The effects of climate change on marine organisms act through multiple pathways, as ocean warming and acidification can affect both their physiology and interspecies interactions. Asymmetries in species-specific physiological responses to climate change may alter the strength of interactions, such as those between predator and prey, which will have cascading effects on ecosystem structure. How foundation species and their interactions are affected by climate change will profoundly affect their community due to their dominance. I assessed the physiological responses of two common California rocky intertidal consumer–resource pairs across multiple trophic levels. I measured metabolic rates after four weeks of exposure to a range of nine pH levels (7.2–8.0) at two temperature levels (ambient, +4°C). At the lowest trophic level, I examined the effects of climate change on a primary producer foundation species, Silvetia compressa (golden rockweed), and its herbivore, Tegula eiseni, under differing upwelling regimes in early and late spring. Rockweed responded more to acidification than warming, decreasing photosynthetic rates in early spring and increasing rates during late spring. Their snail consumer, however, responded most strongly to temperature—increasing both respiration rates and calcification under warm conditions in late spring. In addition to species specific responses to climate stressors, the rockweed–snail pair had context-dependent responses based on background environmental conditions. Greater upwelling during late spring, combined with a younger snail population could explain differences in responses between early and late spring. Next, I examined asymmetries between a calcifying foundation species, Mytilus californianus, and its whelk predator, Nucella emarginata. Specifically, mussels were generally resistant to acute exposure to ocean warming and acidification, while whelks were highly sensitive to temperature. Whelks decreased their calcification, respiration, shell extension, and probability of drilling a mussel under warmer conditions. Across both experiments, I observed asymmetries in response to changes in pH and temperature between consumer and resource, which can shift ecosystems between bottom-up and top-down processes. Overall, I showed that mesopredators, such as herbivorous and carnivorous snails, appeared to be the most sensitive to changes in temperature relative to their foundation species prey. Climate change may reshape rocky intertidal communities by altering predation patterns on foundation species, which could either facilitate or threaten the survival of other associated species in a changing environment.
Continue reading ‘Asymmetric effects of acidification and warming on foundation species and their predators in the California rocky intertidal zone’Posts Tagged 'respiration'
Asymmetric effects of acidification and warming on foundation species and their predators in the California rocky intertidal zone
Published 11 December 2025 Science Leave a CommentTags: algae, BRcommunity, calcification, laboratory, mesocosms, mollusks, morphology, multiple factors, North Pacific, performance, photosynthesis, respiration, temperature
Ocean acidification alters phytoplankton diversity and community structure in the coastal water of the East China Sea
Published 5 December 2025 Science ClosedTags: biogeochemistry, biological response, community composition, laboratory, mesocosms, North Pacific, otherprocess, phytoplankton, primary production, respiration
Anthropogenic CO2 emissions and their continuous dissolution into seawater lead to seawater pCO2 rise and ocean acidification (OA). Phytoplankton groups are known to be differentially affected by carbonate chemistry changes associated with OA in different regions of contrasting physical and chemical features. To explore responses of phytoplankton to OA in the Chinese coastal waters, we conducted a mesocosm experiment in a eutrophic bay of the southern East China Sea under ambient (410 μatm, AC) and elevated (1000 μatm, HC) pCO2 levels. The HC stimulated phytoplankton growth and primary production during the initial nutrient-replete stage, while the community diversity and evenness were reduced during this stage due to the rapid nutrient consumption and diatom blooms, and the subsequent shift from diatoms to hetero-dinoflagellates led to a decline in primary production during the mid and later phases under nutrient depletion. Such suppression of diatom-to-dinoflagellate succession occurred with enhanced remineralization of organic matter under the HC conditions, with smaller phytoplankton becoming dominant for the sustained primary production. Our findings indicate that, the impacts of OA on phytoplankton diversity in the coastal water of the southern East China Sea depend on availability of nutrients, with primary productivity and biodiversity of phytoplankton reduced in the eutrophicated coastal water.
