Ocean acidification (OA), driven by rising atmospheric carbon dioxide (CO2) levels, is a critical issue affecting our oceans. The Eastern Mediterranean Sea (EMS) remains poorly understood in terms of the carbonate system and the impact of OA, despite its key role in Levantine Intermediate Water (LIW) formation and its peculiar characteristics in buffering capacity and ongoing OA. This study provides the first comprehensive spatial and temporal assessment of carbonate system in the North-Eastern Levantine Basin, in EMS, providing essential reference data for Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), and Anthropogenic Carbon (CANT). The mean TA of the measurements was 2622.11 μmol/kg, with higher surface values in summer, reflected also in the surface salinity (S) maximum caused by strong evaporation. A clear vertical gradient was observed, with TA decreasing with depth. Hot and dry meteorological conditions contribute to increased S and TA, resulting in seasonal and vertical variations in the water column. The mean DIC of the measurements was 2291.23 μmol/kg. In contrast to the observations for TA, surface DIC values were higher in winter than in summer. The higher DIC values in winter are attributed to thermodynamic equilibrium and vertical mixing in the surface waters. This study has also investigates the presence of CANT, has infiltrated deep layers, with a mean concentration of 52.07 μmol/kg, decreasing significantly throughout the water column. These findings confirms the ongoing influence of human activities on intermediate and deep layers in EMS. To reconstruct past carbonate system dynamics, the relationships of TA and DIC were determined with salinity (S) and temperature (T) data. Long-term data from METU-IMS Erdemli Time Series (ETS) stations, collected monthly for a decade, provided valuable findings into seasonal patterns and temporal shifts in TA, DIC, and pH. The coastal station displayed clear trends in the carbonate system over time, reflecting its sensitivity to local environmental changes. In contrast, the offshore station exhibited minimal variability, indicating greater stability against seasonal and long-term fluctuations. These results highlight the heightened vulnerability of coastal waters to carbonate system changes, while offshore waters remain more stable. Understanding carbonate chemistry and acidification levels is crucial for assessing impacts on marine life. In addition to the characterization of carbonate chemistry, this study also explores OA’s biological impacts on two key organisms of the Mediterranean ecosystem: phytoplankton and mussels. Firstly, effects of elevated CO₂ on phytoplankton, an essential primary producer in aquatic food webs and global biogeochemical cycles are explored. Specifically, the study explores the impacts on phytoplankton physiology, focusing on growth rates, respiration, and photopigment content in selected species from the coccolithophores, dinoflagellates, and diatoms groups. While growth rates and respiration remained relatively stable under reduced pH conditions, photopigment content was significantly influenced by changes in seawater pH, highlighting the importance of considering environmental influences on photopigment composition. The study further investigated the effects of acidification on calcifying organisms through a global program aimed at understanding the long-term effects of acidification on key seafood species and exploring adaptation strategies with a collaborative approach. This study focused on the long-term (6 months long experiment) physiological impacts of OA on marine calcifiers, specifically Mediterranean mussel, Mytilus galloprovincialis, an abundant species and one of the most consumed non-fish marine species in Türkiye. Results indicate that OA poses a substantial threat to mussel health and survival. Reduced pH levels negatively impacted survival rates, while other physiological parameters like clearance rate, condition index, respiration, and the distribution of a radionuclide, 210Po, did not significantly change. However, lipid content and immune response were affected. Oxygen consumption decreased over time, especially at lower pH. This study underscores the potential risks of OA to the fitness of the commercially important mussel species, indicating that future OA may impact both this key seafood species and its associated ecosystems. The established baseline data are crucial for future monitoring and provide valuable insights into the vulnerability of marine organisms and ecosystems to ongoing OA. By integrating chemical, biological, and ecological perspectives, this dissertation offers a comprehensive assessment of OA in EMS. It establishes baseline data for carbonate system variables, revealing distinct spatial and temporal variations influenced by S, T, and mixing processes. By linking changes in carbonate chemistry to physiological responses in primary producers and a commercially vital shellfish species, this study highlights the ecological and economic impacts of OA in EMS. The findings emphasize the need for continued research and mitigation efforts to protect marine ecosystems and commercially important species. This integrated approach provides valuable insights into the vulnerability of marine organisms and ecosystems to ongoing OA, underscoring the significance of this research for the Mediterranean Sea.
