Posts Tagged 'echinoderms'

Mitigation of biogenic acidification via increased total alkalinity in high stocking density culture waters of Strongylocentrotus intermedius: effects on growth and metabolism

Published 6 October 2026 Science Closed
Tags: , , , , , , , , ,

Highlights

  • Biogenic acidification increases with stocking density in sea urchin culture.
  • Total alkalinity mitigates acidification and promotes growth and gonadal development.
  • Higher alkalinity shifts metabolism toward biosynthesis and energy storage.

Abstract

Among cultured sea urchins in China, Strongylocentrotus intermedius has the highest annual production, with seed production and grow-out primarily conducted under high-density intensive conditions where biogenic acidification readily develops. To investigate its development, effects, and mitigation, we conducted a short-term incubation experiment (1 d) and a 20-day cultivation experiment. In the short-term incubation experiment, a control group with initial pH ≈ 8.1 and TA ≈ 2300 μmol/kg and a TA-elevated group with initial pH ≈ 8.1 and TA ≈ 3600 μmol/kg were established, and sea urchins were cultured across a density gradient of 20–80 g/3 L. In the 20-d experiment, stocking density was 88 g/3 L with the same initial pH and TA settings. The short-term experiment showed that seawater acidification occurred in the control group, and stocking density was significantly correlated to pCO2, ΔpH (pH reduction), TA–DIC, and Ωarag. With increasing stocking density, pCO2 increased significantly, whereas ΔpH and TA–DIC significantly decreased simultaneously. In the TA-elevated group, all parameters except pCO2 were higher than those in the control group across all stocking densities. At the lowest stocking density, ΔpH, TA–DIC, and Ωarag in the control group were −0.09 ± 0.01, 111.48 ± 1.73 μmol/kg, and 1.43 ± 0.00, respectively, whereas the corresponding values in the TA-elevated group were 0.11 ± 0.01, 252.26 ± 6.98 μmol/kg, and 3.23 ± 0.08. These results indicate that increasing TA mitigates biogenic acidification and works to strengthen the buffering capacity of the carbonate system. At the end of the 20-day cultivation experiment, urchins from the TA-elevated group showed significantly higher specific growth rate (1.60 ± 0.08% vs. 1.27 ± 0.06%), weight gain rate (37.72 ± 2.25% vs. 29.04 ± 1.48%), and gonad index (6.09 ± 1.58% vs. 3.54 ± 0.49%) than those from the control group. Metabolomics analysis revealed that TA elevation enriched pathways related to protein biosynthesis, glycerophospholipid metabolism, and sphingolipid signaling, with higher abundances of essential amino acids (L-methionine, DL-isoleucine), sphingomyelins, and the antioxidant indole-3-pyruvic acid. In contrast, the oxidative stress marker DL-2-aminoadipic acid was upregulated in the control group. Overall, increasing seawater TA mitigates biogenic acidification in high-density sea urchin culture, shifting metabolism from stress defense toward biosynthesis and reserve accumulation, thereby supporting growth and gonadal development in juvenile sea urchins.

Continue reading ‘Mitigation of biogenic acidification via increased total alkalinity in high stocking density culture waters of Strongylocentrotus intermedius: effects on growth and metabolism’

A key seawater acidification-enriched gut bacterium, Pseudoalteromonas carrageenovora P1, enhances growth performance, antioxidant status, and disease resistance in sea cucumbers under seawater acidification

Published 28 September 2026 Science Closed
Tags: , , , , , , , , , , , ,

Highlights

  • First discovery of Pseudoalteromonas enrichment in A. japonicus gut under acidification.
  • The dominant strain P. carrageenovora P1 was successfully isolated.
  • P. carrageenovora P1 activates host antioxidant and immune pathways to bolster stress resilience.
  • P. carrageenovora P1 significantly enhances resistance to V. splendidus 21,915 infection in A. japonicus.

Abstract

The sea cucumber (Apostichopus japonicus) is a key mariculture species of high economic value in East Asia. However, Ocean acidification, resulting from the increased uptake of anthropogenic CO₂ by seawater, severely impairs its growth, survival, and reproductive performance, thereby threatening the sustainable development of this aquaculture industry. The gut microbiota play a critical role in host adaptation to environmental stress; however, their involvement in mediating A. japonicus responses to seawater acidification remains unclear. Therefore, this study first compared the gut microbial communities of juvenile and adult A. japonicus under acidified and ambient seawater conditions. The results showed that Pseudoalteromonas abundance was significantly enriched under seawater acidification, from which the dominant strain, Pseudoalteromonas carrageenovora P1, was screened and isolated. This strain, when supplied as a dietary supplement under seawater acidification, improved A. japonicus growth performance and intestinal morphology, activated the Keap1-Nrf2-ARE and NF-κB pathways, enhanced antioxidant capacity and immune function, and increased resistance against Vibrio splendidus 21915 infection. Moreover, P. carrageenovora P1 modulated gut microbial structure by promoting beneficial bacteria such as Lutibacter while suppressing potential pathogens, including Vibrio, thereby maintaining intestinal homeostasis under acidification stress. This study reveals the important value of the gut microbiota of A. japonicus in regulating environmental tolerance of benthic invertebrates, and also provides a scientific reference for stress resistance regulation and health maintenance in A. japonicus aquaculture under seawater acidification.

