Posts Tagged 'biological response'

Physiological responses of Atlantic surfclams (Spisula solidissima) to moderate ocean acidification across thermal regimes

Published 23 October 2026 Science Leave a Comment
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Highlights

  • Interactive effects of warming and acidification tested in surfclams.
  • Growth, feeding, and metabolic rates measured after 6-week exposure.
  • Moderate acidification had limited effects under warming conditions.
  • Surfclams showed resilience to near-future ocean acidification.
  • Multi-stressor design improves ecological relevance of lab studies.

Abstract

Understanding marine organismal responses to co-occurring climate stressors is critical for predicting changes in ecosystems and commercial fisheries. The Atlantic surfclam supports a major commercial fishery in the Northeastern United States, where ocean warming and acidification are rapidly altering marine habitats. To evaluate how changing ocean conditions may affect bivalve physiology, surfclams were exposed to conditions reflective of ocean warming and acidification, respectively. One-year-old surfclams were exposed to nine conditions in a fully crossed design of temperature (ambient, +2 °C, and + 5 °C) and pH (7.88 ± 0.05, 7.76 ± 0.05, and 7.51 ± 0.07) for six weeks in a flow-through laboratory experiment using natural seawater. We quantified several physiological responses including growth, feeding, digestion, respiration rates, and shell weight and thickness to assess organismal performance across treatments.

Surfclams generally exhibited resistance to moderate ocean acidification across warming, but non-thermally stressful, temperatures. No effects of ocean acidification were observed on surfclam growth or respiration, although other physiological metrics (shell thickness and absorption rate) decreased with decreasing pH at some temperatures. These findings provide experimentally-derived insight into species-specific responses to interacting climate stressors. Further, the experimental design highlights the importance of integrating natural environmental variability into laboratory studies and studying multiple environmental stressors concurrently. This study contributes a basis for refining models of surfclam growth and distribution in potential future climate scenarios, with implications for sustainable fisheries management.

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Ocean warming and acidification reveal transcriptional plasticity in the gastropod Hexaplex trunculus

Published 23 October 2026 Science Leave a Comment
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Coastal ecosystems, particularly in the rapidly warming Mediterranean Sea, are increasingly impacted by climate change driven by ocean warming and acidification. Calcifying marine invertebrates are especially vulnerable, yet their molecular responses remain poorly understood. Gene expression dynamics in the ecologically and commercially important gastropod Hexaplex trunculus were investigated under simulated scenarios combining elevated temperature and reduced pH. High-throughput RNA sequencing was used to generate a de novo assembly of the foot transcriptome, followed by differential gene expression analyses to characterize molecular responses to individual and interactive stressors under high-emission (RCP 8.5) projections. The foot tissue – central to locomotion, adhesion, and environmental interaction – exhibited pronounced transcriptional changes in genes associated with calcium signaling, ion transport, aerobic respiration, muscle contraction, and transmembrane transport. Ocean acidification emerged as the dominant driver of transcriptional change, inducing substantial shifts in metabolic demand and ion regulatory pathways, which might suggest increased energetic costs and potential functional constraints. The results demonstrate marked transcriptional plasticity in H. trunculus under combined climate stressors. By providing foundational transcriptomic resources for this species and mechanistic insight into its response to projected environmental changes, this study advances the understanding of molecular processes in vulnerable Mediterranean gastropods and informs ecological assessment efforts in rapidly warming marine ecosystems.

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Global projections of coral reef sediment dissolution in the 21st century

Published 22 October 2026 Science Leave a Comment
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Abstract

Coral reefs build carbonate frameworks, but ocean acidification threatens to reverse this role by accelerating dissolution of permeable reef sediments. We combined Earth system model projections across five emission pathways with an aragonite saturation state-dissolution relationship to project global reef sediment dissolution through 2100. Under stringent mitigation, less than 2% of reef area experiences dissolution by 2100, compared with 30% under intermediate emissions and nearly all reefs under high emissions. Cumulative calcium carbonate loss reaches 2.5 gigatonnes under the highest-emission pathway, accompanied by 0.7 gigatonnes of potential carbon dioxide uptake that is globally negligible but signals framework degradation. Model-derived aragonite saturation states exceeded in situ observations in most regions, suggesting that reef sediment dissolution may begin earlier than gridded projections indicate. The southern Central Pacific emerges as a candidate acidification refugium warranting reef-scale evaluation. Continued high emissions could shift reefs from net carbonate accretion toward widespread structural loss.

