Posts Tagged 'mortality'

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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 Closed
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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 Closed
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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 Closed
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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.

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Selective breeding boosts oyster resilience to ocean acidification via energy budget modulation

Published 12 September 2025 Science Closed
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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.

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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 Closed
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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.

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Impacts of ocean acidification on survival of the brown mussel (Perna perna) in Brazil

Published 27 August 2025 Science Closed
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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.

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Within and cross-generational effects of elevated seawater pCO2 on larval bay scallops Argopecten irradians (L)

Published 27 August 2025 Science Closed
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Bivalve larvae are highly susceptible to ocean acidification (OA), but there is little knowledge of the capacity of bivalve species to acclimate or adapt to changing ocean conditions. It is challenging to compare results among studies of OA reported in the literature, as there is little consistency among studies in water chemistry across OA treatments used or how OA conditions were determined. In addition, it is difficult to predict from short-term experiments how populations might respond across generations. The bay scallop, Argopecten irradians, is a good model species for such experiments because of its short generation time and importance commercially and ecologically. Bay scallops were exposed to OA conditions from embryos to metamorphosis across two generations. Ocean acidification treatment levels included historical or preindustrial “low” (pCO2 ∼450 µatm), current average “moderate” (∼800 µatm), and future “high” (∼1,350 µatm). In the first generation, high OA had negative effects on larval performance, with no survival to metamorphosis, preventing its inclusion in the second generation. Moderate OA reduced performance (survivorship and growth) relative to the low OA. In the second generation, however, there was no difference in survival between the moderate and low OA treatments, but the difference in size at metamorphosis remained. These results suggest that over two generations, bay scallops either acclimated or adapted to moderate OA. Further work is needed to determine the extent to which long-term, generational adaptation to OA is possible in the bay scallop.

Continue reading ‘Within and cross-generational effects of elevated seawater pCO2 on larval bay scallops Argopecten irradians (L)’

Synergistic effects of ocean acidification and copper on gamete health and fertilization potential of the Pacific oyster Magallana (Crassostrea) gigas

Published 26 August 2025 Science Closed
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Highlights

  • Ocean acidification exacerbates copper toxicity in Pacific oyster gametes.
  • Sperm show higher sensitivity to combined stressors than oocytes.
  • Fertilization success decreases at low pH and high copper concentrations.

Abstract

Ocean acidification (OA) and metal pollution pose significant threats to marine ecosystems, particularly in coastal areas. This study investigated the synergistic effects of OA and copper toxicity on Pacific oyster (Magallana gigas) gametes. Spermatozoa and oocytes were exposed to varying pCO2 levels and copper concentrations for 2 h. Flow cytometry was used to assess cell mortality, reactive oxygen species (ROS) production, and fertilization success. Results showed increased mortality in both sperm and oocytes with rising copper and pCO2 levels, with sperm exhibiting higher sensitivity. ROS production in gametes displayed complex patterns, suggesting adaptive responses at lower copper concentrations and potential cell death at higher levels. Fertilization success decreased significantly at lower pH combined with higher copper concentrations (> 10 μg Cu/L). These findings demonstrate that OA exacerbates copper toxicity in M. gigas gametes through interactive effects, highlighting the need to consider multiple stressors when assessing pollutant impacts on coastal ecosystems.

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Ocean acidification changes diet effects and differentially impacts two populations of red abalone (Haliotis rufescens)

