Posts Tagged 'laboratory'

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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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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Plastic pollution as a pathway to ocean acidification and disruption of the seawater carbonate system

Published 22 October 2026 Science Leave a Comment
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Ocean acidification threatens calcifying organisms by reducing seawater pH and carbonate ion availability, while plastic pollution may intensify this effect through chemical and microbial processes, exacerbating impacts on calcification. Here, we investigated, for the first time, the biogeochemical mechanisms of plastic-pollution-induced ocean acidification and the role of plastic as a modifier of the seawater carbonate system. Microcosm experiments were conducted using naturally weathered plastic particles incubated in seawater under irradiated and dark conditions. The experiment comprised two seven-day phases: (1) an abiotic phase evaluating the physicochemical effects of plastic degradation and (2) a biotic phase assessing microbial contributions to plastic-induced acidification. Variations in pH, dissolved CO₂, Ωarag, and Ωcalc were monitored as acidification indicators. During the abiotic phase, plastic increased dissolved CO₂ concentrations threefold under irradiation (27.08 µmol kg⁻¹) compared with the dark treatment (9.65 µmol kg⁻¹), reducing pH, Ωarag, and Ωcalc. By the end of this phase, irradiated plastic reached pH = 7.6, Ωarag = 2.16, and Ωcalc = 3.25, corresponding to values associated with impacts on calcifying organisms and considered terminal for coral reef development. During the biotic phase, no significant changes were observed, likely due to limited dissolved organic carbon release, indicating that UV-driven abiotic processes, rather than microbial activity, predominated in CO₂ release. The observed chemical changes matched end-of-century projections under high-emission scenarios, highlighting that plastic pollution may intensify reductions in carbonate ion concentration and calcium carbonate saturation states, accelerating calcifier mortality and biodiversity loss.

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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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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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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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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.

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High CO2 at stable pH disrupts olfactory homeostasis and function in largemouth bass

Published 6 October 2026 Science Closed
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Elevated CO₂ is a common water-quality challenge in recirculating aquaculture systems. Although its effects are often accompanied by environmental acidification, the direct impact of elevated CO₂ under stable-pH conditions on fish olfactory function remains poorly understood. This study investigated the effects of elevated CO₂ on olfactory function and olfactory epithelial homeostasis in juvenile largemouth bass (Micropterus salmoides). Fish were exposed to approximately 5 mg L−1 (control), 10 mg L−1, and 15 mg L−1 CO₂ for 4 days while maintaining stable pH. Olfactory function and olfactory epithelial responses were evaluated using behavioral assays, calcium imaging, histological analyses, Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, immunofluorescence, and gene-expression analyses. Exposure to 10 and 15 mg L−1 CO₂ significantly reduced attraction to food odor without affecting swimming activity, indicating impaired olfactory sensitivity. Calcium imaging revealed attenuated olfactory responses to L-alanine, accompanied by altered expression of genes involved in olfactory signal transduction. Elevated CO₂ also increased the number and area of acidic mucous cells, reduced the abundance of mature olfactory sensory neurons, increased apoptosis in the olfactory epithelium, and altered the expression of genes associated with apoptosis, cell proliferation, and neurogenesis. These findings indicate that elevated CO₂ under stable-pH conditions impairs olfactory function and disrupts olfactory epithelial homeostasis in juvenile largemouth bass. The present study demonstrates that dissolved CO₂, independent of environmental acidification, adversely affects the fish olfactory system and highlights the importance of monitoring CO₂ as a key water-quality parameter in recirculating aquaculture systems.

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Mitigation of biogenic acidification via increased total alkalinity in high stocking density culture waters of Strongylocentrotus intermedius: effects on growth and metabolism

Published 6 October 2026 Science Closed
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Highlights

  • Biogenic acidification increases with stocking density in sea urchin culture.
  • Total alkalinity mitigates acidification and promotes growth and gonadal development.
  • Higher alkalinity shifts metabolism toward biosynthesis and energy storage.

