Bivalve larvae are highly susceptible to ocean acidification (OA), but there is little knowledge of the capacity of bivalve species to acclimate or adapt to changing ocean conditions. It is challenging to compare results among studies of OA reported in the literature, as there is little consistency among studies in water chemistry across OA treatments used or how OA conditions were determined. In addition, it is difficult to predict from short-term experiments how populations might respond across generations. The bay scallop, Argopecten irradians, is a good model species for such experiments because of its short generation time and importance commercially and ecologically. Bay scallops were exposed to OA conditions from embryos to metamorphosis across two generations. Ocean acidification treatment levels included historical or preindustrial “low” (pCO2 ∼450 µatm), current average “moderate” (∼800 µatm), and future “high” (∼1,350 µatm). In the first generation, high OA had negative effects on larval performance, with no survival to metamorphosis, preventing its inclusion in the second generation. Moderate OA reduced performance (survivorship and growth) relative to the low OA. In the second generation, however, there was no difference in survival between the moderate and low OA treatments, but the difference in size at metamorphosis remained. These results suggest that over two generations, bay scallops either acclimated or adapted to moderate OA. Further work is needed to determine the extent to which long-term, generational adaptation to OA is possible in the bay scallop.
Continue reading ‘Within and cross-generational effects of elevated seawater pCO2 on larval bay scallops Argopecten irradians (L)’Posts Tagged 'mortality'
Within and cross-generational effects of elevated seawater pCO2 on larval bay scallops Argopecten irradians (L)
Published 27 August 2025 Science ClosedTags: adaptation, biological response, growth, laboratory, mollusks, morphology, mortality, North Atlantic, otherprocess, reproduction
Ocean acidification changes diet effects and differentially impacts two populations of red abalone (Haliotis rufescens)
Published 15 August 2025 Science ClosedTags: adaptation, biological response, mollusks, morphology, mortality, multiple factors, North Pacific, otherprocess, physiology, reproduction
Absorption of CO2 by global oceans is decreasing pH resulting in ocean acidification (OA). Impacts on shellfish have been documented in ecologically and commercially important species. We examined the influence of diet and OA between two populations of red abalone (Haliotis rufescens) a species of aquaculture importance and declining wild populations. Populations experience different exposure histories: strong upwelling (Van Damme, California [VD]) historically exposed to low-pH conditions and weak-intermittent upwelling (Santa Barbara, California [SB]). Abalone were cultured under control-pH or OA-conditions and fed crustose coralline algae (CCA) or diatoms used in aquaculture. We tested treatment effects of population, settlement diet, and OA-exposure on survival as influenced by larval-energy stores. Survival in both populations was enhanced by CCA when cultured under both treatment conditions; however, by later stages, this effect remained only for SB. SB had reduced post-settlement survival when cultured under OA-conditions, whereas post-settlement survival of VD was not. Diet affected the relationship between larval-energy and post-settlement survival; a positive relationship when fed diatoms and a negative relationship with CCA. The relationship between larval-energy and post-settlement survival was stronger in VD. CCA enhanced juvenile growth in SB cultured abalone at both three-months and one-year post-settlement. Settlement diets can reduce the impacts of OA on early-life stages of abalone, but population differences driven by underlying energetics affect the consistency of this outcome. These findings illuminate the impacts from OA, suggesting populations may be at risk, and inform strategies for developing and sustaining shellfish aquaculture in the face of changing ocean conditions.
Continue reading ‘Ocean acidification changes diet effects and differentially impacts two populations of red abalone (Haliotis rufescens)’Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans
Published 12 August 2025 Science ClosedTags: abundance, adaptation, biological response, BRcommunity, bryozoa, community composition, communitymodeling, field, Mediterranean, modeling, molecular biology, morphology, mortality, otherprocess, prokaryotes, vents
Marine habitat-forming species provide crucial ecosystem functions and services worldwide. Still, the individual and combined long-term effects of ocean acidification and warming on bryozoan populations, structures, and microbiomes remain unexplored. Here, we investigate the skeletal properties, microbiome shifts, and population trends of two bryozoan species living inside and outside a volcanic CO2 vent, a natural analog to future ocean acidification conditions. We show that bryozoans can acclimatize to acidification by adjusting skeletal properties and maintaining stable microbiomes. However, we document a decrease in microbial genera playing essential functions under acidified conditions. Moreover, we show that ocean acidification exacerbates bryozoan cover loss and mortality caused by ocean warming. The observed shifts in the microbiome and cover suggest that, despite their morphological plasticity, bryozoan species will be heavily impacted by future ocean conditions, posing a threat to many benthic ecosystems in which they play a pivotal role.
