Posts Tagged 'reproduction'

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

Published 29 June 2026 Science Leave a Comment
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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.

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

Published 26 June 2026 Science Leave a Comment
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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.

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Will the Mediterranean sea be a cul-de-sac for marine gastropods under climate change?

Published 23 June 2026 Science Leave a Comment
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Marine ecosystems are undergoing rapid transformation under climate change, yet the responses of many marine invertebrates remain vastly understudied. In particular, for many benthic gastropods there is a striking imbalance between their traditional appreciation by shell collectors—and, consequently, their consistent representation in Natural History Collections—and the limited attention they receive in ecological and conservation studies. Focusing on the northeastern Atlantic and the Mediterranean, the cowries Luria lurida, Naria spurca, Zonaria pyrum and the frog-shell Talisman scrobilator are emblematic examples of this knowledge gap, despite being frequently mentioned as species of conservation concern. Using long-term occurrence records spanning more than a century, we modelled past and present distributions of these species and explored their potential responses to future climate scenarios through a multi-temporal Species Distribution Modelling framework. Our results show that intermediate climatic conditions—both in time (2050–2060 vs. 2090–2100) and scenario intensity (moderate SSP2-4.5 versus high-emission SSP5-8.5)—may represent a critical transition phase, leading to habitat contractions without compensatory gains in newly emerging suitable areas. The Mediterranean Sea is expected to increasingly function as a cul-de-sac, with the dominant circulation patterns strongly limiting outward movements towards cooler regions for species relying on planktic larvae for dispersal. Furthermore, incorporating larval sensitivity to reduced pH suggests that large areas of the Atlantic Ocean may actually result unsuitable for larval persistence, substantially reducing the habitat effectively available for completion of the full life cycle; this highlights the need to account for connectivity, life-history constraints and juvenile-stage sensitivity when assessing climate-driven range shifts in shelled organisms with planktic larvae.

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

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

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Response mechanism of Sepia esculenta larvae under global warming, ocean acidification and salinity fluctuation: Integrated biochemical and transcriptome profiling

Published 12 June 2026 Science Closed
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Highlights

  • Analysis based on global warming, ocean acidification and salinity fluctuation.
  • Multi-angle analysis of Sepia esculenta under temperature, pH and salinity stress.
  • Different stress enhanced the immune defense and antioxidant defense of S.esculenta.
  • The hub genes closely related to stress resistance were identified and screened out.

Abstract

The Sepia esculenta occupies a significant economic proportion in the squid family, and it is also the squid with the largest economic value in the northern sea area of China. With the occurrence of global warming, ocean acidification and ocean salinity fluctuations, it has caused serious negative effects on the development of the S. esculenta artificial breeding industry. Therefore, in the research, we employed weighted gene co-expression network analysis (WGCNA) to investigate the effects of three environmental factors, including salinity, temperature and pH, on the molecular mechanism of S. esculenta larvae, and proved the reliability of transcriptome results through physiological indicators. Enrichment analysis of each module indicated that environmental exposure markedly influenced immune function, oxidative stress responses, and other physiological processes in S. esculenta larvae. Our research elucidates the comprehensive response mechanism of S. esculenta under different environmental stresses, clarifies the significant molecular pathways essential for its growth and development.

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

Published 10 June 2026 Science Closed
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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.

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

Published 4 June 2026 Science Closed
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Highlights

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

Abstract

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

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Chemical cues and molecular mechanisms suspected in abiotic stress communication

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

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

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

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Genome-wide characterization of the Pacific oyster Crassostrea gigas SLC4 gene family and expression profiles in response to acidification

Published 20 May 2026 Science Closed
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Highlights

  • Eight CgSLC4 genes family members were identified.
  • CgSLC4s exhibited tissue-specific and developmentally variable expression patterns.
  • CgSLC4 gene family responds to acidification stress in different mantle folds.
  • CgSLC4A10-1 shows marked acidification responsiveness, especially in mantle epithelium cell.