Continue reading ‘Ocean acidification alters phytoplankton diversity and community structure in the coastal water of the East China Sea’Experimental evidence of climate change effects on plankton community respiration in European coastal waters: current insights and knowledge gaps in tested disturbances and studied areas
Published 2 December 2025 Science ClosedTags: biological response, physiology, phytoplankton, respiration, review
Plankton community respiration (PCR) plays a central role in aquatic ecosystems, driving the breakdown of organic matter and influencing global carbon cycling through its contribution to the production and consumption of carbon and oxygen. Coastal areas, which serve as critical interfaces between terrestrial and marine ecosystems, are regarded as metabolic hotspots in the oceans, due to their intense biological and biogeochemical activities. Additionally, they are particularly sensitive to the impacts of global climate change. In this regard, this review synthesizes experimental evidence to explore how environmental constraints and climate drivers affect PCR in European coastal waters. In total, 46 studies were found in which PCR was measured during experiments testing the effects of one or multiple global climate change drivers in European coastal waters. Among them, the majority of experiments focused on changes in temperature, nutrient concentrations and stoichiometry, and/or pH, while other stressors were less studied. Many experiments confirmed theoretical predictions, notably regarding the predicted positive effects of increased temperature and nutrient concentrations on metabolism, but more complex responses, often linked to trophic cascade mechanisms and thresholds between positive and negative feedbacks were also often reported. Overall, this review, the first comprehensive synthesis of experimental evidence on PCR in European coastal waters, highlights critical knowledge gaps, notably regarding non- and understudied areas and understudied interactions between stressors that occurs jointly in natural ecosystems. Future research should aim to integrate controlled experiments, long-term monitoring, and modeling approaches to deepen our understanding of PCR dynamics under changing environmental conditions and to predict potential feedbacks to global climate processes.
Continue reading ‘Experimental evidence of climate change effects on plankton community respiration in European coastal waters: current insights and knowledge gaps in tested disturbances and studied areas’Stressed overwintering bottleneck hypothesis: ocean warming and acidification synergistically disrupt Arctic zooplankton overwintering
Published 1 December 2025 Science ClosedTags: Arctic, biological response, crustaceans, laboratory, molecular biology, mortality, multiple factors, physiology, reproduction, respiration, temperature, zooplankton
Ocean warming (OW), driven by the influx of warm Atlantic water masses, and acidification (OA) are threatening Arctic marine ecosystems. However, their potential synergistic effects are poorly understood, especially during the Polar Night when marine species are particularly vulnerable to stressors. Here, we tested our novel Stressed Overwintering Bottleneck Hypothesis (SOBH): warming will disrupt the overwintering of the keystone pan-Arctic copepod Calanus glacialis, a pivotal secondary producer, by impairing fitness-related traits underpinning survival and reproduction. We exposed C. glacialis to current and projected future OW levels (0 °C and 4 °C) and OA levels (pH 8.0 and 7.4-7.3) for 53 days during the mid-Arctic Polar Night. We assessed survival, development, and physiological and molecular mechanisms (oxygen consumption, lipid depletion, the expression of nine targeted genes related to oxidative stress and damage repair, and DNA damage). OW alone did not affect C. glacialis mortality; however, OA increased copepod survival at 0 °C. Notably, their combined effects (OWA) synergistically doubled mortality, as predicted by SOBH. Warming also accelerated moulting from copepodite stage V to adulthood in December, and increased respiration, exhausted lipid reserves entirely by early March, approximately one to four months before the spring algal bloom, further supporting SOBH. DNA damage and gene expression patterns indicated low investment in maintenance and damage repair. Collectively, these findings reveal hidden mechanisms by which OW and OA synergistically threaten overwintering Calanus copepods by drastically increasing mortality, accelerating moulting, raising metabolic rates, and causing early lipid depletion. These effects generate cross-seasonal phenological mismatches among overwintering survival, energy reserves, reproduction, and primary production. Such stressed overwintering bottlenecks in foundational secondary producers like Calanus copepods provide novel explanations for how OW and OA can constrict Arctic marine food webs. At a broader perspective, SOBH highlights how multiple stressors induced overwintering disruption could reshape pan-Arctic and global biodiversity.
Continue reading ‘Stressed overwintering bottleneck hypothesis: ocean warming and acidification synergistically disrupt Arctic zooplankton overwintering’Resistance of the cold-water coral Dendrophyllia cornigera to single and combined global change stressors
Published 28 November 2025 Science ClosedTags: biological response, corals, growth, laboratory, morphology, mortality, multiple factors, North Atlantic, oxygen, respiration, temperature
Current knowledge of the consequences on global change in deep marine ecosystems is still limited, especially since environmental pressures do not act separately, and their potential interactions are mostly unknown. Cold-water corals (CWC) play a significant role in the deep sea, being ecosystem engineers supporting high biodiversity. However, global change may impact CWCs, compromising their integrity and survival. In this study, a nine-month aquaria experiment was conducted on the CWC Dendrophyllia cornigera from the NW Iberian Shelf (NE Atlantic Ocean). The aim was to assess the individual and combined effects of elevated temperature (12 vs. 15 °C), low pH (~ 7.99 vs. 7.69 pHT) and low oxygen (~ 6.4 vs. 4.7 mL L−1), based on the IPCC RCP 8.5 scenario. During the experiment, coral survival, skeletal growth, tissue cover and respiration were monitored as response variables. No significant effects were found on any of the response variables for either individual or combined stressors, pointing to the resistance of D. cornigera to different global change scenarios. Such a physiological resistance may support D. cornigera persistence under future conditions where other CWCs with narrower tolerance ranges may face greater limitations. However, further research is needed to assess potential trade-offs to cope with environmental change, which might impact the long-term survival capacity of this species.
