Posts Tagged 'reproduction'

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Identification, characterization, and expression analysis reveal regulatory roles of MCM genes in Patinopecten yessoensis under low-pH stress

Published 12 August 2025 Science Closed
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Highlights

  • Nine MCM genes are systematically identified from Patinopecten yessoensis genome.
  • PyMCMs are widely expressed during development and adult tissues, especially PyMCM6.
  • PyMCM5 is particularly sensitive to low pH stress, whereas PyMCM8 and PyMCM9 are not.
  • Scallops reduce DNA replication but maintain DNA repair in response to low-pH stress.

Abstract

The Yesso scallop (Patinopecten yessoensis), an ecomically important bivalve species, exhibits high susceptibility to ocean acidification. The growth retardation induced by low-pH stress poses a significant challenge for Yesso scallop aquaculture. However, the molecular mechanisms underlying this phenomenon are not well understood. Considering the pivotal role of cell proliferation in organism growth, we investigated the minichromosome maintenance (MCM) family in P. yessoensis, which are key regulators of DNA replication initiation and cell cycle regulation. In this study, we identified nine MCM genes (PyMCM2–10) in the P. yessoensis genome. These PyMCMs exhibit highly conserved sequence characteristics and typical MCM domains. Phylogenetic analysis showed that PyMCMs cluster into nine distinct clades, underscoring their strong evolutionary conservation across species homologs. Spatiotemporal expression profiling demonstrated widespread expressions of PyMCMs throughout all developmental stages and adult tissues, with particularly high levels in vigorous cell proliferation (e.g., up to 318 TPM in multicell stage and up to 202 TPM in gonad tissue). Notably, PyMCM6 exhibited consistently high expression across development and across tissues (> 44 TPM), suggesting a key regulatory role in both development and tissue maintenance. Under low-pH stress, the expressions of PyMCMs were downregulated to varying degrees, with PyMCM5 showing the most significant reduction (|log2FC| up to 3.5), while PyMCM8 and PyMCM9 remained relatively stable. This pattern suggests a strategic response that scallops reduce DNA replication capacity (mediated by PyMCM2–7) but potentially maintain DNA repair functions (associated with PyMCM8/9 stability) to mitigate damage induced by low-pH, potentially explaining the intrinsic inhibition of cell proliferation. Quantitative real-time PCR and in situ hybridization further confirmed that low-pH stress inhibits PyMCMs expressions (p < 0.05), with the effect amplified as pH decreases. Collectively, these findings enhance our understanding of PyMCMs in regulating bivalve growth retardation under low-pH stress and provide valuable insights into the mechanisms of environmental adaptation in bivalves.

Continue reading ‘Identification, characterization, and expression analysis reveal regulatory roles of MCM genes in Patinopecten yessoensis under low-pH stress’

Epigenetic insights into physiological resilience: multigenerational readouts of CO2-induced seawater acidification effects on fish embryos

Published 5 August 2025 Science Closed
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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.

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Abalone and seaweed co-culture: growth and shell biomineralization of an iconic California gastropod

Published 5 August 2025 Science Closed
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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.

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Impacts of multiple coastal stressors across life-history stages in the eastern oyster

Published 31 July 2025 Science Closed
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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.

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Effect of acidification on the chronic toxicity of diclofenac to Daphnia magna

Published 28 July 2025 Science Closed
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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.

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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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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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Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings 