Abstract

The solute carrier 4 (SLC4) family represents a category of integral membrane transporters responsible for bicarbonate mediation, which is vital for numerous fundamental biological functions. In this study, eight SLC4 genes were identified and annotated in Crassostrea gigas genome, comprising one member of Cl−/HCO3− exchanger, five genes coding Na+-dependent HCO3− transporters, and two Na+-coupled borate transporter copies, which were located on three chromosomes. In general, the expression of CgSLC4s showed tissue specificity, and differential expression patterns of CgSLC4s was observed at different developmental stages. The CgSLC4 family genes displayed divergent responses to acidification across different mantle folds. Among these family members, CgSLC4A10-1 exhibited the most dramatic and statistically significant expression changes in response to acidification across mantle folds, with fold changes ranging from 0.008-fold down-regulation to 85.95-fold up-regulation. According to the results of RT-qPCR and immunofluorescence, after 14 days of acidification treatment, CgSLC4A10-1 mRNA expression level was significantly increased, immunoblotting signal intensity was also enhanced in the epithelial cells. These results provide a general characterization of the SLC4 gene family in C. gigas, which may provide a systematic overview of the SLC4 gene family in C. gigas, and lay a foundation for future studies to explore its potential involvement in ion homeostasis and acidification adaptation in bivalve mollusks.

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Impacts of ocean acidification and warming (OAW) on abalone growth and reproduction: a dynamic energy budget model approach across SSP scenarios

Published 18 May 2026 Science Closed
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Ocean acidification and warming (OAW) are expected to alter physiology, growth and reproduction of marine ectotherms, yet their combined effects on life-history traits remain unresolved, particularly under poorly defined future food conditions. Using a Dynamic Energy Budget (DEB) model, we investigated how interacting changes in temperature, seawater pH, and food quality may shape somatic growth and reproductive phenology of the European abalone Haliotis tuberculata across four contrasting coastal environments and three Shared Socioeconomic Pathway (SSP) climate scenarios. OAW effects were modeled as increased metabolic maintenance costs, while reduced food quality, driven by OAW, lowered assimilation efficiency, aligning with experimentally-supported limited compensatory feeding.,Our results reveal that warming and food quality strongly drive somatic growth, whit ocean acidification playing a minor role within the modeled range. Food quality remained the primary determinant of maximum body size, while warming amplified growth across all locations, with the largest proportional increases in cooler northern bays. Individuals in the warmest areas remained the largest across scenarios within the model framework. Reproductive timing also shifted consistently, with first spawning occurring markedly earlier under end-of-century conditions, advancing consistently with scenario intensity. Food quality modulated reproductive investment but had weaker effects on the timing of first spawning., These findings highlight that food quality critically mediates organismal responses to OAW and can offset temperature-driven gains in growth and reproduction. By combining expected nutritional constraints with SSP scenarios, our DEB-based approach provide mechanistic insights into the future responses of benthic marine invertebrates to climate change, highlighting the value of these scenario-based projections for better management strategies.

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High-resolution temporal biogeochemical variations in a seagrass-coral cohabitate ecosystem: day-night, rain, and coral spawning

Published 14 May 2026 Science Closed
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Highlights

  • Seagrass-coral habitats act as CO2 sources driven by intense nighttime respiration
  • High-resolution data enable predictive modeling of DIC, DOC, and POC dynamics
  • Metabolic cues govern DIC, while temperature and alkalinity regulate POC and DOC
  • Episodic coral spawning and rainfall trigger rapid ocean acidification
  • Short-term disturbances dramatically shift organic and inorganic nutrient loads

