing marine life. In this research, the interactions between two species of fish (the gold mollies and tiger barb) were investigated under two different environmental conditions, an elevated temperature of 28 °C and a low pH of 5 and a normal pH of 7 and a normal temperature of 24 °C. The mollies at pH 7 and a temperature of 24 °C exhibited scary interactions with the tiger barb. They were scared and ran fast away from the tiger barb. At the same time, the mollies at pH 5 and a temperature of 28 °C interacted normally as though both species were one species showing behavioral changes due to these two stressors (pH 5 and elevated temperature 28 °C). This could be the only research that has addressed how the kinematics and swimming interactions of two species of fish changed in response to elevated temperature and low pH.
Continue reading ‘The swimming performance of mollies and their interaction with tiger barb fish when exposed to concurrent low pH and elevated temperature’Toothless sharks? Ocean acidification could erode predator’s vital weapon, study finds
Published 1 September 2025 Press releases ClosedTags: fish
Sharks without teeth might sound like the stuff of dreams to swimmers and surfers. Now a new study has found that ocean acidification could leave the apex predators without their critical survival weapon.
Shark jaws carry several rows of teeth and new ones quickly push forward to replace losses. However, rapidly acidifying oceans are damaging shark teeth and could speed losses past replacement rates. Sharks with bad teeth could struggle to feed themselves efficiently, “potentially affecting shark populations and marine ecosystem stability”, the study said.
Ocean acidification is caused by rapid carbon dioxide absorption creating a chain reaction that lowers pH levels. Projections suggest oceans could be far more acidic by the year 2300, falling from a current average pH of about 8.1 to 7.3, a change that will have “profound implications for marine organisms”, the study said.
To test acidification effects, researchers kept 60 freshly fallen shark teeth in artificial seawater tanks, one matching the current ocean average pH of 8.1, another with the projected 7.3 pH. The teeth, safely collected from a German aquarium, had already been naturally discarded by six male and four female blacktip reef sharks.
Maximilian Baum, who conducted the study, with a blacktip reef shark jaw. He found increased root corrosion and altered serration. Photograph: Roman Müller-Böhm
Continue reading ‘Toothless sharks? Ocean acidification could erode predator’s vital weapon, study finds’Simulated ocean acidification affects shark tooth morphology
Published 29 August 2025 Science ClosedTags: biological response, fish, laboratory, morphology
Changing ecological factors pose a challenge to many organisms. Global changes and the associated environmental changes have major impacts on marine organisms and threaten the biodiversity of marine ecosystems. It has been shown in previous experimental studies that ocean acidification caused by anthropogenic CO2 release into the atmosphere and subsequent dissolution in seawater will have a significant impact on various marine organisms. Here, we investigated the corrosive effects from acidification on the morphology of isolated shark teeth in an eight-week incubation at a pH of 7.3, the expected seawater pH in the year 2300. The typical littoral blacktip reef shark (Carcharhinus melanopterus), which is often kept in display aquaria under controlled conditions, has been used for this purpose, greatly facilitating minimally invasive sampling for in-situ investigation. The teeth of this typical Requiem Shark species are orthodont teeth, which show strong serration in the teeth of the upper jaw. Using scanning electron microscopy (SEM) we could observe the corrosive effects of acidification on the different tooth structures, such as the root, primary and secondary serrations and the crown of the blacktip reef sharks teeth. Our results show that ocean acidification will have significant effects on the morphological properties of teeth, including visible corrosion on the crown, degradation of root structures, and loss of fine serration details under low pH conditions which could lead to changes in foraging efficiency, energy uptake, and ultimately elasmobranch fitness in future oceans.
Continue reading ‘Simulated ocean acidification affects shark tooth morphology’Assessing the physiological and oxidative stress status of Etroplus suratensis under elevated temperature and ocean acidification
Published 27 August 2025 Science ClosedTags: biological response, fish, Indian, laboratory, multiple factors, physiology, temperature
Highlights
- Current study delves into the impacts of ocean warming (OW) and acidification (OA) on E. suratensis.