Abstract

Among cultured sea urchins in China, Strongylocentrotus intermedius has the highest annual production, with seed production and grow-out primarily conducted under high-density intensive conditions where biogenic acidification readily develops. To investigate its development, effects, and mitigation, we conducted a short-term incubation experiment (1 d) and a 20-day cultivation experiment. In the short-term incubation experiment, a control group with initial pH ≈ 8.1 and TA ≈ 2300 μmol/kg and a TA-elevated group with initial pH ≈ 8.1 and TA ≈ 3600 μmol/kg were established, and sea urchins were cultured across a density gradient of 20–80 g/3 L. In the 20-d experiment, stocking density was 88 g/3 L with the same initial pH and TA settings. The short-term experiment showed that seawater acidification occurred in the control group, and stocking density was significantly correlated to pCO2, ΔpH (pH reduction), TA–DIC, and Ωarag. With increasing stocking density, pCO2 increased significantly, whereas ΔpH and TA–DIC significantly decreased simultaneously. In the TA-elevated group, all parameters except pCO2 were higher than those in the control group across all stocking densities. At the lowest stocking density, ΔpH, TA–DIC, and Ωarag in the control group were −0.09 ± 0.01, 111.48 ± 1.73 μmol/kg, and 1.43 ± 0.00, respectively, whereas the corresponding values in the TA-elevated group were 0.11 ± 0.01, 252.26 ± 6.98 μmol/kg, and 3.23 ± 0.08. These results indicate that increasing TA mitigates biogenic acidification and works to strengthen the buffering capacity of the carbonate system. At the end of the 20-day cultivation experiment, urchins from the TA-elevated group showed significantly higher specific growth rate (1.60 ± 0.08% vs. 1.27 ± 0.06%), weight gain rate (37.72 ± 2.25% vs. 29.04 ± 1.48%), and gonad index (6.09 ± 1.58% vs. 3.54 ± 0.49%) than those from the control group. Metabolomics analysis revealed that TA elevation enriched pathways related to protein biosynthesis, glycerophospholipid metabolism, and sphingolipid signaling, with higher abundances of essential amino acids (L-methionine, DL-isoleucine), sphingomyelins, and the antioxidant indole-3-pyruvic acid. In contrast, the oxidative stress marker DL-2-aminoadipic acid was upregulated in the control group. Overall, increasing seawater TA mitigates biogenic acidification in high-density sea urchin culture, shifting metabolism from stress defense toward biosynthesis and reserve accumulation, thereby supporting growth and gonadal development in juvenile sea urchins.

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Single-larva transcriptomics resolve phenotype-anchored Na+ K+ ATPase expression during first shell formation in Pacific oyster larvae under ocean acidification conditions

Published 5 October 2026 Science Closed
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Bivalve larvae are highly sensitive to ocean acidification (OA) conditions, a global climate shift that applies selective pressure on calcareous marine organisms. Although a growing body of work exists on the effects of OA on bivalve larvae, most studies rely on pooled-larval sampling, which may obscure gene expression patterns by including larvae with severely underdeveloped or deformed phenotypes, which are common in OA conditions but are unlikely to survive to metamorphosis. Here, we tested a combination of single-larva transcriptomic techniques to investigate the expression of a candidate gene previously shown to be upregulated in OA conditions, Na+ K+ ATPase (NKA), in Pacific oyster larvae of known phenotypes. We found that upregulation of the NKA gene is detected primarily in larvae with a developed first shell (prodissoconch I), and was not pronounced in underdeveloped or deformed larvae, suggesting its expression reflects active shell formation under OA conditions, rather than a generalized stress response. Further, NKA mRNA was primarily localized along the dorsal shell hinge, the site of CaCO3 deposition, substantiating its role in early shell development. This study provides a methodological framework for phenotype-anchored sampling to investigate the expressional signatures underpinning successful shell development in OA conditions.