Continue reading ‘Resistance of the cold-water coral Dendrophyllia cornigera to single and combined global change stressors’The multiple responses of Mytilus galloprovincialis in the multi-stressor scenario: impacts of low pH, low dissolved oxygen, and microplastics
Published 18 November 2025 Science ClosedTags: biological response, laboratory, Mediterranean, mollusks, multiple factors, oxygen, physiology, plastics, respiration
Highlights
- Low pH, low dissolved oxygen (DO), and microplastics (MPs) did not notably affect organismal parameters or ETS activity.
- Stressors significantly affected hemocytes, genotoxicity, and gill metabolites individually and interactively.
- Hemolymph phagocytic activity, granulocyte/hyalinocyte ratio, and mantle lipid peroxidation were partly affected.
- Metabolomic analyses showed that mussel gills are valuable indicators of metabolic status under stress.
Abstract
Along with high temperatures, acidification, deoxygenation, and microplastics (MPs) pollution represent key drivers in coastal marine ecosystems. Sessile invertebrates living in coastal habitats are primarily exposed to the combination of these drivers, often at severe levels. Here, we investigated the individual and combined impacts of low pH (pHT: 7.35), low dissolved oxygen (DO) (1.91 mg L−1), and MP (26 μg L−1) in the Mediterranean mussel Mytilus galloprovincialis by measuring organismal and cellular parameters after a 15-day exposure period. Organismal parameters (respiration rate, ammonia excretion rate, absorption efficiency) as well as electron transport system (ETS) activity were not impacted by the stressors, either individually or combined. At the cellular level, however, we observed significant effects of these stressors individually and interactively on the hemocyte count, hemocyte viability, genotoxicity (comet assay), and gill metabolite profiles. In addition, we observed partial effects on the hemolymph phagocytic activity (PA) and granulocyte/hyalinocyte (G/H) ratio, and mantle lipid peroxidation (LPO). Metabolomics results manifested that the gill of mussels can serve as a valuable indicator of metabolic status under the stress of low pH, low DO and MP. Metabolites involved in osmoregulation, membrane stability, oxidative stress, energy, amino acid and nitrogen metabolism were significantly affected by the stressors, with low DO being the main driver of metabolic changes. We suggest that the individual and variable interactions of these stressors negatively impact M. galloprovincialis, except for the organismal and, to some extent, biochemical parameters.
Continue reading ‘The multiple responses of Mytilus galloprovincialis in the multi-stressor scenario: impacts of low pH, low dissolved oxygen, and microplastics’Sediment topography enhances the response of coral reef carbonate sediment dissolution to ocean acidification
Published 13 November 2025 Science ClosedTags: annelids, biological response, BRcommunity, calcification, chemistry, community composition, laboratory, mollusks, otherprocess, primary production, respiration, sediment
The interaction between water flow and sediment topography (e.g., surface ripples) in shallow, permeable coral reef carbonate sediments establishes pressure gradients that increase the rate of sediment–water solute exchange relative to water flow along a flat bottom. It is unknown how this effect from surface ripples may modify the rate at which the sediment porewater is exposed to future chemical changes in the overlying water column, such as elevated pCO2 that is causing ocean acidification (OA). To address this question, this study used a series of 22-h incubations in flume aquaria with live permeable calcium carbonate sediment communities and examined the interactive effect of pCO2 (400 and 1000 µatm) and surface topography (flat and rippled sediments) on invertebrate infaunal activity, carbonate sediment microbial metabolism, and inorganic carbonate dissolution. Results show that the introduction of oxygen into flat sediments was largely driven by infaunal activity, whereas introduction of oxygen into rippled sediments was largely driven by physical flow processes. Rippled sediments exhibited rates of respiration and gross primary production that were ~ 45% and ~ 50% higher, respectively, than flat sediments. An increase in pCO2 shifted the sediments in the flat flumes from net calcifying to net dissolving, an effect that was amplified an additional ~ 60% in rippled sediments. These results suggest that current estimates of coral reef carbonate sediment calcification may be underestimating the dissolution response to OA where the carbonate sediment environment exhibits ripples in the topography.