Continue reading ‘A key seawater acidification-enriched gut bacterium, Pseudoalteromonas carrageenovora P1, enhances growth performance, antioxidant status, and disease resistance in sea cucumbers under seawater acidification’

Ocean acidification drives grazer niche convergence and trophic homogenization in benthic communities

Published 22 September 2026 Science Closed
Tags: , , , , , , , , , , , ,

Highlights

  • Acidification compresses benthic community isotopic space via carbon homogenization.
  • Functional groups show differential isotopic responses consistent with bottom-up trophic reorganization.
  • Arbacia lixula shifts from a sponge-dominated diet to herbivory under low pH.
  • Paracentrotus lividus maintains stable trophic niche despite acidification.
  • Asymmetric grazer responses drive site-specific increases in isotopic niche overlap under acidification.

Abstract

Ocean acidification is expected to alter marine food webs, yet community-level evidence from long-term, naturally acidified systems remains limited. We used stable isotope ratios (δ13C and δ15N) to investigate how natural acidification restructures benthic trophic interactions, from basal resources to consumer niche dynamics, a naturally acidified system (pH gradient: 8.1 to ~7.4; pHT scale) spanning present-day to end-of-century projected conditions (SSP2–4.5 to SSP5–8.5). After accounting for local differences in the isotopic baseline, we found that: (1) community isotopic space contracted under acidification, with the carbon range decreasing as primary producers converged toward 13C-depleted values, while the nitrogen range expanded, indicating species-specific trophic adjustments; (2) functional groups responded asymmetrically, with primary producers showing the strongest δ13C shifts, filter-feeders remaining relatively stable, and omnivorous consumers showing reduced δ13C and δ15N values; (3) the two dominant sea urchin grazers responded in opposite directions — the macrophyte-based omnivore Paracentrotus lividus maintained stable isotopic values across the pH gradient, whereas the invertebrate-based omnivore Arbacia lixula exhibited pronounced isotopic shifts — resulting in markedly increased, though site-dependent, niche overlap at the most acidified sites (up to 27%); (4) Bayesian mixing models revealed that this convergence was driven by dietary shifts in A. lixula, which transitioned from a predominantly invertebrate-based diet (70–79% animal prey) toward algal-based feeding under acidification (19–24% animal prey), while P. lividus maintained relatively consistent dietary composition (50–70% algae). Together, these results indicate that acidification-driven homogenization of primary producers, combined with asymmetric consumer responses, compresses trophic niche space, with broad implications for the resilience and functioning of benthic ecosystems under future ocean change.

Graphical abstract

Along a natural CO2 gradient in the Canary Islands (pH 8.1–7.4, pHT scale; spanning present-day to end-of-century projected conditions, SSP2-4.5–SSP5-8.5), ocean acidification compresses community isotopic space through homogenization of primary producers. The two dominant sea urchin grazers respond asymmetrically: Paracentrotus lividus maintains a stable trophic niche, while Arbacia lixula shifts toward algal-based feeding, increasing niche overlap up to 27% at the most acidified sites.

Continue reading ‘Ocean acidification drives grazer niche convergence and trophic homogenization in benthic communities’

Pre-harvest thermal and pH stress modulate macronutrient digestibility and protein bioaccessibility of the sea cucumber Isostichopus badionotus under in vitro gastrointestinal digestion

Published 18 September 2026 Science Closed
Tags: , , , , ,

Highlights

  • Thermal stress modulates protein digestibility and bioaccessibility in I. badionotus.
  • Induction at 28 °C maximized protein digestibility and intestinal bioaccessibility.
  • Sublethal 34 °C for 12 h peaked digestibility; longer exposure caused decline.
  • Intestinal bioaccessibility was the most sensitive indicator to pre-harvest stress.
  • Pre-harvest thermal and pH stress can alter the macronutrient nutritional quality in I. badionotus.