Published 15 August 2025 Science Closed
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Absorption of CO2 by global oceans is decreasing pH resulting in ocean acidification (OA). Impacts on shellfish have been documented in ecologically and commercially important species. We examined the influence of diet and OA between two populations of red abalone (Haliotis rufescens) a species of aquaculture importance and declining wild populations. Populations experience different exposure histories: strong upwelling (Van Damme, California [VD]) historically exposed to low-pH conditions and weak-intermittent upwelling (Santa Barbara, California [SB]). Abalone were cultured under control-pH or OA-conditions and fed crustose coralline algae (CCA) or diatoms used in aquaculture. We tested treatment effects of population, settlement diet, and OA-exposure on survival as influenced by larval-energy stores. Survival in both populations was enhanced by CCA when cultured under both treatment conditions; however, by later stages, this effect remained only for SB. SB had reduced post-settlement survival when cultured under OA-conditions, whereas post-settlement survival of VD was not. Diet affected the relationship between larval-energy and post-settlement survival; a positive relationship when fed diatoms and a negative relationship with CCA. The relationship between larval-energy and post-settlement survival was stronger in VD. CCA enhanced juvenile growth in SB cultured abalone at both three-months and one-year post-settlement. Settlement diets can reduce the impacts of OA on early-life stages of abalone, but population differences driven by underlying energetics affect the consistency of this outcome. These findings illuminate the impacts from OA, suggesting populations may be at risk, and inform strategies for developing and sustaining shellfish aquaculture in the face of changing ocean conditions.

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Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans

Published 12 August 2025 Science Closed
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Marine habitat-forming species provide crucial ecosystem functions and services worldwide. Still, the individual and combined long-term effects of ocean acidification and warming on bryozoan populations, structures, and microbiomes remain unexplored. Here, we investigate the skeletal properties, microbiome shifts, and population trends of two bryozoan species living inside and outside a volcanic CO2 vent, a natural analog to future ocean acidification conditions. We show that bryozoans can acclimatize to acidification by adjusting skeletal properties and maintaining stable microbiomes. However, we document a decrease in microbial genera playing essential functions under acidified conditions. Moreover, we show that ocean acidification exacerbates bryozoan cover loss and mortality caused by ocean warming. The observed shifts in the microbiome and cover suggest that, despite their morphological plasticity, bryozoan species will be heavily impacted by future ocean conditions, posing a threat to many benthic ecosystems in which they play a pivotal role.

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Species-specific mechanisms of benthic foraminifera in response to shell dissolution

Published 31 July 2025 Science Closed
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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.

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Stage-dependent life-history, physiological, and behavioral responses to low pH in an estuarine crab

Published 18 July 2025 Science Closed
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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.

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High sensitivity to ocean acidification in wild out-migrating juvenile Pacific salmon is not impacted by feeding success

Published 18 July 2025 Science Closed
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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.

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Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification

Published 17 July 2025 Science Closed
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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.

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Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2

Published 11 July 2025 Science Closed
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Highlights

  • In the lab we explore environmental stress impacts on diploid and triploid oysters.
  • At mid pCO2 (1450–1700 μatm) mated triploids had lower survival than other groups.
  • Differences between mated and induced triploids may impact performance.
  • Consider the environment when selecting which ploidy for shellfish aquaculture.

Abstract

Pacific oysters (Crassostrea gigas) are an important aquaculture species due to their fast growth, high market demand, and adaptability. Triploid oysters, have an additional set of chromosomes relative to diploids, grow faster and are functionally sterile. Thus, triploids comprise a large proportion of oysters grown worldwide. Triploid oysters are reported to experience higher mortality than diploids. Growers must make decisions that balance the risks and rewards of growing triploids. Understanding how stressors affect oysters is essential to understanding the drivers of triploid mortality and to prepare for the impacts of climate change on individuals in aquaculture. Here, we examined impacts of temperature, dissolved oxygen (DO), and pCO2 on genetically related juvenile diploid, chemically induced triploid, and mated triploid Pacific oysters. Diploid and induced triploid groups were full siblings, mated triploids were half-siblings. We measured whole organism physiological responses—growth, mortality and respiration — after a 4-week exposure to different environmental conditions. Survival was high in all groups across a broad range of temperature and DO levels. Survival of mated triploids was negatively impacted at lower (but higher than ambient) pCO2 levels. Diploids and induced triploids had similar respiration across temperature and pCO2 experiments. Diploids respired more across all dissolved oxygen treatments. Differing performance of mated triploids suggests that production method or genetic background may contribute to their resilience or susceptibility to stress. Considering the stressors that will be placed on individuals in commercial aquaculture when making ploidy selections is essential to ensure the resilience of aquaculture as the climate changes.