Plain Language Summary

Human carbon emissions are making the oceans more acidic, threatening not only living corals but also the carbonate sand and rubble that help build and support reef structures. Using climate model projections and reef observations, we estimated how reef sediment dissolution may change worldwide through 2100. Under high-emission scenarios, nearly all coral reefs are projected to experience sediment dissolution by the end of the century, with cumulative calcium carbonate losses reaching 2.5 billion metric tons. Although this process can absorb carbon dioxide, the amount is far too small to meaningfully slow climate change and instead reflects the physical breakdown of reef structures. The southern Central Pacific may acidify more slowly and could offer some protection, but local water chemistry and heat stress must be evaluated before the region can be considered a reliable refuge.

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Climate change and fish reproduction: a meta-analysis of global laboratory-based experimental evidence across species and ecosystems

Published 22 October 2026 Science Leave a Comment
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Climate change is altering fish reproduction by disrupting spawning cycles, reducing egg viability, and altering reproductive behaviours essential for population sustainability, to our knowledge, this is the first synthesis to integrate laboratory-based evidence for temperature, hypoxia, ocean acidification, and their combined exposure across reproductive performance, physiological, developmental, and molecular endpoints, and across freshwater, brackish, and marine habitats. Following PICOS and PRISMA criteria, we synthesised 779 effect sizes (740 retained after outlier exclusion) from 80 controlled laboratory studies (38,500 observations; 54 species; 28 countries). A three-level multilevel model accounting for non-independence among effect sizes drawn from the same study showed a significant overall negative effect of climate stressors on fish reproduction (Hedges’ g = −0.421, 95% CI: −0.631 to −0.210, p < 0.001; I² = 94.9%, decomposed into 36.3% between-study and 58.6% within-study heterogeneity). Hypoxia was the dominant and statistically distinct driver (g = −1.145, 95% CI: −1.648 to −0.643, p < 0.0001), most severely impairing gonadal development and sperm quality. The overall warming effect did not reach significance once non-independence was accounted for (g = −0.221, 95% CI: −0.448–0.006, p = 0.057), an uncertain negative trend rather than confirmed impairment, although tropical freshwater species showed significant subgroup-specific declines in reproductive physiology and genetic parameters. Ocean acidification showed a small positive effect (g = 0.199, 95% CI: 0.056–0.343, p = 0.006) that was not robust under robust variance estimation (p = 0.133) and is interpreted with caution. Combined multi-stressor exposure showed a negative trend (g = −0.901, 95% CI: −1.992–0.190, p = 0.106) that did not reach significance, based on only three studies. A formal omnibus test confirmed that stressor categories differ significantly in their effects (QM = 18.61,df = 3, p = 0.0003), with hypoxia statistically distinct from both temperature and ocean acidification. Leave-one-out and cumulative meta-analyses confirmed the robustness of the overall finding.

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Carry-over effects of low salinity during embryonic development modulate larval responses to combined salinity-pH stress in an estuarine crab

Published 21 October 2026 Science Leave a Comment
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Early life stages of estuarine organisms are exposed to concurrent environmental stressors, but the extent to which embryonic conditions shape larval responses to multiple stressors remains largely unexplored. We evaluated whether salinity during embryogenesis modulates larval responses to combined salinity and pH stress in the estuarine crab Neohelice granulata. Embryos were reared at two salinities (15 and 33), and larvae were subsequently exposed to combinations of pH (8 and 6.9) and salinity (15 and 33). Salinity during embryogenesis did not affect development duration or eye size, but altered other embryonic traits: embryos at low salinity showed higher heart rate, larger egg volume, and increased egg mass at late stages. In larvae, salinity was the main driver, strongly affecting development, survival, and metabolic performance, whereas pH alone had limited or stage-dependent effects. However, their interaction intensified responses, particularly increasing mortality. Low salinity during the larval stage increased intermolt duration and mortality, effects further exacerbated under low pH. The strongest negative responses occurred under combined low salinity and low pH, with delayed development, higher mortality, and reduced oxygen consumption rates. Although low salinity during embryogenesis influenced larval performance under low pH, larval responses were primarily driven by current environmental conditions. These results highlight that co-occurring stressors can outweigh early-life conditioning. Given that low salinity events and acidification frequently co-occur in estuarine systems, their interaction is critical for understanding organismal responses.