Continue reading ‘Sediment topography enhances the response of coral reef carbonate sediment dissolution to ocean acidification’Physiological and metabolic plasticity in Patella caerulea enables survival in the CO2 vent systems of the Castello Aragonese (Ischia Island)
Published 20 October 2025 Science ClosedTags: adaptation, biological response, field, Mediterranean, mollusks, otherprocess, physiology, respiration, vents
Highlights:
- OA induced physiological and metabolic adjustment in P. caerulea to allow survival
- Increased RR at low pH only during summer to potentially boost energy production
- Reduced ER at low pH during summer and transplant to preserve more energy resources
- Induction of carnitine metabolism to produce more energy in low pH
- Increase of osmoregulation, oxidative stress, and nucleic acid metabolites at low pH
Abstract
Ocean acidification (OA) represents a major threat to marine ecosystems, causing detrimental effects mainly on calcifying organisms. However, the limpet Patella caerulea is one of the few calcifiers that can inhabit the naturally acidified areas of the Castello Aragonese vent systems (Ischia Island, Italy). Its presence suggests that this species may have developed tolerance or adaptive strategies to cope with OA.
Nevertheless, the specific biological mechanisms remain largely unknown. To address this gap of knowledge, in our study we conducted physiological and metabolomics analyses on resident limpet populations collected along the acidification gradient of the Castello vent systems. Additionally, we investigated the same mechanisms in specimens transplanted for 30 days from ambient pH conditions to the different pH sites of the vent.
Only during summer, OA increased respiration rates in limpets from the most acidified site and, simultaneously, reduced excretion rates and likely protein catabolism, probably to preserve more energy resources while coping with this environmental stress. Furthermore, the individuals up-regulated carnitine metabolism, potentially enhancing energy production through β-oxidation, and several metabolites involved in osmoregulation, oxidative stress, and nucleic acid mechanisms. Similar results were obtained also in limpets transplanted to low pH sites.
Overall, our results suggest that limpets exposed to acidified conditions may have developed tolerance strategies to maintain energetic reserves and allocate them among metabolic processes, which are fundamental in maintaining biological and ecological traits and distribution when facing environmental disturbance such as OA.
Continue reading ‘Physiological and metabolic plasticity in Patella caerulea enables survival in the CO2 vent systems of the Castello Aragonese (Ischia Island)’Effect of ocean acidification on the metabolism and behavior of tropical sea cucumbers
Published 16 September 2025 Science ClosedTags: biological response, echinoderms, mitigation, performance, physiology, respiration, review
In recent years, CO₂ emitted by human activities has continued to rise. The ocean absorbs these CO₂ and has caused seawater acidification. It is expected that the pH of the sea surface will drop by 0.3~0.4 by the end of this century. Tropical sea cucumbers are the “engineers” of the subsea ecosystem, promoting organic degradation and nutrient circulation through feeding disturbances. This study reviews the effects of marine acidification on the metabolism and behavior of tropical sea cucumbers. Studies have shown that under low pH conditions, sea cucumbers have increased respiratory metabolic pressure, digestive enzyme activity is reduced, and more energy is used to maintain the acid-base balance in the body, and their growth and reproduction are limited. At the same time, sea cucumber feeding rate and defense behavior are inhibited, and habitat distribution may change. These changes will have a chain effect on tropical ecosystems such as coral reefs, weaken the nutrient circulation function, and affect ecological balance. In-depth research on the impact mechanism of marine acidification on sea cucumbers will help predict the response of marine ecosystems under climate change and provide scientific basis for resource conservation and aquaculture management.
Continue reading ‘Effect of ocean acidification on the metabolism and behavior of tropical sea cucumbers’Transgenerational plasticity responses differ across genetically distinct families in the Sydney rock oyster, Saccostrea glomerata
Published 12 September 2025 Science ClosedTags: adaptation, biological response, laboratory, mollusks, morphology, otherprocess, reproduction, respiration, South Pacific
Across the globe, marine organisms need to rapidly respond to climate change. Acclimation through the mechanism of transgenerational plasticity (TGP) is now at the forefront of research, providing hope that some marine organisms may persist into the future. To date, however, because most studies have focussed on the average phenotypic species response to climate change, we do not know whether phenotypic responses vary among genotypes. Here, we take a next critical step in TGP research to assess whether TGP responses to ocean acidification (OA) differ among genotypes of the culturally significant and iconic Sydney Rock Oyster (SRO), Saccostrea glomerata. Adults of four genetically distinct families of the SRO were exposed to ambient (410 μatm) and elevated (1000 μatm) pCO2 for 9 weeks during reproductive conditioning. Following this exposure, we performed a within family cross of each family and measured the percentage development, abnormality, shell length and respiration rate of D-veliger larvae after 48 hours in the same ambient and elevated pCO2 treatments. We found significant variability in TGP responses among families to elevated pCO2, with positive, negative, and neutral responses in larval offspring. How well we understand the adaptive potential of oysters and their capacity to mount fast responses through TGP to climate change will determine our ability to ensure the sustainability of SRO populations, marine food security and the cultural heritage of this iconic species. Combined approaches quantifying both genetic and non-genetic TGP responses are needed to determine the total adaptive potential of other marine organisms to climate change.