Published 8 July 2025 Science Closed
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Ocean acidification (OA) and marine heatwaves (MHWs) are key drivers of marine ecosystem changes that can interact and influence marine organisms. Seagrasses, including the long-lived Posidonia oceanica endemic to the Mediterranean Sea, are widely distributed along coastal habitats, forming highly valuable underwater meadows. The germination and survival of the early life stages of P. oceanica are strongly affected by environmental changes. To assess the impact of warming and acidification on its future, we conducted a multifactorial experiment where P. oceanica seedlings were grown under OA conditions for six months and then exposed to a seawater warming event. Seedlings’ performance was investigated by analyzing photo-physiology, antioxidant capacity, energetic metabolism and transcriptomic profiles. The Weighted Gene Correlation Network Analysis (WGCNA) was used to integrate phenotypic plant traits with transcriptomic results to identify central genes involved in plant responses to OA and temperature exposure. Results demonstrated that prolonged OA exposure enhances P. oceanica seedling resilience to MHW. Specifically, seedlings regulated their antioxidant systems and transcriptomic machinery to better cope with thermal stress. Under current CO2 concentrations, elevated temperatures induced stress in P. oceanica seedlings, impacting photosynthesis and respiration. However, OA could mitigate the impact of warming in the future, enhancing P. oceanica‘s resilience to global stressors.

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Robustness of gametogenesis in the scleractinian coral, Tubastraea aurea, in the shallow-water hydrothermal vent field off Kueishan Island, northeastern Taiwan

Published 8 July 2025 Science Closed
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Highlights

  • Stony corals (Tubastraea aurea) can colonize in acidified shallow-water hydrothermal vent fields.
  • T. aurea is a gynodioecious brooder; mostly females with a low percent of hermaphroditism.
  • HV colonies maintained the similar gametogenic process and seasonal timing of reproduction as NHV colonies.
  • Elevated gametogenic activity of vent T. aurea could facilitate success in extreme conditions.
  • Hydrothermal vents as natural laboratories offer insights on the resiliency of scleractinians.

Abstract

Understanding the reproductive resiliency of scleractinian corals is imperative as ocean acidification and rising sea surface temperatures threaten the foundation of coral reef ecosystems. However, the limited temporal scales of laboratory and transplantation-based methods fail to consider evolutionary time frames offered by natural analogues of future climate conditions, like hydrothermal vents (HV). Accordingly, we characterized the presence of scleractinians surrounding a major shallow-water HV near Kueishan Island in northeastern Taiwan, identified a candidate species, Tubastraea aurea, and investigated its sexual reproductive strategies. Since this was the first study to describe the sexual reproduction of T. aurea, we characterized the gametogenetic process of T. aurea colonies from the HV and three non-HV locations (NHV1, NHV2, NHV3). Oogenesis was similar between HV and NHV sites and mature oocytes reached the same size. The seasonal timing of reproduction was comparable between HV and NHV1 colonies, likely related to the similar seasonal variation of water temperatures. HV colonies showed an even higher gametogenetic activity (100 % of polyps containing developing gametes in HV colonies versus 73.5 % in NHV colonies). As assessed by the presence of larvae, T. aurea is a brooder, with mostly female polyps (97.6 %,) and a low percent of hermaphroditism (2.4 %, as observed in 2 in HV and 1 in NHV colonies). This suggests that parthenogenesis may contribute to larval production. Taken together, we demonstrated the robustness of gametogenesis in T. aurea and propose the heightened reproductive effort of T. aurea at the Kueishan Island HV could be facilitating its success in acidified conditions. Overall, this study exemplified the importance of using unique ecosystems to uncover clues on scleractinian resiliency.

Continue reading ‘Robustness of gametogenesis in the scleractinian coral, Tubastraea aurea, in the shallow-water hydrothermal vent field off Kueishan Island, northeastern Taiwan’

Increased temperature and acidification elevate the risk of starvation in American lobster larvae 

