High carbonate alkalinity can impose composite hydrochemical stress on bivalves by altering inorganic carbon speciation, buffering capacity and ion-exchange conditions. The Hong Kong oyster (Crassostrea hongkongensis) naturally inhabits estuarine areas where low salinity can occur together with carbonate-system disturbance, yet its physiological response to high carbonate alkalinity under a low-salinity background remains unclear. In this study, oysters were exposed at salinity 5 to a Control treatment, A10 (carbonate alkalinity 10 mmol L⁻¹) and A20 (carbonate alkalinity 20 mmol L⁻¹). Salinity was treated as a controlled background condition, whereas the alkalinity treatments represented a composite carbonate-alkalinity perturbation involving alkalinity, pH and carbonate chemistry. Survival, feeding rate, oxygen consumption, ammonia excretion and hemolymph ammonia were measured across Control, A10 and A20. Hemolymph catalase (CAT), glutathione peroxidase (GSH-Px), glucose and ATP were analyzed as A10 and A20 time-course endpoints because a parallel Control was not included for these assays. A 24-h mantle transcriptome was used to screen candidate transcripts associated with innate defense and glutathione metabolism. Oysters under A10 retained partial compensatory capacity, whereas A20 significantly reduced survival. A10 and A20 suppressed early oxygen consumption and ammonia excretion, and altered feeding allocation among microalgae. Within the A10 and A20 biochemical time-course dataset, CAT, GSH-Px, glucose and ATP showed stage-specific variation, suggesting redox and energy-metabolism adjustment under alkalinity stress. Overall, high carbonate alkalinity reduced survival and was associated with metabolic depression, feeding compensation and hemolymph redox-energy remodeling in C. hongkongensis. This study will provide a theoretical basis for water quality regulation in saline-alkaline water aquaculture and the sustainable development of aquaculture.
Continue reading ‘The effects of high carbonate alkalinity under low salinity on the survival, physiological metabolism, and redox homeostasis of Crassostrea hongkongensis’Posts Tagged 'physiology'
The effects of high carbonate alkalinity under low salinity on the survival, physiological metabolism, and redox homeostasis of Crassostrea hongkongensis
Published 28 July 2026 Science Leave a CommentTags: biological response, laboratory, mollusks, mortality, multiple factors, oxygen, performance, physiology, salinity
Warming and acidification alter essential fatty acid profiles in marine diatom Skeletonema marinoi
Published 28 July 2026 Science Leave a CommentTags: biological response, BRcommunity, laboratory, molecular biology, North Atlantic, physiology, phytoplankton
Marine diatoms are key components of the planetary ocean, playing crucial roles in trophic networks: fixing carbon, producing fatty acids (FA) that cannot be synthesized de novo by higher trophic organisms. To better comprehend how the combined action of climatic change influences the dietary value and the impacts on the upper trophic levels, we used a 2 × 2 factorial experiment to investigate how the FA profiles of Skeletonema marinoi changed in response to the individual and combined effects of warming (7, 19°C) and acidification (400, 1 000 ppm CO2). Three S. marinoi strains were exposed for ~ 40 weeks to ambient conditions, warming, acidification and their combination and analyzed for FA profiles, focusing on polyunsaturated (PUFA), omega-3 and omega-6 FA. We found that omega-3 FA increased under warming exposure, while acidification alone led to lower omega-3/omega-6 ratios. In contrast, the ratios increased under warming, alone or coupled with acidification, in all three strains, indicating better food quality for higher trophic levels. Our results suggest the long-term exposure to both drivers will help the marine diatoms to acclimatize to their combined effects, allowing them to buffer the changes brought by warming and ocean acidification.
Continue reading ‘Warming and acidification alter essential fatty acid profiles in marine diatom Skeletonema marinoi’pH–salinity-driven regulation in carbon utilization kinetics of the intertidal seagrass Zostera japonica along China’s coastline
Published 27 July 2026 Science Leave a CommentTags: biological response, BRcommunity, field, laboratory, methods, morphology, North Pacific, phanerogams, photosynthesis, physiology
Highlights
- We innovatively define two biophysical parameters (pH change rate and acceleration) of Zostera japonica photosynthesis.
- pH change acceleration is sensitive to the regulation of carbon utilization pathways during Z. japonica photosynthesis.