Continue reading ‘Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans’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’Stage-dependent life-history, physiological, and behavioral responses to low pH in an estuarine crab
Published 18 July 2025 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, mortality, otherprocess, performance, physiology, reproduction, South Atlantic
Highlights
- We assessed the effects of low pH on larval stages of the crab Neohelice granulata.
- Low pH affects intermolt period, mortality, and oxygen consumption.
- Low pH also impacts swimming velocity and distance traveled.
- Marine larval stages were more adversely affected than the exported (first) larval stage.
Abstract
Early stages of marine invertebrates are vulnerable to ocean acidification. We investigated low pH effects on larval stages of the crab Neohelice granulata. We hypothesized that Zoea I, adapted to fluctuating environments, would show greater resilience than Zoea II and III, which develop in stable nearshore areas. We assessed pH 8 -control-, pH 7.5, and pH 6.9 effects on intermolt duration, mortality, oxygen consumption, and swimming behavior. Zoea I tolerated low pH with no changes in development or mortality, though oxygen consumption decreased at pH 6.9. In contrast, Zoea II and III showed delayed development, higher mortality, and reduced oxygen consumption at pH 6.9. While Zoea I showed no changes in swimming, Zoea II and III exhibited reduced swimming velocity and distance traveled under acidified conditions. These findings show that Zoea II and III are more sensitive to low pH, while Zoea I is more resilient.
Continue reading ‘Stage-dependent life-history, physiological, and behavioral responses to low pH in an estuarine crab’High sensitivity to ocean acidification in wild out-migrating juvenile Pacific salmon is not impacted by feeding success
Published 18 July 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, mortality, multiple factors, North Pacific, physiology, reproduction
Salmon populations are declining worldwide, with high mortality rates during juvenile marine migration presenting a bottleneck to recruitment. The ocean conditions along the main migratory route of juvenile salmon in British Columbia are characterized by high variability in CO2, with the amplitude, duration, and frequency of ocean acidification events exacerbated by climate change. Similarly, the variability in ocean conditions affects the abundance and diversity of plankton prey, leading to areas of food paucity for juvenile salmon. We investigated the combined effects of ocean acidification (control and 3200 μatm CO2) and food limitation (ad libitum, ½ ration, and food deprived) on the survival, condition, and gene expression profiles of juvenile Chum salmon (Oncorhynchus keta) to develop predictive biomarkers for CO2 exposure and food deprivation. Ocean acidification caused a direct 3-fold increase in mortality over 25 days of exposure, which was unaffected by food availability but differentially affected smaller fish. CO2 exposure induced transcriptomic changes in a suite of genes associated with ion regulation, while food deprivation was associated with a differential expression of stress, immune, and mortality markers, as well as reduced condition factor. Our data indicate that CO2 directly impairs ionoregulatory capacity to the point of failure in juvenile Chum salmon and that these effects cannot be compensated through increased energy from food. Applying our gene panels as biomarkers to a subset of fish with known exposure, we were able to accurately predict exposure to CO2 and food deprivation (74% and 90%, respectively). By combining these gene panels with previously established biomarkers for other environmental stressors, the recent environmental stress history of wild fish can be determined and can be used in models to predict salmon returns, informing fisheries management and conservation efforts.