Continue reading ‘Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2’

Larval Arctic cod (Boreogadus saida) exhibit stronger developmental and physiological responses to temperature than to elevated pCO2

Published 10 July 2025 Science Closed
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High-latitude ecosystems are simultaneously warming and acidifying under ongoing climate change. Arctic cod (Boreogadus saida) are a key species in the Arctic Ocean and have demonstrated sensitivity to ocean warming and acidification as adults and embryos, but their larval sensitivity to the combined stressors is unknown. In a laboratory multistressor experiment, larval Arctic cod were exposed to a combination of three temperatures (1.8, 5 and 7.3°C) and two carbon dioxide (pCO2) levels (ambient: 330 μatm, high: 1470 μatm) from hatching to 6-weeks of growth. Mortality rates were highest at 7.3°C (5% day°1); however, both growth and morphometric-based condition were also highest at this temperature. When these metrics were assessed via a mortality: growth (M:G) ratio, 5°C appeared to be an optimal temperature for net population biomass, as faster growth at 7.3°C did not fully compensate for higher mortality. In contrast, although morphometric-based condition was lowest at 1.8°C, lipid-based condition was highest, which may reflect prioritization of lipid storage at cold temperatures. The capacity of larval Arctic cod to acclimate to a range of temperatures was exhibited by two lipid-based indicators of membrane fluidity, including a ratio of unsaturated to saturated fatty acids and a ratio of polar lipids to sterols. The effects of elevated pCO2 were subtle, as well as temperature- and metric dependent. When exposed to elevated pCO2 levels, Arctic cod at 1.8°C exhibited signs of lipid dysregulation, suggesting potential interference with membrane acclimation; larvae at 5°C were in lower morphometric-based condition; and larvae at 7.3°C had higher activity eicosanoid substrates, indicating possible physiological stress. Overall, Arctic cod physiological response to temperature variation was more pronounced than their response to elevated pCO2. Future projections of pCO2 effects on Arctic cod health in a warming ecosystem will need to consider the complexity of temperature-dependence and the specificity of multiple physiological responses.

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Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis

Published 10 July 2025 Science Closed
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Ocean acidification refers to a decrease in the pH of the world’s oceans from the oceanic uptake of human-derived atmospheric CO2. Low pH is known to decrease the calcification and survival of many calcifying invertebrates. Shallow, hard bottom communities along the Western Antarctic Peninsula often have incredibly large numbers of invertebrate mesograzers that shelter on and are mutualists with the dominant brown macroalgae. The common amphipod species Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis were collected from the immediate vicinity of Palmer Station, Antarctica (64°46′S, 64°03′W) in January–February 2023 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.0), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 8 weeks. Molt number and mortality were monitored throughout the course of the experiment. After the 8 week exposure, amphipods were analyzed for their biochemical compositions including the Mg/Ca ratio of their exoskeletons. There was no significant difference in biochemical composition or survival among the pH treatments for any of the amphipod species. All three species, however, had significantly fewer total numbers of molts in the pH 7.3 treatment than in the ambient treatment. These results suggest that amphipods may be able to maintain their survival in decreased pH by reallocating energy into compensatory behaviors, such as acid–base regulation, and away from energy expensive processes like molting.

Continue reading ‘Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis’

Impacts of ocean acidification and altered prey fatty acids on the early development of northern rock sole (Lepidopsetta polyxystra) larvae

Published 3 July 2025 Science Closed
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Highlights

  • Carbon dioxide (CO2) and dietary fatty acids (FAs) had stage-specific effects on northern rock sole larvae.
  • After 2-weeks of feeding, larvae had faster growth under elevated CO2 conditions.
  • After 5-weeks of feeding, larvae had higher lipid storage when fed a diet with balanced-essential FAs.

