Anticipated future increases in CO2 levels are predicted to have a diverse array of lethal and non-lethal effects on the marine ecosystem. While there has been extensive research on the physiological impacts of ocean acidification on marine species, our understanding of how increasing levels of carbon dioxide affect the shedding and decay of environmental DNA and RNA (eDNA/ eRNA) in marine habitats is limited. This may impede the effective adoption of environmental nucleic acid–based molecular tools for monitoring marine biodiversity and detecting rare or invasive species. In the present study, we conducted mesocosm experiments to determine the shedding and decay rate constants of eDNA and eRNA in M. gigas (Magallana [Crassostrea] gigas) using mitochondrially encoded tRNA leucine 1 (mt-tl1) marker at various partial pressures of CO2 in seawater. To our knowledge, this is the first study manipulating seawater pH using CO2. We developed a sensitive and specific quantitative PCR-based assay to detect M. gigas eDNA and eRNA. Higher CO2 levels increased shedding rates, indicating greater organism stress and biological effects on oysters. Additionally, increased CO2 accelerates DNA and RNA decay, suggesting that ocean acidification may impact the reliability of eDNA-based biodiversity monitoring. Furthermore, eRNA displayed lower steady-state concentrations and a shorter persistence time in comparison to eDNA, as is consistent with known biochemical properties of the molecules. These findings are presented in the context of previous work that adjusted pH through acid–base adjustment and temperature and highlight the importance of considering ocean acidification caused by differing CO2 levels when using molecular tools for marine conservation and fisheries management.
Continue reading ‘Impact of CO2-induced aquatic acidification on environmental DNA and RNA shedding and persistence’Posts Tagged 'laboratory'
Impact of CO2-induced aquatic acidification on environmental DNA and RNA shedding and persistence
Published 5 August 2025 Science ClosedTags: biological response, laboratory, mesocosms, molecular biology, mollusks
Epigenetic insights into physiological resilience: multigenerational readouts of CO2-induced seawater acidification effects on fish embryos
Published 5 August 2025 Science ClosedTags: adaptation, biological response, fish, laboratory, molecular biology, morphology, otherprocess, physiology, reproduction
Highlights
- Ocean acidification causes generation-specific developmental and metabolic changes.
- F2 embryos show enhanced resilience through transcriptional recovery mechanisms.
- Hypomethylation of ion transport genes drives adaptive acid-base regulation.
- Epigenetic inheritance facilitates multigenerational acclimation to acidification.
Summary
Anthropogenic CO2 emissions are acidifying oceans, threatening marine organisms during early development. We investigated multigenerational effects of projected 2100 acidification (pH 7.6) on marine medaka (Oryzias melastigma) embryos across three generations using integrated phenotypic, physiological, transcriptomic, and epigenetic analyses. Prolonged acidification altered developmental trajectories, with F2 embryos showing size reductions. Metabolic responses were generation-specific: F0 embryos displayed decreased ammonium excretion, while F1 and F2 maintained stable profiles. Transcriptomic analysis revealed generational changes in neurotransmission, ion regulation, and epigenetic pathways. F2 embryos exhibited attenuated transcriptional perturbations and partial restoration of acid-base homeostasis, suggesting enhanced adaptability. Adaptive gene expression correlated with hypomethylation recovery of ion transport genes AE1a and NHE2 in F2 embryos. Increased hypomethylated AE1a promoter CpG sites in F1 and F2 generations aligned with elevated transcription, indicating epigenetically-driven enhancement. These results demonstrate epigenetic control’s crucial role in multigenerational plasticity and adaptive responses to ocean acidification.