Published 4 July 2025 Science Closed
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The geographic range of the American lobster, Homarus americanus, spans a steep thermal gradient along the coastal Northwest Atlantic. As CO2 emissions increase globally, this range is rapidly warming and acidifying. Larval H. americanus hatch with a finite amount of maternally sourced lipid stores in their yolk sac, which provide an energetic buffer during the intermediate period between hatch and first feed. This study examines the response of newly-hatched, unfed H. americanus larvae to the combined effects of elevated pCO2 and temperature. Using a space-for-time approach, we compared larvae of two distinct sub-populations from thermally contrasting regions: Rhode Island, at the warmer, southern limit of the species range, and Midcoast, Maine, a cooler northern region. Average larval initial post-hatch weight was similar across regions and variability therein could be explained by maternal effects. Under 6 days of starvation, larvae from the two regions lost ∼14% of their initial dry weight and 25% of their Carbon weight. Still, end-century elevated temperature or acidification did not substantially alter those rates for larvae from either region. However, under an identical range of conditions over the 6-day experiment, larvae from the warmer regime maintained relatively stable oxygen consumption rates, while those from the cooler regime started 50% higher, then dropped by 80% within 2 days. If depressed metabolic functioning translates to reduced feeding efficiency for cool regime larvae, our findings suggest that subpopulations in the southern edge of the species range have a relative advantage in food-scarce environments under these conditions, adding to previous evidence for countergradient variation in this species. Further analysis of total fatty acid losses conducted on Midcoast larvae suggested starved larvae exposed to elevated temperature (19°C) experienced considerably greater losses of key lipid groups than larvae under ambient conditions (16°C, 400 ppm), particularly within the first 2 days of exposure. Our results highlight the short time frames over which ocean warming can accelerate the depletion of energy stores and make larvae more vulnerable to starvation.

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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.

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Ocean acidity extremes retard shell formation of bivalve larvae: insights from transcriptomics and lipidomics

Published 2 July 2025 Science Closed
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Highlights

  • Effects of ocean acidity extremes (OAX) on early development of clams were assessed.
  • OAX retarded shell formation of clam larvae.
  • Reduced Ca2+ uptake and HCO3− production led to larval developmental retardation.
  • OAX decreased cell membrane fluidity, limiting the uptake of calcification substrates.
  • Larval shell formation under OAX was inhibited by depletion of energy reserves.

Abstract

In view of climate change and human activities, ocean acidity extreme (OAX) events have been increasingly reported worldwide over the last decades, which possibly retard the growth and development of marine organisms, particularly at their early life-history stages (e.g., embryos or larvae). Thus, understanding whether they can adjust to the sudden increase in seawater acidity has drawn growing attention. Using a commercially and ecologically important bivalve species (Ruditapes philippinarum) with a widespread distribution in the world, we assessed the impact of OAX on its embryonic and larval development as well as expressions of functional genes and lipids to indicate physiological and cellular performance. We found that embryonic development and larval shell formation were inhibited by OAX mainly due to the downregulation of key genes responsible for the uptake of calcium ions from ambient seawater (e.g., NCX, VGCC and SERCA) and the reduced production of bicarbonate ions through the catalytic action of carbonic anhydrase. In addition, a major remodelling in membrane lipids (e.g., PC, PE, PG, PI and PS) indicated that OAX impacted the fluidity and stability of cell membrane, hindering the uptake of calcification substrates. The depletion in energy reserves, such as triacylglycerol, can also account for the impairment in larval shell formation under OAX conditions. By integrating transcriptomics and lipidomics, our findings illustrate a novel molecular mechanism underlying the detrimental effect of OAX on larval development and hence population maintenance of marine organisms, which can have profound implications for sustaining ecosystem stability and aquaculture management.

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Developmental and transgenerational effects of climate change on inorganic mercury toxicity in a marine copepod

Published 25 June 2025 Science Closed
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Highlights

  • Offspring/persistent OA plus OW aggravated IHg toxicity in T. japonicus.
  • Persistent OA had stronger mitigating effect on IHg toxicity than offspring OA.
  • OA plus OW intensified IHg toxicity in copepods mainly via lysosome dysfunction.
  • Persistent OA enhanced energy metabolism and Hg efflux, decreasing IHg toxicity.
  • Different scenarios of climate change can variably affect IHg toxicity in copepods.

