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.
Continue reading ‘Thermal history and behavioural plasticity shape reef fish tolerance to marine heatwaves’Posts Tagged 'multiple factors'
Thermal history and behavioural plasticity shape reef fish tolerance to marine heatwaves
Published 25 September 2026 Science ClosedTags: adaptation, biological response, field, fish, laboratory, morphology, multiple factors, North Pacific, performance, physiology, temperature
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’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 ClosedTags: biological response, corals, laboratory, multiple factors, North Atlantic, physiology, temperature
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’The effects of ocean warming and acidification on fatty acid contents of marine organisms: a global meta-analysis
Published 23 September 2026 Science ClosedTags: algae, biological response, crustaceans, fish, mollusks, multiple factors, physiology, phytoplankton, review, temperature, zooplankton
Ocean warming and acidification pose significant threats to marine biodiversity and human nutrition by fundamentally altering the biochemical composition of marine organisms. A primary concern is the potential decline in omega-3 fatty acids (FAs) that are essential to human health and primarily obtained through seafood consumption. The influence of these climate stressors on FA content across marine food webs remains poorly understood. To address this critical knowledge gap, we conducted a global meta-analysis of 489 experiments across 143 publications and 132 marine species, quantifying the effects of warming and acidification on nutritionally important FAs in marine primary producers, invertebrates and fishes. Under warmer conditions, we detected reductions of up to 34% and 50% in omega-3 FA proportions and concentrations, respectively, and up to 53% in omega-3: omega-6 ratios, together with increases of up to 22% and 17% in saturated FA proportions and concentrations, respectively across taxa groups. Critically, these effects were intensified as warming increased. The most severe reductions in omega-3 FAs were observed in primary producers, suggesting that climate-driven changes at the base of the food web could impair trophic transfer of these micronutrients, limiting nutrient availability for higher trophic levels and ultimately humans. Ocean acidification, conversely, demonstrated a minor overall effect on FA levels, although this result was based on substantially fewer studies. Furthermore, we identified species from environments with broader temperature ranges, diatoms, herbivorous invertebrates and low-resilience fish to display larger reductions in omega-3 FA proportions under warming. Our meta-analysis further highlighted the need for long-term studies under ecologically realistic conditions to improve predictions of nutritional responses to climate change. These findings are essential for understanding how the nutritional value of species change under climate change, and can inform fisheries management, aquaculture and public health policy aimed at securing the future availability of these vital micronutrients.
Continue reading ‘The effects of ocean warming and acidification on fatty acid contents of marine organisms: a global meta-analysis’Asymmetric metabolic responses of rockweed and herbivores reveal seasonal vulnerabilities to warming and acidification
Published 22 September 2026 Science ClosedTags: algae, biological response, BRcommunity, calcification, mollusks, multiple factors, photosynthesis, respiration, temperature
Macroalgal-herbivore interactions are fundamental to the stability of coastal ecosystems and their vulnerability to climate-driven shifts will affect biodiversity and ecosystem functioning. However, the effects of climate change on species interactions may be context dependent and vary by seasonal oceanographic processes. We examined the effects of warming and acidification on an intertidal primary producer foundation species, Silvetia compressa, and its herbivore, Agathistoma eiseni, under differing upwelling regimes in early (low upwelling) and late spring (high upwelling). We measured metabolic rates including photosynthesis, respiration, and calcification after four weeks of exposure to a range of nine pH levels (7.2–8.0) at two temperature levels (16°C, 20°C). Rockweed responded more to acidification than to warming, but showed different seasonal responses, decreasing photosynthetic rates in early spring and increasing rates during late spring. Their snail consumer, however, responded most strongly to temperature, increasing both respiration and calcification rates under warm conditions in late spring. Our findings demonstrate that seasonal differences can modulate responses of macroalgae and herbivores to changing environmental conditions. Warming may increase top-down effects through increased snail metabolism, while acidification affects rockweed production to affect bottom-up forcing. By assessing physiological responses across different ecological regimes, our study advances understanding of how top-down and bottom-up processes interact in intertidal ecosystems under global change.
Continue reading ‘Asymmetric metabolic responses of rockweed and herbivores reveal seasonal vulnerabilities to warming and acidification’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.
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 ClosedTags: biological response, echinoderms, fisheries, laboratory, multiple factors, physiology
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.