Abstract

The impact of in vivo thermal and pH stress on the macronutrient nutritional quality of the sea cucumber Isostichopus badionotus remains poorly understood from a food-nutrition perspective. This study investigated how acute induction temperatures (16–36 °C) and sublethal thermal exposure (34 °C, 3–48 h), combined with two ambient pH levels (7 and 8), modulate in vitro protein, lipid and carbohydrate digestibility and protein bioaccessibility of the sea cucumber I. badionotus, a collagen-rich tropical food, using the standardized static INFOGEST gastrointestinal simulation. In the acute induction experiment, protein digestibility, total bioaccessibility and intestinal bioaccessibility were strongly affected by temperature, with a narrow optimum at 28 °C (digestibility ∼58–66%; intestinal bioaccessibility ∼64–68% at both pH levels). Lipid digestibility varied within a relatively narrow range across treatments, whereas carbohydrate digestibility showed a marked temperature × pH interaction, with higher values at 28 and 36 °C under alkaline conditions. In the sublethal-stress experiment, protein digestibility and bioaccessibility followed a time-dependent pattern, with a peak at 12 h followed by a decline at 24–48 h, consistent with patterns of progressive collagen oxidation reported in other holothuroids. Across both experiments, intestinal bioaccessibility was the most responsive nutritional indicator to pre-harvest stress. These results demonstrate that pre-harvest thermal and pH stress can qualitatively alter the macronutrient nutritional quality of I. badionotus, with implications for harvest timing, processing optimization and seafood quality management under ongoing ocean warming and acidification.

Graphical abstract

Live sea cucumbers (Isostichopus badionotus) were exposed in vivo to controlled thermal and pH stress (16–36 °C, pH 7–8; 6 h acute induction and 3–48 h sublethal exposure), inducing proteolysis, oxidative responses, heat-shock protein expression and structural remodeling of the collagen-rich body-wall matrix. Samples were then subjected to standardized INFOGEST in vitro digestion (oral, gastric and intestinal phases with pepsin, pancreatin and bile salts), followed by dialysis at 12–14 kDa to quantify intestinal bioaccessibility. A narrow optimum at 28 °C and a sublethal window around 12 h at 34 °C tended to maximize protein digestibility and intestinal bioaccessibility, whereas conditions outside this window were associated with increased oxidative crosslinking and reduced protein quality.

Continue reading ‘Pre-harvest thermal and pH stress modulate macronutrient digestibility and protein bioaccessibility of the sea cucumber Isostichopus badionotus under in vitro gastrointestinal digestion’

Parental CO₂-vent history does not improve larval performance of the sea urchin Arbacia lixula under copper and acidification

Published 9 September 2026 Science Closed
Tags: , , , , , , , ,

CO₂-driven ocean acidification (OA) threatens marine calcifiers, while coastal ecosystems face increasing trace-metal contamination; their combined effects, and the modulating role of parental environmental history, remain poorly understood. We used the sea urchin Arbacia lixula from a naturally acidified CO₂ vent and a nearby ambient site at Ischia (Tyrrhenian Sea) to test how chronic adult exposure to low pH shapes larval responses to copper and low pH. Offspring from ambient (pH ~ 8.1) and vent (pH ~ 7.7) adults were reared for 48 h in a fully crossed design (two pH levels × three copper concentrations: 0, 5, 20 µg L⁻¹). At 24 hpf, development was dominated by parental history: ambient-derived larvae advanced rapidly, whereas vent-derived larvae showed higher arrest and slower progression, especially under low pH and high copper. By 48 hpf these effects diminished and pH and its interaction with copper became dominant, with both origins converging toward the echinopluteus stage. Nonetheless, malformations rose sharply under low pH regardless of copper, and skeletal-rod morphometrics revealed additional copper-related effects invisible to binary abnormality classifications. Chronic parental exposure did not enhance larval tolerance and sometimes increased sensitivity, underscoring the need to integrate multiple stressors and parental legacy.

Continue reading ‘Parental CO₂-vent history does not improve larval performance of the sea urchin Arbacia lixula under copper and acidification’

Biological impacts of ocean change in upwelling systems: from organismal responses to fishery outcomes

Published 3 September 2026 Science Closed
Tags: , , , , , , , , ,

Climate change is altering marine ecosystems through concurrent changes in temperature, carbonate chemistry, and dissolved oxygen. These changes are particularly important in coastal upwelling systems, where organisms already experience naturally variable environmental conditions. This dissertation integrates synthesis, experimentation, and modeling to evaluate how ocean change influences marine invertebrates and the fisheries they support. First, I conducted a meta analysis examining the effects of ocean acidification and deoxygenation on marine invertebrates. Both stressors produced broadly negative effects on fitness-related
traits, including survival, growth, development, and reproduction. Although vulnerability varied among taxa, responses were not strongly structured across broad taxonomic groups, suggesting that species-specific traits and environmental history are important determinants of sensitivity. Second, I investigated the effects of multi-stressor upwelling conditions on juvenile Dungeness crab (Metacarcinus magister). Crabs maintained net calcification across a range of moderate conditions but exhibited significant declines under the most severe treatments, indicating threshold responses to environmental stress. Short-term environmental variability had little effect relative to mean conditions, suggesting that exposure severity is a stronger driver of performance than exposure pattern. Finally, I incorporated experimentally observed reductions in calcification into a size-structured yield-per
recruit model to evaluate potential fishery consequences. Reduced growth delayed attainment of legal harvest size and decreased projected fishery yield, demonstrating how sublethal physiological responses can scale to population and management-relevant outcomes. Together, these chapters show that ocean change can affect biological systems across levels of organization, from individual performance to fishery productivity. By linking broad patterns of vulnerability to species-specific responses and applied fishery outcomes, this dissertation provides a framework for understanding and managing the impacts of global change in coastal
marine ecosystems.

