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.
Continue reading ‘Gravity-driven feeding currents in veliger larvae of the eastern oyster’Posts Tagged 'reproduction'
Gravity-driven feeding currents in veliger larvae of the eastern oyster
Published 16 October 2026 Science Leave a CommentTags: biological response, individualmodeling, modeling, mollusks, reproduction
Ocean warming and acidification alter larval development and swimming behavior in the Atlantic sea scallop, Placopecten magellanicus
Published 13 October 2026 Science Leave a CommentTags: biological response, growth, laboratory, mollusks, mortality, multiple factors, performance, reproduction, temperature
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.
Continue reading ‘Ocean warming and acidification alter larval development and swimming behavior in the Atlantic sea scallop, Placopecten magellanicus’Behavioural responses of fishes to abiotic stressors: a comparative synthesis of shared physiological mechanisms and ecological consequences
Published 8 October 2026 Science Leave a CommentTags: biological response, fish, performance, physiology, reproduction, review
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
Stage-specific vulnerability: ocean acidification and hypoxia impair copepod recruitment through a naupliar bottleneck
Published 7 October 2026 Science Leave a CommentTags: biological response, crustaceans, laboratory, mortality, multiple factors, North Pacific, oxygen, reproduction, zooplankton
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.
Continue reading ‘Stage-specific vulnerability: ocean acidification and hypoxia impair copepod recruitment through a naupliar bottleneck’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 Leave a CommentTags: algae, biological response, laboratory, multiple factors, North Pacific, nutrients, physiology, reproduction, salinity
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’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 Leave a CommentTags: biological response, chemistry, echinoderms, fisheries, growth, laboratory, mitigation, morphology, physiology, reproduction
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.
Continue reading ‘Mitigation of biogenic acidification via increased total alkalinity in high stocking density culture waters of Strongylocentrotus intermedius: effects on growth and metabolism’Substrate stability drives zoobenthic recruitment in sessile polychaetes in interstitial marine habitats
Published 25 September 2026 Science ClosedTags: annelids, biological response, BRcommunity, field, Mediterranean, multiple factors, reproduction, substrate
Early life stages play a key role in structuring marine benthic communities, yet the mechanisms controlling recruitment in confined habitats remain poorly understood. In particular, the relative importance of substrate stability and visual cues under low-exchange, low-light conditions is unresolved. We investigated zoobenthic recruitment on 8 natural rock types differing in mineral composition, grain size, and surface reflectance, in simulated interstitial sub-boulder conditions in the Ligurian Sea (NW Mediterranean). After 90 d immersion, recruitment was dominated by spirorbid and serpulid polychaetes. Settlement intensity differed markedly among lithotypes, decreasing from granitoids (239.4 ± 37.7 spirorbids and 23.9 ± 3.4 serpulids) to marbles (128.7 ± 45.5 and 13.6 ± 4.8, respectively) and highly porous travertines (55.4 ± 18.5 and 8.4 ± 2.8), in agreement with their estimated dissolution rates. These results suggest that substrate stability is a primary driver of recruitment under confined conditions, likely mediated by localized acidification and enhanced dissolution of calcareous substrates. Within lithotypes, differences in recruitment were also associated with surface reflectance: specifically, a clear preference for darker surfaces emerged within marbles, whereas the colour effect was overridden by structural or mineralogical traits within the heterogeneous matrix of granitoids. These findings indicate that both chemical stability and optical properties contribute to recruitment patterns, although their relative importance varies with environmental context. The modulation of the early colonization in these restricted sub-boulder environments provide a valuable hypothetical framework to investigate the effects of large-scale environmental stressors like future ocean acidification scenario.
Continue reading ‘Substrate stability drives zoobenthic recruitment in sessile polychaetes in interstitial marine habitats’Impact of ocean acidification on coastal copepod Pseudodiaptomus serricaudatus: implications for futuristic coastal dynamics
Published 21 September 2026 Science ClosedTags: biological response, crustaceans, Indian, laboratory, mortality, reproduction, zooplankton
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.
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 ClosedTags: biological response, communityMF, crustaceans, laboratory, morphology, multiple factors, North Atlantic, reproduction, toxicants, zooplankton
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.