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’Coral acclimatization to novel, co-varying stressors is associated with fitness trade-offs
Published 18 September 2026 Science ClosedTags: adaptation, biological response, calcification, corals, field, morphology, mortality, multiple factors, North Atlantic, oxygen, photosynthesis, physiology, respiration, temperature
Reef-building corals are under pressure to acclimatize and/or adapt to multiple co-occurring stressors, including climate change and declines in water quality. However, their capacity to do so is largely unknown. Yet, some corals naturally persist in habitats with multi-stressor conditions which can provide crucial insight into coral adaptive capacity under future ocean conditions. To assess the role of phenotypic plasticity and local adaptation in coral acclimatory responses to novel conditions, we reciprocally transplanted two coral species (Siderastrea siderea, branching Porites) between an inland bay characterized by multiple, co-varying stressors, including warmer seawater temperatures, higher pollution and more variable temperatures, pH and dissolved oxygen concentrations, and an environmentally less extreme, more stable fringing reef. We measured key phenotypic traits (e.g., calcification, tissue biomass, metabolic rates, chlorophyll concentrations) of all transplant groups after 0, 4 and 12 months. Reef-origin corals demonstrated high plasticity when transplanted to the bay, as both species maintained high survival and calcification, and matched bay natives’ other phenotypic traits. Yet, reef-to-bay transplants of both species had reduced photosynthesis-to-respiration ratios in the bay, highlighting the risk of metabolic trade-offs unless compensated for through increased heterotrophy. Conversely, bay-origin corals had enhanced photosynthetic performance but lower calcification on the reef. Reaction norms provided stronger evidence for environmental specialization in bay-origin than reef-origin corals, which could limit their use as stress-tolerant source corals for reef restoration. Overall, our findings suggest multi-stressor variability may promote specialized genotypes, rather than increased phenotypic plasticity, though this may also depend on predictability of environmental variability.
Continue reading ‘Coral acclimatization to novel, co-varying stressors is associated with fitness trade-offs’Ocean acidification and nanoplastics disrupt mussel calcification in synergy: a multi-omics analysis
Published 14 September 2026 Science ClosedTags: biological response, calcification, laboratory, molecular biology, mollusks, multiple factors, North Pacific, physiology, plastics
Highlights
- Ocean acidification disrupts calcium homeostasis in the mantle of mussels.
- Ocean acidification and N-NPs together intensify the inhibition of calcification.
- Surface charge determines distinct, mechanism-specific response pathways.
- Both omics reveal key roles for calcium transport, CA, and ECM synthesis.
Abstract
Ocean acidification (OA) and nanoplastics (NPs) increasingly co-occur in coastal ecosystems, yet their combined mechanistic impacts on calcifying invertebrates remain poorly resolved. Here, the mussel Mytilus coruscus was exposed for 30 days to factorial combinations of OA (pH 7.7 vs 8.1), surface-modified polystyrene NPs at a concentration of 100 μg/L (positively and negatively charged), and experimental shell damage to assess effects on shell repair, ion homeostasis, and energy metabolism. OA reduced shell repair quality by thinning repair layers, increasing porosity, and lowering calcium content, effects that were further enhanced by co-exposure to NPs, particularly negatively charged particles. OA and NPs jointly altered Ca2+ and Mg2+ levels, alkaline phosphatase activity, Ca2+Mg2+-ATPase activity, and key indicators of energy metabolism, including ATP content and cellular energy allocation. Transcriptomic and proteomic analyses revealed enrichment of ion transport, extracellular matrix, TGF-β signaling and other pathways, with divergent patterns linked to NPs surface charge. Together, these results suggest that nanoplastic surface charge under OA may impair mussel shell repair through associated alterations in ion homeostasis and energy metabolism. These findings highlight that particle surface properties shape how organisms respond to combined environmental stressors in acidifying marine environments.
Continue reading ‘Ocean acidification and nanoplastics disrupt mussel calcification in synergy: a multi-omics analysis’Ocean acidification drives species-specific and time-dependent pigment responses in three phytoplankton taxa
Published 9 September 2026 Science ClosedTags: biological response, BRcommunity, growth, laboratory, light, multiple factors, photosynthesis, physiology, phytoplankton, respiration
Phytoplankton are primary producers in marine ecosystems and play a central role in biogeochemical cycles, yet their physiological responses to altered seawater pH vary among taxa and over time. Here, we examined the effects of sustained pH manipulation on pigment composition, growth, and dark respiration in three ecologically important phytoplankton taxa – a diatom (Pseudo-nitzschia spp.), a dinoflagellate (Heterocapsa pygmaea), and a haptophyte (Emiliania huxleyi) – during a 15-day controlled laboratory experiment. Cultures were maintained at pH 8.1, 7.8, and 7.5, representing present-day and enhanced acidification conditions. Responses to pH were species-specific and strongly time-dependent. Growth and cell-specific respiration rates showed relatively small and often transient differences among pH treatments, suggesting short-term metabolic adjustment under altered pH. In contrast, pigment composition exhibited clearer and more consistent pH-related responses, primarily expressed as shifts in temporal patterns rather than uniform directional changes. In Pseudo-nitzschia spp. and H. pygmaea, several key pigments displayed pronounced pH-dependent trajectories, whereas E. huxleyi showed greater temporal variability and weaker separation among pH treatments. Overall, these results demonstrate that photophysiological traits respond sensitively to sustained pH changes even when population-level growth and respiration remain comparatively stable, highlighting pigment composition as a potentially sensitive indicator of short-term phytoplankton acclimation to ocean acidification.