Continue reading ‘High sensitivity to ocean acidification in wild out-migrating juvenile Pacific salmon is not impacted by feeding success’Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification
Published 17 July 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, mortality, multiple factors, North Atlantic, oxygen, physiology, reproduction
We investigated the potential for cross-generational plasticity to influence how offspring respond to hypoxia and ocean acidification (hereafter HypOA) in the coastal forage fish Atlantic silverside (Menidia menidia). Mature wild silversides were treated with a control (dissolved oxygen (DO):100% air saturation (a.s.) / pCO2: 650 µatm) or HypOA conditions (DO: 40% a.s. / pCO2: 2300 µatm) for 10 days prior to spawning. Their offspring were reared under both treatments in factorial experimental design. Parental environment had minimal effects on offspring phenotype: exposure to HypOA reduced survival and developmental rates regardless of parental treatment. However, RNAseq analysis revealed that direct offspring exposure to HypOA induced substantial transcriptional changes, with 1,606 differentially expressed transcripts (DETs) in larvae from control parents. These changes affected neural development, synaptic signaling, oxygen acquisition, and extracellular matrix organization. In contrast, larvae from HypOA-exposed parents exhibited a muted transcriptional response to HypOA, with only 4 DETs. Although we did not detect a statistically significant interaction between parental and offspring environments at the gene-wise level, a gene set test supported a consistent attenuation of expression changes in offspring from HypOA-treated parents. This pattern may be consistent with transcriptional frontloading, when stress-induced changes are retained and may modify future responses. However, because this effect did not improve offspring performance under HypOA, they are unlikely to represent an adaptive response. Instead, they may reflect non-adaptive carryover effects of parental exposure. Our findings highlight the potential for cross-generational effects to shape transcriptional plasticity, even in the absence of benefits to offspring.
Continue reading ‘Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification’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’Larval Arctic cod (Boreogadus saida) exhibit stronger developmental and physiological responses to temperature than to elevated pCO2
Published 10 July 2025 Science ClosedTags: Arctic, biological response, fish, growth, laboratory, morphology, mortality, multiple factors, physiology, reproduction, temperature
High-latitude ecosystems are simultaneously warming and acidifying under ongoing climate change. Arctic cod (Boreogadus saida) are a key species in the Arctic Ocean and have demonstrated sensitivity to ocean warming and acidification as adults and embryos, but their larval sensitivity to the combined stressors is unknown. In a laboratory multistressor experiment, larval Arctic cod were exposed to a combination of three temperatures (1.8, 5 and 7.3°C) and two carbon dioxide (pCO2) levels (ambient: 330 μatm, high: 1470 μatm) from hatching to 6-weeks of growth. Mortality rates were highest at 7.3°C (5% day°1); however, both growth and morphometric-based condition were also highest at this temperature. When these metrics were assessed via a mortality: growth (M:G) ratio, 5°C appeared to be an optimal temperature for net population biomass, as faster growth at 7.3°C did not fully compensate for higher mortality. In contrast, although morphometric-based condition was lowest at 1.8°C, lipid-based condition was highest, which may reflect prioritization of lipid storage at cold temperatures. The capacity of larval Arctic cod to acclimate to a range of temperatures was exhibited by two lipid-based indicators of membrane fluidity, including a ratio of unsaturated to saturated fatty acids and a ratio of polar lipids to sterols. The effects of elevated pCO2 were subtle, as well as temperature- and metric dependent. When exposed to elevated pCO2 levels, Arctic cod at 1.8°C exhibited signs of lipid dysregulation, suggesting potential interference with membrane acclimation; larvae at 5°C were in lower morphometric-based condition; and larvae at 7.3°C had higher activity eicosanoid substrates, indicating possible physiological stress. Overall, Arctic cod physiological response to temperature variation was more pronounced than their response to elevated pCO2. Future projections of pCO2 effects on Arctic cod health in a warming ecosystem will need to consider the complexity of temperature-dependence and the specificity of multiple physiological responses.
Continue reading ‘Larval Arctic cod (Boreogadus saida) exhibit stronger developmental and physiological responses to temperature than to elevated pCO2’Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis
Published 10 July 2025 Science ClosedTags: Antarctic, biological response, crustaceans, laboratory, morphology, mortality, physiology, zooplankton
Ocean acidification refers to a decrease in the pH of the world’s oceans from the oceanic uptake of human-derived atmospheric CO2. Low pH is known to decrease the calcification and survival of many calcifying invertebrates. Shallow, hard bottom communities along the Western Antarctic Peninsula often have incredibly large numbers of invertebrate mesograzers that shelter on and are mutualists with the dominant brown macroalgae. The common amphipod species Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis were collected from the immediate vicinity of Palmer Station, Antarctica (64°46′S, 64°03′W) in January–February 2023 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.0), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 8 weeks. Molt number and mortality were monitored throughout the course of the experiment. After the 8 week exposure, amphipods were analyzed for their biochemical compositions including the Mg/Ca ratio of their exoskeletons. There was no significant difference in biochemical composition or survival among the pH treatments for any of the amphipod species. All three species, however, had significantly fewer total numbers of molts in the pH 7.3 treatment than in the ambient treatment. These results suggest that amphipods may be able to maintain their survival in decreased pH by reallocating energy into compensatory behaviors, such as acid–base regulation, and away from energy expensive processes like molting.