- A progressive pH–salinity-driven regulation mode of carbon utilization pathways in Z. japonica photosynthesis is summarized.
- The impact of ocean acidification and alkalization on seagrass is characterized from a new biophysical standpoint.
Abstract
Seagrass carbon concentration mechanisms are modulated by seawater pH and salinity, yet their progressive regulation in photosynthetic inorganic carbon utilization pathways remain poorly characterized. This study novelly mathematically characterized first-order (pH change rate) and second-order (pH change acceleration) derivatives from pH-drift experiments in the intertidal seagrass Zostera japonica along China’s coastline. The pH change-based method effectively highlights the dissolved inorganic carbon (DIC) utilization and biomass accumulation of seagrass, while pH change acceleration is sensitive to the progressive switch of DIC utilization pathways during Z. japonica photosynthesis. As pH increases, six significant regulations emerge that have ecophysiological significance: a. primary regulation via reaching the CO2 compensation point; b. extracellular carbonic anhydrase (exCA) activity dropping to negligible levels; c. diminished efficiency of proton pump-mediated extracellular acidification in supplying CO2; d. regulation via reaching the bicarbonate saturation point; e. regulation via reaching the bicarbonate compensation point; and f. regulation via enhanced respiratory CO2 into seawater temporarily stimulating photosynthesis as a feedback. We summarize a progressive and universal pH–salinity-driven regulation mode reflecting different combinations of DIC utilization pathways and their respective intensities. Specifically, seawater pH modulates the mode’s fluctuating thresholds, while salinity governs the amplitude. Unexpectedly, elevated salinity serves as an effective stimulant for Z. japonica to maintain strong DIC utilization intensity in high pH (> 9.1) environments. Ocean acidification could increase pH change acceleration by 166%, enhancing carbon fixation, whereas artificial ocean alkalinity enhancement (Ca(OH)2 supplementation and olivine-seawater weathering) could reduce it by 165% and 105%, respectively, risking mortality of Z. japonica. Additionally, the salinity-dependent braking point (where acceleration drops to zero) serves as a critical threshold for seagrass photosynthesis and a new factor for transplantation-based restoration.
Continue reading ‘pH–salinity-driven regulation in carbon utilization kinetics of the intertidal seagrass Zostera japonica along China’s coastline’Changes in photosynthesis and grazing facilitate growth of a mixotrophic protist under ocean acidification and warming
Published 22 July 2026 Science Leave a CommentTags: algae, biological response, BRcommunity, growth, laboratory, multiple factors, photosynthesis, physiology, protists, temperature
Summary
- Mixotrophic protists capable of both photosynthesis and phagotrophy are key members of marine plankton communities. Yet, little is known about their responses to the combination of ocean acidification and warming.
- A marine mixotrophic chrysophyte, Ochromonas CCMP2951, was subjected to two levels of pCO2 (300 and 800 ppm, resulting in pH of 8.2 and 7.8) and temperature (21°C and 26°C) in a factorial design.
- Enhanced growth rates were observed in both the high CO2 and high temperature treatments, while cell size significantly decreased with temperature. Strongly decreased cellular phosphorus content led to increased N : P and C : P ratios of Ochromonas with temperature. Furthermore, warming increased grazing rates, while elevated CO2 reduced the Chl content but increased photosynthetic carbon acquisition, albeit only at low temperature. The combination of warming and elevated CO2 had antagonistic effects on the balance between autotrophic and heterotrophic carbon acquisition, keeping the net role of this mixotroph in the marine carbon cycle stable.
- Altogether, both the direct stimulation of growth and the indirect effects of altered stoichiometry may favor mixotrophs under future ocean conditions. However, their contribution to future carbon cycling in complex natural communities will need further study.
Graphical Abstract
Grazing rates of Ochromonas CCMP2951 expressed as carbon obtained per mean cell volume (a) and Caut/het-photosynthetically fixed carbon divided by carbon obtained through grazing (b) in the four experimental treatments.