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Present but overlooked: biogenic acidification in aquaculture waters and its implication for mollusc mariculture

Published 21 October 2026 Science Leave a Comment
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Mollusc mariculture, a critical global source of high-quality protein, is increasingly threatened by seawater acidification. While climate-driven ocean acidification (OA) has been widely studied, intensive aquaculture systems face an additional, locally exacerbated phenomenon: biogenic acidification. In this review, we comprehensively compare biogenic acidification with OA and other seawater acidification types, highlighting its occurrence across various aquaculture systems and its capacity to induce conditions more corrosive than end-of-century OA projections under densely stocked settings. Driven by the respiration and calcification of high-density mollusc populations, biogenic acidification leads to distinct alterations in the carbonate chemistry of mollusc farming systems—notably a reduction in total alkalinity (TA)—that are mechanistically different from OA. We further discuss how biogenic acidification imposes stronger physiological stresses on molluscs, impairing calcification, growth, and energy allocation, and how it synergistically interacts with climate change. Finally, we propose practical mitigation strategies, including TA supplementation and integrated multi-trophic aquaculture, to enhance the resilience and sustainability of mollusc farming. This review underscores the necessity to address biogenic acidification as a distinct and ongoing challenge in global mariculture.

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The impact of the CO2 fertilization effect in seagrasses: a comparative perspective with terrestrial plants

Published 20 October 2026 Science Leave a Comment
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This article comments on:

Pazzaglia J, Marín-Guirao L, Ambrosino L, Pes K, Costa M, Barrote I, Silva J, Procaccini G. 2025. Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings. Journal of Experimental Botany 76, 6958–6973. https://doi.org/10.1093/jxb/eraf276.

Seagrass meadows are among the world’s most ecologically and economically important marine ecosystems. Although they cover only 0.1% of the seafloor, they sequester carbon at rates rivalling tropical rainforests, protect coastlines, and support marine biodiversity (do Amaral Camara Lima et al., 2023). Yet they are declining globally due to anthropogenic pressures including coastal development, pollution, and climate change (Waycott et al., 2009; Dunic et al., 2021). While ocean acidification and ocean warming are pervasive stressors under accelerating global change, Pazzaglia et al. (2025) have demonstrated that elevated dissolved CO2 may enhance seagrass resilience by increasing thermal tolerance in Posidonia oceanica seedlings through the CO2 fertilization effect.

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Long-term coral responses to high CO2: insights from volcanic vents and semi-enclosed bays

Published 20 October 2026 Science Leave a Comment
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This chapter provides a comprehensive review of natural laboratories used to study the effects of ocean acidification (OA) on coral reefs, emphasizing volcanic CO2 vents and semi-enclosed bays. It examines key environmental conditions at these study sites and their implications for coral physiology, biodiversity, and reef resilience. Two prominent natural analogues are highlighted: the Shikine Island warm-temperate shallow CO2 vent system in Japan and the semi-enclosed lagoon of Bouraké in New Caledonia.

Shikine Island represents a unique high-latitude coral environment influenced by the Kuroshio Current. The island’s CO2 vents provide a natural setting to investigate the community level effects of ocean acidification and how elevated CO2 levels interact with ocean warming and influence coral tropicalization. Findings suggest that while some corals persist at high CO2 levels, biodiversity declines significantly, with sensitive species unable to establish stable populations. Corals growing in these conditions exhibit reduced calcification, and the community structure shifts toward simpler, lower-complexity ecosystems dominated by turf algae. These results indicate that ocean acidification may act as a constraint on the poleward expansion of tropical corals, counteracting warming-induced range shifts.