Continue reading ‘Ocean acidification and anthropogenic carbon in the Eastern Mediterranean Sea and the effects of acidification on marine organisms’Posts Tagged 'mortality'
Ocean acidification and anthropogenic carbon in the Eastern Mediterranean Sea and the effects of acidification on marine organisms
Published 15 January 2026 Science ClosedTags: biological response, chemistry, field, fisheries, growth, laboratory, Mediterranean, mollusks, mortality, photosynthesis, physiology, phytoplankton, respiration
Acute CO2 toxicity and the effects of seawater acidification on health status, histopathology, immunity and disease resistance in Asian Seabass (Lates calcarifer)
Published 12 January 2026 Science ClosedTags: biological response, fish, laboratory, molecular biology, mortality, physiology, reproduction
Carbon dioxide capture and storage (CCS) is a technology that can be used to reduce carbon dioxide (CO2) emissions generated by both natural and anthropogenic industrial processes, particularly petroleum production. To mimic and investigate the effects of CO2 leakage that may result from CCS, the acute toxicity of seawater acidification induced by continuous CO2 injection was studied in Asian seabass (Lates calcarifer) fry under static bioassay conditions. Fry (0.828 ± 0.22 g) were exposed to seawater with different pH levels (5.5, 6.0, 6.5, 7.5, and 8.3). Rapid and 100% mortality within 15 min was observed in the pH 5.5 exposure group, while mortality rates ranging from 10.00–41.67% were recorded at 6–96 h in the pH 6.0 exposure group; no mortality was noted in the other pH exposure groups. According to these mortality data, the median lethal concentration at 96 h (96 h LC50) was determined to be a pH of 5.884. Interestingly, after exposure to seawater with pH levels of 5.5 and 6.0, histopathological alterations in the skin, gills, trunk kidney and liver were evident. Additionally, some water quality parameters, especially dissolved oxygen (DO) levels, alkalinity, ammonia levels, and nitrite levels, vary depending on the pH. To further investigate the effects of seawater with pH levels of 8.3 and 5.884 (96 h LC50) and 6.5 (10% safety level) on health status, immune responses and disease susceptibility, fingerling fish (21.25 ± 3.89 g) were studied. Unexpectedly, fish exposed to seawater with a pH of 5.884 rapidly lost muscle control and gradually died, reaching 100% mortality within 24 h, and all response analyses were aborted. Interestingly, with the exception of hematocrit and some immune parameters, various serum innate immune indices, blood biochemistry parameters and immune-related gene expression patterns were similar in fish exposed to seawater with pH levels of 8.3 and 6.5. Additionally, fish were challenged with 0 (control), 1 × 107 and 1 × 109 CFU/mL Vibrio vulnificus, and fish in seawater with a pH level of 6.5 showed a higher sensitivity to 1 × 109 CFU/mL Vibrio vulnificus than fish in seawater with a pH level of 8.3, with mortality rates of 71.24% and 25.44%, respectively (p < 0.05). These findings enhance the understanding of the toxicity effects of seawater acidification caused by CO2, which will be useful for further assessing the site-specific effects of CCS projects.
Continue reading ‘Acute CO2 toxicity and the effects of seawater acidification on health status, histopathology, immunity and disease resistance in Asian Seabass (Lates calcarifer)’Strength and duration of diel pH and dissolved oxygen cycles control the survival and performance of early life stage North Atlantic bivalves (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians and Mytilus edulis)
Published 9 January 2026 Science ClosedTags: biological response, growth, laboratory, mollusks, mortality, multiple factors, North Atlantic, oxygen, physiology, reproduction, respiration
Highlights
- Cycling from nocturnal hypoxia – acidification to mild hyperoxia- hypocapnia reduced larval survival in all experiments.
- Cycling from nocturnal hypoxia – acidification to normoxia- normocapnia reduced survival of larvae in 50 % of experiments.
- Nocturnal hypoxia and acidification caused increased clearance and respiration rates in juvenile mussels.
- The impacts of diel DO and pH cycles on early life stage bivalves depend on cycle duration, cycle intensity, and species.
Abstract
Many economically important bivalves spawn during the summer months when diel cycles of dissolved oxygen (DO) and pH occur in estuaries. Little is known, however, regarding how cycles of differing durations and magnitudes affect these organisms. Here, larval bivalves (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians) and juvenile mussels (Mytilus edulis) were exposed to cycles of low DO and pH of varying duration (4-, 6-, 8-, and 12-h) and strength (moderate: DO range ∼ 6 mg L−1, pH range ∼ 0.6 and severe: DO range ∼ 10 mg L−1, pH range ∼ 0.9) compared to positive (normoxic and normocapnic) and negative (hypoxic and acidified) static controls. Growth, survival, respiration and clearance rates were measured. During experiments, 12 h of nocturnal hypoxia and acidification coupled with mildly hyperoxic (∼11.3 mg L−1 DO) and hypocapnic (∼8.13 pH) conditions by day significantly reduced survival in larval C. virginica, M. mercenaria, and A. irradians in all experiments (p < 0.05), while 12 h of nocturnal hypoxia and acidification without hyperoxic and hypocapnic conditions did so in only half of experiments indicating that hyperoxia and hypocapnia were additional and significant stressors. Six hours of low DO/pH significantly reduced survival in only 16 % of experiments, indicating that larval bivalves are more impacted by longer duration and greater magnitude cycles of DO and pH compared to cycles of shorter duration or lower magnitude. Across species, M. mercenaria larvae were more resilient to nocturnal hypoxia and acidification than A. irradians and C. virginica. The growth and survival of juvenile M. edulis were unaffected by nocturnal hypoxia and acidification but mussels experienced significantly increased clearance and respiration rates under these conditions (p < 0.01) evidencing physiological mechanisms for coping with these stressors. Collectively, this study demonstrates that the impacts of diel DO and pH cycles on early life stage bivalves are dependent upon cycle duration, cycle intensity, bivalve life stage, and bivalve species.