The molecular footprint of global change in Antarctic coral
Published 21 July 2026 Science Leave a CommentTags: Antarctic, biological response, BRcommunity, corals, laboratory, molecular biology, multiple factors, physiology, temperature
Anthropogenic CO2 emissions are altering marine ecosystems through two interconnected processes: climate change and ocean acidification, both of which are particularly affecting the Southern Ocean. However, the molecular responses of cold-water corals to these stressors remain poorly understood. In this study, we investigated the transcriptomic response of the Antarctic coral Malacobelemnon daytoni exposed to ocean acidification (pH ~7.7; LpH) and elevated temperatures (+2°C and +4°C above ambient; T1 and T2, respectively) under controlled laboratory conditions. Using high-throughput RNA sequencing (RNA-Seq), we compared gene expression profiles across six treatments, including a control (pH ~8.1, CpH; 0–1°C; CT), acidification, warming, and their combinations. Principal component analysis revealed treatment-specific clustering and greater transcriptomic dispersion under LpH conditions. Differential expression analysis identified between 475 and 767 differentially expressed genes (DEGs), with the strongest transcriptional responses observed under combined stress conditions (LpH + T1 and LpH + T2). Combined exposure to ocean acidification and warming elicited the largest gene expression response, suggesting enhanced, potentially non-additive effects of multiple stressors. Functional enrichment analyses revealed differential regulation of genes associated with protein folding, signal transduction, energy metabolism, oxidative stress, and regulation of cell death. Our findings demonstrate that Malacobelemnon daytoni exhibits complex, treatment-dependent gene expression responses to environmental stressors. These results highlight the capacity of this Antarctic octocoral to mount molecular responses to projected future ocean conditions while also emphasizing its potential vulnerability to the interacting effects of ocean warming and acidification.
Continue reading ‘The molecular footprint of global change in Antarctic coral’The effects of decreased pH and increased temperature on survival and shell development of the larvae of the endemic Hawaiian oyster Dendostrea sandvichensis
Published 17 July 2026 Science Leave a CommentTags: biological response, BRcommunity, growth, laboratory, mollusks, mortality, multiple factors, physiology, reproduction, temperature
Climate change models predict future ocean-wide decreases in pH and increases in temperature, posing a serious threat to calcifying marine invertebrates. In Hawaiʻi, local seawater temperature and pH are predicted to change even more rapidly. The Hawaiian oyster Dendostrea sandvichensis, an endemic species, remains understudied despite its ecological roles in reef- building, biofiltration, and as a food source. While previous studies have revealed the alarming impacts of ocean acidification and warming on bivalves, little is known about how the planktonic larvae of D. sandvichensis will respond to projected climate conditions.
To investigate these effects, the larvae of D. Sandvichensis were reared under present-day conditions in Pearl Harbor, HI (pH 8.1, 26.5 °C) and projected future conditions (pH 7.7, 30.0°C) for one week. Shell growth, density, and degradation were then measured using micro-CT, confocal, and scanning electron microscopy. Additionally, two larval husbandry methods were evaluated, with a static-flow system paired with UV water treatment yielding approximately 11- fold higher survival than an open-flow system. Elevated temperature reduced larval survival (~67%) compared to ambient conditions. Reduced pH significantly decreased shell length (~11.8μm), while both stressors reduced shell density in Experiment 3. Shell density decreased by ~12% under elevated temperature, ~18% under reduced pH, and ~43% under the combined stressors, and was accompanied by increased shell degradation and abnormalities.
These findings indicate that elevated temperature and reduced pH impact larval oysters through multiple pathways, including reduced survival and compromised shell integrity. This study provides new insights into the vulnerability of an endemic Hawaiian species and essential data for predicting its resilience under future climate change scenarios.
Continue reading ‘The effects of decreased pH and increased temperature on survival and shell development of the larvae of the endemic Hawaiian oyster Dendostrea sandvichensis’Impacts of ocean acidification on reproduction and early life development in marine teleost fish—a synthesis
Published 17 July 2026 Science Leave a CommentTags: biological response, fish, physiology, reproduction, review
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.
Continue reading ‘Impacts of ocean acidification on reproduction and early life development in marine teleost fish—a synthesis’Ocean acidification exacerbates UVR-induced inhibition of photosystem II and I in Corallina officinalis
Published 16 July 2026 Science Leave a CommentTags: algae, biological response, calcification, laboratory, North Pacific, physiology
Highlights
- OA reduces calcification, compromising the UV shield and exacerbating photoinhibition in C. officinalis.