Continue reading ‘Transgenerational plasticity responses differ across genetically distinct families in the Sydney rock oyster, Saccostrea glomerata’Coping with ocean acidification: metabolic shifts in Porites corals from the Palau Archipelago
Published 9 September 2025 Science ClosedTags: adaptation, biological response, calcification, corals, field, growth, North Pacific, otherprocess, photosynthesis, physiology, respiration
Increased atmospheric CO2 levels lead to ocean acidification, threatening coral reefs. However, certain coral species thrive in naturally acidified environments, offering unique opportunities to explore potential acclimatization or adaptation strategies. We assessed the physiological and biochemical parameters of Porites cf. lobata. colonies from control and acidified sites in the Palau Archipelago. Using a holistic approach, we compared markers related to trophic state, symbiotic state, physiology, energy storage, and redox status, along with calcification and oxidative metabolism. Our findings indicate that these colonies can acclimatize to low-pH conditions by utilizing CO2 more effectively. The increased passive diffusion of CO2 through their tissues enables them to maintain photosynthesis and calcification rates by reallocating energy that would typically go toward bicarbonate uptake. However, this energy reallocation cannot maintain skeleton density. Corals expend energy to elevate pH in the extracellular calcifying fluid, which is highly energy-demanding and reduces lipid reserves, potentially compromising long-term resilience. Despite the heightened energy production requirements, oxidative stress does not appear to worsen; the colonies exhibited lower antioxidant defenses and protein damage under low-pH conditions. The absence of metabolic suppression due to stable respiration rates and increased biomass suggests modifications in metabolic pathways, likely shifting toward a Warburg-like effect. These findings highlight the potential for some corals to tolerate near-future ocean acidification, the trade-offs associated with this resilience, and the potential for cascading effects on reef ecosystems. Further research should explore corals metabolic pathways as potential coping mechanisms.
Continue reading ‘Coping with ocean acidification: metabolic shifts in Porites corals from the Palau Archipelago’Tubastraea coccinea (Lesson, 1830), a coral species with high invasive potential, can benefit from the synergistic effects of ocean warming and acidification
Published 14 August 2025 Science ClosedTags: biological response, calcification, corals, laboratory, morphology, multiple factors, North Atlantic, reproduction, respiration, temperature
Temperature rise and pH decrease, coupled with increasing maritime traffic, are inducing modifications in the distribution of many exotic species, such as Tubastraea coccinea, a species with high invasive potential recently recorded in the Canary Islands. This study assessed the effect of the expected end-of-century temperature and pH (26°C and pH 7.50) on this coral species through manipulative laboratory experiments conducted over different time periods (30 days vs. 80 days). The impact of acidification, warming, and time on variables such as weight, buoyant weight, number of new polyps, area, respiration, calcification and reproduction rates were analysed. Results revealed a negative effect of acidification on growth and respiration rates of T. coccinea, with significant differences between experimental treatments in weight, buoyant weight, number of polyps, area, and respired carbon. However, in future, T. coccinea may not be adversely affected by low pH values, as the negative effect is mitigated when colonies are exposed to 26°C. Using different experimental periods showed how this species’ response is liable to change over time under future climate change conditions.
Continue reading ‘Tubastraea coccinea (Lesson, 1830), a coral species with high invasive potential, can benefit from the synergistic effects of ocean warming and acidification’Dynamics of ocean acidity, CO2 fluxes and metabolic rates on a shallow reef of Weizhou Island: a buoy-based observational study
Published 5 August 2025 Science ClosedTags: biological response, BRcommunity, chemistry, corals, dissolution, field, North Pacific, physiology, respiration
Highlights
- Diel cycles of reef seawater pH, calcification, and production were documented through a 37-day high-frequency time series.
- Daily net ecosystem production and calcification maintain a strong linear relationship even during dark periods.
- The studied reef exhibited persistent daily net heterotrophy and net CaCO3 dissolution for over weeks.