Abstract

Seagrass meadows and coral reefs are global hotspots for productivity, yet they are often studied in isolation despite their intense biogeochemical connectivity. Significant gaps remain in understanding how coupled inorganic and organic processes within the water column drive blue carbon services in such mixed habitats, particularly during rapid environmental disturbances. Here, we investigated a unique, intertwined ecosystem in the Dongsha Atoll, where massive Porites corals are distributed on seagrass meadows, creating a natural laboratory for studying water column carbon biogeochemistry. During a 10-day sampling period, we collected continuous hydrological and discrete biogeochemical data at two- to four-hour intervals. Our results reveal that the dissolved inorganic carbon (DIC) covaried with dissolved oxygen and pH in strong diurnal patterns, which were governed by photosynthesis and respiration. As an outcome, variable but mostly high pCO2 values (141–2070 μatm) indicate the seagrass meadow was a source of CO2 to the atmosphere due to strong night-time respiration. Particulate organic carbon (POC) increased with temperature but showed no diurnal pattern. Dissolved organic carbon (DOC) showed a weak diurnal pattern and was linked to variations in POC and total alkalinity, highlighting the tight coupling between the organic production of the meadow and the inorganic chemistry of the calcification framework. Additionally, coral spawning led to a surge in organic content and changed inorganic nutrient levels. Rainfall events significantly acidified the ocean and enhanced submarine groundwater discharge to the seagrass-coral habitat. The distinctive contributions of this study are the extremely high temporal resolution of discrete samples, allowing the simultaneous tracking of multiple organic and inorganic pools during natural disturbances. The high-resolution data provide fundamental information for parametrizing models that explain DIC, POC, and DOC, which yield insights into organic carbon cycling in seagrass meadow-coral habitats.

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

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

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Controls on boron isotope ratios in marine bivalve shells: insights from a controlled experiment across pH and temperature gradients

Published 8 May 2026 Science Closed
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Documenting spatial and temporal patterns of ocean acidification and understanding the way marine organisms build carbonate skeletons is critical to assessing their potential vulnerability to present and future stressors. The boron isotopic composition (δ11Bc) of many marine carbonates provides insight into the pH at the site of calcification within biocalcifiers and, by extension, the pH of ambient seawater when the carbonate formed. The modification of seawater carbonate chemistry at the site of calcification by marine calcifiers and the utility of different taxa as paleo-pH proxy archives remains an area of active research. Despite the significance of marine bivalves to ecosystem function, high-resolution paleoclimatic studies, and the shellfish industry, their biocalcification mechanisms, controls on internal pH, and potential for reconstructing records of past seawater pH remain unclear. To address these gaps, a 20.5-week flowthrough tank experiment was conducted in which four species of commercially important bivalves from the northwest Atlantic Ocean were grown in tanks with controlled pHT (pH 7.4 to 8.0) and temperature conditions (6 to 12 °C). A total of 106 shell samples from 99 individuals of adult and juvenile Arctica islandica (ocean quahog), juvenile Mercenaria mercenaria (northern quahog or hard clam), juvenile Mya arenaria (soft-shell clam) and juvenile Placopecten magellanicus (Atlantic sea scallop) were analyzed from this controlled experiment to assess the seawater pH, temperature, and growth rate controls on shell δ11Bc.These four bivalve species, grown under identical, controlled conditions, showed differential responses to the same seawater temperature and pH, likely due to differences in how they regulate the pH of their internal fluids. Juvenile P. magellanicus and juvenile M. mercenaria demonstrated significant relationships (R≥0.60; p-value <0.006) between tank pHT and δ11Bc, suggesting potential utility as proxies for past ambient seawater pH. Conversely, the δ11Bc of juvenile A. islandica and juvenile M. arenaria did not yield a strong relationship with seawater pHT but instead yielded significant relationships with shell growth rate (linear extension), with a positive relationship for M. arenaria and a negative relationship for juvenile A. islandica. The δ11B results from the few (n=9) adult A. islandica shells measured show the most variability across the range of pH and temperatures (range of 16‰) and no significant relationship was found with seawater pH or growth rate. Despite rigorous oxidative cleaning of samples, the data suggest that adult A. islandica shells contain boron-rich organic phases resistant to traditional cleaning techniques. This suggests that the next step in the development of boron-based pH proxies in A. islandica requires additional research into robust cleaning and sampling methods of periostracum and other organics. Despite the need for further investigations to constrain growth rate effects and cleaning techniques in A. islandica and M. arenaria, there is potential for developing paleo-pH proxies from P. magellanicus and M. mercenaria to better understand spatial and temporal patterns of past, present and future ocean acidification.