Continue reading ‘Strength and duration of diel pH and dissolved oxygen cycles control the survival and performance of early life stage North Atlantic bivalves (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians and Mytilus edulis)’Effect of experimental seawater acidification on the prooxidant-antioxidant system of the Pacific oyster Magallana gigas (Thunberg, 1793) under normoxic and hypoxic conditions
Published 8 January 2026 Science ClosedTags: biological response, Black Sea, fisheries, laboratory, mollusks, mortality, multiple factors, oxygen, physiology
Highlights
- Lipid peroxidation in oyster gills was enhanced during exposure to acidification + hypoxia.
- SOD and GPx activities changed in gills and hepatopancreas, while CAT activity unchanged in both.
- Water acidification does not promote DNA strand breaks in hemocytes of M. gigas.
- Acidification + hypoxia more severe damaging than acidification under normoxia.
Abstract
Bivalve mollusks, particularly the Pacific oyster (Magallana gigas), are both environmentally and commercially significant species that live in coastal waters and may be affected by global climate change factors including hypoxia and acidification. In this study, we investigated the impact of acidification in combination with normoxia and hypoxia on oxidative stress markers in the gills and hepatopancreas of M. gigas oysters. Oysters were collected from a shellfish farm and subjected to acidified conditions (pH 7.3 ± 0.05) in combination with either normoxic (8.0 ± 0.3 mg/L O2) or hypoxic (2.0 ± 0.3 mg/L O2) conditions for an 8-day period. Changes of DNA damage levels, reactive oxygen species (ROS) production in hemocytes, as well as antioxidant enzyme activities (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx)) and lipid peroxidation in the gills and hepatopancreas were evaluated. Additionally, the mortality rate in experimental groups was monitored throughout the experiment. Our results showed that lipid peroxidation in gills was enhanced during prolonged acidification in combination with hypoxia (6–8 days). We observed rapid and consistent changes in SOD and GPx activity in gills and hepatopancreas. CAT activity remained stable in both tissues. The results of the study indicate that acidification was shown to induce oxidative stress in oysters. Combination of acidic environment to hypoxia had a more severe effect on oysters compared to acidification under normal oxygen conditions, leading to their death after 8 days of exposure.
Continue reading ‘Effect of experimental seawater acidification on the prooxidant-antioxidant system of the Pacific oyster Magallana gigas (Thunberg, 1793) under normoxic and hypoxic conditions’Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH
Published 2 January 2026 Science ClosedTags: biological response, crustaceans, growth, laboratory, mortality, multiple factors, reproduction, temperature, zooplankton
Cirolanid isopods play important ecological roles as predators and scavengers, but when populations increase, they can form swarms that attack fish and humans. Understanding how the reproduction of cirolanid isopods will be affected by future warmer and more acidic oceans is therefore important. Samples of the viviparous species Cirolana harfordi were held in 4 combinations of 2 temperatures (18 and 24°C) and 2 pH levels (7.7 and 8.1), and the development of embryos and mancas was investigated by microscopic examination of each pregnant female through the transparent ventral cuticle of their thorax. Higher temperature increased the rate of development, thereby reducing pregnancy duration and accelerating the growth of mancas postpartum. By contrast, increased acidity had no significant effect on these parameters and had no deleterious effects on the development of the mancas. Higher temperature did not have a significant effect on the number of postpartum mancas after the 22 weeks that the adults spent in treatments. Increased temperature and/or lowered pH had no effect on the adult survival or growth. These data are in keeping with the hypothesis that C. harfordi may be able to withstand future warmer and more acidic oceans. Longer-term studies are needed to determine whether decreasing pregnancy durations in higher temperatures increases the number of times females can become pregnant over their lifetime, potentially leading to greater population numbers.
