Posts Tagged 'mortality'

Witness to ocean acidification

Published 20 August 2026 Science Leave a Comment
Tags: , , , , ,

Foraminifera inhabit coastal and deep-sea marine environments. These microscopic, single-celled organisms are widely used as proxies for relative age determination and reconstructing past climates. The ratio of calcium isotopes (44Ca/40Ca) in their calcium carbonate shells depends on the amount of carbon dioxide (CO2) and carbonate saturation in seawater at the time of the shells’ formation. On page 527 of this issue, Chen et al. (1) report geochemical evidence that a rise in atmospheric CO2 concentration and ocean acidification at the end of the Aptian Stage [~113 million years ago (Ma)] may have caused the largest extinction of planktic foraminifera of the Cretaceous Period (146 to 66 Ma) (2–4), which is second only to the extinction event at the end of the Cretaceous Period (66 Ma) (5–7). The findings could be important for understanding potential effects of present-day increases in atmospheric CO2 levels on marine organisms.

Paraticinella rohri collected from the South Atlantic is a species of planktic foraminifera that went extinct at the Aptian–Albian boundary. IMAGE: HUBER AND LECKIE (3)

Seafloor-dwelling benthic foraminifera appeared more than 500 million years ago. It took at least 350 million years for them to evolve into planktic species that float in the upper ocean (8–10). The earliest species of planktic foraminifera lacked morphological diversity and were minor constituents of marine sediments. The first major morphological diversification of planktic foraminifera occurred (2, 11) during the Aptian Stage (125 to 113 Ma) of the mid-Cretaceous Period. New species of planktic foraminifera arose, with elongated chambers (Leupoldina) and larger, more heavily calcified shells (Globigerinelloides and Hedbergella), and the first species with a peripheral keel (Pseudoplanomalina cheniourensis) appeared by the late Aptian. Large increases in atmospheric CO2 concentration caused by massive volcanic eruptions triggered substantial depletion of oxygen in the oceans, including Oceanic Anoxic Event 1a and other similar events. Atmospheric CO2 likely drove warming of the atmosphere and water; warmer waters hold less dissolved oxygen compared to cooler water.

…

Continue reading ‘Witness to ocean acidification’

Calcium isotopes link ocean acidification to Aptian–Albian foraminiferal extinctions

Published 19 August 2026 Science Leave a Comment
Tags: , , , , ,

Editor’s summary

About three quarters of planktic foraminifera species disappeared in the Aptian-Albian extinction event. What role might ocean acidification (OA) have played in this die-out? Chen et al. measured calcium isotope ratios in foraminifera, using them as a proxy for biocalcification and carbonate saturation (see the Perspective by Leckie). Their data reveal a dramatic reduction in calcification rates accompanied by decreases in the size, abundance, and diversity of planktic foraminifera. These results are consistent with the hypothesis that ocean acidification drove the extinctions of these organisms at the Aptian-Albian boundary. —Jesse Smith

Abstract

The second-largest extinction event in the evolutionary history of planktic foraminifera occurred at the Aptian–Albian boundary. This extinction may reflect ocean acidification (OA) associated with Oceanic Anoxic Event 1b. As calcium isotope ratios (δ44/40Ca) can track how biocalcification rates respond to OA, we measured δ44/40Ca records for planktic and benthic foraminifera, bulk carbonates, and authigenic calcite across the Aptian–Albian boundary in the South Atlantic. Benthic and bulk δ44/40Ca data display a distinct sequence of negative and positive excursions, similar to δ44/40Ca variations across other OA events. Planktic δ44/40Ca values increase markedly, tracking a reduction in calcification rates coincident with decreases in the size, diversity, and shell thickness of planktic foraminifera. These results suggest that OA drove extinctions of planktic foraminifera at the Aptian–Albian boundary.

Continue reading ‘Calcium isotopes link ocean acidification to Aptian–Albian foraminiferal extinctions’

Vulnerability to low salinity but compensatory responses to low pH in an intertidal limpet

Published 7 August 2026 Science Leave a Comment
Tags: , , , , , , , , ,

Highlights

  • Low salinity linked to warming may intensify coastal pH reduction.
  • Low salinity reduced righting and emergence in the limpet Patelloida pygmaea.
  • Low salinity reduces Mg/Ca ratios in newly formed shell layers.
  • Low pH increases shell thickness and Mg/Ca ratios despite dissolution.
  • CHS2 upregulation suggests compensatory resistance to low pH.