In contrast, the semi-enclosed lagoon of Bouraké experiences extreme environmental fluctuations in pH, oxygen, and temperature, providing a window into the multifactorial stressors coral reefs may face in the future. Despite prolonged exposure to acidified, hypoxic, and thermally variable waters, corals in Bouraké demonstrate remarkable resilience. The system harbors diverse coral assemblages, with species exhibiting metabolic adjustments, increased heterotrophy, and shifts in symbiotic algae communities. This site suggests that coral ecosystems can develop physiological adaptations that enhance their survival in extreme conditions, offering valuable insights into the potential for long-term acclimatization.

By comparing these two contrasting natural analogues, this chapter highlights the complex interplay between acidification, warming, and other environmental stressors on coral reefs. While both sites provide critical insights into the future of coral ecosystems, they also underscore the urgent need for continued research and conservation efforts to mitigate the effects of climate change on marine biodiversity.

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Genomic responses of fishes to ocean acidification: insights from volcanic CO2 seeps

Published 20 October 2026 Science Leave a Comment
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Extreme and marginal reef environments provide valuable opportunities to examine the effects of altered seawater parameters that resemble predicted end-of-century ocean conditions under climate change. Volcanic CO2 seeps, in particular, have proven useful for studying the effects of ocean acidification (OA) in natural settings. In this chapter, we present a case study from a volcanic CO2 seep at Shikine Island, Japan, investigating the genomic response of the neon damselfish (Pomacentrus coelestis) to OA conditions. We examined transcriptomic profiles from brain and gill tissues collected across two seasons (July and November) and compared them to samples from multiple control sites to assess consistent patterns of gene expression under elevated CO2. Our results found that genes involved in blood oxygen regulation, immune response, and circadian rhythm were differentially expressed across seasons and tissues, suggesting their key role in the response to OA in P. coelestis. We also detected seasonal shifts in gene expression patterns, highlighting the complexity of the physiological responses to OA in natural environments. Many of the differentially expressed genes align with findings from previous laboratory and field studies, reinforcing the value of volcanic CO2 seeps for OA research. Finally, we discuss the challenges of working in natural seep environments, including variability across control sites and seasons, and emphasize the future potential of CO2 seeps for advancing our understanding of fish responses to ocean acidification.

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Developmental and behavioural responses of the non-indigenous amphipod Melita palmata (Montagu, 1804) at individual and population under reduced pH scenarios

Published 19 October 2026 Science Leave a Comment
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Highlights

  • Reduced pH disrupted early development, causing brood failure and incomplete eggs.
  • Broods and cohorts showed high mortality, limited growth and irregular sex traits.
  • Reduced pH altered behaviours, with sex-specific substrate use and slower escape.
  • Multilevel responses suggest reduced pH may affect population stability and invasion.

Abstract

Non-indigenous species (NIS) and reduced pH conditions are key stressors shaping coastal biodiversity and population performance. We examined how decreased pH influences developmental, demographic, and behavioural traits of the non-indigenous amphipod Melita palmata from the Mar Chiquita coastal lagoon (Argentina). Individuals, broods, and cohorts were reared under current pH (8.07) and a reduced pH scenario (7.5) to assess egg maturation, brood and cohort survival, growth, sexual differentiation, habitat use, and escape responses. Reduced pH disrupted early developmental processes, leading to incomplete egg maturation, brood failure, and the absence of post-breeding moults. Broods and cohorts exhibited low survival, limited growth, and irregular sexual differentiation, and no ovigerous females were detected. Behavioural responses were also altered, with sex-specific shifts in substrate use and slower escape reactions. Together, these multilevel responses indicate that decreased pH induce physiological and behavioural constraints that propagate into demographic instability. Such response at both individual and population levels suggests that reduced pH conditions could limit the capacity of M. palmata to sustain populations and may influence its future invasion dynamics, although field-level consequences remain to be determined. These findings highlight how early acting individual responses can scale up to shape population persistence under projected coastal acidification scenarios.