Continue reading ‘Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH’Shell proteome plasticity assists oyster larval biomineralization in adverse carbonate chemistry
Published 30 December 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, physiology, reproduction
Bivalve planktonic development is a critical phase during which larvae must secrete the first calcium carbonate shell, the prodissoconch I (PD I). As PD I formation is in close contact with seawater, this process can be negatively affected by adverse seawater carbonate chemistry. It is hypothesized that bivalves can regulate shell formation under environmental stress through biologically controlled biomineralization involving a complex extracellular shell proteome. However, the plasticity of this regulatory mechanism during PD I development is unknown. We assessed the PD I shell proteome of the Hong Kong oyster (Magallana hongkongensis) in carbonate chemistry that was adverse or favorable for biomineralization to understand the regulatory capacity of larval shell formation. While survival rates were not affected in adverse carbonate chemistry, there were significant changes, including the upregulation of several calcium-binding proteins and downregulation of proton-generating processes and putative calcification inhibitors. With 198 sequences, the oyster larval shell proteome was twice to over six times larger than those reported for other bivalve species at the same developmental stage. However, in adverse carbonate chemistry, the oyster larval shells were thinner and smaller, and protein diversity decreased to 131 sequences, with overall lower functional redundancy and reduced expression of structural proteins, indicating potential trade-offs. The proteomic and shell structural data also suggest that direct cellular control and biologically induced mechanisms, which will require further investigation, may be involved in PD I formation.
Continue reading ‘Shell proteome plasticity assists oyster larval biomineralization in adverse carbonate chemistry’Ocean acidification reduces juvenile snow crab, Chionoecetes opilio, survival but does not affect growth or morphometrics
Published 18 December 2025 Science ClosedTags: biological response, crustaceans, laboratory, morphology, mortality, North Pacific, reproduction
Highlights
- Snow crab were reared at 3 pHs for 396 days.
- Low pH did not affect size at molt.
- Low pH did not affect intermolt period.
- Survival was lower at a pH of 7.5 than at ambient or pH 7.8.
- Snow crab are moderately sensitive to ocean acidification.
Abstract
Anthropogenic release of CO2 and its subsequent dissolution in the oceans results in a decrease in the pH of seawater, known as ocean acidification, which can negatively affect marine organisms. Little is known about the response of snow crab, Chionoecetes opilio, to reduced pH. Juvenile snow crab were captured in the Bering Sea and exposed to three different pH treatments (Ambient (pH ∼7.95), pH 7.8, and pH 7.5) for 396 days at a constant temperature of 4 °C with thirty crabs randomly assigned to each treatment. Crabs were checked daily for molting or mortality. Wet mass and carapace morphometrics were measured after every molt. Reduced pH did not affect the intermolt duration, the carapace width after each molt, or wet mass of the crabs after each molt, giving no indication that growth rate was changed by reduced pH. There also was no change in morphometrics caused by reduced pH. However, the mortality rate of crabs held at pH 7.5 was 40 % higher than those held at pH 7.8 or Ambient. Such a substantial increase in mortality without accompanying sublethal effects is surprising; individuals susceptible to reduced pH might have died early in the experiment, or that differences in growth rate might have become apparent with longer exposure. Regardless, juvenile snow crab are somewhat sensitive to ocean acidification, although, consistent with studies at other life-history stages, snow crab may be more resistant to changes in pH than other Alaska crab species.
Continue reading ‘Ocean acidification reduces juvenile snow crab, Chionoecetes opilio, survival but does not affect growth or morphometrics’A global meta-analysis reveals consistently negative effects of ocean acidification on marine cultured bivalves: implications for future bivalve aquaculture
Published 16 December 2025 Science ClosedTags: biological response, calcification, fisheries, growth, mitigation, mollusks, mortality, performance, physiology, reproduction, review
The exponential rise in atmospheric CO₂ driven by human activities is accelerating climate change and causing ocean acidification (OA). While the effects of elevated CO₂ on a wide range of marine species have been well documented, the implications of OA for bivalve aquaculture have received comparatively little attention. Using a multi-level meta-analytical approach, we evaluated the impacts of two elevated pCO₂ levels—classified as high and extreme—on cultured bivalves, based on 266 observations from 24 species across tropical and temperate regions. Overall, both elevated pCO₂ levels negatively affected bivalves, reducing survival, growth, feeding rates, development, and calcification. Larvae were generally more vulnerable than juveniles and adults. Our analyses further indicated that temperate bivalves were more sensitive to OA than tropical and subtropical counterparts. Among taxa, clams were the most vulnerable under high CO₂ emission scenarios, whereas scallops were the most sensitive under extreme pCO₂ levels. We also discuss potential mitigation strategies for the bivalve aquaculture industry. With advancements in local and regional monitoring, coupled with targeted measures such as buffering sites, selective breeding, and integrated multi-trophic aquaculture, the adverse effects of OA on bivalve farming could be mitigated.