Abstract

Rising anthropogenic carbon dioxide emissions have driven ongoing ocean warming and associated climate changes. In the Yellow Sea, this warming is associated with enhanced monsoonal rainfall, which increases freshwater inputs and lowers coastal salinity. Increased freshwater input can weaken seawater buffering capacity, thereby leading to lower pH conditions in coastal environments. Here, we examined the effects of low pH and low salinity on the intertidal limpet Patelloida pygmaea. Adult limpets were exposed for 31 days to four experimental artificial seawater conditions combining two pH levels (8.0 and 7.5) and two salinity levels (30 and 21 psu). Survival and condition factor were not influenced by pH or salinity. However, low salinity reduced righting and emergence behavior. In addition, the Mg/Ca ratio in the M + 1 layer was lower at 21 psu than at 30 psu. Low pH resulted in a thicker M + 2 layer with higher Mg/Ca ratios despite shell dissolution, potentially helping to maintain shell integrity. While there was no change in heat shock protein (HSP70) expression, these shell modifications were accompanied by an upregulation of chitin synthase (CHS2) genes under low pH. These findings suggest that P. pygmaea is negatively influenced by low pH and low salinity, but also demonstrate compensatory mechanisms that enhance resistance to low pH.

Continue reading ‘Vulnerability to low salinity but compensatory responses to low pH in an intertidal limpet’

Isotocin receptor-adenylyl cyclase signaling mediates pH compensation in marine fish exposed to CO2-induced acidification

Published 4 August 2026 Science Closed
Tags: , , , , ,

Marine fish survival is threatened by ocean acidification, but the hormonal mechanisms for pH compensation are not well understood, limiting mechanistic understanding of stress responses in marine fish. We examined isotocin signaling in marine medaka (Oryzias melastigma) exposed to year-2100 ocean acidification conditions (Pco2 ∼0.14 kPa, pH 7.6). Our analysis demonstrated that isotocin receptor b (ITRb) was selectively upregulated at 6 h postexposure in adult gills, though it showed only a nonsignificant trend at 5 days postfertilization (dpf) embryos, whereas adenylyl cyclase 5 (ADCY5) showed hypercapnia responsiveness primarily at hatching. Using immunofluorescence and confocal microscopy, we found that both ITRb and ADCY5 proteins localize to the basolateral membrane of Na+-K+-ATPase-positive ionocytes, partially separated from apical H+-secretion machinery. Knockdown experiments showed that ITRb-ADCY5 coupling is crucial for pH compensation, with individual knockdown moderately reducing H+ secretion and combined knockdown causing severe impairment (>70% reduction) and decreasing transcription of acid-secretion genes (nhe3, ca2, and rhcgb) by 44%–60%. Paradoxically, double knockdown triggered a twofold cAMP increase that failed to restore function, whereas wild-type embryos maintained stable cAMP levels across pH conditions, consistent with the hypothesis that ITRb-ADCY5 coupling may organize cAMP production within specific basolateral microdomains, though direct subcellular imaging would be required to validate this compartmentalization model. The developmental asynchrony between ITRb (5 dpf) and ADCY5 (hatching) responses indicates life-stage-specific vulnerabilities. Our findings reveal that basolateral ITRb-ADCY5 coupling represents a critical control point for pH compensation capacity.

NEW & NOTEWORTHY Isotocin signaling, through ITRb-ADCY5 coupling, enables marine fish to compensate for ocean acidification via compartmentalized rather than global cAMP production. Paradoxically, disrupting this pathway doubles cAMP levels yet abolishes H+ secretion, revealing that signal localization determines function. The developmental asynchrony between ITRb and ADCY5 responses suggests that pH-stress vulnerabilities are specific to each life stage and require further investigation.