Continue reading ‘Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis’Impacts of ocean acidification and altered prey fatty acids on the early development of northern rock sole (Lepidopsetta polyxystra) larvae
Published 3 July 2025 Science ClosedTags: biological response, fish, laboratory, morphology, mortality, multiple factors, North Pacific, physiology, reproduction
Highlights
- Carbon dioxide (CO2) and dietary fatty acids (FAs) had stage-specific effects on northern rock sole larvae.
- After 2-weeks of feeding, larvae had faster growth under elevated CO2 conditions.
- After 5-weeks of feeding, larvae had higher lipid storage when fed a diet with balanced-essential FAs.
Abstract
Ocean acidification (OA) is predicted to affect the physiological rates of larval fish and invertebrates and is also expected to significantly impact marine fisheries through alteration of food webs. We examined whether mortality rates, body size, and condition of first-feeding larval northern rock sole, Lepidopsetta polyxystra, were synergistically influenced by prey quality (essential fatty acids, EFAs) and high carbon dioxide (CO2) exposure. Larvae were exposed to ambient and high CO2 levels (∼ 330 vs. 1020 μatm) and were fed diets with balanced or unbalanced EFA ratios for 7 weeks immediately following hatch. After 2 weeks, significant effects from CO2 and diet were observed, with the largest larvae occurring in the high CO2 exposure group that received a balanced EFA diet. After 5 weeks of exposure, the effects of elevated CO2 had a diminished impact on larval size, but larvae reared on the balanced EFA diet maintained higher lipid-based condition metrics than those fed an unbalanced EFA diet. Survival was variable across replicate tanks and not significantly different between treatments. This study suggests that L. polyxystra larvae are most vulnerable to OA and food web change at different points in their development. Further understanding of these ecosystem effects will be required to predict the impacts of OA on northern rock sole fisheries.
Continue reading ‘Impacts of ocean acidification and altered prey fatty acids on the early development of northern rock sole (Lepidopsetta polyxystra) larvae’Antarctic macroalgal-associated amphipod assemblages exhibit long-term resistance to ocean acidification
Published 19 June 2025 Science ClosedTags: abundance, algae, Antarctic, biological response, BRcommunity, community composition, crustaceans, laboratory, mortality, otherprocess
The pH of the world’s oceans has decreased since the Industrial Revolution due to the oceanic uptake of increased atmospheric CO2 in a process called ocean acidification. Low pH has been linked to negative impacts on the calcification, growth, and survival of calcifying invertebrates. Along the Western Antarctic Peninsula, dominant brown macroalgae often shelter large numbers of diverse invertebrate mesograzers, many of which are calcified. Mesograzer assemblages in this region are often composed of large numbers of amphipods which have key roles in Antarctic macroalgal communities. Understanding the impacts of acidification on amphipods is vital for understanding how these communities will be impacted by climate change. To assess how long-term acidification may influence the survival of different members in these assemblages, mesograzers, particularly amphipods, associated with the brown alga Desmarestia menziesii were collected from the immediate vicinity of Palmer Station, Antarctica (S64°46′, W64°03′) in January 2020 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.1), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 52 days then enumerated. Total assemblage number and the relative proportion of each species in the assemblage were found to be similar across the pH treatments. These results suggest that amphipod assemblages associated with D. menziesii may be resistant to long-term exposure to decreased pH.
Population and maternal variation in the sensitivity of Dungeness crab Metacarcinus magister zoeae to elevated CO2
Published 10 June 2025 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, morphology, mortality, North Pacific, otherprocess, reproduction
The response of marine organisms to ocean acidification depends on their adaptive capacity, which can be partially understood by evaluating the amount of existing variability in CO2 sensitivity within a species. The process of local adaptation is a mechanism that can drive variability in CO2 sensitivity. In this study, we measured the survival and molt rate of Dungeness crab Metacarcinus magister zoeae that were produced by gravid crabs collected from 3 locations in waters off of Washington State, USA, and reared in a common laboratory in ambient, medium, and high CO2 treatments. The 3 locations from which crabs were collected have different carbonate chemistry dynamics, and Dungeness crabs in these locations are to some extent genetically distinct. We hypothesized that these conditions may favor local adaptation. We did not find evidence of local adaptation, but did see different levels of CO2 sensitivity associated with the mother. This variation in CO2 sensitivity suggests an adaptive capacity that is likely to influence Dungeness crab response to future acidification.