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Combined effects of ammonium and pH on sea urchin embryogenesis: insights for sediment quality assessment

Published 30 April 2026 Science Closed
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Highlights

  • Reduced pH enhances ammonium toxicity on sea urchin embryos in filtered seawater.
  • In elutriates ammonium is a major driver of P. lividus embryotoxicity.
  • Data support setting ammonium thresholds in sediment quality frameworks.
  • Ocean acidification potentially increases ammonium toxicity for sea urchin larvae.

Abstract

Ammonium is a key component of coastal marine systems, originating from both natural and anthropogenic sources, with possible toxic effects on marine organisms depending on the concentration and pH. This study evaluates, for the first time, the combined effects of ammonium and seawater acidification on early development of the sea urchin Paracentrotus lividus under both laboratory conditions and exposure to environmental matrices derived by dredged sediments from harbor area. Embryos were incubated with increasing concentrations of ammonium in filtered seawater at pH 8.1 and 7.6, as well as in sediment elutriates from the Pescara harbor (Adriatic Sea, Italy), selected as a case study with relevant concentrations of ammonium (0.1–3.5 mg/L). A combined effect between ammonium and pH was observed, with increasing ammonium toxicity by ∼20% at pH 7. Moreover, in sediment elutriates, ammonium affect sea urchin embryo development, with EC50 ranging between 1.388 and 1.538 mg/L NH4+ at pH 8.1 and 7.6, respectively, without significant differences due to pH. Chemical analyses of sediments confirmed low levels of trace metals and organic pollutants, indicating that ammonium is the primary driver of embryotoxicity without a direct toxic effect of other contaminants. The results further underscore the need to integrate ammonium assessment into sediment quality frameworks and for management strategies, particularly in the context of future ocean acidification, to safeguard the early life stages of sensitive marine invertebrates.

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Ocean acidification and harmful algal blooms combine to suppress the growth and survival of North Atlantic bivalve larvae

Published 29 April 2026 Science Closed
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While harmful algal blooms (HABs) and ocean acidification (OA) are environmental factors that can impair bivalves, the manner in which these two stressors may act and interact to impact bivalve larvae is poorly understood. This study exposed larvae of hard clams (Mercenaria mercenaria) and Eastern oysters (Crassostrea virginica) to a range of pCO2 levels found in estuaries (400–3,000 µatm) and three harmful algae, Alexandrium catenella, Dinophysis acuminata, and Margalefidinium polykrikoides, at densities found during HABs (500–7,000 cells mL-1), with one HAB species exposure per experiment. The combined OA and HAB treatment significantly reduced larval survival in all 21 experiments by 91 ± 4.6% (SE) compared to controls and reduced larval sizes in 92% of experiments by 40 ± 3.5%. Cultured M. polykrikoides had a stronger negative effect on larvae than cellular equivalent bloom populations. Densities of D. acuminata >750 cells mL-1 reduced larval survival and size (p < 0.01), but the addition of OA to D. acuminata did not suppress survival further. While the combined A. catenella and OA treatment reduced larval growth and survival at all densities (p < 0.01), A. catenella alone did not impact M. mercenaria survival or size at or below 1,000 cells mL-1 and did not impact C. virginica at any density. Oyster larvae were less impacted than hard clams by OA (33 vs. 67% of experiments) and by HABs (67 vs. 100% of experiments). Given the very low survival of bivalve larvae when exposed to combined HABs and OA in all experiments (<0.1–5%), bivalve restoration and conservation efforts should seek to avoid regions that experience these co-stressors.

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The impact of climate change on lobster production: a systematic synthesis of literature