Continue reading ‘Isotocin receptor-adenylyl cyclase signaling mediates pH compensation in marine fish exposed to CO2-induced acidification’

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 Closed
Tags: , , , , , , , ,

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’

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 Closed
Tags: , , , , , , , , ,

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’

Ocean acidification changes diet effects and differentially impacts two populations of red abalone (Haliotis rufescens)

Published 14 July 2026 Science Closed
Tags: , , , , , , , , , , ,

Absorption of CO2 by global oceans is decreasing pH resulting in ocean acidification (OA). Impacts on shellfish have been documented in ecologically and commercially important species. We examined the influence of diet and OA between two populations of red abalone (Haliotis rufescens) a species of aquaculture importance and declining wild populations. Populations experience different exposure histories: strong upwelling (Van Damme, California [VD]) historically exposed to low-pH conditions and weak-intermittent upwelling (Santa Barbara, California [SB]). Abalone were cultured under control-pH or OA-conditions and fed crustose coralline algae (CCA) or diatoms used in aquaculture. We tested treatment effects of population, settlement diet, and OA-exposure on survival as influenced by larval-energy stores. Survival in both populations was enhanced by CCA when cultured under both treatment conditions; however, by later stages, this effect remained only for SB. SB had reduced post-settlement survival when cultured under OA-conditions, whereas post-settlement survival of VD was not. Diet affected the relationship between larval-energy and post-settlement survival; a positive relationship when fed diatoms and a negative relationship with CCA. The relationship between larval energy and post-settlement survival was stronger in VD. CCA enhanced juvenile growth in SB cultured abalone at both three-months and one-year post-settlement. Settlement diets can reduce the impacts of OA on early-life stages of abalone, but population differences driven by underlying energetics affect the consistency of this outcome. These findings illuminate the impacts from OA, suggesting populations may be at risk, and inform strategies for developing and sustaining shellfish aquaculture in the face of changing ocean conditions.

Continue reading ‘Ocean acidification changes diet effects and differentially impacts two populations of red abalone (Haliotis rufescens)’

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

Published 13 July 2026 Science Closed
Tags: , , , , , , , ,

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 Closed
Tags: , , , , , , , , ,

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’

Impact of water quality and gear type on Eastern oyster (Crassostrea virginica) growth in Narragansett Bay, RI

Published 1 July 2026 Science Closed
Tags: , , , , , ,

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’

Climate change and aquatic ecosystems: impacts on salinity, species survival, and ecological resilience

Published 29 June 2026 Science Closed
Tags: , , , , , , ,

Highlights

  • Unveils Climate-Driven Disease Mechanisms Across Aquatic Systems.
  • Integrates Multistressor Impacts Including Pollution, Eutrophication, and Salinity Fluctuations.
  • Explores Shifts in Species Distribution, Reproduction, and Food Web Dynamics.
  • Highlights Adaptive Traits and Resilience Mechanisms in Aquatic Organisms.
  • Provides Science-Based Recommendations for Climate-Responsive Management.

Abstract

Climate change is rapidly transforming aquatic ecosystems, posing complex environmental challenges with far-reaching ecological and socio-economic implications. Rising temperatures, sea-level rise, altered precipitation patterns, shifting hydrological regimes, and sea-ice loss are intensifying pressures on coastal, estuarine, freshwater, and polar systems. These stressors contribute to habitat degradation, increased frequency of hypoxic events, and altered species distributions. Crucially, while some dual stressors, such as warming and acidification, can paradoxically increase primary producer biomass, our findings reveal that this resultant biomass often accumulates as detritus rather than being efficiently transferred to higher trophic levels. This observation directly challenges the simplistic assumption that “more growth” is invariably beneficial, highlighting complex indirect effects on food web dynamics and ecosystem function. Ecological perturbations propagate through trophic networks, resulting in biodiversity loss, reduced ecosystem resilience, and declining fisheries productivity, thereby threatening food security and coastal livelihoods. Marine and freshwater organisms are increasingly exposed to multiple, interacting stressors, including warming, acidification, salinity fluctuations (requiring distinct osmoregulatory strategies, e.g., heterosmotic regulation in teleosts vs. isosmotic intracellular regulation in crustaceans), pollution, and overexploitation. These cumulative pressures can exacerbate disease outbreaks, modify host–pathogen dynamics, and facilitate the emergence and spread of aquatic pathogens, with consequences for ecosystem stability and human health. In aquaculture systems, climate-driven stress often acts synergistically with anthropogenic disturbances, amplifying production risks and economic vulnerability. Furthermore, anthropogenic infrastructure like reservoirs can act as unintended hubs facilitating species dispersal following extreme events like floods, altering community structures. At the biogeochemical scale, climate-induced alterations in nutrient cycling, primary productivity, and carbon sequestration are reshaping ecosystem functioning, particularly in high-latitude and freshwater environments where adaptive capacity is comparatively constrained. Changes in food web architecture and energy transfer efficiency further compromise ecosystem services. This review specifically centers on the biological and ecological mechanisms underlying these climate-driven changes, including organism-level stress responses, shifts in species interactions, and alterations in pathogen dynamics. Recognizing the societal implications and public discourse surrounding climate change underscores the urgency of examining its tangible impacts on sensitive environments, such as estuarine ecosystems, which serve as critical interfaces between terrestrial and marine realms and are thus highly susceptible to both climatic shifts and human influence.