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Gravity-driven feeding currents in veliger larvae of the eastern oyster

Published 16 October 2026 Science Leave a Comment
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Feeding by marine invertebrate larvae depends critically on the low-Reynolds-number fluid mechanics of the feeding currents they generate. Yet the relative importance of gravity-driven versus drag-driven mechanisms in small invertebrate larvae has remained unresolved. Here, high-speed microscale imaging, micro-particle image velocimetry (μPIV), and an analytical axisymmetric Stokes-flow model are combined to quantify the feeding currents of free-swimming veliger larvae of the eastern oyster Crassostrea virginica. Despite their small body size (<330µm), the larvae possess a high excess density (∼181g/m3), shifting the force balance such that gravity-driven feeding currents dominate. μPIV measurements reveal flow fields with first-order (Stokeslet-type) spatial decay, yielding ecologically sufficient body-volume-specific maximal clearance rates of ∼2.5×106/day. These values agree with predictions from the Stokes-flow model, which decomposes the clearance into gravity-driven and drag-driven components and shows that the former consistently outweighs the latter across observed swimming speeds. The model further explains how slow swimming modulates clearance by ±44% relative to hovering. Together, these results demonstrate that C. virginica veligers operate in a gravity-dominated feeding regime similar to that of larger calanoid copepods, and that their feeding strategy is shaped by an interplay of excess weight, swimming kinematics, and ciliary propulsion. This work highlights the fundamental role of gravity in larval feeding mechanics and underscores the need to incorporate excess weight when evaluating form-and-function relationships in marine invertebrate larvae, particularly for shelled bivalve and gastropod larvae with high excess density.

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Bioturbation under stress: linking coastal environmental change to the physiology and function of marine bioturbators

Published 13 October 2026 Science Leave a Comment
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Coastal benthic habitats are increasingly exposed to human-driven environmental changes, resulting in multiple co-occurring stressors. Bioturbators, which provide vital ecosystem services, are particularly vulnerable due to their limited mobility and are directly exposed to these multiple stressors. However, the ecological impacts of these stressors on bioturbators, especially their activity levels, remain poorly understood. This review synthesizes current knowledge on how selected environmental stressors, including extreme weather events, eutrophication, and anthropogenic emissions, affect bioturbation, organismal physiology and survival. Reported impacts vary widely depending on the species and stressors’ intensity. The strongest negative effects were typically observed under high-intensity stressor scenarios, which sometimes exceeded environmentally relevant thresholds. However, only a few studies examined the combined effects of multiple stressors. Their effects on bioturbators can be neutral, antagonistic, synergistic or additive, highlighting the complexity of stressor interactions in natural systems. The summary of this review suggests that key ecosystem functions provided by bioturbators are threatened by constant exposure to multiple environmental stressors and that ongoing environmental changes are further exacerbating this situation. To better understand the risks faced by these organisms, it is important to explore the combined effects of multiple stressors, to support more accurate predictions and effective conservation and restoration efforts.

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Ocean warming and acidification alter larval development and swimming behavior in the Atlantic sea scallop, Placopecten magellanicus

Published 13 October 2026 Science Leave a Comment
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Ocean warming (OW) and ocean acidification (OA) are expected to have wide-ranging consequences for populations in marine systems caused by organism-level responses at a range of life history stages, including early larval stages. The Atlantic sea scallop, Placopecten magellanicus, is an economically important bivalve species that may be vulnerable to ocean change, but larval responses remain unclear. While the effects of OW and OA are known to impact adult sea scallops, little is known about the interactive effects of these two factors on early life stages. Larval dispersal is key to population-level patterns (e.g. abundance and distribution), but is contingent on growth rates and vertical swimming behaviors, which are both influenced by environmental conditions. Here, we evaluate the combined effects of OW and OA on larval development and behavior in a factorial lab experiment. We maintained larval sea scallop cultures up to metamorphosis under a range of physico-chemical conditions (17℃ and 14℃, and pH 7.3, 7.6, 7.9). Sea scallop larval development time was temperature dependent (1 vs. 1.5 months). There was an interactive effect of OW and OA on growth, where OA limited gains in growth experienced in warmer conditions. OA limited a decline in distribution late in development, while OW dominated individual vertical swimming behavior in intermediate development. Finally, ΩAr growth sensitivity was intermediate compared to that of other bivalve taxa. These results contribute to an improved understanding of developmental and behavioral responses to OW and OA, and provide information necessary for improved larval dispersal models under ocean change.