- Combined stressor-induced metabolic depression which indicated energy conservation strategy.
- Lower Scope for Growth advocates impaired energy allocation under stress.
- Oxidative stress biomarkers and apoptosis augmented due to combined stress.
- Anticipated OA and OW could threaten future fish populations and marine ecosystem balance.
Abstract
The incessant release of anthropogenic CO2 in the atmosphere has accentuated ocean warming (OW) and elevated the partial pressure of dissolved CO₂, culminating in a foreseeable decline in oceanic pH. Thus, the present study endeavors to elucidate the concomitant impacts of OW and ocean acidification (OA) on the eco-physiological responses of Etroplus suratensis over a 30-day mesocosm experiment. Physiological parametres, encompassing ingestion, absorption, respiration, and excretion rates, were measured to gauge the scope for growth (SfG). Additionally, a comprehensive evaluation of biomarkers, comprising antioxidant defenses, detoxification pathways, lipid peroxidation, and apoptotic markers, was assessed at various biological levels. Results revealed that combined stressors curtailed the feeding activity, as substantiated by a significant reduction in ingestion and absorption rate. Metabolic depression, illustrated by reduced respiration and excretion rates, insinuated an energy conservation strategy amidst dual stressors. Despite these adaptations, SfG remained depressed, accentuating the detrimental effects of the combined stressors on the energy allocation strategy of this fish. Furthermore, oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST), exhibited heightened activities, albeit these defenses were insufficient to counteract persistent environmental stressors, resulting in increased lipid peroxidation (LPO) and apoptosis. Notably, cleaved caspase-3 expression was significantly upregulated, which suggested that apoptosis was a key cellular response against combined stressors. Overall, anticipated OA and OW significantly impacted the energy budget, oxidative stress biomarkers, and key cellular responses of E. suratensis, compromising growth, survival, and reproductive fitness. These potentially jeopardize population structure and disrupt trophic interactions which may impair functional integrity of estuarine ecosystem.
Continue reading ‘Assessing the physiological and oxidative stress status of Etroplus suratensis under elevated temperature and ocean acidification’The development and plasticity of acid excretion mechanisms in early life stage red drum, Sciaenops ocellatus
Published 21 August 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, North Atlantic, physiology, reproduction
Highlights
- Components of acid-base pathways are present and stable in very early development.
- NHE3 is localized to the apical pit of epithelial ionocytes.
- Epithelial proton excretion is responsive to elevated CO2 and governed by NHEs.
- nhe2/3 transcript abundance is elevated following development in high CO2.
- Low level CO2 causes reductions in survival.
Abstract
Ocean acidification (OA) has been shown to affect early life stage fishes in a variety of ways, including reduced survival and growth, and increased tissue damage. Yet, there is also substantial interspecies variability in the sensitivity of early life stage fishes to high CO2, and it has been theorized that this may relate to the ontogeny of systemic acid-base regulatory pathways; an area that has been surprisingly understudied in obligate marine species. Here, we used an integrative set of approaches to describe the development and plasticity of acid excretion pathways in developing red drum (Sciaenops ocellatus), a marine fish native to the Gulf of Mexico. We observed mRNA expression of relevant transporters and ionocytes immediately post-hatch (36 h post-fertilization, hpf) with relatively stable abundance throughout the pre-metamorphic stages. Consistent with work in adults and seawater acclimated euryhaline larvae, we demonstrate strong co-localization of acid excretion proteins within a single epithelial ionocyte cell-type. Measurements of epithelial Δ[H]+, an indicator of proton efflux, showed that by 72 hpf larvae had CO2-responsive EIPA-sensitive acid excretion, confirming the presence of sodium proton exchanger (NHE)-mediated acid excretion. Elevated mRNA expression of nhe2 and nhe3 was induced following exposure to 5500 and 12,000 μatm CO2, which coincided with the absence of further survival effects relative to lower dose CO2. Overall, these data confirm that red drum have fully functional epithelial acid excretion pathways in early life, and that plasticity in these pathways may offer survival benefits.