Continue reading ‘Population and maternal variation in the sensitivity of Dungeness crab Metacarcinus magister zoeae to elevated CO2’Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size
Published 13 May 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, reproduction, temperature
Pinto abalone (Haliotis kamtschatkana), the only abalone species native to Washington, declined by 97% in the state from 1992 to 2017. Their decline is a loss for indigenous tribes, recreational divers, and the health of subtidal rocky reefs and kelp beds. Current restoration actions are facing threats of ocean acidification and warming in the northeast Pacific. This research aims to deepen our understanding of the tolerance and physiological flexibility of early life history stages of pinto abalone and inform hatchery practices under future climate change scenarios. We conducted an experiment to test how seawater pH and temperature stress impact abalone larvae. We exposed abalone post-fertilization to elevated temperature and reduced seawater pH for ten days spanning their larval development period: (1) 7.95pH/14°C (ambient), (2) 7.60pH/14°C, (3) 7.95pH/18°C, and (4) 7.60pH/18°C. Abalone in the ambient treatment had the best survival, those in the 7.60pH/18°C treatment had the worst survival, and those in the two single-stressor treatments had survival in between. Among the surviving larvae, pH was the dominant stressor influencing settlement success, with higher settlement rates under ambient pH treatments at both temperatures. pH also had a stronger effect than temperature on shell length. The information gleaned from this study is essential for optimizing future restoration aquaculture for pinto abalone and determining their ideal habitat and potential geographic range.
Continue reading ‘Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size’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)’Evaluating the impact of ocean acidification on seafood – a global approach
Published 23 April 2025 Science ClosedTags: biological response, crustaceans, echinoderms, fish, fisheries, growth, mitigation, mollusks, mortality, review
The quality of human life and food security are closely linked to the health of the ocean and the many goods and services it provides. However, the ocean is under cumulative stress from various human-driven pressures, leading to eutrophication, deoxygenation, loss of genetic biodiversity, contamination with emerging pollutants (e.g., microplastics and pesticides), and climate change (warming and ocean acidification). The effects of multiple ocean stressors and their interplay on marine life and ecosystems remain poorly understood. This underscores the urgent need for innovative science to resolve the complexity of the interplay of stressors and the resulting impacts. This paper reports findings from the Coordinated Research Project CRP K41018, a five-year program framed by the IAEA. The project was explicitly designed to advance Member States’ understanding of both quantitative and qualitative impacts of ocean acidification on key economically relevant seafood species across different world regions. Furthermore, based on different sensitivity baselines across species, it aimed at exploring adaptation pathways for aquaculture and food industries. As a result, Member States would have improved their comprehension of resilience building in specific local contexts (e.g., types of environments, geographical parameters, human dimension). In this context, it is essential to look for ocean solutions to mitigate adverse impacts on seafood and support adaptation strategies based on nature that can counteract stressors. It is concluded that there is great synergy in planning integrated mitigation and adaptation strategies to multiple stressors in marine ecosystems.
Continue reading ‘Evaluating the impact of ocean acidification on seafood – a global approach’Long-term impacts of ocean acidification on the Mediterranean mussel Mytilus galloprovincialis
Published 10 April 2025 Science ClosedTags: biological response, laboratory, Mediterranean, mollusks, mortality, physiology
This study aims to elucidate the long-term physiological impacts of ocean acidification on a key seafood species. The Mediterranean mussel Mytilus galloprovincialis, was subjected to three pH conditions over a period of six months: two pH values within the present range of natural variability (pHT: 8.10 and 7.80) and a lower pH condition (pHT: 7.50) relevant in the context of near-future ocean acidification. A comprehensive assessment was conducted at the conclusion of the fourth and sixth months and encompassed a suite of physiological endpoints, including mortality, oxygen consumption, clearance rate, total haemocyte count (THC), nutritional content analysis, and polonium-210 (210Po) depuration rates. The findings revealed a marked decrease in survival rates at pH 7.50 compared with those at pH 8.10 and 7.80 after six months of exposure. This was associated with a significant increase in THC and a decrease in lipid content. No significant pH effects were observed for other endpoints (namely clearance rate, condition index, oxygen consumption rate, protein and carbohydrate contents, and 210Po). While the lack of response to low pH at some of these physiological endpoints may be a consequence of a lack of statistical power, our data clearly demonstrate the effects of low pH on the survival, THC, and lipid content of M. galloprovincialis. Such effects on a species’ overall fitness have the potential to negatively impact this key seafood species, associated ecosystems, and the socioeconomic dynamics of communities depending on this resource.