Published 6 April 2026 Science Closed
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Climatic impact-drivers are projected to change in coastal and marine regions globally, especially towards the fisheries production of the commercially important global shellfish, such as lobster species. Thus, there is an immediate need for ongoing, rigorous systematic review that continuously assesses and analyzes the risk of climatic factors towards lobsters’ production (i.e., growth, reproduction, etc.). A global relevant literature was analyzed from the inception to 31st December 2024. The review targets commercially important lobster, across various life history stages. The current study presents a systematic analysis of the research articles on lobster growth, reproduction, and development from relevant literature through two main academic databases, Scopus (n = 284) and Web of Science (n = 310). During literature search, duplicate articles were removed manually (n = 177). A total of 46 research articles were generated from the strict systematic selection process at various life history stages of lobsters. Climate change elements such as temperature, salinity, carbon dioxide, pH, and hypoxia significantly impact ovigerous females, reproduction, hatching success, larval stages, and juvenile development of lobsters. As global climate change intensifies, the reproductive and developmental capacity of lobster populations may be increasingly compromised, particularly in early life history stages. To date, a comprehensive synthesis of reproductive and biological impacts across taxa and regions has been lacking. This review provides a foundational reference for future assessments and adaptation strategies for sustainable management of lobsters under climate change.

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Combined ecotoxicity of microplastics and crude oil co-pollutants: occurrence, distribution and its synergistic impact with ocean acidification on Artemia franciscana

Published 3 April 2026 Science Closed
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Microplastics (MPs) are recognized as a global concern, with specific attention shifted towards marine MPs pollution. This particular study investigates the abundance and distribution of crude oil-loaded microplastics (COMPs) along the Chennai coastline, Tamil Nadu, India and evaluates their combined toxicological effects with ocean acidification on Artemia franciscana. Spatial analysis revealed that Ennore Creek exhibited the highest MP concentration (10.82 ± 0.2 items/L). Polypropylene was recorded as the predominant polymer type followed by low density polyethylene and polyethylene terephthalate, with particle size ranging from 250 to 500 µm. COMPs were detected across all sampling sites, with concentrations declining from Ennore Creek (0.21 ± 0.03 items/L) to Kasimedu Beach (0.10 ± 0.02 items/L). The adsorption of crude oil on MPs is primarily mediated by physical interaction with multi-layer adsorption behaviour. The results highlighted that increase in MP concentration and decrease in seawater pH significantly induced acute toxicity and oxidative stress responses in A. franciscana. At pH 7.8, experimental groups exposed to 0.5 mg/mL of COMPs developed higher ROS, SOD and catalase activity (p<0.001). Whereas control groups alone showed significant increase in oxidative stress responses at lower pH level such as pH 7.8 and 8.0. Combined exposure of COMPs and low pH conditions significantly increased oxidative damages in A. franciscana and affected its hatching ability. The observations from this study emphasize the urgent need for integrated monitoring and further research to explore combined toxicological effects of MPs and ocean acidification to other marine organisms as well.

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

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

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Impacts of ocean acidification on marine zooplankton: a review of physiological, developmental, and reproductive responses

Published 31 March 2026 Science Closed
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Acidification. The increasing levels of carbon dioxide CO₂ in the atmosphere are leading to ocean acidification, and this is altering the chemical content of marine water and is endangering life in the oceans. The examples of marine zooplankton, including Copepods, Pteropods, krill, and larvae of invertebrates are essential to the pelagic food webs and carbon cycles, even though they differ in their tolerance to low PH concentration and high pCO₂ levels. Early developmental phases are particularly vulnerable, with them showing retardation in developmental stages, reduced hatch rates, physical deformities as well as a lack of calcification. Higher carbon dioxide CO₂ levels interfere with the acid-base balance, increase oxidative stress and alter the allocation of metabolism, leading to trade-offs that lower growth, reproduction and survival rates. Calcifying organisms such as the pteropods are highly susceptible whereas some of the non-calcifying copepods exhibit a level of physiological resilience. Negative effects of other stressors may be affected by increased temperature, oxygen depletion, and nutrient enrichment which may further compound negative effects. There is some evidence that there is some possible acclimation in the short term and that there might be transgenerational plasticity but we do not understand adaptive capacity in the long term. Knowledge gaps exist in regard to multigenerational response, non-calcifying and gelatinous species and how physiological plasticity occurs. Species-specific responses are an important aspect of predictive models to estimate the impact of the ecosystem and guide conservation efforts. To ensure marine ecosystems remain stable as ocean acidification continues, vulnerable zooplankton should be safeguarded to preserve tropic structure, nutrient cycling, and nutrient stability.

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