Continue reading ‘Epigenetic insights into physiological resilience: multigenerational readouts of CO2-induced seawater acidification effects on fish embryos’Abalone and seaweed co-culture: growth and shell biomineralization of an iconic California gastropod
Published 5 August 2025 Science ClosedTags: algae, biological response, chemistry, fisheries, laboratory, mitigation, mollusks, morphology, physiology, reproduction
Climate change threatens shellfish aquaculture worldwide, with ocean acidification (OA) accelerating shell dissolution and reducing calcification, hindering growth. This study addressed the negative impacts of OA on juvenile red abalone (Haliotis rufescens), a life stage that is particularly susceptible to climate stressors, and the ability of the red seaweed, dulse (Devaleraea mollis), to mitigate these effects. I tested the hypothesis that Integrated Multi-Trophic Aquaculture (IMTA), with abalone and seaweed grown in co-culture, can raise seawater pH through photosynthesis to yield more favorable conditions for abalone growth and shell construction. A 5-month experiment was conducted to determine the benefits of IMTA on abalone growth, shell composition, and morphology under simulated ocean acidification conditions. In each tank, 620 abalone were raised in either High (8.1 ± 0.3), Ambient (7.9 ± 0.2), Medium (7.8 ± 0.3), or Low pH (7.6 ± 0.2). Abalone raised in High and Ambient pH treatments exhibited greater shell length, weight, area, and condition compared to those raised in medium and low pH treatments. Shell analyses indicated that these growth differences translate into differences in physical and chemical properties, with shells from the high and ambient pH treatments containing higher levels of Mg2+ and being more resistant to fracturing. These findings indicate that IMTA could shepherd abalone through the susceptible juvenile stage, increasing resilience of abalone aquaculture even within the context of future climate change.
Continue reading ‘Abalone and seaweed co-culture: growth and shell biomineralization of an iconic California gastropod’Ocean acidification interacts with low salinity and phosphorus limitation to modulate growth, photosynthesis, and physiology of mass-cultivated Gracilariopsis lemaneiformis
Published 4 August 2025 Science ClosedTags: algae, biological response, fisheries, growth, laboratory, multiple factors, nutrients, photosynthesis, physiology, salinity
Due to the effective removal of phosphorus during eutrophication control and intensive macroalgal cultivation, phosphorus limitation in coastal waters is normalized. As an economic macroalga cultivated on a large scale in production, Gracilariopsis lemaneiformis is also inevitably influenced by the combination of phosphorus limitation, ocean acidification caused by the increase of dissolved CO2 concentration and salinity decrease as a consequence of rainfall. In this study, G. lemaneiformis was cultured for 15 days under two pCO2 levels (LC: 400 μatm, HC: 1000 μatm), two salinities (LS: 22, HS: 30) and two phosphorus concentrations (LP: 0.1 μmol L−1, HP: 10.1 μmol L−1) to study the growth and photophysiology responses of this macroalga to the coupling of phosphorus limitation, ocean acidification and low salinity. Lower phosphorus (LP) treatment substantially reduced multiple parameters compared to higher phosphorus (HP) condition, including relative growth rate (RGR), photosynthetic rate, chlorophyll fluorescence parameters, and the contents of pigments, soluble protein, and soluble carbohydrate. Elevated CO₂ (HC) exposure induced a significant reduction in algal RGR under LP condition, while demonstrating no statistically significant impact on RGR under HP condition. Furthermore, HC treatment significantly inhibited carotenoid biosynthesis under LP condition. Notably, lower salinity (LS) stimulation significantly enhanced RGR in the ambient CO₂ (LC) group, but this promotive effect was completely negated under HC condition. These findings demonstrated that phosphorus limitation had an adverse outcome on algal growth, and phosphorus limitation exacerbated the adverse effect of ocean acidification on its growth. Moreover, the promotion effect of low salinity on algal growth could be neutralized by ocean acidification. This study provided important information about the influence of environmental changes on the photophysiological characteristics of G. lemaneiformis and new breeding directions for large-scale cultivation of coastal economic macroalgae.
Continue reading ‘Ocean acidification interacts with low salinity and phosphorus limitation to modulate growth, photosynthesis, and physiology of mass-cultivated Gracilariopsis lemaneiformis’Multi generational acclimation of Scrippsiella trochoidea to ocean warming and acidification
Published 4 August 2025 Science ClosedTags: adaptation, biological response, growth, laboratory, multiple factors, otherprocess, physiology, phytoplankton, temperature
Dinoflagellates, particularly harmful algal bloom (HAB)-forming species, exhibit remarkable resilience to climate change stressors, including ocean warming and acidification. However, their specific acclimation strategies compared to other phytoplankton groups remain poorly understood. This study investigates the multi-generational acclimation mechanisms of Scrippsiella trochoidea under simulated future ocean conditions (25°C, 1000 ppm pCO₂; HTHC) compared to present-day conditions (21°C, 400 ppm pCO₂; LTLC). Over 10 generations, S. trochoidea demonstrated significant physiological and biochemical adjustments, including a 79% increase in growth rate, a 73% rise in cell volume, and notable elevations in macromolecular components such as carbohydrates (38%), lipids (48%), proteins (90%), and chlorophyll (158%). These changes were accompanied by enhanced carbon fixation and nutrient acquisition. During the compensation phase (fifth generation), S. trochoidea exhibited a unique nitrate-phosphate trade-off, redirecting nitrates to nucleic acid biosynthesis and chlorophyll production while utilizing phosphorus storage for phospholipid synthesis. This strategy resulted in increased residual phosphorus and alternative lipid sources, highlighting a distinct acclimation mechanism compared to other phytoplankton groups. These findings underscore the ecological importance of dinoflagellates in shaping biogeochemical cycles under future ocean scenarios. By revealing their unique adaptive strategies, this study provides essential insights into predicting HAB dynamics and mitigating their ecological and economic impacts. Incorporating these results into predictive models will enhance our ability to forecast bloom events and guide effective marine management strategies, such as nutrient runoff control and habitat restoration, in the context of climate change.