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Differential gene expression reveals molecular mechanisms for physiological resilience to ocean acidification stress in native and introduced oyster species

Published 9 October 2026 Science Closed
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Coastal-estuarine habitats are rapidly changing with respect to ocean acidification (OA). Along the West Coast of the United States, coastal upwelling regions are high in productivity and rich in nutrients, making them key areas for aquaculture oyster production. The native Olympia oyster Ostrea lurida has experienced population collapse due increased commercial harvest, habitat loss, and the introduction of the non-native Pacific oyster Magallana gigas. Despite intense focus on physiological responses of oysters to OA stress, molecular underpinnings of have yet to be fully described, particularly in niche species. Juvenile oysters of both M. gigas and O. lurida were exposed to a range of experimental OA conditions for six weeks to investigate transcriptomic and biomineralization responses under fluctuating and chronic low pH. Low pH had a significant effect on shell dissolution for both Pacific and Olympia oysters, with no statistical difference observed between the two species. Differential gene expression revealed distinct differences in responses of the Pacific and Olympia oysters to OA on the transcriptomic level, with M. gigas showing elevated molecular responses to OA stress. Our findings suggest that the two species may employ distinct adaptive strategies to mitigate low pH that are informative for species-specific management strategies.

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Behavioural responses of fishes to abiotic stressors: a comparative synthesis of shared physiological mechanisms and ecological consequences

Published 8 October 2026 Science Closed
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Highlights

  • Comparative review of behavioural responses to major abiotic stressors
  • Conserved physiological mechanisms underlie diverse behavioural responses
  • Cross-stressor synthesis identifies common and stressor-specific effects
  • Ecological consequences extend from individuals to populations
  • Research priorities for predicting fish responses to global environmental change

Abstract

Anthropogenic activities, including global warming, deforestation, urbanization, intensive agriculture, and aquaculture, are accelerating environmental change with consequences for aquatic ecosystems. As ectothermic vertebrates, fishes are sensitive to alterations in abiotic conditions, responding through behavioural changes that influence survival, reproduction, and species interactions. Although several studies have investigated the effects of abiotic stressors, comparative syntheses across stressors remain limited, constraining our understanding of how environmental drivers influence fish behaviour. In this review, we synthesize evidence on the impacts of six abiotic stressors, including temperature, hypoxia, acidification, turbidity, salinity, and ammonia, and examine the processes underlying responses. Across these stressors, behavioural alterations affect swimming performance, feeding, predator avoidance, social interactions, habitat selection, exploration, courtship, and anxiety-like behaviours. Despite differences in their primary modes of action, these stressors frequently converge on physiological disturbances involving oxidative stress, neurotransmitter regulation, sensory impairment, ion homeostasis, and energy metabolism, ultimately producing behavioural outcomes with ecological consequences. Most studies have been conducted under controlled laboratory settings, limiting ecological relevance. Furthermore, the combined effects of multiple abiotic stressors, together with long-term, multigenerational, and transgenerational responses, remain poorly understood despite their potential consequences for fish growth, reproduction, recruitment, and community structure. This review highlights the urgent need for integrative, multi-stressor, and multigenerational studies spanning diverse species, developmental stages, and ecosystems to improve predictions of fish responses under environmental change. By identifying shared and stressor-specific responses, this synthesis provides a conceptual framework for understanding how abiotic stressors affect fish through physiological pathways that ultimately converge on common behavioural outcomes with important ecological implications.