Abstract

Dynamic shifts in multiple stressors are frequent in the marine environment. Here, we conducted a multigenerational experiment (F1-F4) to explore how different temporal scenarios of climate change, i.e., offspring/persistent ocean acidification (OA), warming (OW), and their combination (AW), could affect inorganic mercury (IHg) toxicity in the marine copepod Tigriopus japonicus. We found that persistent OA exhibited stronger mitigating effect on IHg toxicity in copepods than offspring OA, while offspring/persistent OW and AW aggravated its toxicity effects. We specifically performed transcriptomic analysis for the copepods of F4. Our transcriptomic result showed energy metabolism and detoxification were activated by persistent OA, enabling the copepods to resist IHg exposure. Instead, detoxification- and reproduction-related processes were inhibited in IHg-treated copepods under offspring/persistent OW and AW scenarios. Although apoptosis was suppressed to probably protect IHg-treated copepods under persistent AW, oxidative stress and lysosomal dysfunction ultimately caused reproductive impairment. Our study highlights that offspring/persistent (i.e., developmental/transgenerational) OA and OW could differentially modulate Hg toxicity in marine copepods, and more studies should focus on the temporal variation and complex interaction of multiple stressors, helping accurately project marine biota’s response in the future ocean.

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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.

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Effects of ocean warming and acidification on the embryonic development of Doryteuthis opalescens and Doryteuthis pealeii

Published 9 June 2025 Science Closed
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Projected increases in ocean temperature and partial pressure of carbon dioxide (pCO2) due to anthropogenic carbon emissions are expected to significantly alter coastal marine ecosystems, particularly within the Southern California Bight and Northwest Atlantic Ecoregion. These changes may disrupt food web stability through alterations in abiotic conditions. To assess the impacts of elevated temperature and pCO2 on embryonic development in the superorder Decapodiformes, I investigated two mid-trophic squid species, Doryteuthis opalescens and Doryteuthis pealeii, during their paralarval stage. Specifically, I examined metabolic and morphological responses in squid reared in four seawater treatments: combinations of present-day and projected levels of temperature and pCO2 by the end of the century. The results revealed species-specific responses. D. opalescens paralarvae exhibited generally negative responses, including reduced morphological development, under elevated temperature and pCO2 conditions. In contrast, D. pealeii paralarvae demonstrated positive responses, with increased morphological dimensions under the same conditions. Additionally, D. pealeii paralarvae showed elevated O2 consumption rates, while D. opalescens paralarvae exhibited a more subdued metabolic response to temperature increases. These findings highlight significant interspecific variability in responses to future ocean conditions, despite the similarity in life history traits between the two species. This study underscores the complexity of climate change impacts on Decapodiformes and emphasizes the necessity of species-specific assessments to predict ecological consequences for marine organisms.

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Positive interactions in a warmer and more acidic ocean: crustose coralline algae holobionts enhance gorgonian larval settlement under climate change

Published 21 May 2025 Science Closed
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Background: The increasing frequency of marine heatwaves is leading to mass mortality of gorgonians in the Mediterranean Sea, threatening some populations with local extinction. A better understanding of the dynamics of gorgonians’ early life stages under climate change is urgent to ensure their conservation. Crustose coralline algae (CCAs) and their associated bacteria are known to induce the larval settlement of several coral species through the production of chemical cues. The larvae of the white gorgonian Eunicella singularis have been observed to preferentially settle and metamorphose on CCAs. Here, we investigated this positive interaction, and explored how it might be altered by climate change. Specifically, we tested the capacity of two Mediterranean CCA holobionts, Macroblastum dendrospermum and Lithophyllum stictiforme, to foster E. singularis larval settlement after exposure to SSP5-8.5 projected conditions for 2100 (warming and acidification), combined or not with a simulated marine heatwave event.

Results: Our results showed a threefold increase of larval settlement in presence of the CCAs previously exposed to acidification and warming treatments. After these treatments, both CCAs hosted a consistently high abundance of bacteria belonging to the Pirellulaceae family, and exhibited a higher abundance of monosaccharides in their exudates. We hypothesize that the enhanced larval settlement was driven by the bacterial breakdown and utilization of CCA polysaccharides, in combination with their release through the CCA cell walls. This release may have been enhanced by a decalcification process induced by climate change conditions. Furthermore, we showed that CCAs act as sources of bacterial taxa that can establish and persist in adult E. singularis holobiont, independently of climate change effects.