Continue reading ‘Biological impacts of ocean change in upwelling systems: from organismal responses to fishery outcomes’

Coral reef community structure and photophysiology differ between upwelling and non-upwelling locations on the Pacific Coast of Costa Rica

Published 28 August 2026 Science Closed
Tags: , , , , , , , ,

Reef-building corals and coralline algae form the calcium carbonate frameworks that underpin tropical coral reefs, yet in some locations, coral cover has declined by ~50% in recent decades due to marine heatwaves and other stressors. Identifying refugia environments, such as upwelling systems, that may buffer stress, promote recovery, and could enhance resilience by promoting physiological plasticity that supports thermotolerance is therefore critical. Here, we compared benthic community composition, coral percent cover, and photophysiology between an upwelling location in the Gulf of Papagayo and a non-upwelling location in Sámara on the Pacific coast of Costa Rica. Waters in Papagayo were cooler, more acidic, and had higher chlorophyll-a concentrations. Reefs at this location exhibited higher crustose coralline algae, higher sea urchin abundance, and lower macroalgae cover, compared to Sámara. Papagayo also showed higher stony coral cover, driven by Pocillopora spp., while Sámara was dominated by massive, heat-tolerant Porites spp. Photophysiological parameters were significantly different between locations. Specifically, photosynthetic efficiency (Fv′/Fm′) was 10–45% higher, and maximum photosynthetic rate (Pmax) was 20–40% lower in corals from Papagayo than in those from Sámara. These results reveal that two locations differing in environmental regime within a relatively small geographic area also differ in coral community composition and photophysiological features. Although further research is needed to resolve whether these environmental contrasts shape the observed biological differences, the observed patterns are consistent with the hypothesis that such regimes may support reef persistence or refugia, providing a basis for future work to test this hypothesis directly.

Continue reading ‘Coral reef community structure and photophysiology differ between upwelling and non-upwelling locations on the Pacific Coast of Costa Rica’

Interactive effects of triclosan, microplastic vectors, and ocean warming–acidification on sea urchin embryo development

Published 6 July 2026 Science Closed
Tags: , , , , , , , , , ,

Highlights

  • Microplastics modulate triclosan toxicity in a concentration-dependent manner.
  • Microplastic loads reverse triclosan attenuation affecting larval development.
  • Acidification amplifies triclosan–microplastic toxicity in sea urchin embryos.
  • Ocean Warming modulates toxicity; degree-day normalization reveals hidden stress.

Abstract

Understanding how emerging contaminants interact with climate-driven stressors is essential for accurate ecological risk assessment in coastal ecosystems. This study evaluates the individual and combined effects of triclosan (TC), polyethylene microplastics (MP), ocean warming (OW), and ocean acidification (OA) on the early development of Paracentrotus lividus embryos. A tiered experimental design was implemented to: (i) characterize TC dose–response curves alone and in combination with increasing concentrations of MP (300–3000 particles mL−1), and (ii) assess how OW (24 °C) and OA (pH 7.6) modulate contaminant toxicity. TC showed concentration-dependent growth inhibition, while MP exhibited a biphasic interaction with TC: at moderate concentrations, MP increased EC10 values and steepened dose–response slopes, consistent with contaminant sorption reducing freely dissolved TC. At 3000 particles mL−1, this trend reversed, lowering EC50 values and enhancing toxicity. Morphometric analyses revealed that co-exposure to TC alone and with MP loads impaired arm elongation, increased body-width ratios, and reduced stomach volume, indicating compromised feeding and skeletal development. Climate stressors significantly altered toxicological outcomes. OA strongly amplified the combined toxicity of TC + MP, reducing larval growth to near-zero levels, whereas OW alone did not exacerbate toxicity and partially mitigated OA-driven effects in MP-TC treated groups. Degree-day normalization demonstrated that warming accelerates development but reduces growth efficiency across treatments. Overall, these results reveal threshold-dependent MP–TC interactions and highlight acidification as a critical amplifier of contaminant effects. Incorporating realistic MP–pollutant interactions and climate variables is crucial for improving hazard assessments under future ocean scenarios.

Continue reading ‘Interactive effects of triclosan, microplastic vectors, and ocean warming–acidification on sea urchin embryo development’

Short-term plasticity and long-term transcriptomic rewiring under natural ocean acidification in an ecosystem-relevant sea urchin

Published 1 July 2026 Science Closed
Tags: , , , , , ,

Highlights

  • Natural CO2 vents reveal transcriptomic responses to chronic ocean acidification.
  • Acute low-pH exposure triggers rapid but limited plastic responses in Arbacia lixula.
  • Vent-origin Arbacia lixula exhibit extensive metabolic reprogramming and antioxidant activation.
  • Low pH supresses biomineralization genes and up-regulates collagen and extracellular matrix pathways.
  • Persistence under ocean acidification is associated with energetic trade-offs and skeletal homeostasis.