Continue reading ‘Multi generational acclimation of Scrippsiella trochoidea to ocean warming and acidification’Complementary genetic and epigenetic changes facilitate rapid adaptation to multiple global change stressors
Published 1 August 2025 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, molecular biology, multiple factors, otherprocess, temperature, zooplankton
Significance
Organisms must adapt or acclimate to survive global change, but how these processes interact and the role of epigenetic variation is unknown. We experimentally evolved the marine copepod Acartia tonsa for 25 generations in global change conditions and measured their genomic, epigenomic, and gene expression responses. We found that both genetic and epigenetic changes contributed to resilience and were inversely related, acting in different regions of the genome. Epigenetic changes were functionally linked to the regulation of stress and transposable elements and correlated with shifts in gene expression. These findings paint a surprising picture of the complementary contributions of both genetic and epigenetic mechanisms to population resilience in global change conditions.
Abstract
To persist under unprecedented rates of global change, populations can adapt or acclimate. However, how these resilience mechanisms interact, particularly the role of epigenetic variation in long-term adaptation, is unknown. To address this gap, we experimentally evolved the foundational marine copepod Acartia tonsa for 25 generations under ocean acidification, warming, and their combination and then measured epigenomic, genomic, and transcriptomic responses. We observed clear and consistent epigenomic and genomic divergence between treatments, with epigenomic divergence concentrated in genes related to stress response and the regulation of transposable elements. However, epigenetic and genetic changes were inversely related and occurred in different regions of the genome; levels of genetic differentiation (FST) were up to 2.5× higher in regions where methylation did not differ between treatments compared to regions with significant methylation changes. This negative relationship between epigenetic and genetic divergence could be driven by local inhibition of one another or distinct functional targets of selection. Finally, epigenetic divergence was positively, though weakly, associated with gene expression divergence, suggesting that epigenetic changes may facilitate phenotypic change. Taken together, these results suggest that unique, complementary genetic and epigenetic mechanisms promote resilience to global change.
Continue reading ‘Complementary genetic and epigenetic changes facilitate rapid adaptation to multiple global change stressors’Shell dissolution rates differ fourfold between mussel species
Published 1 August 2025 Science ClosedTags: biological response, dissolution, laboratory, mollusks, North Pacific
Ocean acidification poses a critical threat to marine calcifiers globally and is particularly severe in the California Current System, where ecologically and economically important bivalves experience reduced calcification under climate change. Marine mussels display differential habitat preferences, with species like Mytilus californianus favouring fully saline environments and M. trossulus inhabiting sites with greater freshwater input. Determining abiotic dissolution rates of these species under ocean acidification is essential for predicting future consequences of climate change for coastal populations. We examined shell dissolution rates of mussel congeners under a range of pH (6.5–9.3) and aragonite saturation states (0.1–9.0). We also experimentally quantified the relative importance of dissolution from interior versus exterior shell surfaces. M. trossulus exhibited fourfold higher shell dissolution rates than M. californianus. When the shell interior was sealed against seawater exposure, dissolution rates decreased significantly in both species, indicating high abiotic dissolution on the shell interior. Results demonstrate that dissolution rates can vary between congeners inhabiting the same biogeographic region. Our finding that freshwater-tolerant M. trossulus has higher abiotic dissolution under ocean acidification is important because low salinity may further retard calcification, altering future intertidal population structure along freshwater-influenced coastlines.