Continue reading ‘Climate change and aquatic ecosystems: impacts on salinity, species survival, and ecological resilience’

Acute low pH associated with coastal acidification is detrimental to larval development of the Cape urchin Parechinus angulosus

Published 26 June 2026 Science Closed
Tags: , , , , , , , ,

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’

Geographic variation in proteomic responses to ocean acidification in a cold-water coral (Balanophyllia elegans)

Published 16 June 2026 Science Closed
Tags: , , , , , , ,

In the face of a rapidly changing climate, assessing organismal responses to future stressors in the context of current, natural exposure to stress could provide key insights to understanding marine ecosystem resilience. I used Balanophyllia elegans, a cold-water, solitary, azooxanthellate coral as a model to better understand how varying oceanographic conditions across its geographic range have shaped its ability to tolerate and potentially adapt to current and future ocean acidification conditions. I collected B. elegans individuals from four sites across 2,500km of their range and subjected them to two pH treatments to investigate site-specific protein expression in response to low pH. Using proteomic analysis, I found that corals from each site responded differentially to low pH, mainly through changes in regulation of metabolism, calcification, and homeostasis-related proteins. Additionally, health condition varied significantly between sites after exposure to low pH, providing further evidence of site-specific responses. These results demonstrate site-specific variation in responses and tolerance to low pH, a pattern that could inform future investigations into environmental-driven adaptive expression. Such site-specific responses highlight the importance of multi-source studies for predicting a species’ ability to navigate future climate changes.

Continue reading ‘Geographic variation in proteomic responses to ocean acidification in a cold-water coral (Balanophyllia elegans)’

Ocean acidification effects on larval development and survival in commercially important shellfish

Published 10 June 2026 Science Closed
Tags: , , , , , , , , ,

This paper studies the consequences of ocean acidification (OA) on the growth and survival of the larvae of commercially significant shellfish species such as oysters, mussels, and scallops. The authors of the study are particularly concerned with the negative processes of OA with respect to the growth of larvae, shell development, and behavior, which result in decreased survival rates, particularly the consequences of the reduced availability of calcium carbonate on the weakening of shells and larvae, which are preyed upon. The paper also studies the interference with the behavior of larvae, particularly with respect to the adequate detection of sites to settle, which is harmful to recruitment success. Additionally, the study looks at the OA-induced metabolic stress, where the larvae are expected to expend higher energy to maintain homeostasis at the expense of growth and immunity. By focusing on this issue, the paper outlines the OA’s impacts on the shellfish populations and industries. The paper also looks at the available soft measures, such as the implementation of buffering solutions to limit the acidification in hatcheries, the use of genetic selection to incorporate acidification-resistant traits, and coastal management measures to limit local sources of acidification. The paper also suggests some potential new ways to increase the resilience of shellfish stock, including more flexible adaptive aquaculture practices. With commercial shellfish interests emerging, this paper fills some of the more critical gaps in the existing literature and offers insight into the impact of OA on the sustainability of the shellfish industry. It also provides OA mitigation strategies to preserve shellfish stocks in a changing climate.