Abstract

Ocean acidification is reshaping coastal ecosystems as a consequence of anthropogenic CO2 emissions. Natural CO2 vent systems provide valuable analogues for investigating organismal responses to long-term acidified conditions under ecologically realistic scenarios. Here, we examined genome-wide transcriptomic responses of the sea urchin Arbacia lixula, an ecosystem-relevant grazer inhabiting a natural CO2 vent system in La Palma (Canary Islands, Spain). Using RNA sequencing of 24 adults (n = 8 per treatment), we compared: (i) acute experimental exposure of ambient-origin individuals to low pH, (ii) chronic exposure by comparing ambient and vent-origin populations in their native pH conditions, and (iii) a genotype-of-origin comparison under shared low pH. Acute exposure triggered a limited transcriptional response (116 differentially expressed genes, DEG), characterized by activation of ion transport, redox regulation, and NAD-associated metabolism. In contrast, chronically exposed vent-origin urchins showed a tenfold increase in transcriptional changes (1053 DEG), reflecting metabolic reprogramming involving lipid, carbohydrate and amino acid pathways, and strengthened antioxidant capacity. Chronic low-pH exposure was also associated with suppression of biomineralization and developmental genes, alongside strong upregulation of collagen and extracellular matrix–associated genes that may help maintain skeletal performance under reduced carbonate availability. Genotype-of-origin effects (131 DEGs) revealed constitutive differences in metabolic, redox, extracellular matrix, and biomineralization pathways in vent populations. Together, these findings indicate that persistence under natural acidification involves both rapid plastic responses and sustained physiological reorganization, providing mechanistic insight into how calcifying species maintain functional performance under ongoing ocean acidification.

Continue reading ‘Short-term plasticity and long-term transcriptomic rewiring under natural ocean acidification in an ecosystem-relevant sea urchin’

Acute low pH associated with coastal acidification is detrimental to larval development of the Cape urchin Parechinus angulosus

Published 26 June 2026 Science Closed
Tags: , , , , , , , ,

Acidification in coastal habitats is increasing in duration and amplitude under the continued influence of ocean acidification and contributing coastal processes. The impacts of low pH conditions on calcifying organisms, especially echinoderms, is well established, with the early developmental stages being especially vulnerable. This is the first study to assess the impact of locally relevant coastal acidification scenarios on the early development of the Cape urchin Parechinus angulosus. Our findings suggest that the early larval stages of this species are unlikely to survive when exposed to low pH conditions, specifically during the onset of skeletogenesis. In our laboratory experiments, larvae that were exposed to the low pH treatment (pH 7.32) showed significantly reduced growth (GLMM, Time × Treatment interaction: β = −0.361 ± 0.019, z = −19.06, p < 0.001) and developmental regression compared with those from the control treatment (pH 7.95). Substantially slower growth rates were observed in the low pH treatment (length = 72.3 hpf0.18) compared with in the control treatment (length = 24.24 hpf0.54). There was also evidence of abnormal and delayed development and potential dissolution of skeletal structures under the low pH condition. However, fertilisation success and larval survival did not differ significantly between the experimental treatments, suggesting that developmental impacts of low pH over short durations, even though substantial, may be sublethal. The developmental impacts are likely to impair the transition of larvae to the adult stages, which may ultimately affect populations of this ecologically important species under future coastal acidification scenarios.

Continue reading ‘Acute low pH associated with coastal acidification is detrimental to larval development of the Cape urchin Parechinus angulosus’

Marine invertebrates and fishes exhibit inconsistent body size responses to ocean acidification

Published 18 June 2026 Science Closed
Tags: , , , , , , , , , , , , , , , , , ,

Body size is a fundamental characteristic of all living organisms that determines physiological functions and life-history traits. Ecological theory predicts that ocean acidification can cause body size reductions, confirmed by several studies reporting miniaturization in ectotherms. Based on this prediction, we would expect a broad suite of species to show similar plastic body-size responses to elevated CO2. Using four natural climate change analogues of ocean acidification across the northern and southern hemispheres, we quantified body size alterations across 18 marine invertebrate and fish taxa to test for climate-driven miniaturization. Only three species consistently showed body-size reductions under ocean acidification: one urchin and two fish species. In contrast, 15 other species, ranging from highly calcified to non-calcified, displayed unchanged or increased body sizes or inconsistent miniaturization. If body-size miniaturization responses were consistently reproducible across taxa we would have observed it more frequently, suggesting that species responses to ocean acidification are more variable than previously thought and likely vary depending on a species’ physiology and life history. Thus, rather than entire communities undergoing miniaturization, species are likely to display a spectrum of responses, with some exhibiting size reductions, others demonstrating physiological resistance to elevated CO2, and others potentially benefiting from the indirect effects of ocean acidification.