Graphical abstract

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Diversity and dynamics of sponge microbiomes under ocean acidification: insights from natural CO₂ vents and reciprocal transplant experiments

Published 8 October 2026 Science Closed
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Marine sponges are key benthic organisms whose ecological success is closely linked to their associated microbial communities. This thesis investigated the microbiome responses of three Mediterranean HMA demosponges, Chondrosia reniformis, Petrosia ficiformis, and Chondrilla nucula, inhabiting natural CO₂ vents off Ischia Island. By comparing wild populations under ambient and reduced pH with in situ transplants, this work explored long-term acclimatization and short-term responses. Species-specific transplantation protocols were optimized to ensure survival of the three sponges and experimental reliability. Then, 16S rRNA gene metabarcoding was used to characterize sponge-associated and seawater microbial communities. Results showed that sponge microbiomes were distinct from seawater and structured by host identity but each species displayed different degrees of stability and plasticity under acidified conditions. Chondrosia reniformis exhibited a highly stable microbiome, with acidification inducing only fine-scale shifts within a conserved core. Petrosia ficiformis showed greater flexibility, but short-term responses were strongly constrained by donor identity and source-associated signatures. In C. nucula, light availability emerged as the main driver of microbiome reorganization, while low pH modulated this response, promoting shifts from photosymbiosis-related taxa toward lineages potentially linked to nitrification and chemoautotrophy. Overall, sponge holobiont resilience appears to rely not on extensive microbial replacement, but on species-specific rearrangements of resident symbionts within persistent host-associated frameworks.

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Carbon dynamics and water quality regulation in Ruditapes philippinarum-Chlorella vulgaris co-culture with cardiac monitoring

Published 8 October 2026 Science Closed
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Highlights

  • Clam addition rapidly altered nitrogen, oxygen and dissolved-carbon dynamics.
  • All chamber treatments maintained negative CO₂ fluxes during incubation.
  • Algal monoculture showed stronger 6-h CO₂ uptake than co-culture.
  • Hydrochemical variables and cardiac activity were recorded concurrently.

Abstract

Global warming and ocean acidification threaten marine aquaculture. Bivalve-microalgae co-culture is considered a promising approach for low-carbon aquaculture, but its effects on water quality, carbon dynamics and bivalve physiology are not fully understood. This study tested Ruditapes philippinarum and Chlorella vulgaris in sealed static chambers with three treatments: sterile seawater (NP-C), Chlorella monoculture (WP-C) and clam-Chlorella co-culture (WP). Water-quality variables, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), air-water CO₂ flux and clam heart rate were measured in separate 3-h and 6-h incubations. At the end of incubation, WP had higher ammonium concentrations and lower dissolved oxygen than WP-C, indicating that clam addition changed nitrogen and oxygen conditions. DOC and DIC also changed differently in the two biological treatments. All treatments showed negative air-water CO₂ fluxes. In the 6-h experiment, CO₂ uptake was strongest in WP-C and intermediate in WP. Heartbeats were recorded continuously in four clams for 7.07 h. Overall, the co-culture rapidly altered water-quality and dissolved-carbon dynamics but did not result in greater short-term CO₂ uptake than the algal monoculture under the present chamber conditions.

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Stage-specific vulnerability: ocean acidification and hypoxia impair copepod recruitment through a naupliar bottleneck

Published 7 October 2026 Science Closed
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Progressive ocean acidification and deoxygenation are expected to threaten many marine zooplankton, but their combined effects across life stages remain poorly understood. We investigated stage-specific responses of the egg-carrying copepod Pseudodiaptomus annandalei to changes in pHT (5.97–8.05) and dissolved oxygen (DO; 0.90–8.20 mg L−1). Nauplii were the most sensitive stage in 24-h exposures, with survival dropping below 40% at pHT 6.1 and declining to 55–70% when DO fell below 1 mg O2 L−1. Under combined stress, naupliar survival declined to about 65% in the most severe treatment (pHT 7.11, DO 1.74 mg O2 L−1), whereas copepodites and adults showed no significant short-term survival response. In contrast, moderate combined stress (pHT 7.62, DO 4.11 mg O2 L−1) produced sublethal effects, increasing development time by approximately 70%, reducing development success from 86% to 28%, and decreasing nauplii production by approximately one-third. Thus, nauplii form a critical bottleneck for recruitment under combined stress.