- OA amplifies PSII donor-side damage, disrupts electron flow to PSI, and suppresses PSI function.
- OA shifts PSII damage-repair balance toward irreversible photoinhibition by increasing damage and suppressing repair.
Abstract
Ocean acidification (OA) exerts diverse effects on marine macroalgae, with calcified species being particularly vulnerable. Due to calcified skeletons can contribute to physical screening against solar ultraviolet radiation (UVR), OA-driven calcification loss may increase exposure of the photosynthetic apparatus to UVR. Here, we cultured Corallina officinalis under ambient CO₂ (∼420 μatm) or elevated CO₂ (∼1000 μatm), with or without UVR, under natural solar radiation. Our results confirmed that OA reduced calcification and, under UVR, enhanced donor-side impairment of photosystem II (PSII), as evidenced by an increase in the relative K-step (Wk, an indicator of OEC damage) and a decrease in the maximum quantum yield of PSII (Fᵥ/Fₘ). This donor-side injury was accompanied by a reconfiguration of energy fluxes per PSII reaction center, particularly under combined OA and UVR. These impairments further extended to intersystem electron transport and limited the linear electron flow from PSII to the intersystem chain. Photosystem I (PSI) related electron transport was also functionally constrained, as evidenced by the reduced electron transfer probability and terminal reduction yield. This, together with the reduction of cyclic electron transport around PSI, resulted in over-reduction of the intersystem chain and making PSI the limiting photosystem. Together, these results indicate that OA amplified UVR-induced net photodamage and weakened PSII repair capacity in C. officinalis, while also constraining PSI-related electron transport. These findings highlight the potential vulnerability of calcified red algae under future high-CO₂, high-UVR coastal oceans.
Continue reading ‘Ocean acidification exacerbates UVR-induced inhibition of photosystem II and I in Corallina officinalis’Multigenerational physiological plasticity of the marine copepod Acartia tonsa in response to ocean acidification
Published 16 July 2026 Science Leave a CommentTags: biological response, BRcommunity, crustaceans, laboratory, morphology, physiology, reproduction, zooplankton
Ocean acidification (OA) refers to the increase in the partial pressure of CO2 and decrease in the pH of seawater resulting from the absorption of atmospheric CO2 by the ocean. This study investigated OA impacts across multiple generations (F0-F3) of the copepod Acartia tonsa which were exposed to four pH conditions (8.1, 7.8, 7.6 and 7.1). Key reproductive and developmental traits were evaluated, including egg production, hatchability, development time, fecal pellet production, and sex ratio. Results showed that pH 7.1 significantly reduced egg production, hatchability and fecal pellet production, while prolonging the N–C time; N-A time remained unaffected by pH across all groups. For sex ratio, a downward trend was observed with increasing generations and decreasing pH: in F3, female proportion in pH 7.8, 7.6 and 7.1 groups was significantly lower than in the control group, and pH 7.1 and 7.6 groups had lower F3 female proportion than in the F1 generation. A. tonsa showed some tolerance under short-term acidification conditions at pH 7.1, but its physiological functions were further reduced after long-term exposure, suggesting a limited adaptive capacity. Ecologically, A. tonsa is a dominant coastal zooplankton species that links phytoplankton to higher trophic levels (e.g., fish larvae) and mediates energy flow and biogeochemical cycling. These results highlight the risks to key zooplankton populations and associated ecosystem functioning. Future studies should focus on the long-term effects of acidification on A. tonsa and combine multi-species experiments with field surveys to assess the ecological risks of OA.
Continue reading ‘Multigenerational physiological plasticity of the marine copepod Acartia tonsa in response to ocean acidification’Climate change and ocean acidification outweigh local stressors in Mediterranean mussels: a multi-method convergence analysis
Published 15 July 2026 Science ClosedTags: biological response, BRcommunity, field, laboratory, Mediterranean, metals, mollusks, multiple factors, physiology
Highlights
- Climate change explains ∼40% of biological stress variance in Mediterranean mussels.
- Ocean acidification drives 67% of metal bioavailability changes via pH-metal speciation.
- 64% of climate effects on biomarkers operate indirectly through metal bioaccumulation.
- Multi-method convergence (LMG, GAM, SEM, Bayesian Networks) confirms stressor ranking.