Continue reading ‘Marine invertebrates and fishes exhibit inconsistent body size responses to ocean acidification’

Seasonal upwelling shapes coral reef community structure and photophysiology on the Pacific Coast of Costa Rica

Published 3 June 2026 Science Closed
Tags: , , , , , , , , , , ,

Reef-building corals form the calcium-carbonate frameworks that underpin tropical coral reefs, yet global coral cover has declined by ~50% in recent decades, due to marine heatwaves and other stressors. Identifying refugia environments, such as upwelling systems, that buffer stress, promote recovery, and enhance resilience by promoting physiological plasticity that supports thermotolerance is therefore critical. Here, we compared benthic community composition, coral percent cover, and photo-physiology between an upwelling location in the Gulf of Papagayo and a non-upwelling location in Sámara on the Pacific coast of Costa Rica. Waters in Papagayo were cooler, more acidic, and richer in chlorophyll a. Reefs at this location exhibited higher crustose coralline algae, higher sea urchin cover, and lower macroalgae cover, compared to Sámara. Papagayo also showed higher stony coral cover, driven by Pocillopora spp., while Sámara was dominated by massive, heat-tolerant Porites spp.. When significant, photophysiological measurements showed 9.7 – 44.5% higher photosynthetic efficiency (Fv’/Fm’) in Papagayo corals and 19.94 – 42.75 % higher maximum photosynthetic rates (Pmax) in Sámara corals. These results highlight how contrasting environmental regimes within a relatively small geographic area can shape distinct coral community compositions and photophysiological strategies, with implications for identifying areas of reef persistence or refugia.

Continue reading ‘Seasonal upwelling shapes coral reef community structure and photophysiology on the Pacific Coast of Costa Rica’

Combined effects of ammonium and pH on sea urchin embryogenesis: insights for sediment quality assessment

Published 30 April 2026 Science Closed
Tags: , , , , , , , ,

Highlights

  • Reduced pH enhances ammonium toxicity on sea urchin embryos in filtered seawater.
  • In elutriates ammonium is a major driver of P. lividus embryotoxicity.
  • Data support setting ammonium thresholds in sediment quality frameworks.
  • Ocean acidification potentially increases ammonium toxicity for sea urchin larvae.

Abstract

Ammonium is a key component of coastal marine systems, originating from both natural and anthropogenic sources, with possible toxic effects on marine organisms depending on the concentration and pH. This study evaluates, for the first time, the combined effects of ammonium and seawater acidification on early development of the sea urchin Paracentrotus lividus under both laboratory conditions and exposure to environmental matrices derived by dredged sediments from harbor area. Embryos were incubated with increasing concentrations of ammonium in filtered seawater at pH 8.1 and 7.6, as well as in sediment elutriates from the Pescara harbor (Adriatic Sea, Italy), selected as a case study with relevant concentrations of ammonium (0.1–3.5 mg/L). A combined effect between ammonium and pH was observed, with increasing ammonium toxicity by ∼20% at pH 7. Moreover, in sediment elutriates, ammonium affect sea urchin embryo development, with EC50 ranging between 1.388 and 1.538 mg/L NH4+ at pH 8.1 and 7.6, respectively, without significant differences due to pH. Chemical analyses of sediments confirmed low levels of trace metals and organic pollutants, indicating that ammonium is the primary driver of embryotoxicity without a direct toxic effect of other contaminants. The results further underscore the need to integrate ammonium assessment into sediment quality frameworks and for management strategies, particularly in the context of future ocean acidification, to safeguard the early life stages of sensitive marine invertebrates.

Continue reading ‘Combined effects of ammonium and pH on sea urchin embryogenesis: insights for sediment quality assessment’

Short-term tolerance to ocean acidification of the sub-antarctic sea-urchin arbacia dufresnii

Published 29 January 2026 Science Closed
Tags: , , , , , ,

The accumulation of anthropogenic CO2 in the ocean is impacting the carbonate system chemistry in seawater, particularly in polar regions. Acidified seawater can impair the echinoderms internal regulation of pH due to an increase in hydrogen ions concentration, potentially affecting growth, and calcification, among other physiological activities. The goal of this work was to assess the effects of Ocean Acidification (OA) on Arbacia dufresnii, a sub-Antarctic sea urchin species. Adult specimens were exposed to three pH treatments: 7.4, 7.7, and 8.0 (control), for 21 up to 23 days. We assessed spine regeneration, a proxy of calcification, by cutting spines at the base of the shaft and evaluating the magnesium content, height, and weight of the regenerated part. The coelomic fluid was sampled for pH assessment and magnesium and calcium content analysis. The RNA/DNA ratio, a proxy of metabolic activity, was assessed in the gonads and body walls. The spine regenerated weight was significantly correlated to regenerated height but not to treatments. The coelomic fluid pH (6.77 ± 0.34) did not differ between treatments (pANOVA = 0.15). No significant differences were observed between treatments regarding RNA/DNA ratio in both body wall (pANOVA = 0.65) and gonads (pKruskal-Wallis = 0.34), the spine regenerated height (pANOVA = 0.35) and Mg regenerate content (pANOVA = 0.58). Our results suggest that A. dufresnii owns physiological mechanisms to cope with OA conditions during short-term exposure.