Continue reading ‘Shell dissolution rates differ fourfold between mussel species’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’Impacts of multiple coastal stressors across life-history stages in the eastern oyster
Published 31 July 2025 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, multiple factors, otherprocess, oxygen, reproduction
Urbanized estuaries are characterized as a complex of biotic and abiotic stressors, which currently challenge marine life and are expected to intensify and become increasingly unpredictable under the ongoing impacts of climate change. The persistence of coastal species that inhabit these stressful environments will ultimately depend on their ability to adapt. Many of these species have complex life cycles, featuring distinct morphological and physiological developmental stages that can exhibit unique responses to environmental pressures. However, since all stages share the same genome, selective pressures acting on one stage can have cascading effects throughout the life cycle. The larval stage, being particularly sensitive to environmental stressors and often the only free-moving stage, plays a crucial role in gene flow across populations. Consequently, selection during this stage can set the trajectory for the entire life cycle and significantly influence the adaptive structure of populations. This dissertation explores the impacts of multiple environmental stressors across the life-history stages of the eastern oyster (Crassostrea virginica). In Chapter 1, we integrated genomic information about larval stressor response into a seascape genomics framework, using adult oysters sampled from various localities with differing environmental profiles in Narragansett Bay, Rhode Island. We identified environmentally driven signatures of local adaptation corresponding to different genomic regions, even amidst high gene flow. In loci putatively under selection in larvae exposed to coastal stressors, we found stressor-specific associations with environmental conditions that aligned with adult candidate loci, highlighting the critical role of the larval stage in shaping population adaptive divergence. In Chapter 2, we exposed genetically diverse pools of larval oysters to diurnal fluctuating acidification and hypoxia for most of their development. Genomic analysis of samples taken before and after exposure revealed substantial shifts in allele frequencies at loci putatively under selection, suggesting a potential for rapid adaptation to future environmental conditions. Chapter 3 extended this work by exposing oysters to these stressors from the pediveliger stage, through settlement, and into early juvenile development. Genomic analysis from the larval and settlement exposure periods revealed both unique and shared signatures of selection across the early developmental stages. While the juvenile stage was more tolerant to the stressor conditions, we found that stressor exposure through the pediveliger larval and settlement stages had short-term carryover effects on juvenile performance. These findings demonstrate the complex connection of evolutionary responses across the full life cycle. While early developmental stages are sensitive to coastal stressors, our analysis reveals adaptive responses that highlight the resilience of this species. Specifically, these early life-stage responses can influence later developmental stages, shaping the species’ overall adaptive capacity and impacting population structure dynamics. Consequently, understanding these dynamics is crucial for predicting how population structure and adaptive divergence will evolve in response to intensifying coastal stressors.
Continue reading ‘Impacts of multiple coastal stressors across life-history stages in the eastern oyster’Effect of acidification on the chronic toxicity of diclofenac to Daphnia magna
Published 28 July 2025 Science ClosedTags: biological response, laboratory, multiple factors, phytoplankton, reproduction, toxicants
Highlights
- Chronic diclofenac (DCF) exposure was tested in Daphnia magna at pH 7.0 and 8.7.
- An unexpected pH increase in M4 medium was observed during the experiment.
- The NOEC (no observed effect concentration) of DCF was 5 mg l-1 at pH 8.7.
- Initial pH 7.0 prolonged the time to release of the first hatchlings.
- At 1.3 mg l-1 DCF, fewer neonates were observed at pH 7.0 than at pH 8.7.
Abstract
Pharmaceuticals, as ionizable compounds, are a challenging group of pollutants to analyze because the pH of the environment can alter its ecotoxicological features. However, changes in the toxicity of pharmaceuticals toward aquatic organisms were observed even when there was no change in the ionization of the molecules with a pH shift. Therefore, we conducted a study that aimed to check how pH influences the chronic toxicity of diclofenac (DCF, pKa ≈ 4.0) toward Daphnia magna at two pH levels, 7.0 and 8.7, where DCF is obtained as relatively polar anion. The performance of the experiment with OECD 211 was found to be challenging because of the medium pH shift during the exposure test. Acidification increased the toxicity of DCF, reducing the number of neonates (at a concentration of 1.3 mg l-1) and showing a tendency towards delayed hatching and reduced number of hatchings. In addition, the acidification itself also changes D. magna reproduction, affecting the number of hatchings and the first day of hatching. We conclude that the pH, as a factor of toxicity modulation for ionizable compounds, needs to be evaluated and presented in scientific protocols.