- Only SSP1-2.6 keeps biological stress below the chronic-stress threshold through 2050.
Abstract
Marine coastal ecosystems face concurrent pressure from climate change and anthropogenic contamination, yet their relative contributions to biological stress remain poorly quantified. Here we present a decade-long (2014–2023) biomonitoring study on Mytilus galloprovincialis in the Ligurian Sea (NW Mediterranean), integrating quarterly biomarker measurements, heavy metal bioaccumulation data (12 metals), and high-resolution oceanographic records at a control site (Gorgona Island Marine Protected Area) and an offshore regasification terminal.
Biological stress variance was partitioned using five complementary analytical frameworks — Lindeman–Merenda–Gold (LMG) variance decomposition, Hierarchical and Generalised Additive Models (HGAM/GAM), Structural Equation Modelling (SEM), and Bayesian Networks — applied to four biomarkers: DNA damage, lysosomal membrane stability, gill tissue integrity, and immune response. A campaign-specific T0 baseline normalisation isolated environmental signals from initial population variability.
Climate change emerged as the dominant driver, consistently explaining ∼40% of variance across all methods, significantly exceeding metal bioaccumulation (∼30%), terminal influence (∼13%), and seasonal effects (∼2%). Ocean acidification was the primary climate mechanism, influencing 67% of analysed metals. Causal mediation analysis revealed that 64% of the climate effect operates indirectly through enhanced metal bioaccumulation (Climate→Metals→Biomarkers), while 36% acts directly. Climate and biological stress indices co-varied strongly (ρ = 0.78, p < 0.001), with marine heatwaves coinciding with peak biomarker responses.
Under IPCC Shared Socioeconomic Pathway (SSP) scenarios, the Biological Stress Index is projected to cross chronic-stress thresholds by 2035–2040 under the high-emission scenario (SSP5-8.5) and the intermediate-emission scenario (SSP2-4.5), with only the low-emission scenario (SSP1-2.6) maintaining stress below critical levels through 2050.
These findings challenge pollution-centric monitoring paradigms and demonstrate that CO2 mitigation now constitutes the highest-leverage intervention for marine invertebrate health in the Mediterranean.
Graphical abstract
This graphical abstract illustrates the main findings of a decade-long field study (2014–2023) on the effects of climate change and metal contamination on Mytilus galloprovincialis in the Ligurian Sea (NW Mediterranean). Three panels summarise the causal chain from environmental drivers to biological outcomes. The first panel depicts the key oceanographic trends recorded at the study site: ocean warming (+0.41°C/decade), acidification (−0.020 pH units/decade), deoxygenation, and a doubling of marine heatwave frequency after 2018. The second panel shows how pH decline enhances the bioavailability of 67% of the metals analysed, driving a predominantly indirect pathway (64%) from climate stressors to biological stress, mediated by metal bioaccumulation, as revealed by structural equation modelling and Bayesian network analysis. The final panel presents the four biomarkers used to compute the Biological Stress Index (BSI), its strong temporal correlation with the Climate Change Index (ρ = 0.78), and BSI projections to 2050 under three IPCC emission scenarios, showing that only SSP1-2.6 keeps BSI below the chronic-stress threshold throughout the projection period.
Brown algae as winners: divergent resilience to high light under acidified conditions shapes macroalgal communities around a carbon dioxide vent
Published 14 July 2026 Science ClosedTags: algae, biological response, BRcommunity, community composition, field, laboratory, light, multiple factors, North Pacific, otherprocess, physiology, vents
To investigate the effects of ocean acidification (OA) on macroalgae, we conducted in situ surveys along a natural CO2 vent gradient in Shikine Island, Japan, together with complementary laboratory culture experiments. The in-situ surveys revealed that near the CO2 vent (where pH dropped by 0.37), macroalgal diversity and species-richness were less than half those at the reference sites under ambient pH conditions. Nevertheless, the rates of CO2 assimilation of several common macroalgae increased from the reference site to the areas near the CO2 vent. This enhancement coincided with decreased photosynthetic CO2 affinity, reflecting that the acidified area down-regulated CO2-concentrating mechanisms in the algae. Measured photosystem II activity revealed that macroalgae at reference sites had lower electron transport rate and light utilization efficiency. The laboratory culture experiments, in which the dominant species (Gelidium elegans and Dictyopteris undulata), were cross-exposed to ambient and elevated CO2 conditions, further demonstrated that the stress near the CO2 vent significantly exacerbated photoinhibition under high light stress. Our results demonstrate that reduced pH and high sunlight act synergistically to impair macroalgal photosynthesis through exacerbated photoinhibition. This effect was more pronounced in red algae (e.g., G. elegans) than in brown algae (e.g., D. undulata). These different physiological responses provide a mechanistic explanation for an observed community shift, from red algal dominance in ambient pCO2 areas to brown algal dominance near the vent. Our findings imply that future OA, when combined with high-light stress, may selectively disadvantage high-light-sensitive species, thereby altering macroalgal community structure in coastal waters.