Continue reading ‘Short-term tolerance to ocean acidification of the sub-antarctic sea-urchin arbacia dufresnii’

Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins

Published 9 January 2026 Science Closed
Tags: , , , , , , ,

Anthropogenic stressors, including ocean acidification (OA), ocean warming (OW), and salinity changes, are rapidly altering marine ecosystems, with Arctic regions being particularly vulnerable. This study investigates the combined effects of these stressors on the fertilization success of the green sea urchin (Strongylocentrotus droebachiensis) from Kongsfjorden, Svalbard. We exposed gametes to various levels of pH, temperature, and salinity to assess their individual and combined impacts on fertilization performance. Our results show that temperature and pH significantly influenced fertilization success, with temperature having the strongest effect, while salinity had no significant impact. A significant statistical interaction between temperature and pH indicated that warming enhanced fertilization more effectively at higher pH levels, while low pH suppressed this increase. To compare the relative influence of each stressor, we used a conceptual model based on standardized slopes, which supported temperature as the dominant driver, followed by pH. These findings highlight the importance of considering the effects of combined stressors when assessing marine organism responses to climate change, especially in polar ecosystems. Our study underscores the need for further research into the mechanisms driving these combined effects, given that Arctic ecosystems face accelerated environmental changes.

Continue reading ‘Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins’

Effects of long-term ocean acidification exposure on the structural, mineralogical, and mechanical properties of sea urchin (Echinometra spp.) skeletons at a natural volcanic CO2 seep

Published 23 December 2025 Science Closed
Tags: , , , , ,

Two decades of mesocosm studies document generally negative effects of ocean acidification (OA) on adult sea urchin growth, feeding performance, skeletal structure, and strength. Whether experimental observations hold true in natural systems will determine whether they can be extrapolated to predict responses under ecologically relevant contexts. Here, we employ a suite of imaging, chemical, and mechanical techniques to examine the skeletal properties of two closely related sea urchin species (genus Echinometra) living at a natural carbon dioxide (CO2) seep in Japan. Test plates and spines from urchins living under elevated CO2 conditions were thinner, more porous, and had less biomineral than those at reference sites; however, tooth structure was resilient to elevated CO2. The magnesium content of the test and spines did not differ between sites; however, they exhibited reduced nanohardness and became more brittle under elevated CO2. Together, altered structural and mechanical properties may compromise the protective function of urchin skeletons at the CO2 seep. These responses have implications for ecosystem structure if urchin function is suppressed at the population level. Future work might explore the repeatability of these findings across successive species and localities to recognize generality, its limits, and the conditions that mediate the influence of OA.

Continue reading ‘Effects of long-term ocean acidification exposure on the structural, mineralogical, and mechanical properties of sea urchin (Echinometra spp.) skeletons at a natural volcanic CO2 seep’

Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification

Published 10 December 2025 Science Closed
Tags: , , , , ,

Ocean acidification can reduce the size of calcified structures produced by marine calcifiers, raising questions about their competitiveness and persistence in future oceans. Yet, size reduction in calcified structures may represent a plastic response to ocean acidification if these structures remain functional. To test this hypothesis and examine whether morphological plasticity can influence the functionality of calcified structures, we assessed the effects of ocean acidification on the morphological, mechanical and chemical properties of the calcified structures of a sea urchin species prevailing at natural CO2 vents. We found that the rigid shells covering sea urchins’ bodies (‘tests’) were thinner and that they had smaller teeth and lower spine density at vents, but the mechanical performance of these calcified structures (mechanical resilience, wear resistance and bending strength) was maintained, possibly mediated by the capacity of sea urchins to sustain acid-base balance for calcification (i.e. increased Na/Ca). Our findings suggest that such morphological shifts in calcified structures may enable sea urchins to maintain structural performance under ocean acidification. Since ocean acidification is a slow process relative to the life cycle of sea urchins, some sea urchin species may acclimate, or even adapt, to ocean acidification so that their populations and ecological functions can persist in a future high-CO2 world.

Continue reading ‘Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification’

Dynamics of a coral reef system under climate change

Published 28 November 2025 Science Closed
Tags: , , , , , , ,

Highlights

  • It is established that a new a stochastic coral-starfish model with global warming and ocean acidification.
  • It is revealed that the change in global warming has a decisive impact on the dominant position of corals and starfish.
  • It is found that the variation of pH is able to destabilize coral-starfish interactions.