Continue reading ‘A global meta-analysis reveals consistently negative effects of ocean acidification on marine cultured bivalves: implications for future bivalve aquaculture’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’Acidification-mediated perturbations of developmental pathways and life-stage transitions in Artemia salina
Published 27 November 2025 Science ClosedTags: biological response, crustaceans, fisheries, laboratory, mortality, reproduction
Projected increases in atmospheric carbon dioxide are anticipated to induce a 0.3–0.5 unit decline in oceanic pH by the year 2100, posing a significant threat to marine ecosystems. This study investigated the sub lethal effects of simulated ocean acidification on the ontogenetic success of Artemia salina, a key trophic link in aquaculture systems. A controlled, in vitro experiment employing a Completely Randomized Design (CRD) was conducted, maintaining constant temperature, salinity, and dissolved oxygen. Embryonic development and larval survival were assessed across a gradient of pH levels, representing projected future ocean acidification scenarios. Preliminary data indicate a negative correlation between decreasing pH and both hatching success and larval survivorship. Further investigations are warranted to elucidate the long-term ecological consequences of ocean acidification on Artemia salina populations and their role in aquaculture.
Continue reading ‘Acidification-mediated perturbations of developmental pathways and life-stage transitions in Artemia salina’Mothers know best: maternal signaling boosts larval resilience under ocean acidification conditions
Published 12 November 2025 Science ClosedTags: adaptation, biological response, fisheries, molecular biology, mollusks, morphology, mortality, otherprocess, physiology, reproduction
Highlights
- Environmental priming effectively rescued larval phenotype under OA conditions.
- Egg ‘omics were investigated to elucidate mechanism of priming across generations.
- Clam egg lipidomes were largely unperturbed by maternal low-pH exposure.
- Differentially expressed genes were identified in eggs of low-pH primed clams.
Abstract
Bivalve aquaculture is a growing sector worldwide, producing sustainable animal protein to meet growing demand from consumers. Yet, the industry remains vulnerable to environmental changes that can impact their product across life stages, especially at the larval stage. Parental priming, or the exposure of broodstock to adverse environmental conditions as they undergo gametogenesis, holds promise as a method to increase resilience in bivalve offspring. We exposed Manila clam (Ruditapes philippinarum) broodstock to low pH conditions (pH 7.4 for 78 days during gametogenesis). Larvae were produced from primed (low pH) and unprimed (ambient pH) broodstock and exposed to ambient or low pH conditions in a full factorial design. Larval phenotype in response to low pH was partially rescued by broodstock priming: larvae from low pH-exposed broodstock had better survival and growth than larvae from broodstock held under ambient conditions. Clam egg lipidomic and transcriptomic analyses were performed to determine the physiological differences associated with broodstock environmental conditions. Egg lipid abundance profiles were not significantly different between parental treatments. The egg transcriptome revealed 48 differentially expressed transcripts associated with parental environmental conditions. These genes are involved in important processes for early larval physiology, including metabolism, cell cycle, and transcriptional regulation. Broodstock clams were minimally impacted by their exposure to low pH for 78 days, however we show here that subtle maternal signals may contribute to the vastly improved larval performance observed under low pH conditions.
Continue reading ‘Mothers know best: maternal signaling boosts larval resilience under ocean acidification conditions’Impact of crustose coralline algae, ocean acidification, and ocean warming on larval pinto abalone settlement and juvenile survival
Published 11 November 2025 Science ClosedTags: algae, biological response, BRcommunity, communityMF, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, reproduction, temperature
Highlights
- Ocean acidification reduced pinto abalone settlement and survival in the hatchery.
- Ocean acidification is likely a greater threat than warming to Washington pinto abalone.
- Use of a natural settlement inducer improves abalone settlement and survival.
- Coralline algae may improve survival of pinto abalone under ocean acidification.
Abstract
Since 1994, Washington State (USA) has experienced a 97 % drop in the native pinto abalone population. Since 2007, conservation aquaculture initiatives have been underway to return the population to a self-sustaining level. Successful restoration, however, depends on both the ability to successfully raise juveniles in hatchery settings and the capacity of outplanted pinto abalone to survive and reproduce in the wild as threats of ocean acidification and warming continue to increase. Crustose coralline algae (CCA) can play an important role in restoration efforts by acting as natural inducers of larval settlement. Additionally, studies have shown that CCA can create a boundary layer with elevated pH, potentially providing a refuge for benthic species. We examined the settlement of pinto abalone under different environmental conditions (7.90 pH/14 °C (ambient), 7.90 pH/18 °C, 7.55 pH/14 °C; and 7.55 pH/18 °C) using two substrates: CCA-covered rocks and clean rocks with GABA (a chemical settlement inducer). Low pH negatively impacted larval settlement. Though settlement was higher with CCA than with GABA, this difference was not statistically significant. Juvenile survival was negatively impacted by low pH, but positively impacted by CCA presence, demonstrating the potential of CCA to increase juvenile pinto abalone survival and ameliorate the negative effects of low pH. Using CCA in hatchery culture and selecting sites with CCA cover for pinto abalone outplants may improve the efficiency of restoration in Washington.