Physiological responses of coralline algae to climate change
Published 18 September 2026 Science ClosedTags: adaptation, algae, biological response, calcification, community composition, field, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, otherprocess, photosynthesis, reproduction, South Pacific, temperature, vents
Ocean acidification and ocean warming are among the most pressing threats to marine ecosystems, with significant implications for calcifying organisms such as crustose coralline algae (CCA). These habitat-forming species play critical ecological roles in reef systems, yet they are particularly vulnerable to ocean acidification and ocean warming. While laboratory studies have documented declines in coralline algal growth and calcification under elevated CO₂ and temperature, less is known about their responses in natural settings where environmental variability and potential acclimatization may modulate stress impacts. Furthermore, the interactive effects of multiple stressors across generations remain poorly understood, limiting our ability to predict ecosystem-level consequences of climate change. This thesis explores the physiological responses of coralline algae to ocean acidification, ocean warming, and marine heatwaves through complementary field and laboratory approaches. Using natural climate analogues, I investigated how CCA communities respond to chronic exposure to low pH and elevated temperatures in situ (Chapters 2 and 3). These natural systems provide unique opportunities to assess long-term acclimatization and identify potentially resilient populations. To disentangle the mechanisms underlying stress responses and examine multi-generational effects, I conducted a multigenerational, multi-stressor laboratory experiment exposing coralline algae to factorial combinations of elevated pCO₂ and temperature over successive generations (Chapter 4). Together, these approaches enabled assessment of single-driver impacts, stressor interactions, and the capacity for phenotypic plasticity and acclimatization under both fluctuating natural conditions and controlled experimental regimes. Results from natural analogues revealed species-specific variation in stress tolerance, with some CCA populations maintaining growth and calcification despite chronic exposure to conditions projected for year 2100. The laboratory experiment revealed that growth significantly declined when exposed to ocean acidification and the combined effect of ocean acidification and ocean warming over multiple generations. This research advances our understanding of how marine calcifiers respond to climate change across ecological and temporal scales. The findings have important implications for predicting ecosystem trajectories and identifying potential climate refugia in an increasingly acidic and warming ocean.
Continue reading ‘Physiological responses of coralline algae to climate change’Brood chamber carbonate chemistry in the oyster Ostrea edulis is dynamically shaped by warming, acidification, and ventilation
Published 14 September 2026 Science ClosedTags: biological response, BRcommunity, laboratory, mollusks, performance, physiology, reproduction
Brooding organisms can modify the chemical environment experienced by developing offspring, potentially altering their exposure to climate change. In marine systems, however, the carbonate chemistry of brood chambers, and the mechanisms governing it, remain poorly resolved. Here, we combine high-resolution pH and CO2 measurements of the empty brood chamber (i.e., mantle cavity above gills) in the European flat oyster (Ostrea edulis) while also tracking valve gape to quantify how warming, ocean acidification, and ventilation interact to shape the internal environment experienced by larvae during incubation. Brood chamber pH was consistently lower than that of the surrounding seawater and responded to external conditions in a state-dependent manner governed by ventilation and respiration. When oysters were actively ventilating, brood chamber chemistry tracked ambient seawater with a persistent offset, whereas valve closure led to rapid CO2 accumulation and pronounced declines in pH. These dynamics generated highly variable and behaviorally mediated exposure regimes, in which metabolic processes distorted ambient chemical signals over short timescales. Paired pH and CO2 measurements provided preliminary constraints on aragonite saturation state (Ωar), revealing that brood chambers can remain undersaturated (Ωar < 1) for prolonged periods even in ventilating oysters and while overlying seawater remains favorable. Together, these results demonstrate that brood chambers function as dynamic microenvironments in which larval exposure to ocean acidification is governed not only by external conditions, but also by behavior. Because warming enhances metabolic CO2 production and intensifies acidification within the chamber, future climate change is likely to amplify both the magnitude and variability of larval exposure. These findings help explain the apparent resilience of brooding species to ocean acidification, while also highlighting potential limits as environmental conditions move beyond historical bounds.
Continue reading ‘Brood chamber carbonate chemistry in the oyster Ostrea edulis is dynamically shaped by warming, acidification, and ventilation’Environmental regulation and disruption of shell biomineralization in bivalves and gastropods: a mechanistic review
Published 10 September 2026 Science ClosedTags: biological response, molecular biology, mollusks, physiology, reproduction, review
Molluscan shells are increasingly threatened by a complex array of environmental stressors—climate-related drivers, changes in seawater chemistry, contaminants, and biotic cues. This review provides a mechanistic synthesis of how these stressors disrupt the biomineralization process across life stages. We develop a conditional hierarchical response framework from the reviewed evidence. The framework links ionoregulatory and acid-base disturbances with molecular, microstructural, and shell-level responses, while allowing for compensatory, nonlinear, species-specific, and life-stage-specific outcomes. This molecular disruption manifests as defects in calcium carbonate (CaCO3) crystalline microstructure, which may in turn compromise shell macro-scale physical properties (strength, hardness, growth). We synthesize combined and context-dependent effects of co-occurring stressors and distinguish formally tested interactions from qualitative comparisons of combined treatments. Future research must leverage integrated multi-omics, advanced in vivo imaging, and multi-stressor experimental designs to unravel candidate molecular and physiological thresholds and predict adaptive potential. This framework may help identify testable mechanisms, evidence gaps, and context-dependent vulnerabilities relevant to conservation.