Continue reading ‘Ocean acidification effects on larval development and survival in commercially important shellfish’

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

Published 28 May 2026 Science Closed
Tags: , , , , , , ,

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’

Feeding and excreting ecology in coastal systems

Published 26 May 2026 Science Closed
Tags: , , , , , , , , ,

Oysters (Crassostrea virginica) are critical foundation species in estuaries, providing numerous ecological and economic benefits. However, oyster populations have diminished worldwide. Effective oyster restoration and aquaculture require a mechanistic understanding of the physiological and environmental factors that govern oyster feeding, growth, and resilience under changing coastal conditions. We investigated how oyster ploidy and environmental conditions influenced oyster feeding and investigated how changes in abiotic conditions affected behavioral performance of oyster drills (Stramonita spp.), a key oyster predator. To better understand feeding responses and behaviors of both predator and prey we 1) used in-situ filter feeding assays to determine feeding differences existed amongst diploid and triploid oysters, 2) gathered a baseline for growth and in-situ feeding rates of oysters across Mississippi Sound in the Northern Gulf in the Spring, Summer, and Fall, 3) simulated present-day and projected future pH conditions (7.0-8.8) to analyze oyster feeding responses, and 4) introduced oyster drills to acidified conditions (7.0-8.8) to monitor behavior and foraging rates. Diploid oysters exhibited higher overall feeding rates, yet equivalent absorption efficiency between ploidies demonstrates a difference in energy allocation which might be the key to triploids’ ability to grow quickly. These findings highlight the role of intrinsic genetic and physiological traits in shaping oyster performance and provide a baseline for interpreting responses to environmental variability. Across spatial and seasonal variation in oyster in-situ feeding and growth across three contrasting sites in Mobile Bay and Mississippi Sound, in the Northern Gulf on the western border of Alabama and Mississippi, results revealed strong spatial and seasonal variability in feeding and growth. This was driven primarily by seston composition and salinity. Under present-day and projected future ocean acidification conditions, overall oyster feeding rates declined with lower pH’s, absorption efficiency remained stable, suggesting partial physiological compensation. These results indicate that pH can impose sublethal constraints on energy acquisition and growth, with individual variability at extreme pH highlighting potential acclimation or tolerance thresholds. When subjecting the oyster’s predator, the oyster drill, to similar pH conditions (7.0-8.8) experimental results indicate that decreased pH may increase drill foraging times. Behaviors like inactivity and climbing out of the water indicate a stress response under both high and low pH, demonstrating the complexity of predicting predator-prey outcomes under more acidic conditions. Collectively, these chapters demonstrate that oyster feeding, growth, and survival are shaped by both intrinsic traits, such as ploidy, and extrinsic factors including environmental variability and ocean acidification. Understanding the interplay between physiological plasticity, seston quality, and predator-prey interactions is essential for informing restoration and aquaculture strategies that sustain ecological function and the ecosystem services oysters provide.

Continue reading ‘Feeding and excreting ecology in coastal systems’

Immunosuppression and gill damage of acidification and hypoxia on the Pacific oyster Magallana gigas

Published 22 May 2026 Science Closed
Tags: , , , ,

Highlights

  • Combined acidification and hypoxia trigger significant mortality in Magallana gigas.
  • Seawater acidification suppresses the nonspecific immune response in Magallana gigas.
  • Gill histopathology and immunosuppression are most pronounced with combined exposure.

Abstract

Rising atmospheric carbon dioxide leads to oxygen depletion and increased acidification in marine areas worldwide. The combined effects of these two stressors on the health of commercially important bivalves have not been sufficiently studied. We experimentally studied the effects of water acidification in combination with normoxic and hypoxic conditions on the parameters of cellular immunity and the gills microstructure of the Magallana gigas. We evaluated the hemolymph cellular composition, the total number and phagocytosis capacity of hemocytes, and also evaluated the histopathology of oyster gills during an 8-day experimental period. The oysters were exposed to low pH conditions (7.3), either under normoxic conditions (dissolved oxygen concentration of 8.0 mg/L) or hypoxic conditions (dissolved oxygen concentration of 2.0 mg/L). The parameters were assessed at days 1, 3, 6, and 8 of the experiment. It was shown that acidification of the aquatic environment causes significant suppression of oyster immunity in both normoxia and hypoxia, leading to a decrease in phagocytic capacity and ROS production by hemocytes. The combined effect of these factors increased the negative impact, ultimately leading to the oyster death at the end of the experiment. In addition, the effects of acidification caused serious and progressive histopathological damage to the oyster gills, while the most severe and frequent pathologies, such as almost complete expansion of the water chambers and severe dilation of the hemal sinuses, were caused by the combined effects of acidification and hypoxia. Therefore, the synergistic impact of acidification and hypoxia poses a substantial threat to oyster health.