Continue reading ‘Impact of crustose coralline algae, ocean acidification, and ocean warming on larval pinto abalone settlement and juvenile survival’DNA methylation plasticity drives copepod resilience to coastal high pCO2 and cadmium pollution under multigenerational exposure
Published 20 October 2025 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, metals, molecular biology, mortality, multiple factors, North Pacific, otherprocess, reproduction, zooplankton
Highlights
- Fluctuating acidification caused the most Cd multigenerational toxicity in copepods.
- The adverse effects of acidification and Cd tended to intensify during F1-F3.
- The copepods potentially adapted to combined exposure in F4.
- DNA hypomethylation rendered copepods presenting the adaptive potential.
ABSTRACT
The vast majority of coastal organisms have been facing multigenerational scenarios of fluctuatingly high pCO2 and Cd pollution in their natural habitats. However, the adaptive capacity of these organisms to such combined stressors and the underlying mechanisms remain poorly understood. In this study, we conducted a multigenerational experiment (F1-F4) to investigate the adaptive responses of the marine copepod Tigriopus japonicus to combined fluctuatingly high pCO2 and Cd exposure, along with the associated mechanisms. Our findings revealed that steady high pCO2 aggravated Cd multigenerational toxicity, and it was more under fluctuating acidification. Notably, by the F4 generation, copepods potentially adapted to the combined stressors. Through transcriptomic and DNA methylation analyses of copepods from the F1 and F4 generations, we found that under combined exposure, F1 copepods likely reallocated more energy to counteract Cd toxicity; however, DNA hypermethylation inhibited Cd exclusion and detoxification/stress response pathways, ultimately compromising development and reproduction. In contrast, in the F4 generation, DNA hypomethylation enhanced processes such as cuticle repair program, compensatory mechanism (e.g., detoxification and immune response), and reproduction, consequently increasing the copepod’s fitness. These findings reveal an epigenetic basis for phenotypic acclimatization, offering marine copepods a supplementary mechanism to cope with combined stressors.
Continue reading ‘DNA methylation plasticity drives copepod resilience to coastal high pCO2 and cadmium pollution under multigenerational exposure’Can ocean acidification alleviate carbon deficiency in eelgrass Zostera marina clonal ramets under conditions of nutrients, sulfate and ocean acidification?
Published 16 October 2025 Science ClosedTags: biological response, laboratory, mortality, multiple factors, North Pacific, nutrients, phanerogams, physiology
Highlights
- The ratio of Chl a/b is reduced by the interaction between CO2 and NO3-N.
- The interaction between CO2 and NO3-N reduces the soluble sugar contents in leaves.
- CO2 promotes the content of soluble protein in leaves while reduces that in roots.
- CO2 reduces both the SOD activities of the rhizomes and the eelgrass mortality rate.
- Eelgrass has complex carbon supply and conversion mechanisms to ensure its survival.
Abstract
Carbon deficiency in the eelgrass caused by nutrient eutrophication and high concentrations of sulfate causes eelgrass mortality; however, ocean acidification provides sufficient carbon. Thus, it is inferred that ocean acidification might reduce the carbon deficiency. To verify this hypothesis, eelgrass clonal ramets were exposed to 72—h combined conditions of ocean acidification (CO2), nitrate (NO3-N), ammonia (NH4-N), phosphate (PO4-P) and sulfate (SO4-S). The pigment contents were affected by nutrients; however, the Chl a/b ratio was inhibited by the interaction between CO2 and NO3-N and was promoted by interaction between NO3-N and NH4-N. The soluble protein contents in leaves were increased by CO2; however, the soluble protein contents in roots were reduced by CO2. The soluble sugar contents in the leaves had negatively correlation with the interaction between NO3-N and CO2. Moreover, the SOD activities of the rhizomes were inhibited by CO2. All these findings suggest that ocean acidification does not seem to effectively alleviate the deficiency of soluble carbon in eelgrass under eutrophication and high concentrations of sulfate; however, the eelgrass mortality rate was inhibited by CO2 and the interaction between PO4-P and SO4-S. Thus, eelgrass has extremely complex carbon supply and conversion mechanisms to ensure its survival under composite conditions or eelgrass has another mechanism of death in eutrophication.
Continue reading ‘Can ocean acidification alleviate carbon deficiency in eelgrass Zostera marina clonal ramets under conditions of nutrients, sulfate and ocean acidification?’The impact of an early exposure to 17α-ethynylestradiol on the physiology of the three-spined stickleback (Gasterosteus aculeatus) under current and future climatic scenarios
Published 9 October 2025 Science ClosedTags: biological response, fish, laboratory, molecular biology, morphology, mortality, multiple factors, reproduction, temperature, toxicants
Highlights
- RCP8.5 scenario modulated some of the long-lasting physiological responses to EE2.
- RCP8.5-EE2 group led to sex and tissue specific responses.
- RCP8.5-EE2 scenario resulted in lower body length at five months post-contamination.