Highlights
- A conditional framework links molecular, microstructural, and shell-level responses.
- Early stages often show high sensitivity, although direct ontogenetic comparisons remain limited.
- Energy limitation is a recurrent, but often indirectly inferred, physiological constraint.
Preferential impairment of later mating stages and sex-dependent metabolic shifts in Japanese medaka exposed to acute acidification
Published 12 August 2026 Science ClosedTags: biological response, fish, laboratory, performance, physiology, reproduction
Highlights
- Acute acid stress (pH 4.5) preferentially impairs later mating stages in medaka, rather than causing a generalized reproductive collapse.
- Early initiation phases (following and courtship) are relatively less affected, whereas progression to the crossing stage and spawning is strongly suppressed.
- General locomotion and territorial aggression show no detectable change under acute acidification.
- Females exhibit increased ammonia excretion and oxygen consumption, indicating sex-specific physiological strain under acid stress.
- The behavioral impairment is consistent with an energy reallocation toward acid–base homeostasis, reducing investment in energetically costly terminal mating behaviors.
Abstract
Environmental acidification poses a significant threat to aquatic organisms, yet the underlying mechanisms of how acid stress disrupts complex social and reproductive behaviors remain incompletely understood. In the present study, we investigated the behavioral and physiological responses of adult Japanese medaka (Oryzias latipes) under acute acid exposure (pH 4.5, 24 h). Our results showed that acute acid stress reduced mating success, with a stronger impairment observed in the transition to the crossing stage and subsequent spawning, while the earlier, male-driven stages of following and courtship were relatively less affected under the present experimental conditions. This reproductive impairment did not coincide with detectable changes in generalized emotional-like behavior. Fish showed normal performance in the novel tank test and maintained territorial aggression. Physiologically, we observed a clear sexual dimorphism. Under acid stress, males maintained relatively stable MO₂ and JAmm, whereas females showed elevated MO₂ and JAmm. These findings suggest that reproductive impairment may be more pronounced in energetically demanding mating stages and may be associated with sex-dependent physiological strain. We further propose that the increased metabolic cost of acid-base regulation in females could shift energy allocation, and that high-cost coordination behaviors may be reduced in order to maintain short-term survival. This study provides evidence linking bioenergetics, acid-base regulation, and reproductive behavior in a teleost model under acidification.
Invasive macroalgae exert stronger effects than elevated CO₂ on seagrass (Posidonia oceanica) seedling performance and associated microbiomes
Published 11 August 2026 Science ClosedTags: algae, biological response, laboratory, Mediterranean, mesocosms, multiple factors, oxygen, phanerogams, physiology, primary production, reproduction, respiration
Highlights
- Invasive macroalgae reduced P. oceanica seedling biomass and leaf development.
- Macroalgal invasion depleted carbohydrate reserves in seedling roots and rhizomes.
- Elevated CO2 increased rhizome starch but did not mitigate invasion impacts.
- Root microbiome diversity declined markedly under macroalgal invasion.
- Future CO2 enrichment unlikely to buffer invasion stress at recruitment stage.
Abstract
Seagrass seedlings are key to meadow recovery under global change, as they enable recolonization of degraded areas and provide genetic variability needed for adaptation. While invasive macroalgae increasingly threaten seagrass communities, elevated CO2 has been proposed to enhance seagrass performance and potentially buffer other stressors. Here, we conducted a mesocosm experiment to test the combined effects of two invasive macroalgae (Lophocladia trichoclados and Caulerpa cylindracea) and elevated CO2 on Posidonia oceanica seedlings. CO2 enrichment increased carbohydrate reserves in rhizomes and induced subtle shifts in root-associated microbiomes. In contrast, invasive macroalgae had consistently negative effects on seedling development and physiology and strongly altered both above- and belowground microbial communities. Despite its potential to stimulate seagrass productivity, elevated CO2 did not mitigate the detrimental impacts of invasive macroalgae. These findings indicate that future CO2 conditions may not offset invasion-driven stress at the recruitment stage, highlighting the need for targeted management efforts to limit macroalgal proliferation and support seagrass meadow regeneration.