Continue reading ‘Long-term impacts of ocean acidification on the Mediterranean mussel Mytilus galloprovincialis’Transcriptomic reaction norms highlight metabolic depression as a divergence in phenotypic plasticity between oyster species under ocean acidification
Published 21 February 2025 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, mortality, otherprocess, physiology
Ocean acidification occurs at a rate unprecedented for millions of years, forcing sessile organisms, such as oysters, to respond in the short term by relying on their phenotypic plasticity. Phenotypic plasticity has limits, tipping points, beyond which species will have to adapt or disappear. These limits could be related to the adaptation of species to different habitat variabilities. Here we expose juvenile pearl oysters, Pinctada margaritifera, to a broad range of pH and determine the response at the gross physiological, lipidome and transcriptome levels. Thus, we identify its high tolerance with low tipping points at pH 7.3-6.8 below which most physiological parameters are impacted. We then compare the transcriptomic reaction norms of the tropical subtidal P. margaritifera, with those of an intertidal temperate oyster, Crassostrea gigas, reusing data from a previous study. Despite showing similar tipping points with C. gigas, P. margaritifera exhibits strong mortalities and depletion of energy reserves below the tipping points, which is not the case for C. gigas. This divergence relies mainly on the induction of metabolic depression, an adaptation to intertidal habitats in C. gigas, but not in P. margaritifera. Our method makes it possible to detect divergences in phenotypic plasticity, probably linked to the species’ specific life-history strategies related to different habitats, which will determine the survival of species to ongoing global changes. Such an approach is particularly relevant for studying the physiology of species in a world where physiological tipping points will be increasingly exceeded.
Continue reading ‘Transcriptomic reaction norms highlight metabolic depression as a divergence in phenotypic plasticity between oyster species under ocean acidification’Transcriptome‐to‐phenome response of larval Eastern oysters under multiple drivers of aragonite undersaturation
Published 19 February 2025 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, morphology, mortality, multiple factors, reproduction, respiration, salinity, temperature
Understanding how interactive environmental challenges affect marine species is critical to long‐term ecological and economic stability under global change. Marine calcifiers are thought to be vulnerable to ocean acidification (OA; elevated pCO2); active dissolution of aragonite (Ωar) is associated with disrupted development, survivorship, and gene expression in bivalve larvae, resulting in an early life‐stage bottleneck. Dynamic carbonate chemistry in coastal systems emphasizes the importance of multiple stressors, e.g., warming and low salinity events may change organismal responses relative to OA alone. We exposed Eastern oyster larvae ( Crassostrea virginica ) to a full‐factorial experimental design using two temperatures (23°C and 27°C), salinities (17 and 27), and pCO2 levels (~700 μatm and 1850 μatm pCO2), resulting in Ωar conditions 0.3–1.7. Ωar reduced by low salinity, elevated pCO2, and low temperature, each slowed early development and reduced survival. Low salinity × elevated pCO2 was linked to severe Ωar undersaturation (< 0.5) that suppressed expression of bicarbonate transport, biomineralization and augmented expression for ciliary locomotion, proteostasis, and histone modifiers. In isolation and under moderate Ωar intensity (0.5 < Ωar < 1), larvae increased transcription for osmoregulatory activity and endocytosis under low salinity, and suppressed transcription for iron metabolism under elevated pCO2. Although shell growth and survival were affected by Ωar undersaturation, gene expression patterns of D‐stage oyster larvae and oyster juveniles suggests tolerance to dynamic estuarine environments. Genes and expression patterns that confer survival of postmetamorphosed oysters can improve our understanding of environmental‐organismal interactions and improve breeding programs enabling sustainable production.
Continue reading ‘Transcriptome‐to‐phenome response of larval Eastern oysters under multiple drivers of aragonite undersaturation’