Continue reading ‘Brown algae as winners: divergent resilience to high light under acidified conditions shapes macroalgal communities around a carbon dioxide vent’Strong effects of sun exposure on oyster shell corrosion and compensatory calcification: a factor confounding coastal acidification responses
Published 13 July 2026 Science ClosedTags: biological response, calcification, field, laboratory, molecular biology, mollusks, North Pacific, physiology
The dynamics of calcium carbonate structures in marine organisms (skeletons and shells) has become increasingly important due to heightened interest in marine environmental acidification. Research into molluscan shell corrosion and calcification in response to acidification is typically carried out in laboratory-controlled settings, which often overlooks the intricate interactions found in natural environments. Mollusks inhabiting intertidal zones are especially susceptible to intense shell weathering caused by tidal cycles of heating, cooling, wetting, and drying, exacerbated by solar radiation during periods of air exposure. We investigated the effect of sun exposure (solar radiative heating) on both outer shell corrosion and inner shell compensatory calcification in the tropical oyster, Saccostrea scyphophilla. Shell properties were compared between oysters from neighboring populations in sun-exposed and shaded habitats. Habitat temperatures were measured using iButtons, and right shell valve corrosion was quantified. Compensatory calcification was assessed through measurements of shell thickness, shell density, shell compression strength, and mineralogical properties. Our results revealed that oysters in the sun that experience global irradiance, higher temperature peaks and broader daily temperature ranges (averaging an increase of 10 °C) show considerably greater outer shell surface corrosion (87%) compared to shaded oysters (31%) that experience only diffuse irradiance. Sun-exposed shells also become thickened in the midsection and around the adductor muscle, and they are slightly stronger, indicating compensation for the outer shell loss. These findings highlight the need for caution when interpreting molluscan shell dynamics based on laboratory marine acidification protocols that fail to account for the many natural environmental factors influencing shell formation and dissolution.
Continue reading ‘Strong effects of sun exposure on oyster shell corrosion and compensatory calcification: a factor confounding coastal acidification responses’Impacts of warming, acidification, and deoxygenation on embryos and larvae of gilthead seabream (Sparus aurata)
Published 13 July 2026 Science ClosedTags: biological response, fish, laboratory, mortality, multiple factors, oxygen, physiology, reproduction, temperature
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.
Continue reading ‘Impacts of warming, acidification, and deoxygenation on embryos and larvae of gilthead seabream (Sparus aurata)’Evaluating the combined effects of ocean acidification and harmful algal blooms on the fitness of Artemia salina
Published 6 July 2026 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, performance, physiology, reproduction, toxicants, zooplankton
This study assessed the potential synergistic effects of harmful algal blooms (HABs) and ocean acidification (OA) on the survival and grazing potential on HABs by brine shrimp (Artemia salina). The effects on the fitness of three life stages (i.e. newly hatched, 1-week old, and 2-week old post hatch) of A. salina was evaluated over a 24-hour period. Using well plates, A. salina were individually exposed to toxin producing HABs (i.e. Alexandrium catenella or Margalefidinium polykrikoides), a non-toxin producing HAB (i.e. Gymnodinium aureolum), and fed or unfed non-HAB controls. pH conditions administered were ambient (pH ~ 8) or acidified (pH ~ 7.2). Survival analysis revealed a significant effect of treatment on mortality across life stages. Hazard ratios showed elevated mortality in HAB treatments relative to controls, while OA alone did not. HAB exposure or ontogeny are more important for survival of A. salina than short-term OA exposure. Regarding grazing potential, significant reductions in HAB cell density were more commonly found in treatments with older individuals than younger conspecifics. Cell density of A. catenella was never significantly reduced as compared with other HAB treatments. Overall, exposure to OA conditions did not affect the survival or grazing potential of A. salina, but the species of HAB did.