Continue reading ‘Ocean acidification drives species-specific and time-dependent pigment responses in three phytoplankton taxa’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’Vulnerability to low salinity but compensatory responses to low pH in an intertidal limpet
Published 7 August 2026 Science ClosedTags: biological response, BRcommunity, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, physiology, salinity
Highlights
- Low salinity linked to warming may intensify coastal pH reduction.
- Low salinity reduced righting and emergence in the limpet Patelloida pygmaea.
- Low salinity reduces Mg/Ca ratios in newly formed shell layers.
- Low pH increases shell thickness and Mg/Ca ratios despite dissolution.
- CHS2 upregulation suggests compensatory resistance to low pH.
Abstract
Rising anthropogenic carbon dioxide emissions have driven ongoing ocean warming and associated climate changes. In the Yellow Sea, this warming is associated with enhanced monsoonal rainfall, which increases freshwater inputs and lowers coastal salinity. Increased freshwater input can weaken seawater buffering capacity, thereby leading to lower pH conditions in coastal environments. Here, we examined the effects of low pH and low salinity on the intertidal limpet Patelloida pygmaea. Adult limpets were exposed for 31 days to four experimental artificial seawater conditions combining two pH levels (8.0 and 7.5) and two salinity levels (30 and 21 psu). Survival and condition factor were not influenced by pH or salinity. However, low salinity reduced righting and emergence behavior. In addition, the Mg/Ca ratio in the M + 1 layer was lower at 21 psu than at 30 psu. Low pH resulted in a thicker M + 2 layer with higher Mg/Ca ratios despite shell dissolution, potentially helping to maintain shell integrity. While there was no change in heat shock protein (HSP70) expression, these shell modifications were accompanied by an upregulation of chitin synthase (CHS2) genes under low pH. These findings suggest that P. pygmaea is negatively influenced by low pH and low salinity, but also demonstrate compensatory mechanisms that enhance resistance to low pH.
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)’Interplay between nutrient limitation and ocean acidification: plankton community shifts in the oligotrophic western Bay of Bengal
Published 30 July 2026 Science ClosedTags: biological response, community composition, Indian, morphology, multiple factors, nutrients, otherprocess, phytoplankton
Highlights
- Nutrient limits the phytoplankton growth in the Bay of Bengal due to stratification.
- Picoplankton dominated the phytoplankton community in the Bay.
- An increase in phytoplankton biomass was observed in response to ocean acidification (OA) in nutrient-rich regions.
- Decrease in phytoplankton biomass, bacteria and microzooplankton abundance was found in the nutrient-poor regions.
- Nutrient limitation overshadow the ocean acidification impact in the Bay of Bengal.
Abstract
The perennial rise in atmospheric carbon dioxide (CO2) from anthropogenic activities increased oceanic carbon uptake, thereby lowering seawater pH. Rapid ocean acidification (OA) by 2 to 3 times than other regions of the same latitudinal belts was reported in the Bay of Bengal (BoB) due to the deposition of atmospheric pollutants, in addition to the dissolution of atmospheric CO2. Therefore, the impact of OA on phytoplankton composition is hypothesized to be greater in the BoB than elsewhere in the globe. On the other hand, the BoB experiences intense oligotrophic conditions due to strong stratification driven by nutrient-poor freshwater discharge from major rivers, which is the primary bottleneck for phytoplankton growth, rather than carbon. It is hypothesized that nutrient limitation may overshadow OA’s impact on plankton in the BoB. To test this hypothesis, six microcosm experiments were conducted in the western BoB between 13 and 20°N with different nutrient levels in the surface waters. The pH of the surface water was adjusted by 0.2 units below the ambient pH using CO2 gas bubbling to simulate the projected OA scenario for the year 2100. Following pH adjustment, incubations were carried out for three days. Picoplankton dominated the phytoplankton community (∼96%) at all stations, with prochlorophytes as the dominant group. Among the phytoplankton, procholorophytes, diatoms, and prymeniophytes increased due to OA across all stations, while other groups of phytoplankton were declined. The increase in phytoplankton biomass was observed in the nutrient-rich stations, while a decrease in phytoplankton biomass, bacteria and microzooplankton abundance was found in the nutrient-poor stations, suggesting that nutrient availability dominated over the OA. Under a business-as-usual scenario, an increase in stratification due to melting Himalayan glaciers is projected, leading to strong stratification and reduced nutrient inputs through vertical mixing in the future in the BoB. Under such a scenario, nutrient limitation may possibly overshadow the OA impact in the future, despite a rapid decline in pH driven by increased CO2 dissolution and deposition of atmospheric pollutants.