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Involvement of CgPGC-1α in regulating mitochondrial biogenesis in Pacific oyster Crassostrea gigas under ocean acidification

Published 5 October 2026 Science Closed
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Highlights

  • CgPGC-1α with classical RRM domain was identified from Crassostrea gigas.
  • CgPGC-1α mRNA was ubiquitously expressed with the highest level in gill.
  • CgPGC-1α could respond to acidification treatment, promote mitochondrial biogenesis.
  • Acidification enhanced mitochondrial biogenesis and ATP via AMPKα/PGC-1α.

Abstract

Ocean acidification poses a significant threat to calcifying marine organisms. The Pacific oyster Crassostrea gigas is an economically and ecologically important bivalve species. Understanding the molecular mechanisms underlying its physiological adaptation to acidification stress is therefore of great ecological and aquaculture relevance. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a central regulator of mitochondrial biogenesis and cellular energy metabolism, which plays important roles in response to various stressors. In this study, a PGC-1α homolog was identified from Crassostrea gigas (CgPGC-1α), which harbors an evolutionarily conserved RRM domain. The phylogenetic tree indicated that CgPGC-1α first clustered with PGC-1α from molluscs, then grouped with vertebrate PGC-1α, and finally joined with the PGC-1α of arthropods. During larval development, expression level of CgPGC-1α increased from the early embryonic stages, reached its highest level at blastula stage, and subsequently decreased during later development stages. In adult oysters, expression level of CgPGC-1α were detected in haemocytes and all examined tissues, with the highest level in gills. When the oysters were exposed to acidified seawater at pH 7.4, the expression level of CgPGC-1α in gonad was significantly upregulated at 7 and 21 days. Furthermore, at 7 days after acidification treatment, the mtDNA copy number, the expression level of CgMFN mRNA transcripts, the CgPGC-1α protein levels and the pAMPKα (Thr172) phosphorylation levels all significantly increased (p < 0.05), while the relative mRNA expression level of CgDRP1 significantly decreased (p < 0.05). Moreover, a significant increase in the number of mitochondria with morphology changing from elliptical to irregular and cristae becoming swollen was observed, and the ATP content was significantly elevated. After 28d days of acidification, mtDNA copy number and the expression level of CgMFN and CgNRF2 were significantly decreased, whereas the expression level of CgDRP1 was significantly increased. Collectively, these findings reveal a temporal response to acidification, characterized by an early compensatory activation of the AMPKα/PGC-1α axis and enhanced mitochondrial biogenesis, followed by impaired mitochondrial homeostasis under prolonged acidification stress. This study provides new insights into the molecular mechanisms underlying oyster resilience to ocean acidification and highlights the potential importance of mitochondrial adaptation in coping with future environmental changes.

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Ocean acidification remodels the mantle phosphoproteome and weakens shell mechanical resilience in Mytilus edulis

Published 2 October 2026 Science Closed
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Highlights

  • Ocean acidification causes pH- and time-dependent disruption of nacreous and prismatic microstructures.
  • Shell compressive strength declines progressively with decreasing pH and exposure duration.
  • Quantitative mantle phosphoproteomics identified 3720 phosphoproteins and 10,780 phosphosites.
  • Differential phosphorylation is associated with signaling, vesicular trafficking, autophagy, and metabolic pathways.
  • Molecular and shell-level responses support a proof-of-concept dual-indicator framework.