Continue reading ‘Evaluating the combined effects of ocean acidification and harmful algal blooms on the fitness of Artemia salina’Interactive effects of triclosan, microplastic vectors, and ocean warming–acidification on sea urchin embryo development
Published 6 July 2026 Science ClosedTags: biological response, echinoderms, growth, laboratory, morphology, multiple factors, North Atlantic, physiology, plastics, reproduction, toxicants
Highlights
- Microplastics modulate triclosan toxicity in a concentration-dependent manner.
- Microplastic loads reverse triclosan attenuation affecting larval development.
- Acidification amplifies triclosan–microplastic toxicity in sea urchin embryos.
- Ocean Warming modulates toxicity; degree-day normalization reveals hidden stress.
Abstract
Understanding how emerging contaminants interact with climate-driven stressors is essential for accurate ecological risk assessment in coastal ecosystems. This study evaluates the individual and combined effects of triclosan (TC), polyethylene microplastics (MP), ocean warming (OW), and ocean acidification (OA) on the early development of Paracentrotus lividus embryos. A tiered experimental design was implemented to: (i) characterize TC dose–response curves alone and in combination with increasing concentrations of MP (300–3000 particles mL−1), and (ii) assess how OW (24 °C) and OA (pH 7.6) modulate contaminant toxicity. TC showed concentration-dependent growth inhibition, while MP exhibited a biphasic interaction with TC: at moderate concentrations, MP increased EC10 values and steepened dose–response slopes, consistent with contaminant sorption reducing freely dissolved TC. At 3000 particles mL−1, this trend reversed, lowering EC50 values and enhancing toxicity. Morphometric analyses revealed that co-exposure to TC alone and with MP loads impaired arm elongation, increased body-width ratios, and reduced stomach volume, indicating compromised feeding and skeletal development. Climate stressors significantly altered toxicological outcomes. OA strongly amplified the combined toxicity of TC + MP, reducing larval growth to near-zero levels, whereas OW alone did not exacerbate toxicity and partially mitigated OA-driven effects in MP-TC treated groups. Degree-day normalization demonstrated that warming accelerates development but reduces growth efficiency across treatments. Overall, these results reveal threshold-dependent MP–TC interactions and highlight acidification as a critical amplifier of contaminant effects. Incorporating realistic MP–pollutant interactions and climate variables is crucial for improving hazard assessments under future ocean scenarios.
Continue reading ‘Interactive effects of triclosan, microplastic vectors, and ocean warming–acidification on sea urchin embryo development’Impact of water quality and gear type on Eastern oyster (Crassostrea virginica) growth in Narragansett Bay, RI
Published 1 July 2026 Science ClosedTags: biological response, growth, laboratory, mollusks, mortality, North Atlantic, physiology
Oyster aquaculture is expanding in Rhode Island, yet key farming regions in the lower West Passage of Narragansett Bay (WPNB) lack the in-situ, high-temporal resolution monitoring needed to evaluate emerging stressors and support production. At the same time, the industry is undergoing rapid technological development aimed at improving production while reducing labor and overall costs. In recent years, a low maintenance, alternative surface gear was introduced in WPNB; however, its impact on oyster performance relative to traditional cultivation methods has not been quantified. This study established a 1.5-year continuous water quality time series in WPNB and paired these observations with physiological assessments of Crassostrea virginica grown in three cultivation methods (i.e., traditional surface, alternative surface, and bottom gear). This work aimed to better understand the impact of environmental variability and gear type on oyster health, growth, and survival. Multiparameter sondes and discrete bottle samples were used to monitor water quality and calculate carbonate saturation state (Ω) at a 4-acre oyster farm. Nine mesh bags containing early-life stage C. virginica (16 ± 0.4 mm; n = 300 per bag) were deployed in July 2025, with three replicate bags in each gear type. Subsamples (n = 15) from each gear type were collected over a 6-month period for morphometric measurements and scope for growth (SFG) determinations. Minimal differences in carbonate chemistry were observed among sampling sites and Ω remained supersaturated (Ω >1) for the majority of the study period, indicating that ocean acidification was not a major stressor for farmed oysters. Survival was highest (82 ± 4.5%) in surface gear types compared to bottom gear (27 ± 0.58%), while physical growth (shell and tissue) and SFG were largely similar among all gear types. These results suggest that the alternative surface gear may support comparable production and product quality to traditional gear types, while also reducing maintenance and labor demands. Overall, this study provides important physiological and biological context for oyster aquaculture while informing gear selection and farm management strategies.