Continue reading ‘Interplay between nutrient limitation and ocean acidification: plankton community shifts in the oligotrophic western Bay of Bengal’The effects of high carbonate alkalinity under low salinity on the survival, physiological metabolism, and redox homeostasis of Crassostrea hongkongensis
Published 28 July 2026 Science ClosedTags: biological response, laboratory, mollusks, mortality, multiple factors, oxygen, performance, physiology, salinity
High carbonate alkalinity can impose composite hydrochemical stress on bivalves by altering inorganic carbon speciation, buffering capacity and ion-exchange conditions. The Hong Kong oyster (Crassostrea hongkongensis) naturally inhabits estuarine areas where low salinity can occur together with carbonate-system disturbance, yet its physiological response to high carbonate alkalinity under a low-salinity background remains unclear. In this study, oysters were exposed at salinity 5 to a Control treatment, A10 (carbonate alkalinity 10 mmol L⁻¹) and A20 (carbonate alkalinity 20 mmol L⁻¹). Salinity was treated as a controlled background condition, whereas the alkalinity treatments represented a composite carbonate-alkalinity perturbation involving alkalinity, pH and carbonate chemistry. Survival, feeding rate, oxygen consumption, ammonia excretion and hemolymph ammonia were measured across Control, A10 and A20. Hemolymph catalase (CAT), glutathione peroxidase (GSH-Px), glucose and ATP were analyzed as A10 and A20 time-course endpoints because a parallel Control was not included for these assays. A 24-h mantle transcriptome was used to screen candidate transcripts associated with innate defense and glutathione metabolism. Oysters under A10 retained partial compensatory capacity, whereas A20 significantly reduced survival. A10 and A20 suppressed early oxygen consumption and ammonia excretion, and altered feeding allocation among microalgae. Within the A10 and A20 biochemical time-course dataset, CAT, GSH-Px, glucose and ATP showed stage-specific variation, suggesting redox and energy-metabolism adjustment under alkalinity stress. Overall, high carbonate alkalinity reduced survival and was associated with metabolic depression, feeding compensation and hemolymph redox-energy remodeling in C. hongkongensis. This study will provide a theoretical basis for water quality regulation in saline-alkaline water aquaculture and the sustainable development of aquaculture.
Continue reading ‘The effects of high carbonate alkalinity under low salinity on the survival, physiological metabolism, and redox homeostasis of Crassostrea hongkongensis’Water mass-driven variations in primary production and bacterial respiration during the spring bloom in the Fram Strait
Published 23 July 2026 Science ClosedTags: Arctic, biological response, community composition, field, laboratory, modeling, multiple factors, otherprocess, oxygen, photosynthesis, primary production, prokaryotes, regionalmodeling, respiration
Highlights
- Remote sensing indicates declining bloom in cold and developing bloom in warm water
- Primary production peaks in polar and arctic surface water masses
- Bacterial production is coupled to primary production despite thermal sensitivity
- Oxygen-based community respiration is highest in warmer water masses
- Oxygen-based and INT-based respiration estimates differ by an order of magnitude
Abstract
The Fram Strait is the primary oceanic gateway to the Arctic Ocean and has highly dynamic oceanographic conditions. Oceanographic conditions can shape community compositions, which is increasingly shown using molecular studies, but rate measurements remain scarce, especially for respiration in the Arctic Ocean. Here, we assessed primary production (PP), bacterial production (BP), bacterial abundances (BA), and community respiration (CR) using Winkler titrations and in vivo Iodo-Nitro-Tetrazolium (INT) reduction within the upper 50 m across water masses of the Fram Strait that had varying bloom conditions in spring 2021. We complemented in situ observations with remote sensing of sea surface temperature (SST) and chlorophyll-a (SSC) to infer bloom phenology in warm (θ>2°C), intermediate (2>θ>0°C), and cold (θ<0°C) waters using remote sensing machine-learning. In the cold, nutrient-rich surface waters, a subsiding spring bloom was associated with elevated PP, BP, and BA alongside a high temperature sensitivity (Q10) that indicates active microbial turnover. In contrast, the warm Atlantic-influenced waters exhibit a relatively lower PP but moderate cell-specific BP, suggesting bacterial maintenance metabolism under pre-bloom conditions. Notably, bacterial respiration (BR) estimates differed by 5- to 80-fold between the Winkler and in vivo INT methods. Although the true BR likely lies between these estimates, our results highlight the substantial microbial activity and underscore the need for more accurate BR measurements in Arctic studies.
Continue reading ‘Water mass-driven variations in primary production and bacterial respiration during the spring bloom in the Fram Strait’