Abstract
The metabolic processes of calcification and production serve as crucial indicators of how environmental changes impact reef health. Previous studies suggest that Net Ecosystem Production (NEP) primarily drives Net Ecosystem Calcification (NEC) in the short-term. However, the functional relationship between these two carbon metabolisms remains poorly understood. We employed a mooring buoy approach to obtain simultaneous, high-frequency data of seawater pH, aragonite saturation state, CO2 fluxes, and carbon metabolic rates over a coral reef on Weizhou Island for 37 consecutive days. Our findings revealed a strong linear correlation between NEC and NEP across both diel cycles and day-to-day timescales—this relationship held even when analyzing nighttime periods alone. This indicates an intrinsic link between carbon metabolisms that can operate independently of light. Furthermore, we observed predominantly negative daily NEC and NEP values, indicating persistent net CaCO3 dissolution and net heterotrophy across the studied reef for over weeks. Our results suggest that CaCO3 dissolution is more likely to occur in waters with heterotrophic conditions, implying that heterotrophy contributes to CaCO3 dissolution. This tight coupling could be explained by reef sediment dissolution through the Carbonate Critical Threshold (CCT) mechanism. Our study highlights the significance of ambient respiration in driving reef ecosystem-scale CaCO3 dissolution, especially in reefs with low live hard coral coverage. This process releases alkalinity into the seawater, helping to neutralize respiration-induced acidification. Additionally, we identified a higher rate of respiratory CO₂ release as the primary driver of CO2 emissions from the studied reef.
Continue reading ‘Dynamics of ocean acidity, CO2 fluxes and metabolic rates on a shallow reef of Weizhou Island: a buoy-based observational study’Species-specific mechanisms of benthic foraminifera in response to shell dissolution
Published 31 July 2025 Science ClosedTags: biological response, dissolution, laboratory, light, mortality, multiple factors, North Atlantic, performance, photosynthesis, protists, respiration
Highlights
- Living specimens and empty tests of two benthic foraminifera species were cultured in different pH and light conditions.
- In acidic conditions, greater dissolution of empty tests compared to living specimens was observed.
- No differences in the degrees of dissolution between the two species were observed.
- Living foraminifera have active mechanism(s) to tolerate acidification.
Abstract
Ammonia confertitesta and Haynesina germanica are two common estuarine benthic foraminifera subject to sediment acidification. Nevertheless, mechanisms involved in their response to acidification are still poorly understood. Since H. germanica is kleptoplastic and photosynthetically active, unlike A. confertitesta, these species were cultured in controlled experiments to determine whether these mechanisms could mitigate acidification-induced shell dissolution. Both living and dead specimens were incubated at two pH (8.0 and 6.8) and two light conditions (0 and 24 μmol photon m-2.s-1) for 18 days. For each species, respiration and photosynthesis rates were calculated based on oxygen measurements. At the end of incubation, foraminiferal viability was assessed with CellTracker Green™ biomarker, and each test was categorised according to a dissolution scale (DS) using SEM. For both species, in acidic conditions, the tests of dead specimens were significantly more dissolved than the tests of living specimens, suggesting active mechanisms providing tolerance to acidification. For the living specimens, no significant difference in the DS distribution was observed between the two species at both conditions, suggesting that kleptoplast photosynthetic activity in H. germanica does not provide additional resistance to acidification. Until at least day 12, respiration data revealed a different biological activity for the two species, and we observed distinct behaviours (e.g., encystment and pseudopod emission). These suggest each species exhibits species-specific responses to cope with acidification. On day 18, respiration rates and binocular observations showed low biological activity, suggesting dormancy or death. Further investigation is required to identify the cellular mechanisms involved to counter acidification stress.
Continue reading ‘Species-specific mechanisms of benthic foraminifera in response to shell dissolution’Metabolic responses of the European flat oyster (Ostrea edulis) to combined ocean acidification and hypoxia
Published 18 July 2025 Science ClosedTags: biological response, laboratory, Mediterranean, mollusks, multiple factors, oxygen, performance, physiology, respiration
Ocean acidification and the accompanying hypoxia, which have become increasingly important environmental stress factors, can have varying effects on marine organisms, such as impaired physiological metabolism and immune function. Here, I studied the effects of high pCO2 and low dissolved oxygen (DO) in European flat oyster Ostrea edulis. Changes in physiological and immunological parameters were investigated in oysters during 18 days of exposure at two different pH (7.90 and 7.30) and DO levels (7.5 and 2 mg L-1). Low pH and low DO reduced haemocye count and viability, both individually and in combination. Low pH and combined exposure decreased feeding and respiration, which exacerbated by duration. Low pH and low dissolved oxygen increased ammonia excretion rate, which exacerbated by time. I suggest that the low pH and low DO lead metabolic depression, impaired immune function, and alteration in energy allocation in oysters, which further collectively negatively affect fitness of the oyster.