Continue reading ‘Impact of water quality and gear type on Eastern oyster (Crassostrea virginica) growth in Narragansett Bay, RI’Skeletal porosity of a cold-water coral increases with decreasing aragonite saturation state along a depth gradient in the Mediterranean Sea
Published 29 June 2026 Science ClosedTags: biogeochemistry, biological response, BRcommunity, chemistry, corals, laboratory, Mediterranean, physiology
Background
Cold-water corals (CWCs) are key ecosystem engineers that create complex three-dimensional habitats much like tropical reefs, but in deep, cold seas. However, like other reef-building systems, they are increasingly threatened by climate change and ocean acidification. CWC communities in the Mediterranean Sea may be especially vulnerable because these waters absorb more atmospheric CO2 than the global ocean, making it a mesocosm that mirrors broader global trends affecting marine life. Since calcification is energetically costly and likely becomes even more demanding as pH and carbonate ion availability decline, understanding how the decrease in aragonite saturation state (Ωarag) affects biomineralization is essential for predicting the future of these corals.
Results
Here, we investigated skeletal structural and compositional changes of the scleractinian CWC Desmophyllum dianthus along an Ωarag gradient in the Mediterranean Sea using specimens collected between 400 and 1200 m depth. Our findings indicate that skeletal porosity increases at the macro-scale with decreasing Ωarag, while micro- and nano-scale structural and compositional features remained unaffected.
Conclusions
The persistence of micro- and nano-scale skeletal features across an 800 m depth gradient suggests that D. dianthus maintains tight biological control over mineralization at these scales, even as Ωarag declines. This control does not extend to the macro-scale, where increasing porosity alters the skeleton’s overall architecture under lower Ωarag. D. dianthus thus appears to preserve the fundamental “building blocks” of its skeleton while changing its larger-scale structure, a decoupling that may make macro-scale porosity an early marker of acidification stress in CWCs.
Continue reading ‘Skeletal porosity of a cold-water coral increases with decreasing aragonite saturation state along a depth gradient in the Mediterranean Sea’Acute low pH associated with coastal acidification is detrimental to larval development of the Cape urchin Parechinus angulosus
Published 26 June 2026 Science ClosedTags: biological response, BRcommunity, echinoderms, growth, Indian, laboratory, mortality, physiology, reproduction
Acidification in coastal habitats is increasing in duration and amplitude under the continued influence of ocean acidification and contributing coastal processes. The impacts of low pH conditions on calcifying organisms, especially echinoderms, is well established, with the early developmental stages being especially vulnerable. This is the first study to assess the impact of locally relevant coastal acidification scenarios on the early development of the Cape urchin Parechinus angulosus. Our findings suggest that the early larval stages of this species are unlikely to survive when exposed to low pH conditions, specifically during the onset of skeletogenesis. In our laboratory experiments, larvae that were exposed to the low pH treatment (pH 7.32) showed significantly reduced growth (GLMM, Time × Treatment interaction: β = −0.361 ± 0.019, z = −19.06, p < 0.001) and developmental regression compared with those from the control treatment (pH 7.95). Substantially slower growth rates were observed in the low pH treatment (length = 72.3 hpf0.18) compared with in the control treatment (length = 24.24 hpf0.54). There was also evidence of abnormal and delayed development and potential dissolution of skeletal structures under the low pH condition. However, fertilisation success and larval survival did not differ significantly between the experimental treatments, suggesting that developmental impacts of low pH over short durations, even though substantial, may be sublethal. The developmental impacts are likely to impair the transition of larvae to the adult stages, which may ultimately affect populations of this ecologically important species under future coastal acidification scenarios.
Continue reading ‘Acute low pH associated with coastal acidification is detrimental to larval development of the Cape urchin Parechinus angulosus’