Abstract

Ocean acidification (OA), driven by rising atmospheric CO2, threatens the structural integrity and ecological performance of calcifying marine organisms, yet the mechanistic links between environmental acidification and compromised shell mechanical resilience remain insufficiently understood. Here, we integrate microstructural imaging, mechanical testing, and quantitative phosphoproteomics to characterize the structural, mechanical, and phosphorylation responses of Mytilus edulis to OA and examine their relationships. Adult mussels were exposed to near-future pH conditions (8.1, 7.9, 7.7) for up to 40 days. OA produced progressive disorganization of nacreous tablets and prismatic columns without altering aragonite–calcite polymorphs, indicating that acidification drives structural degradation rather than mineralogical shifts. Correspondingly, shell compressive strength declined in a pH- and time-dependent manner, with an approximately 60% reduction at pH 7.7 after 40 days. Phosphoproteomic profiling identified 3720 phosphoproteins (10,780 sites), revealing extensive acidification-induced remodeling of phosphorylation networks. Proteins corresponding to differentially phosphorylated peptides were predominantly nuclear and were enriched in kinase-, PH-, PDZ-, and RNA-recognition-domain-containing proteins. Functional analyses implicated MAPK signaling, vesicular trafficking, ion transport, glycolysis/gluconeogenesis, autophagy, and calcium-associated processes. Phosphoproteomic remodeling was associated with the deterioration of shell microstructure and compressive strength, supporting an association between mantle phosphorylation responses and compromised biomineralization under acidification. The enriched pathways and protein domains were functionally related to calcium-dependent signaling, vesicular trafficking, cytoskeletal organization, and cellular metabolism, providing testable candidates for future mechanistic validation. Together, these findings support a working model in which ocean acidification is accompanied by coordinated phosphorylation remodeling and progressive loss of shell mechanical resilience. We further propose a proof-of-concept dual-indicator framework that integrates candidate molecular sentinels with organismal metrics, providing a conceptual basis for future assessment of aquaculture resilience and ecosystem vulnerability under progressive ocean acidification.

Graphical abstract

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Survival costs flavor: microplastics reprogram metabolic resource allocation and compromise oyster quality under ocean acidification

Published 30 September 2026 Science Closed
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Ocean acidification (OA) and microplastic (MP) pollution are widespread marine stressors, yet their interactive effects on seafood quality and molecular metabolism remain unclear. This study investigated the combined effects of OA (pH 7.7) and MPs (2 and 200 μg/L) on the Pacific oyster (Magallana gigas). OA was the primary driver of textural deterioration, significantly reducing springiness and chewiness, while combined stress synergistically depleted protein and lipid reserves. Distinct lipid remodeling strategies were identified: OA induced DHA accumulation potentially associated with membrane stabilization, whereas MPs triggered EPA and ARA upregulation associated with stress and immune responses. The flavor profile was severely compromised, characterized by depletion of umami amino acids, nucleotide redistribution, and altered succinate contribution. Transcriptomic analysis revealed that high MP exposure activated genome maintenance and DNA repair-associated pathways, including the Fanconi anemia pathway, superimposed on OA-associated metabolic suppression. Concurrent upregulation of nucleotide salvage (APRT, HPRT) and amino acid catabolic genes (GLS, GDH) suggests increased utilization of flavor metabolites for energetic demands. These findings support a bioenergetic trade-off in which oysters exposed to OA and MPs reallocate resources from nutritional and sensory quality toward cellular maintenance and stress adaptation, highlighting underrecognized consequences of climate change and plastic pollution for seafood quality.

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A key seawater acidification-enriched gut bacterium, Pseudoalteromonas carrageenovora P1, enhances growth performance, antioxidant status, and disease resistance in sea cucumbers under seawater acidification

Published 28 September 2026 Science Closed
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Highlights

  • First discovery of Pseudoalteromonas enrichment in A. japonicus gut under acidification.
  • The dominant strain P. carrageenovora P1 was successfully isolated.
  • P. carrageenovora P1 activates host antioxidant and immune pathways to bolster stress resilience.
  • P. carrageenovora P1 significantly enhances resistance to V. splendidus 21,915 infection in A. japonicus.