Continue reading ‘Effect of acidification on the chronic toxicity of diclofenac to Daphnia magna’Ocean acidification impairs growth and induces oxidative stress in the macroalgae Ulva fasciata and Petalonia fascia
Published 22 July 2025 Science ClosedTags: algae, biological response, growth, laboratory, photosynthesis, physiology, South Atlantic
Ocean acidification (OA), driven by increasing anthropogenic CO2 uptake, poses a significant threat to marine ecosystems; understanding the physiological responses of key primary producers like macroalgae is crucial for predicting ecological consequences. This study investigated the impacts of OA on two common intertidal macroalgae, the green alga Ulva fasciata and the brown alga Petalonia fascia, aiming to determine the effects of decreased seawater pH on their relative growth, photosynthetic performance, biochemical composition, and oxidative stress responses. Algae were exposed for 15 days to three pH levels (8.2, 7.4, and 6.5), and measurements included relative growth rate, membrane damage, total chlorophyll, soluble protein and sugar content, chlorophyll a fluorescence parameters, H2O2 content, lipid peroxidation, and activities of superoxide dismutase and catalase. Results showed that decreasing pH significantly reduced RGR in both species, particularly at pH 6.5, with U. fasciata generally exhibiting higher growth. Photosynthetic efficiency and total chlorophyll content declined under lower pH, while non-photochemical quenching generally increased. Both species exhibited increased membrane damage, H2O2 content, and TBARS levels at lower pH, indicative of oxidative stress. Antioxidant enzyme activities were significantly modulated by pH and showed species-specific patterns, with significant interactions between pH and species observed for most parameters. For instance, U. fasciata maintained higher Fv/Fm at pH 6.5, whereas P. fasciata often showed higher antioxidant enzyme activity; soluble protein and sugar contents were also significantly altered. These findings indicate that both Ulva fasciata and Petalonia fascia are susceptible to detrimental effects from simulated OA, suggesting potential shifts in the competitive balance and structure of intertidal macroalgal communities.
Continue reading ‘Ocean acidification impairs growth and induces oxidative stress in the macroalgae Ulva fasciata and Petalonia fascia’Adaptive responses of large yellow croaker Larimichthys crocea to ocean acidification: integrative analysis of gill and kidney transcriptomics and antioxidant enzyme activities
Published 21 July 2025 Science ClosedTags: adaptation, biological response, fish, laboratory, molecular biology, morphology, North Pacific, otherprocess, physiology
Anthropogenic acidification is a long-term challenge to marine ecosystems. Though coastal acidification is intensifying, the large yellow croaker (Larimichthys crocea) exhibits good adaptability to pH fluctuations, the underlying mechanisms of which remain poorly understood. This study investigated the morphology, antioxidant enzyme activity, and gene expression of L. crocea under varying acidification conditions (pH 8.1 (H group), 7.8 (M group), and 7.4 (L group)). Water pH fluctuations were also monitored to explore the physiological responses and potential adaptive molecular mechanisms of L. crocea under various acidified environments. The results indicated that the water pH decreased in the H group, significantly increased in the L group (p < 0.05), and remained stable in the M group during the experiment. The lowest MDA content and the highest antioxidant enzyme activities (CAT, SOD, GSH-Px) were observed in L. crocea at pH 7.8, suggesting pH 7.8 was optimal for L. crocea. Transcriptomic analysis revealed distinct gene expression patterns between the gills and kidneys under acidification stress. Differentially expressed genes (DEGs) in the gills were primarily observed between the M and L groups (62.3%), whereas in the kidneys, the majority of DEGs were observed between the M and H groups (43.2%). These findings suggested that the gills play a critical role in adapting to low pH in L. crocea, while the kidneys were more responsive to high pH. Enrichment analysis identified critical pathways, including vasopressin-regulated water reabsorption, mineral reabsorption, and aldosterone-regulated sodium reabsorption, which are associated with water and ion metabolism. These pathways play a pivotal role in the acid–base homeostasis and metabolism of L. crocea. These results provide insights into the adaptive mechanisms of L. crocea to acidified environments, with implications for aquaculture management and future ocean acidification adaptation.