Continue reading ‘Metabolic responses of the European flat oyster (Ostrea edulis) to combined ocean acidification and hypoxia’Acidification, warming, and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary
Published 16 July 2025 Science ClosedTags: biological response, communitymodeling, fisheries, modeling, mollusks, morphology, multiple factors, North Atlantic, nutrients, respiration, temperature
Coastal acidification, warming, and nutrient management actions all alter water quality conditions that marine species experience, with potential impacts to their physiological processes. Decreases in calcite saturation state (ΩCa) and food availability, combined with warming water temperatures, pose a threat to calcifying organisms; however, the magnitude of future changes in estuarine systems is challenging to predict and is not well known. This study aims to determine how and where oysters will be affected by future acidification, warming, and nutrient reductions, and the relative effects of these stressors. To address these goals, an oyster growth model for Eastern oysters (Crassostrea virginica) was embedded in a 3-D coupled hydrodynamic-biogeochemistry model implemented for two tributaries in the lower Chesapeake Bay. Model simulations were forced with projected future conditions (mid-21st century atmospheric CO2 and atmospheric temperature under Representative Concentration Pathway (RCP) 8.5, as well as managed nutrient reductions) and compared with a realistic present-day reference run. Together, all three stressors are projected to reduce ΩCa and growth of oyster shell and tissue. Increased atmospheric CO2 is projected to cause widespread reductions in ΩCa. The resulting reductions in oyster shell and tissue growth will be most severe along the tributary shoals. Future warming during peak oyster growing seasons is projected to have the strongest negative influence on tissue and shell growth, due to summer water temperatures reducing filtration rates, enhancing shell dissolution and oyster respiration rates, and increasing organic matter remineralization rates, thus reducing food availability. Nutrient reductions will exacerbate deficits in oyster food availability, contributing to further reductions in growth. Quantifying the effects of these stressors provides insight on the areas in the lower bay where oysters will be most vulnerable to mid 21st-century conditions.
Continue reading ‘Acidification, warming, and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary’Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2
Published 11 July 2025 Science ClosedTags: biological response, fisheries, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, respiration, temperature
Highlights
- In the lab we explore environmental stress impacts on diploid and triploid oysters.
- At mid pCO2 (1450–1700 μatm) mated triploids had lower survival than other groups.
- Differences between mated and induced triploids may impact performance.
- Consider the environment when selecting which ploidy for shellfish aquaculture.
Abstract
Pacific oysters (Crassostrea gigas) are an important aquaculture species due to their fast growth, high market demand, and adaptability. Triploid oysters, have an additional set of chromosomes relative to diploids, grow faster and are functionally sterile. Thus, triploids comprise a large proportion of oysters grown worldwide. Triploid oysters are reported to experience higher mortality than diploids. Growers must make decisions that balance the risks and rewards of growing triploids. Understanding how stressors affect oysters is essential to understanding the drivers of triploid mortality and to prepare for the impacts of climate change on individuals in aquaculture. Here, we examined impacts of temperature, dissolved oxygen (DO), and pCO2 on genetically related juvenile diploid, chemically induced triploid, and mated triploid Pacific oysters. Diploid and induced triploid groups were full siblings, mated triploids were half-siblings. We measured whole organism physiological responses—growth, mortality and respiration — after a 4-week exposure to different environmental conditions. Survival was high in all groups across a broad range of temperature and DO levels. Survival of mated triploids was negatively impacted at lower (but higher than ambient) pCO2 levels. Diploids and induced triploids had similar respiration across temperature and pCO2 experiments. Diploids respired more across all dissolved oxygen treatments. Differing performance of mated triploids suggests that production method or genetic background may contribute to their resilience or susceptibility to stress. Considering the stressors that will be placed on individuals in commercial aquaculture when making ploidy selections is essential to ensure the resilience of aquaculture as the climate changes.
Continue reading ‘Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2’Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings
Published 8 July 2025 Science ClosedTags: biological response, laboratory, Mediterranean, mitigation, molecular biology, multiple factors, phanerogams, photosynthesis, physiology, reproduction, respiration, temperature
Ocean acidification (OA) and marine heatwaves (MHWs) are key drivers of marine ecosystem changes that can interact and influence marine organisms. Seagrasses, including the long-lived Posidonia oceanica endemic to the Mediterranean Sea, are widely distributed along coastal habitats, forming highly valuable underwater meadows. The germination and survival of the early life stages of P. oceanica are strongly affected by environmental changes. To assess the impact of warming and acidification on its future, we conducted a multifactorial experiment where P. oceanica seedlings were grown under OA conditions for six months and then exposed to a seawater warming event. Seedlings’ performance was investigated by analyzing photo-physiology, antioxidant capacity, energetic metabolism and transcriptomic profiles. The Weighted Gene Correlation Network Analysis (WGCNA) was used to integrate phenotypic plant traits with transcriptomic results to identify central genes involved in plant responses to OA and temperature exposure. Results demonstrated that prolonged OA exposure enhances P. oceanica seedling resilience to MHW. Specifically, seedlings regulated their antioxidant systems and transcriptomic machinery to better cope with thermal stress. Under current CO2 concentrations, elevated temperatures induced stress in P. oceanica seedlings, impacting photosynthesis and respiration. However, OA could mitigate the impact of warming in the future, enhancing P. oceanica‘s resilience to global stressors.