Conclusions: Our results highlight that CCA-larvae interaction is critical for E. singularis recruitment success, especially under future climatic conditions, and influences the development of its microbiome. This research underscores the importance of studying positive interspecific interactions across biological levels (from microorganisms to macroorganisms) under climate change scenarios, and provides valuable insights that inform the conservation and restoration of the Mediterranean white gorgonian.

Continue reading ‘Positive interactions in a warmer and more acidic ocean: crustose coralline algae holobionts enhance gorgonian larval settlement under climate change’

Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size

Published 13 May 2025 Science Closed
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Pinto abalone (Haliotis kamtschatkana), the only abalone species native to Washington, declined by 97% in the state from 1992 to 2017. Their decline is a loss for indigenous tribes, recreational divers, and the health of subtidal rocky reefs and kelp beds. Current restoration actions are facing threats of ocean acidification and warming in the northeast Pacific. This research aims to deepen our understanding of the tolerance and physiological flexibility of early life history stages of pinto abalone and inform hatchery practices under future climate change scenarios. We conducted an experiment to test how seawater pH and temperature stress impact abalone larvae. We exposed abalone post-fertilization to elevated temperature and reduced seawater pH for ten days spanning their larval development period: (1) 7.95pH/14°C (ambient), (2) 7.60pH/14°C, (3) 7.95pH/18°C, and (4) 7.60pH/18°C. Abalone in the ambient treatment had the best survival, those in the 7.60pH/18°C treatment had the worst survival, and those in the two single-stressor treatments had survival in between. Among the surviving larvae, pH was the dominant stressor influencing settlement success, with higher settlement rates under ambient pH treatments at both temperatures. pH also had a stronger effect than temperature on shell length. The information gleaned from this study is essential for optimizing future restoration aquaculture for pinto abalone and determining their ideal habitat and potential geographic range.

Continue reading ‘Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size’

Examining behavioral alterations in zebrafish (Danio rerio) larvae in the context of anthropogenic climate change

Published 9 May 2025 Science Closed
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Behavioral responses induced by climate change in fish have received increased attention in recent years. Near future projected CO₂ levels (420 µatm to 1000 µatm) and increased temperature (~4 °C) expected in ocean and freshwater basins by 2100 have been shown to impair various behaviors such as locomotor activity and learning in early life stage fish. Despite widespread characterization, we know little about why these disruptions occur and how compounded effects of climate change might disrupt behavioral paradigms. Using the biomedical research model, the zebrafish (Danio rerio), a species with a well-documented behavioral repertoire and broadly utilized for mapping neural activity linked to behavior, this study aimed to assess how elevated CO₂ and temperature may affect behavior during early development. Larvae 6-7 days post fertilization were acclimated to either control (420 µatm CO₂; 28 °C) or 1,000 µatm pCO₂ and temperatures of 32 °C combined or singly before being subjected to various behavioral assays, consisting of acoustic- and visual stimuli to examine startle responses and their habituation. The results suggest that temperature more than CO₂ significantly altered the startle response, and to some extent, the habituation of this response. Both acoustic- and visual startle response were negatively affected by climate change relevant heat-exposure, while aquatic acidification had no significant effect on the acoustic startle response singly. Conversely, habituation appears to have increased under elevated temperature treatment in isolation compared to ambient levels. This experiment may help highlight zebrafish’s potential as a model organism for further climate- behavioral and physiological investigations, supported by their advanced gene editing and transgenic tools, optical transparency, and compatibility with high-throughput screening approaches.

Continue reading ‘Examining behavioral alterations in zebrafish (Danio rerio) larvae in the context of anthropogenic climate change’

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