Continue reading ‘The development and plasticity of acid excretion mechanisms in early life stage red drum, Sciaenops ocellatus’The influence of cross-generational warming on the juvenile development of a coral reef fish under ocean warming and acidification
Published 20 August 2025 Science ClosedTags: adaptation, biological response, fish, laboratory, morphology, multiple factors, otherprocess, performance, physiology, reproduction, South Pacific, temperature
Marine ecosystems are facing escalating chronic and acute environmental stressors, yet our understanding of how multiple stressors influence individuals is limited. Here, we investigated how projected ocean warming (+1.5°C) during grandparental (F1) and parental (F2) generations of the spiny chromis damselfish (Acanthochromis polyacanthus), influences the sensitivity of F3 juveniles to ocean warming (present-day vs +1.5°C) and/or elevated CO2 (490 μatm vs 825 μatm). After 16 weeks of exposure, aerobic physiology (resting oxygen consumption, maximum oxygen consumption, and absolute aerobic scope), behaviour (boldness and activity), and growth (length and physical condition) were measured in F3 juveniles and the relationships between these performance traits was explored. We found that warming during F3 development resulted in juveniles that were shorter, bolder, and in better physical condition, while elevated CO2 resulted in shorter juveniles with a reduced resting oxygen consumption. However, across juvenile performance traits there was no interaction between ocean warming and acidification, demonstrating the additive nature of these two environmental stressors. Although we found limited signs of transgenerational plasticity, there was evidence of parental and grandparental carry-over effects which resulted in juveniles that were larger and/or in better condition when grandparents and parents experienced warming during their development regardless of the F3 juvenile developmental treatment. These finding illustrate the significant role phenotypic plasticity has on juvenile performance under projected future climate change.
Continue reading ‘The influence of cross-generational warming on the juvenile development of a coral reef fish under ocean warming and acidification’A collaborative climate vulnerability assessment of California marine fishery species
Published 20 August 2025 Science ClosedTags: biological response, crustaceans, fish, fisheries, mollusks, North Pacific, policy, review
Climate change and the associated shifts in species distributions and ecosystem functioning pose a significant challenge to the sustainability of marine fisheries and the human communities dependent upon them. In the California Current, as recent, rapid, and widespread changes have been observed across regional marine ecosystems, there is an urgent need to develop and implement adaptive and climate-ready fisheries management strategies. Climate Vulnerability Assessments (CVA) have been proposed as a first-line approach towards allocating limited resources and identifying those species and stocks most in need of further research and/or management intervention. Here we perform a CVA for 34 California state-managed fish and invertebrate species, following a methodology previously developed for and applied to federally managed species. We found Pacific herring, warty sea cucumber, and California spiny lobster to be three of the species expected to be the most sensitive to climate impacts with California halibut, Pacific bonito, and Pacific hagfish expected to be the least sensitive. When considering climate sensitivity in combination with environmental exposure in both Near (2030–2060) and Far (2070–2100) Exposure climate futures, red abalone was classified as a species with Very High climate vulnerability in both periods. Dungeness and Pacific herring shifted from High to Very High climate vulnerability and Pismo clam and pink shrimp shifted from Moderate to Very High climate vulnerability as exposure conditions progressed. In providing a relative and holistic comparison of the degree to which state-managed marine fishery species are likely to be impacted as climate change progresses, our results can help inform strategic planning initiatives and identify where gaps in scientific knowledge and management capacity may pose the greatest risk to California’s marine resource dependent economies and coastal communities.
Continue reading ‘A collaborative climate vulnerability assessment of California marine fishery species’