Continue reading ‘Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings ‘Alleviation of competitive constraints through long-term adaptation to high CO2 in mixed cultures of two diatom species
Published 27 May 2025 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, growth, North Pacific, otherprocess, photosynthesis, physiology, phytoplankton, respiration
Highlights
- The resources competition of two diatoms reduced most performance parameters.
- High CO₂ adaptation partially alleviates the detrimental effects of competition.
- Resource competition changes phytoplankton’s adaptation strategy to high CO2.
Abstract
Diatoms play a pivotal role in marine ecosystems, contributing significantly to global primary production and carbon cycling. Understanding their responses to high CO₂ is critical for predicting oceanic changes under future climate scenarios. This study investigates the long-term adaptation of two diatom species, Thalassiosira weissflogii and Phaeodactylum tricornutum, to high CO₂ (1000 µatm) over 3.5–4 years and the consequences of their interactions in mixed cultures. Mono- and mixed-species cultures were maintained under both ambient (400 µatm) and high CO₂ conditions to assess various physiological performances. Our results revealed that most measured parameters (growth rate, photosynthesis and respiration rate, chlorophyll fluorescence parameters, and pigment concentration) were significantly reduced in mixed cultures compared to mono-cultures under both CO₂ conditions, underscoring the detrimental effects of interspecific competition. However, long-term adaptation to high CO₂ partially alleviated these reductions, particularly in photosynthesis, respiration, and chlorophyll-a content. These findings highlight the complex interplay between physiological adaptation and interspecific competition in shaping diatom responses to high CO₂. This study advances our understanding of the ecological and evolutionary implications of ocean acidification and underscores the importance of long-term experimental approaches for assessing the impacts of climate change on marine phytoplankton.
Continue reading ‘Alleviation of competitive constraints through long-term adaptation to high CO2 in mixed cultures of two diatom species’Comparative transcriptomic analysis reveals a differential acid response mechanism between estuarine oyster (Crassostrea ariakensis) and Pacific oyster (Crassostrea gigas)
Published 2 May 2025 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, mortality, North Pacific, physiology, respiration
Highlights
- Mechanisms underlying resilience of estuarine oysters to low pH were analyzed.
- Estuarine oysters have evolved enhanced acid-tolerance responding to low pH levels.
- Frontloaded genes contributing to the enhanced acid-tolerance of estuarine oysters.
- Ion transporters and translation are crucial in mitigates low pH effects in estuarine oysters.
- Acid adaptation of estuarine oysters offers new insights into the adaptive potential of mollusks.
Abstract
Ocean and coastal acidification (OCA) poses a significant and rapidly emerging threat to mollusks. The physiological resilience of mollusks to OCA varies considerably; however, the underlying molecular mechanisms remain poorly understood. Seawater in estuaries, being more susceptible to acidification than that in open coastal zones, may enhance the tolerance of resident mollusks to low pH levels. Here, we conducted a comparative analysis between estuarine oysters (Crassostrea ariakensis) and Pacific oysters (Crassostrea gigas) using physiological phenotype and transcriptomic analyses to reveal differential acid-tolerance mechanisms in response to constant pH of 7.8. Our findings indicated that survival and respiration rates of C. ariakensis, which inhabits estuaries with fluctuating pH levels, were higher than those of C. gigas, which inhabits open coastal zones with relative stable pH conditions. Acid-responsive genes identified in C. gigas, including molecular chaperones and immune-related genes, exhibited higher constitutive expression in C. ariakensis under control conditions. Co-expression analyses revealed that C. ariakensis mitigated the effects of low pH by expressing genes involved in ion transporter activity and translation control. C. gigas activated genes associated with glycolipid metabolism while inhibiting cell division during acid stress. These findings suggested that C. ariakensis has evolved into a more energy-efficient regulatory network than C. gigas, incorporating both front-loading and responsive mechanisms to maintain acid-base homeostasis. This study is the first to investigate acid-tolerance differences between mollusks inhabiting estuarine and open coastal environments and provides critical insights into the resilience of mollusks in increasingly acidified oceans.
Continue reading ‘Comparative transcriptomic analysis reveals a differential acid response mechanism between estuarine oyster (Crassostrea ariakensis) and Pacific oyster (Crassostrea gigas)’