- RCP8.5 reduced survival rate of embryo-larval but not juvenile stages.
- Early-life exposure to EE2 led to stickleback feminisation.
- Early-life exposure to EE2, led to long-lasting effect on stickleback physiological responses.
Abstract
Ocean warming and acidification are climate change related drivers that impact the physiology of marine organisms and their ability to cope with future environments. Marine ecosystems are also facing pollution from an ever-growing diversity of chemical contaminants, including endocrine disruptors. A common example is the 17α-ethynylestradiol (EE2), which can affect the endocrine regulation of fish and hence potentially impact their fitness. Thus, fish have to cope to multiple climatic and chemical stresses that can interact, influencing the overall impact on fish physiology. In this study, we investigated whether the direct and carry-over effect of early exposure to EE2 (15 ng.L−1; one month during embryo-larval development) are modulated by the RCP8.5 scenario (+3°C; -0.4 pH unit). Five months post-contamination, we measured survival, growth and reproductive axis of prepubertal sticklebacks. Our findings revealed that the survival of juveniles, when exposed to EE2 during early development, is reduced under Current but not RCP8.5 scenario. Furthermore, under RCP8.5-EE2, a significantly lower body length was observed. Sex and tissue specific responses in terms of the expression profiles of genes related to development and sexual maturation was reported. Interestingly, significant interaction between RCP8.5 and EE2 was observed for the expression of ovarian aromatase (cyp19a1a), suggesting a long-lasting estrogenic effect under RCP8.5 scenario. Additionally, the skewed sex ratios and the presence of intersex individuals in both scenarios early exposed to EE2 suggested a feminization due to EE2, which could potentially disrupt sexual maturation and future reproduction. Hence, the early EE2 exposure had carry-over physiological effects on sticklebacks, and these effects can be modulated by the climate scenario. This underscores the importance of conducting long-term multi-stress studies to comprehensively understand the vulnerability on fish populations in future environments.
Continue reading ‘The impact of an early exposure to 17α-ethynylestradiol on the physiology of the three-spined stickleback (Gasterosteus aculeatus) under current and future climatic scenarios’Thermal and acidification gradients reveal tolerance thresholds in Pocillopora acuta recruits
Published 1 October 2025 Science ClosedTags: biological response, corals, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, reproduction, temperature
Ocean warming and acidification are among the biggest threats to the persistence of coral reefs. Organismal stress tolerance thresholds are life stage specific, can vary across levels of biological organisation and also depend on natural environmental variability. Here, we exposed the early life stages of Pocillopora acuta in Kāne‘ohe Bay, Hawai‘i, USA, a common reef-building coral throughout the Pacific, to projected ocean warming and acidification scenarios. We measured ecological, physiological, biomineralisation and molecular responses across the critical transition from larvae to newly settled recruits following 6 days of exposure to diel fluctuations in temperature and pH in Control (26.8°C–27.9°C, 7.82–7.96 pHTotal), Mid (28.4°C–29.5°C, 7.65–7.79 pHTotal) and High conditions (30.2°C–31.5°C, 7.44–7.59 pHTotal). We found that P. acuta early life stages are capable of survival, settlement and calcification under all scenarios. The High conditions, however, caused a significant reduction in survival and settlement capacity, with changes in the skeletal fibre deposition patterns. Although there was limited impact on the expression of biomineralisation genes, exposure to High conditions resulted in strong transcriptomic responses including depressed metabolism, reduced ATP production and increased activity of DNA damage-repair processes, indicative of a compromised metabolic state. Collectively, our findings demonstrate that coral juveniles living in environments with large diurnal fluctuations in seawater temperature and pH, such as Kāne‘ohe Bay, can tolerate exposure to moderate projected increased temperature and reduced pH. However, under more severe environmental conditions, significant negative effects on coral cellular metabolism and overall organismal survival jeopardise species fitness and recruitment.
Continue reading ‘Thermal and acidification gradients reveal tolerance thresholds in Pocillopora acuta recruits’Selective breeding boosts oyster resilience to ocean acidification via energy budget modulation
Published 12 September 2025 Science ClosedTags: biological response, fisheries, growth, laboratory, mitigation, mollusks, mortality, North Pacific, physiology
Natural pH variability in coastal-estuarine systems exacerbates OAX events through frequent pCO2 spikes, posing severe threats to bivalves and ecosystems they support. While selective breeding has improved growth performance in oysters, its capacity to enhance tolerance to acidic stress remains poorly understood. Here, we evaluated the physiological performance of wild and recently selectively bred oyster variety (Guihao No. 1) under the simulation of recurrent OAX scenarios. In comparison to wild oysters, selectively bred oysters exhibited significantly higher survival rates, fast shell growth, and improved condition index. Energy metabolism suggests that selective breeding confers enhanced stress resilience in oysters by optimizing feeding capacity, increasing oxygen uptake, and reducing ammonia excretion rates. This metabolic efficiency supports more effective protein and glycogen turnover, as evidenced by elevated O:N ratios, and ultimately results in higher SFG. PCA analysis demonstrated that enhanced energy metabolism (CMA, NKA), antioxidant capacity (low MDA), and immune activity (high ACP, AKP) contributed to improved growth and resilience of selectively bred oysters when exposed to OAX, whereas wild oysters showed metabolic suppression and oxidative damage. These results highlight the role of selective breeding in promoting stress tolerance through optimized energy allocation and defense mechanisms, offering valuable guidance for climate-resilient oyster aquaculture in acidifying oceans.