Continue reading ‘Invasive macroalgae exert stronger effects than elevated CO₂ on seagrass (Posidonia oceanica) seedling performance and associated microbiomes’Tracing the imprints of dual stressors: eco-physiological and genotoxic insights from Mystus gulio under acidification and warming scenario
Published 10 August 2026 Science ClosedTags: biological response, fish, Indian, individualmodeling, laboratory, modeling, molecular biology, physiology, reproduction
Global warming has caused a rise in ocean temperature and acidification, which collectively wreak havoc on marine animals. However, the combined ramifications of these stressors on energy metabolism, oxidative balance, and DNA integrity remain inadequately studied in teleosts. The present study aims to unravel the combined effects of warming (34°C) and acidification (pH 7.7) on energetic balance, antioxidant defense, and DNA stability in Mystus gulio at two intervals (15th and 45th day). Furthermore, the Effect Addition model was used to disentangle potential additive or non-additive effects of the combined stressors. Elevated temperature and acidification induced a marked energetic imbalance, as mirrored by suppressed ingestion and absorption rates, reduced scope for growth, and elevated excretion. Oxidative stress biomarkers revealed significant upregulation of SOD, CAT, and GST under combined treatment, which ultimately led to augmented lipid peroxidation. Genotoxic assessment delineated progressive upsurges in tail DNA (%) and olive tail moment, indicating compromised genomic stability. The integrated biomarker response consisted of six parameters, RR, ER, SOD, CAT, GST, and LPO, further corroborating that elevated temperature, alone and in combination with acidification, posed the highest cumulative physiological burden. Furthermore, the model assessment indicated that the interaction between warming and acidification varied among different biomarkers. Collectively, these findings corroborate that concurrent thermal and low pH perturbations destabilise physiological processes, oxidative instability, and DNA damage, which may undermine growth potential and jeopardise population structure and destabilise trophic relationships. The present study provides a mechanistic understanding of the impacts of multiple stressors and offers a robust integrative framework to predict fish vulnerability under future climate-driven oceanic vicissitudes.
Multilevel impacts of ocean acidification on vision: retinal damage, optic tectum hyperexcitability, and behavioral dysfunction in marine medaka
Published 6 August 2026 Science ClosedTags: biological response, fish, laboratory, performance, physiology, reproduction
Ocean acidification (OA), driven by atmospheric carbon dioxide (CO2) emissions, significantly impacts marine organism. This study investigated OA effects on retinal structure and function in marine medaka (Oryzias melastigma) across life stages under controlled CO2 exposures (450 × 10−6, 1 000 × 10−6, and 1 800 × 10−6). Quantitative analyses revealed concentration-dependent retinal pathology, with larval incidence rising from 16.7% (450 × 10−6) to 50.0% (1 800 × 10−6). Significant structural alterations include progressive pigment epithelium thickening and concurrent atrophy in inner plexiform and ganglion cell layers. Electrophysiological recording demonstrated severe neural hyperexcitability, with larval and adult fish showing 91.3% and 154.9% increased firing counts respectively at 1 800 × 10−6. Behavioral analyses revealed significant CO2-induced locomotor dysfunction with distinct light-dependent patterns. Under illumination, larvae exhibited hyperactivity at 1 800 × 10−6, while adults showed progressive impairment (high-performance swimmers declining from 60% to 37.5%). Conversely, dark conditions intensified activity across concentrations, with adults displaying dose-dependent increases in swimming speed (23.5% to 68.8%). These results demonstrated that OA induces significant visual disruption and behavioral changes. The differential responses across life stages and light conditions suggest complex neurophysiological impacts that may have cascading ecological consequences for marine fish in acidifying ocean.