Abstract

The sea cucumber (Apostichopus japonicus) is a key mariculture species of high economic value in East Asia. However, Ocean acidification, resulting from the increased uptake of anthropogenic CO₂ by seawater, severely impairs its growth, survival, and reproductive performance, thereby threatening the sustainable development of this aquaculture industry. The gut microbiota play a critical role in host adaptation to environmental stress; however, their involvement in mediating A. japonicus responses to seawater acidification remains unclear. Therefore, this study first compared the gut microbial communities of juvenile and adult A. japonicus under acidified and ambient seawater conditions. The results showed that Pseudoalteromonas abundance was significantly enriched under seawater acidification, from which the dominant strain, Pseudoalteromonas carrageenovora P1, was screened and isolated. This strain, when supplied as a dietary supplement under seawater acidification, improved A. japonicus growth performance and intestinal morphology, activated the Keap1-Nrf2-ARE and NF-κB pathways, enhanced antioxidant capacity and immune function, and increased resistance against Vibrio splendidus 21915 infection. Moreover, P. carrageenovora P1 modulated gut microbial structure by promoting beneficial bacteria such as Lutibacter while suppressing potential pathogens, including Vibrio, thereby maintaining intestinal homeostasis under acidification stress. This study reveals the important value of the gut microbiota of A. japonicus in regulating environmental tolerance of benthic invertebrates, and also provides a scientific reference for stress resistance regulation and health maintenance in A. japonicus aquaculture under seawater acidification.

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Thermal history and behavioural plasticity shape reef fish tolerance to marine heatwaves

Published 25 September 2026 Science Closed
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Marine heatwaves are becoming more frequent and intense, driving mass fish mortalities and reshaping marine ecosystems, yet the capacity of fishes to tolerate heatwaves remains unclear. We quantified physiological condition and behavioural responses of juvenile warm-water (Abudefduf vaigiensis) and cool-water (Microcanthus strigatus) fishes from three natural climate analogues—an ambient temperate reef, an ocean warming analogue, and a combined warming and extreme acidification analogue—before and during the 2023 global marine heatwave, and under a + 3 °C simulated heatwave in the laboratory. In the laboratory, warm-water fish from the warm reef began the experiment in leaner condition than cool reef fish but increased their bite rates under heatwave conditions, compensating for elevated metabolic demand and maintaining body condition. Cool-water fish showed no behavioural adjustment to the heatwave, and body condition diverged by reef origin: cool reef fish lost weight across all treatments while warm- and extreme-origin fish maintained condition, suggesting tolerance was conferred by prior thermal history rather than acute behavioural responses. In the field, warm-water fish were leaner and had lower protein content during the 2023 heatwave than before it, while cool-water fish from the extreme reef had lower body condition than those from the cool reef prior to the heatwave. Our findings suggest that behavioural plasticity can facilitate warm-water fish tolerance to heatwaves at their cold leading edges, while thermal history supports heatwave tolerance in cool-water fish within their core ranges. Populations inhabiting naturally extreme climate analogues may therefore harbour pre-adapted, climate-resilient fish in a future ocean.

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Projecting the impact of climate change on the lipid profile of the hydrocoral Millepora alcicornis: relative lipid homeostasis under warming and ocean acidification

Published 25 September 2026 Science Closed
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Climate change exerts a strong impact on marine ecosystems, particularly through ocean acidification and rising water temperatures. Within this context, shifts in lipid composition have emerged as valuable stress indicators in many organisms, providing insights into the trophic ecology of ecosystems. The objective of this study was to assess the combined effects of warming and ocean acidification scenarios projected for the end of the century (+5 °C and pH 7.5) on the lipid profiles of the hydrocoral Millepora alcicornis, recently recorded for the first time in Tenerife (Canary Islands, Spain). After an 84-day experiment, corals exhibited significant reductions in total lipid content, key lipid classes and fatty acids, particularly triacylglycerides (TAG) and docosahexaenoic acid (DHA, 22:6n-3), whereas sterol esters (ST) and saturated fatty acids (SFAs) showed the opposite trend. By contrast, symbiont-derived glycolipids and C18 fatty acids characteristic of zooxanthellae were not significantly affected by environmental stress, suggesting relative stability of membrane lipid composition. Overall, the maintenance of membrane lipid composition in symbiotic algae together with evidence of lipid remodelling in the host suggests a capacity for short-term physiological acclimation of M. alcicornis under the simulated climate change conditions. However, reduced DHA availability may have important physiological implications for the colonies, justifying future studies on the molecular regulation of LC-PUFA biosynthesis and the long-term acclimation capacity of Millepora alcicornis under climate change.