Abstract

Ocean acidification (OA) is predicted to affect the physiological rates of larval fish and invertebrates and is also expected to significantly impact marine fisheries through alteration of food webs. We examined whether mortality rates, body size, and condition of first-feeding larval northern rock sole, Lepidopsetta polyxystra, were synergistically influenced by prey quality (essential fatty acids, EFAs) and high carbon dioxide (CO2) exposure. Larvae were exposed to ambient and high CO2 levels (∼ 330 vs. 1020 μatm) and were fed diets with balanced or unbalanced EFA ratios for 7 weeks immediately following hatch. After 2 weeks, significant effects from CO2 and diet were observed, with the largest larvae occurring in the high CO2 exposure group that received a balanced EFA diet. After 5 weeks of exposure, the effects of elevated CO2 had a diminished impact on larval size, but larvae reared on the balanced EFA diet maintained higher lipid-based condition metrics than those fed an unbalanced EFA diet. Survival was variable across replicate tanks and not significantly different between treatments. This study suggests that L. polyxystra larvae are most vulnerable to OA and food web change at different points in their development. Further understanding of these ecosystem effects will be required to predict the impacts of OA on northern rock sole fisheries.

Continue reading ‘Impacts of ocean acidification and altered prey fatty acids on the early development of northern rock sole (Lepidopsetta polyxystra) larvae’

Antarctic macroalgal-associated amphipod assemblages exhibit long-term resistance to ocean acidification

Published 19 June 2025 Science Closed
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The pH of the world’s oceans has decreased since the Industrial Revolution due to the oceanic uptake of increased atmospheric CO2 in a process called ocean acidification. Low pH has been linked to negative impacts on the calcification, growth, and survival of calcifying invertebrates. Along the Western Antarctic Peninsula, dominant brown macroalgae often shelter large numbers of diverse invertebrate mesograzers, many of which are calcified. Mesograzer assemblages in this region are often composed of large numbers of amphipods which have key roles in Antarctic macroalgal communities. Understanding the impacts of acidification on amphipods is vital for understanding how these communities will be impacted by climate change. To assess how long-term acidification may influence the survival of different members in these assemblages, mesograzers, particularly amphipods, associated with the brown alga Desmarestia menziesii were collected from the immediate vicinity of Palmer Station, Antarctica (S64°46′, W64°03′) in January 2020 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.1), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 52 days then enumerated. Total assemblage number and the relative proportion of each species in the assemblage were found to be similar across the pH treatments. These results suggest that amphipod assemblages associated with D. menziesii may be resistant to long-term exposure to decreased pH.

Continue reading ‘Antarctic macroalgal-associated amphipod assemblages exhibit long-term resistance to ocean acidification’

Population and maternal variation in the sensitivity of Dungeness crab Metacarcinus magister zoeae to elevated CO2

Published 10 June 2025 Science Closed
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The response of marine organisms to ocean acidification depends on their adaptive capacity, which can be partially understood by evaluating the amount of existing variability in CO2 sensitivity within a species. The process of local adaptation is a mechanism that can drive variability in CO2 sensitivity. In this study, we measured the survival and molt rate of Dungeness crab Metacarcinus magister zoeae that were produced by gravid crabs collected from 3 locations in waters off of Washington State, USA, and reared in a common laboratory in ambient, medium, and high CO2 treatments. The 3 locations from which crabs were collected have different carbonate chemistry dynamics, and Dungeness crabs in these locations are to some extent genetically distinct. We hypothesized that these conditions may favor local adaptation. We did not find evidence of local adaptation, but did see different levels of CO2 sensitivity associated with the mother. This variation in CO2 sensitivity suggests an adaptive capacity that is likely to influence Dungeness crab response to future acidification.

Continue reading ‘Population and maternal variation in the sensitivity of Dungeness crab Metacarcinus magister zoeae to elevated CO2’

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