Continue reading ‘Multilevel impacts of ocean acidification on vision: retinal damage, optic tectum hyperexcitability, and behavioral dysfunction in marine medaka’Effect of warming and acidification on polar lipid fatty acid composition in juvenile European sea bass (Dicentrarchus labrax)
Published 31 July 2026 Science ClosedTags: biological response, BRcommunity, fish, laboratory, multiple factors, physiology, reproduction, temperature
The present study experimentally investigates how temperature and acidification affect the polar lipid fatty acid (FA) composition of European sea bass (Dicentrarchus labrax) juveniles. Fish were reared for 92 days and fed ad libitum under four conditions: a control (CT; with natural fluctuating temperature and pH); a warming (WT, +4°C above control, and control pH), an acidification (AT, control temperature and −0.4 pH units below the control), and a combined warming and acidification treatment (WAT, +4°C and −0.4 pH units relative to the control). Results showed that warm treatments (WT and WAT) increased final weight and length similarly, whether or not combined with acidification, and that acidification alone (AT) had no effect on these variables. Polar lipid FA profiles of muscle and brain were only mildly impacted by temperature and not by acidification. Overall, the results suggest that European sea bass, under unrestricted quantity of food is able to maintain a very stable polar lipid FA composition. However, complementary studies with individuals under different feeding regimes or from wild populations subject to natural dietary variability are needed.
Continue reading ‘Effect of warming and acidification on polar lipid fatty acid composition in juvenile European sea bass (Dicentrarchus labrax)’The effects of decreased pH and increased temperature on survival and shell development of the larvae of the endemic Hawaiian oyster Dendostrea sandvichensis
Published 17 July 2026 Science ClosedTags: biological response, BRcommunity, growth, laboratory, mollusks, mortality, multiple factors, physiology, reproduction, temperature
Climate change models predict future ocean-wide decreases in pH and increases in temperature, posing a serious threat to calcifying marine invertebrates. In Hawaiʻi, local seawater temperature and pH are predicted to change even more rapidly. The Hawaiian oyster Dendostrea sandvichensis, an endemic species, remains understudied despite its ecological roles in reef- building, biofiltration, and as a food source. While previous studies have revealed the alarming impacts of ocean acidification and warming on bivalves, little is known about how the planktonic larvae of D. sandvichensis will respond to projected climate conditions.
To investigate these effects, the larvae of D. Sandvichensis were reared under present-day conditions in Pearl Harbor, HI (pH 8.1, 26.5 °C) and projected future conditions (pH 7.7, 30.0°C) for one week. Shell growth, density, and degradation were then measured using micro-CT, confocal, and scanning electron microscopy. Additionally, two larval husbandry methods were evaluated, with a static-flow system paired with UV water treatment yielding approximately 11- fold higher survival than an open-flow system. Elevated temperature reduced larval survival (~67%) compared to ambient conditions. Reduced pH significantly decreased shell length (~11.8μm), while both stressors reduced shell density in Experiment 3. Shell density decreased by ~12% under elevated temperature, ~18% under reduced pH, and ~43% under the combined stressors, and was accompanied by increased shell degradation and abnormalities.
These findings indicate that elevated temperature and reduced pH impact larval oysters through multiple pathways, including reduced survival and compromised shell integrity. This study provides new insights into the vulnerability of an endemic Hawaiian species and essential data for predicting its resilience under future climate change scenarios.
Continue reading ‘The effects of decreased pH and increased temperature on survival and shell development of the larvae of the endemic Hawaiian oyster Dendostrea sandvichensis’Impacts of ocean acidification on reproduction and early life development in marine teleost fish—a synthesis
Published 17 July 2026 Science ClosedTags: biological response, fish, physiology, reproduction, review
Ocean acidification (OA) remains a major and underexplored threat to marine fishes, particularly regarding reproductive physiology and early life stages (ELS). Although research over the past 15 years has documented diverse OA effects, substantial knowledge gaps persist. Most studies focussed on a limited set of species from North America and Europe, leaving broad uncertainty across phylogenetic groups, geographic regions and multi-stressor conditions. In adult fish, especially females, elevated pCO2 can shift energy allocation to prioritise reproductive output at the expense of egg or clutch size. While adult and juvenile fish have well-developed acid–base balancing systems, embryos and larvae possess only rudimentary mechanisms, making them more vulnerable to OA. This article stresses the importance of understanding these physiological and mechanistic responses to predict the future of fish stocks and ecosystem health as OA intensifies due to ongoing CO2 emissions. Our results highlight that OA responses in fish are highly variable and often specific to life stage and species, with acute and sometimes stage-specific effects not fully documented. Lastly, our recommendations on targeted research and funding are necessary to address the remaining knowledge gaps, including broadening taxonomic and geographic sampling, exploring multi-stressor scenarios and improving understanding of the downstream effects of OA on fish reproduction and development. Maintaining robust fish populations is vital for food security, employment and ecosystem functioning, making continued investigation into OA’s impacts a scientific and societal priority.
Continue reading ‘Impacts of ocean acidification on reproduction and early life development in marine teleost fish—a synthesis’