Continue reading ‘Projecting the impact of climate change on the lipid profile of the hydrocoral Millepora alcicornis: relative lipid homeostasis under warming and ocean acidification’

Impact of ocean acidification on coastal copepod Pseudodiaptomus serricaudatus: implications for futuristic coastal dynamics

Published 21 September 2026 Science Closed
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Highlights

  • Impact of ocean acidification on coastal copepods is proportional to its intensity.
  • Projected low pH significantly increases Pseudodiaptomus serricaudatus mortality.
  • Lower pH reduces overall population density and alters life-stage composition.
  • Predicted acidification delays larval development in P. serricaudatus.

Abstract

Anthropogenic ocean acidification, driven by increased atmospheric CO2 absorption by seawater, poses significant threats to marine ecosystems, particularly in coastal environments, where pH reductions are expected to be more severe than in the open ocean. Copepods represent a critical link between primary producers and higher trophic levels in the classical marine food chain. However, their responses to the rapid decline in seawater pH expected by the century’s end remain poorly constrained—especially in dynamic coastal regions. The current study quantifies how near-future pH scenarios affect the survival and population dynamics of the Pseudodiaptomus serricaudatus, a perennial coastal and estuarine copepod of the West Coast of India. Adult copepods of this species were incubated at four target pH levels (8.10, 7.81, 7.51, 7.04) using an automated CO2-bubbling system to assess mortality and population dynamics. Mortality was evaluated every three days up to day 10; population stage composition was recorded on day 15. Mortality remained 23% at pH 8.1 (representing open-ocean conditions) but rose to 30% at pH 7.81 (present-day coastal average), 47% at pH 7.51 (projected late-21st-century coastal value), and 77% at pH 7.04 (extreme 23rd-century scenario). Population data revealed declines across life stages and copepodite-to-nauplius (Ct/N) ratio at lower pH values, indicating impaired development. Any potential impact of ocean acidification on copepods could affect the fisheries sector, as these copepods are the chief food source for mackerel, an economically important fish in the region. The critical pH threshold for P. serricaudatus appeared to lie between 7.51 and 7.81, corresponding closely to current coastal conditions and near-future projections. These findings suggest that coastal copepod populations may already be experiencing sublethal stress, with potential demographic collapse occurring within decades rather than by the end of the century.

Continue reading ‘Impact of ocean acidification on coastal copepod Pseudodiaptomus serricaudatus: implications for futuristic coastal dynamics’

Evaluating the combined effects of harmful algal blooms and low pH exposure on the development and hatching success of Artemia salina

Published 21 September 2026 Science Closed
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Highlights

  • Hatching success of Artemia salina was impaired by acidified conditions.
  • Development of Artemia salina pre-nauplii was negatively impacted by both species of harmful algae and low pH exposure.
  • Only toxin-producing harmful algal species produced significant morphological abnormalities of pre-naupliar Artemia salina.
  • No synergistic effects of harmful algae and low pH exposure was seen in this study.

Abstract

Harmful algal blooms (HABs) and ocean acidification are major stressors in coastal marine ecosystems, yet their combined effects on early zooplankton development remain poorly understood. This study tested whether HABs and low pH exposure exert synergistic effects on the embryonic development and hatching success of brine shrimp (Artemia salina) cysts. Cysts were exposed to controls, toxin-producing HAB species (i.e. Margalefidinium polykrikoides or Alexandrium catenella), or a non-toxin producing HAB control (i.e. Gymnodinium aureolum) and at either ambient (pH ∼ 8) or acidified (pH ∼ 7.2) conditions. We hypothesized that the combined exposure to a toxin-producing HAB at acidified pH conditions would reduce hatching success and alter embryonic morphology. Low pH exposure consistently reduced hatching success and slowed developmental progression across treatments, reducing nauplii production. HAB exposure alone did not affect hatching success, but exposure to toxin-producing HABs in ambient pH conditions did significantly increase the morphological abnormalities at the membrane stage. Overall, no synergistic effects of HABs and low pH exposure were found for any response variable. Instead, HABs and low pH exposure exerted distinct, stage-specific impacts that were additive rather than interactive. These findings suggest that while exposure to toxin-producing HABs primarily disrupts morphology and low pH exposure slows development and reduces hatching success, their combined effects do not exceed additive expectations. Future work should explore physiological mechanisms underlying these stress responses and assess whether similar patterns occur in other cyst-producing zooplankton.