Scientific Significance Statement

Coastal marine ecosystems are increasingly exposed to concurrent acidification and deoxygenation, yet the combined effects of these stressors across zooplankton life stages remain poorly resolved. Using the egg-carrying copepod Pseudodiaptomus annandalei, we show that short-term adult survival was relatively insensitive to combined low pH and low oxygen, whereas naupliar development and reproductive output were strongly reduced. These results identify the naupliar stage as a critical bottleneck under combined acidification and hypoxia. This stage-specific vulnerability implies that adult survival alone can underestimate recruitment impacts of changing coastal carbonate and oxygen conditions.

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Response of spore or gamete release of Ulva australis Areschoug to the superimposition of nutrients, salinity and ocean acidification: implication for Ulva sp. green tide outbreak

Published 7 October 2026 Science Closed
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Highlights

  • Sporophytes and gametophytes differed in germ cell release.
  • Sporophytes and gametophytes differed in physiological responses.
  • The different responses lead to Ulva sp. green tide outbreak.

Abstract

The Ulva sp. green tide is one global marine ecological disaster, and its prevention and control have drawn global attention. However, existing control strategies based on ecological mechanisms of Ulva sp. green tide without distinguishing sporophytes from gametophytes have yielded limited success, suggesting that the green tide outbreaks are driven by intrinsic biological mechanisms. Ulva australis Areschoug gametophytes and sporophytes differ in chromosome number; hence, it is inferred that their reproductive strategies respond differentially to environment factors, which explains the biological mechanism of Ulva sp. green tides from the perspective of the origin of germ cells. To verify this hypothesis and for effective control of green tides, the sporophytes and gametophytes of U. australis Areschoug were respectively cultivated and exposed to the conditions of nutrient salts, salinity and carbon dioxide (CO2) superimposed in a uniform design experiment for 48 h to observe the release of germ cells (spores or gametes). The spore release rate of sporophytes was positively correlated with salinity (p<0.05). The gamete release rate of gametophytes had a positive correlation with the interaction between NH4-N and PO4-P (p<0.05), and a negative correlation with CO2 concentration (p<0.05). The difference in responses of sporophytes and gametophytes to environmental factors ensures the availability of germ cells of U. australis Areschoug, which facilitates the green tide outbreak. Thus, the sporophyte and gametophyte respond differently to environmental factors, suggesting that they can adapt to different habitats, which implies that the green tide outbreak of the Ulva sp. has an inherent biological promoting mechanism. Moreover, it is understandable that the effect of a single control strategy in dealing with Ulva sp. green tides is not satisfactory.

Continue reading ‘Response of spore or gamete release of Ulva australis Areschoug to the superimposition of nutrients, salinity and ocean acidification: implication for Ulva sp. green tide outbreak’

Long-term exposure to ocean acidification modifies the biochemical composition of the adductor muscle of the commercial scallop Zygochlamys patagonica

Published 7 October 2026 Science Closed
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The scallop Zygochlamys patagonica is an ecologically and economically important seafood species in the Southwest Atlantic Ocean that has been shown to be sensitive to ocean acidification (OA), a global process caused by anthropogenic carbon dioxide emissions. This study experimentally evaluated the effects of a long-term exposure to low pH, including an OA scenario on the scallop adductor muscle— the commercially valuable tissue. We tested three levels of pH, two pH values within the present range of natural variability (high pHT= 8.00 and medium pHT= 7.80) and a lower pH level representing a true OA scenario (low pHT: 7.52). We examined biochemical alterations induced by low pH and assessed the potential for reversibility following a depuration period. No significant effects were observed for medium pH exposure. However, after 14 and 28 weeks of exposure to low pH (OA), significant reductions in protein and total lipid content were observed, resulting in decreased overall energy reserves, while glycogen levels remained unchanged. The fatty acid profile shifted under OA with an increased PUFA/ SFA ratio and higher sums of EPA and DHA. No signs of recovery were detected after the 2-month depuration period. These results indicate that OA-driven changes in biochemical composition may reflect altered physiological status, with potential socio-ecological implications for the sustainable exploitation of this valuable resource.

Continue reading ‘Long-term exposure to ocean acidification modifies the biochemical composition of the adductor muscle of the commercial scallop Zygochlamys patagonica’

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