Continue reading ‘Adaptive responses of large yellow croaker Larimichthys crocea to ocean acidification: integrative analysis of gill and kidney transcriptomics and antioxidant enzyme activities’Adaptation strategy of the planula strobilation in moon jelly, Aurelia coerulea to acidic environments in terms of statolith formation
Published 21 July 2025 Science ClosedTags: adaptation, biological response, cnidaria, laboratory, morphology, North Pacific, otherprocess
Simple Summary
Ocean acidification poses a significant threat to marine invertebrates with calcium-based structures. This study investigated the effects of low pH on two types of strobilation in Aurelia coerulea: polyp-strobilation (conventional asexual reproduction from polyps) and planula-strobilation (direct development from planulae). Experiments were conducted under pH 6.8, 7.8, and 8.1 conditions to observe morphological changes and statolith formation in ephyrae. Under the pH 6.8 condition, polyp-strobilation failed to produce normal ephyrae, while planula-strobilation succeeded in releasing morphologically normal ephyrae, albeit without statoliths. Under the pH 7.8 condition, both strobilation types produced ephyrae with altered statolith morphology. These statoliths were smaller in size but more numerous than those formed at pH 8.1 as normal pH, suggesting a compensatory mechanism that maintains total statolith mass and potentially preserves function. Planula-strobilated ephyrae had fewer but larger, needle-shaped statoliths, suggesting rapid statolith development. These findings suggest that planula-strobilation functions as a stress-adaptive reproductive strategy, producing the minimum necessary morphology and internal structures to ensure survival in a changing environment. The ability of Aurelia coerulea to adjust reproductive strategy and developmental traits under acidified conditions may contribute to its ecological success and persistence under future climate change scenarios.
Abstract
Ocean acidification, caused by increased atmospheric CO2, threatens marine organisms that depend on calcium-based structures such as jellyfish statoliths. This study investigated the effects of low pH on the morphology and statolith formation of ephyrae in Aurelia coerulea, comparing two developmental pathways to form ephyra: polyp-strobilation and planula-strobilation. Under the pH 6.8 condition, polyps failed to produce viable ephyrae, whereas planula-strobilation succeeded in releasing ephyrae with normal morphology, though statoliths were absent. Under the pH 7.8 condition, both strobilation types produced normal-shaped ephyrae with reduced statolith size but increased statolith number compared with the control (pH 8.1), suggesting a compensatory response to acidification. Statolith morphology differed between pathways: planula-strobilated ephyrae had needle-shaped statoliths with high aspect ratios, indicating a rapid, early-stage crystallization process. Despite their minimal body size and statolith development, planula-strobilated ephyrae maintained the functional mass of statoliths necessary for survival. This rapid, morphologically minimized development suggests that planula-strobilation is an adaptive reproductive strategy in response to environmental stress. Our findings suggest that A. coerulea possesses a flexible life history strategy that may facilitate its resilience to ongoing ocean acidification scenarios.
Continue reading ‘Adaptation strategy of the planula strobilation in moon jelly, Aurelia coerulea to acidic environments in terms of statolith formation’Can sclerosponge skeletons record ocean acidification?: boron and carbon isotope ratios (δ11B and δ13C) in Acanthochaetetes wellsi from Okinoerabu Island, southwestern Japan
Published 21 July 2025 Science ClosedTags: biological response, laboratory, methods, North Pacific, paleo, porifera
Boron stable isotope ratios in biogenic calcium carbonate minerals are known to reflect the decreasing of seawater pH, and thus they can be a useful tracer to track the trend of the ocean acidification. While validation of boron isotopes as a tracer for seawater pH has mainly focused on foraminiferal and coral CaCO3, a few studies examined CaCO3 skeletons produced by sclerosponges. In this study, we investigated stable boron and carbon isotope ratios in two sclerosponge specimens (Acanthochaetetes wellsi), collected from Okinoerabu Island, Japan. Carbon isotope ratios in both specimens showed a continuous decrease over the estimated growth periods, indicating that the Suess effect is recorded in sclerosponge skeletons. In contrast, boron isotope ratios in one specimen decreased over time, but not in the other. These findings suggest further analysis of additional specimens is necessary to determine whether boron isotope ratios in sclerosponge skeletons are reliable recorder of ocean acidification.