Continue reading ‘Evaluating the combined effects of harmful algal blooms and low pH exposure on the development and hatching success of Artemia salina’

Pre-harvest thermal and pH stress modulate macronutrient digestibility and protein bioaccessibility of the sea cucumber Isostichopus badionotus under in vitro gastrointestinal digestion

Published 18 September 2026 Science Closed
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Highlights

  • Thermal stress modulates protein digestibility and bioaccessibility in I. badionotus.
  • Induction at 28 °C maximized protein digestibility and intestinal bioaccessibility.
  • Sublethal 34 °C for 12 h peaked digestibility; longer exposure caused decline.
  • Intestinal bioaccessibility was the most sensitive indicator to pre-harvest stress.
  • Pre-harvest thermal and pH stress can alter the macronutrient nutritional quality in I. badionotus.

Abstract

The impact of in vivo thermal and pH stress on the macronutrient nutritional quality of the sea cucumber Isostichopus badionotus remains poorly understood from a food-nutrition perspective. This study investigated how acute induction temperatures (16–36 °C) and sublethal thermal exposure (34 °C, 3–48 h), combined with two ambient pH levels (7 and 8), modulate in vitro protein, lipid and carbohydrate digestibility and protein bioaccessibility of the sea cucumber I. badionotus, a collagen-rich tropical food, using the standardized static INFOGEST gastrointestinal simulation. In the acute induction experiment, protein digestibility, total bioaccessibility and intestinal bioaccessibility were strongly affected by temperature, with a narrow optimum at 28 °C (digestibility ∼58–66%; intestinal bioaccessibility ∼64–68% at both pH levels). Lipid digestibility varied within a relatively narrow range across treatments, whereas carbohydrate digestibility showed a marked temperature × pH interaction, with higher values at 28 and 36 °C under alkaline conditions. In the sublethal-stress experiment, protein digestibility and bioaccessibility followed a time-dependent pattern, with a peak at 12 h followed by a decline at 24–48 h, consistent with patterns of progressive collagen oxidation reported in other holothuroids. Across both experiments, intestinal bioaccessibility was the most responsive nutritional indicator to pre-harvest stress. These results demonstrate that pre-harvest thermal and pH stress can qualitatively alter the macronutrient nutritional quality of I. badionotus, with implications for harvest timing, processing optimization and seafood quality management under ongoing ocean warming and acidification.

Graphical abstract

Live sea cucumbers (Isostichopus badionotus) were exposed in vivo to controlled thermal and pH stress (16–36 °C, pH 7–8; 6 h acute induction and 3–48 h sublethal exposure), inducing proteolysis, oxidative responses, heat-shock protein expression and structural remodeling of the collagen-rich body-wall matrix. Samples were then subjected to standardized INFOGEST in vitro digestion (oral, gastric and intestinal phases with pepsin, pancreatin and bile salts), followed by dialysis at 12–14 kDa to quantify intestinal bioaccessibility. A narrow optimum at 28 °C and a sublethal window around 12 h at 34 °C tended to maximize protein digestibility and intestinal bioaccessibility, whereas conditions outside this window were associated with increased oxidative crosslinking and reduced protein quality.

Continue reading ‘Pre-harvest thermal and pH stress modulate macronutrient digestibility and protein bioaccessibility of the sea cucumber Isostichopus badionotus under in vitro gastrointestinal digestion’

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