Continue reading ‘Selective breeding boosts oyster resilience to ocean acidification via energy budget modulation’No effect of ocean acidification on individual-level variation in behaviour and susceptibility to predation in a Great Barrier Reef damselfish
Published 9 September 2025 Science ClosedTags: biological response, fish, laboratory, mortality, performance, South Pacific
1) Ocean acidification, caused by rising carbon dioxide (CO2) in the atmosphere, has been reported to negatively impact a wide variety of behaviours in fishes, including activity, exploration, and predator avoidance.
2) These effects have been documented at the population level, but many animal species naturally show large and repeatable individual-level differences in behaviour. How environmental stressors, such as ocean acidification, affect behavioural variation at the individual level remains largely unknown but is critically important to understand adaptation given natural selection operates on variation at the individual rather than population level.
3) Using a statistical approach allowing variation in means and variation in variance to be modeled within a single framework, we quantified individual-level differences across five behaviours in the coral reef damselfish Pomacentrus amboinensis (emergence time, activity level, time spent sheltering, thigmotaxis, novel object inspection). We measured behaviour in a novel environment assay, twice before (CO2 ~450 µatm) and twice following acclimation to predicted end-of-century ocean acidification conditions (~1,100 µatm).
4) Following behavioural assays, we tested individual survival in a live predation experiment. We used predatory rock cod, Cephalopholis microprion, acclimated to the same CO2 treatments as Ambon damsel and examined predictors of survival probability.
5) All behaviours in damselfish were moderately and significantly repeatable, with no marked differences in repeatability estimates between the ambient CO2 and elevated CO2 treatment groups. Exposure to end-of-century ocean acidification conditions had no effect on any of the five behaviours measured, both in terms of group means and residual (within-individual) variance.
6) The probability of survival in the predation trials was similar for damselfish in the elevated and ambient CO2 treatment groups. Smaller damselfish as well as those that spent a greater amount of time inspecting a novel object (i.e., bolder individuals) had a lower probability of survival regardless of their CO2 treatment.
7) Our results challenge assumptions about the impacts of ocean acidification on coral reef fish behaviour and susceptibility to predation, both at the population and individual level. They also provide support for a trade-off between boldness and predation risk in fish.
Continue reading ‘No effect of ocean acidification on individual-level variation in behaviour and susceptibility to predation in a Great Barrier Reef damselfish’Impacts of ocean acidification on survival of the brown mussel (Perna perna) in Brazil
Published 27 August 2025 Science ClosedTags: adaptation, biological response, fisheries, growth, laboratory, mollusks, morphology, mortality, otherprocess, South Atlantic
The impacts of ocean acidification (OA) on seafood are recognized globally as a major threat, and OA is explicitly mentioned in the United Nations 2030 Agenda for Sustainable Development. One target of Goal 14 (SDG 14.3), life below water, is to minimize and address the impacts of OA using all levels of scientific cooperation. In 2018, the International Atomic Energy Agency launched a Coordinated Research Project (CRP), which gathered researchers from 13 different countries and aimed to evaluate the quantitative and qualitative impacts of OA on seafood. The Brazilian brown mussel Perna perna (Linné, 1858) was selected as the target species for these experiments. Low pH can disrupt the life cycle, affect survival and growth rates, and lead to a decline in mussel populations over time. Based on an agreed protocol within the CRP network, brown mussels were exposed to pH scenarios covering the present and future range of pH variability at the sampling site. The impacts on mortality, growth rate, and morphological parameters of juvenile mussels (seed) were evaluated after a 15-wk exposure in the laboratory, followed by an 8-wk recovery period in situ. Although no effect was detected for growth rate and allometric relationships during the laboratory experiment, mussel mortality was significantly higher at low pH. This effect on mortality disappeared when mussels were transferred to the field for a recovery period, and the acclimation to low pH had no carry-over effect on growth, allometric relationships, or sensory quality. Evidence of impacts from chronic lowering of pH is still needed to address species adaptation for long-term changes, which limit the prognostic power of short-term experiments.
Continue reading ‘Impacts of ocean acidification on survival of the brown mussel (Perna perna) in Brazil’