Continue reading ‘Immunosuppression and gill damage of acidification and hypoxia on the Pacific oyster Magallana gigas’

Impacts of coinciding ocean acidification and warming on the fatty acid profile of the pteropod Limacina helicina within the Northeast Pacific coastal region

Published 19 May 2026 Science Closed
Tags: , , , , ,

Under global climate change, co-occurrence of ocean acidification (OA) and warming poses a substantial threat to marine ecosystems. The present study focused on the Strait of Georgia within the Northeast Pacific region, where conditions of aragonite undersaturation exist year-round across the majority of the water column, with further intensification expected under OA. These conditions coincide with persistent rises in mean seasonal seawater temperatures and increased prevalence of acute stressor events, such as marine heatwaves and low-pH upwelling events. Limacina helicina, a pteropod species well-represented within the region’s zooplankton communities, is susceptible to OA and warming, with documented impacts including altered shell development, growth, and survival. To date, however, there has been minimal investigation into the effects of OA and warming on the species’ fatty acid profile under regionally-relevant conditions, thereby contributing to a lack of understanding of how impacts at lower trophic levels may relay across ecosystems. To address this knowledge gap, we examined the survival and fatty acid profile of L. helicina under future conditions via a laboratory experiment during which pteropods were exposed to singular and coinciding warming (mean summer seawater temperature + 4 °C) and OA (Ωarag < 1) conditions, with fatty acid analyses carried out via gas chromatography at 48-h and 5-d timepoints. OA conditions significantly altered fatty acid proportions at 48 h, and there was an additional interactive effect of OA and warming. Temperature significantly affected survival at 5 d, although experimental starvation conditions likely confounded this result. Additionally, fatty acid analyses of L. helicina picked from historical plankton samples collected in the region over 2014–2023 were carried out to examine time-series changes in fatty acid profiles in relation to temperature records. Results indicated no significant differences in fatty acid fractions among years, though there was suggestion of a changing proportion of myristic acid over a number of year groups. Overall, findings suggest that short-term OA conditions may result in altered fatty acid composition in pteropods, potentially leading to shifts in nutritional quality and associated impacts on trophic energy transfer.

Continue reading ‘Impacts of coinciding ocean acidification and warming on the fatty acid profile of the pteropod Limacina helicina within the Northeast Pacific coastal region’

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

Published 14 May 2026 Science Closed
Tags: , , , , , , ,

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.

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

Effects of ocean acidification on radular tooth material properties in Littorina littorea (Gastropoda, Mollusca)

Published 6 May 2026 Science Closed
Tags: , , , ,

Ocean acidification is known to affect calcified structures in marine organisms, yet its impact on non-calcified but functionally essential feeding tools remains poorly understood. The radula is a defining molluscan apomorphy, whose mechanical performance is critical for feeding and survival. Here we investigated the effects of reduced seawater pH on the radular teeth of the intertidal gastropod Littorina littorea. Individuals were maintained for seven weeks under acidified conditions (pH 7.5) or near-present-day conditions (pH 8.1) and compared with a field-collected control group. Radulae were analysed using scanning electron microscopy, confocal laser scanning microscopy, energy-dispersive X-ray spectroscopy, and nanoindentation.

Radulae from acid-treated individuals exhibited markedly increased tooth wear in the working zone despite largely preserved gross morphology. Wear was most pronounced at the cusps of central and lateral teeth and showed rounded profiles indicative of progressive abrasive wear. Acidic conditions caused pronounced changes in the outer tooth coating, including reduced silicon enrichment and substantial decreases in stiffness and hardness, while the inner tooth structure was only weakly affected. Confocal microscopy revealed treatment-specific autofluorescence patterns, suggesting pH-dependent alterations of the organic matrix. Differences between laboratory-maintained and field-collected individuals further indicate that feeding conditions influence radular tooth properties.

These results demonstrate that ocean acidification can impair radular function through material-level degradation of composite feeding structures, potentially reducing grazing efficiency and imposing sublethal fitness costs.

Continue reading ‘Effects of ocean acidification on radular tooth material properties in Littorina littorea (Gastropoda, Mollusca)’

Subscribe

Search

  • Reset

OA-ICC Highlights

Resources