Continue reading ‘Can sclerosponge skeletons record ocean acidification?: boron and carbon isotope ratios (δ11B and δ13C) in Acanthochaetetes wellsi from Okinoerabu Island, southwestern Japan’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’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’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’Morphological responses of a temperate intertidal foraminifer, Haynesina sp., to coastal acidification
Published 17 July 2025 Science ClosedTags: biological response, dissolution, laboratory, morphology, North Atlantic, protists
Coastal acidification could have widespread impact on marine organisms, affecting the ability of calcifying organisms to build shells and skeletons through calcium carbonate precipitation. As an abundant group of calcifying organisms, some protists within the phylum Foraminifera demonstrate potential success under elevated partial pressure of carbon dioxide (pCO2) due to their ability to modulate intracellular pH. However, little is known about their responses under more extreme acidification conditions that are already seen in certain coastal environments. Here we exposed specimens of Haynesina sp., which belongs to a genus that is prevalent in temperate intertidal salt marshes, to moderate (pCO2 = 2386.05+/−97.14 μatm) and high acidification (pCO2 = 4797.64+/−157.82 μatm) conditions through the duration of 28 days. We demonstrate that although this species is capable of withstanding moderate levels of coastal acidification with little impact on overall test thickness, it can experience precipitation deficiency and even dissolution of the calcareous test under highly elevated pCO2. Interestingly, such a deficit was primarily seen among live foraminifera, as compared to dead specimens, throughout the four-week experiment. This study suggests that a combination of environmental stress and the physiological process of test formation (i.e., calcite precipitation) could induce thinning of the test surface. Therefore, with the acceleration of coastal acidification due to anthropogenic production of CO2, benthic foraminifera and other calcifying organisms among coastal ecosystems could reach a tipping point that leads to thinning and dissolution of their calcareous tests, which in turn, will impair their ecological function as a carbon sink.
Continue reading ‘Morphological responses of a temperate intertidal foraminifer, Haynesina sp., to coastal acidification’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’Combined effects of ocean acidification and warming on phytoplankton productivity and community structure in the coastal water of Southern East
Published 17 July 2025 Science ClosedTags: biological response, community composition, laboratory, mesocosms, molecular biology, multiple factors, North Pacific, otherprocess, photosynthesis, physiology, phytoplankton, temperature
Highlights
- Ocean warming partly offsets acidification-driven impacts on primary productivity in a southern coastal water of China.
- Acidification alters phytoplankton communities with increased proportions of dinoflagellates and reduced that of diatoms.
- Combination of warming and acidification reduced overall microbial diversity in the coastal water.
Abstract
Progressive global ocean changes, including ocean acidification and warming, are expected to impact ecosystems differentially due to regional environmental differences that govern biogeochemical and ecological processes. In this study, we investigated the impacts of ocean acidification and warming on the phytoplankton community and primary productivity in the southern coastal water of the East China Sea by running land-based mesocosms controlled under current atmospheric pCO2 (∼430 μatm) and projected levels for the year 2100 (∼1000 μatm, HC, High CO2) at 27°C (ambient) and 30°C (warming, HT, High Temperature). Our results indicate that warming, acidification, and their combined effects (HCHT) initially enhanced community biomass as determined by chl a concentration; however, this effect diminished over time, ultimately resulting in lower biomass density compared to the control in later stages. Primary productivity per volume of seawater in the HT and HCHT treatments was initially suppressed but increased in the later stages compared to the control group, whereas the HC treatment appeared to suppress it consistently. While higher effective photochemical efficiency and non-photochemical quenching coincided with higher photosynthetic carbon fixation per chlorophyll an under the HT and HCHT treatments, their decline under the HC after the acclimation was concurrent with decreased photosynthetic carbon fixation. Analysis of 18S rDNA revealed that diatoms and dinoflagellates dominated under the treatments of HC, HT, and HCHT, but compared to the control, the proportion of diatoms decreased by 23%, 14%, and6 %, while that of dinoflagellates increased by 19%, 9%, and 11%, respectively, under the corresponding treatments. Plankton richness increased under warming, while diversity declined, particularly with combined warming and acidification, highlighting community sensitivity to the stressors. With reference to heterotrophic microbes, the relative abundance of Basidiomycota increased by 16%–18% under HT or HCHT, along with insignificant impacts on prokaryotic communities based on 16S rDNA analysis. In conclusion, the combination of ocean acidification and warming treatment during the experimental period ultimately reduced the phytoplankton biomass density and altered the microbial community structure.
Continue reading ‘Combined effects of ocean acidification and warming on phytoplankton productivity and community structure in the coastal water of Southern East’