Abstract

The intensification of global warming and ocean acidification are important factors affecting coral reef degradation, however, their impact mechanisms on coral reef system are still unclear. In this paper, we study the dynamics of a stochastic coral-starfish model considering the factors of global warming and ocean acidification, where the stochastic environmental fluctuation is characterized by mean-reverting Ornstein-Uhlenbeck (OU) process. A key advantage of considering global warming and ocean acidification in coral reef systems is that it can accurately describe the dynamic mechanisms of coral-starfish interactions, providing a scientifically reliable theoretical basis for exploring the evolutionary succession of coral reef systems. The main purpose of this paper is to investigate how global warming and ocean acidification affect the dynamic mechanisms of coral reef systems in the presence and absence of stochastic disturbances. Mathematically, we mainly study the critical threshold conditions for the transcritical bifurcation, saddle-node bifurcation, and Hopf bifurcation of deterministic coral reef system, as well as the existence of ergodic stationary distribution, precise expressions of probability density function, persistent in the mean, and stochastic extinction dynamics in stochastic coral reef system, which in turn provide a theoretical basis for numerical simulations. Numerical analysis indicates that the variations of global warming and ocean acidification can generate a great influence on the coral-starfish dynamics with and without OU process. Significantly, it is found that coral growth dominates under the increasing global warming effect, while starfish growth dominates under the decreasing global warming effect in a randomly perturbed environment. Furthermore, the change of pH has capacity to destabilize coral-starfish interactions, while the intensified global warming can lead to the extinction of starfish. These findings may contribute to the studies of potential strategies for protecting coral reef ecosystems under the impact of climate change.

Continue reading ‘Dynamics of a coral reef system under climate change’

Gut microbial community plasticity as a climate shield mediating sea cucumber resilience to ocean acidification and warming

Published 28 October 2025 Science Closed
Tags: , , , , , , , , , , ,

Ocean acidification (OA) and ocean warming (OW) pose escalating threats to marine ecosystems, particularly to benthic organisms, such as sea cucumbers, that play pivotal roles in nutrient cycling and sediment health. Existing studies have mostly focused on the physiological responses of sea cucumbers, yet overlooked the critical roles of both gut microbial communities and metabolites in the host’s responses under environmental stress. Herein, a mesocosm experiment was constructed and analyzed by using integrated gut microbiome and metabolomics approaches to investigate the responses of sea cucumbers Apostichopus japonicus to OA and OW. Results revealed that microbial community plasticity underpins holobiont adaptation, with warming restructuring gut microbiota toward thermotolerant taxa, whereas acidification enriches alkalinity-modulating Rhodobacteraceae and Halioglobus sp.. Metabolomic profiling identified 43 amino acid derivatives that exhibit significantly increased concentrations in the OA and OW groups. These derivatives include upregulated N-methyl-aspartic acid and γ-glutamyl peptides, which stabilize macromolecules and enhance redox homeostasis. Conversely, antioxidative metabolites, such as ergothioneine and L-homocystine, are suppressed, reflecting trade-offs between energy allocation and stress protection. In OW group, the antioxidant synthesis pathway is shifted to energy metabolism related to heat tolerance, whereas in OA group, energy is preferentially used for alkalinity regulation pathways rather than oxidative stress defense. Changes in microbial community structure mechanistically explain the trends in metabolite concentrations, as the proliferation of Vibrio spp. in the OW group drives lysine catabolism, leading to a significant increase in L-saccharopine levels. The reduction of Bacteroidetes in the OA group is correlated with the downregulation of L-homocystine, suggesting that pH-driven microbial interactions are disrupted. These findings demonstrate that gut microbiota reconfigure community structure and metabolic landscapes to buffer hosts against climate stress synergies, highlighting the importance of microbiome-mediated resilience in marine ecosystems under global climate change.

Continue reading ‘Gut microbial community plasticity as a climate shield mediating sea cucumber resilience to ocean acidification and warming’

Effect of ocean acidification on the metabolism and behavior of tropical sea cucumbers

Published 16 September 2025 Science Closed
Tags: , , , , , ,

In recent years, CO₂ emitted by human activities has continued to rise. The ocean absorbs these CO₂ and has caused seawater acidification. It is expected that the pH of the sea surface will drop by 0.3~0.4 by the end of this century. Tropical sea cucumbers are the “engineers” of the subsea ecosystem, promoting organic degradation and nutrient circulation through feeding disturbances. This study reviews the effects of marine acidification on the metabolism and behavior of tropical sea cucumbers. Studies have shown that under low pH conditions, sea cucumbers have increased respiratory metabolic pressure, digestive enzyme activity is reduced, and more energy is used to maintain the acid-base balance in the body, and their growth and reproduction are limited. At the same time, sea cucumber feeding rate and defense behavior are inhibited, and habitat distribution may change. These changes will have a chain effect on tropical ecosystems such as coral reefs, weaken the nutrient circulation function, and affect ecological balance. In-depth research on the impact mechanism of marine acidification on sea cucumbers will help predict the response of marine ecosystems under climate change and provide scientific basis for resource conservation and aquaculture management.

Continue reading ‘Effect of ocean acidification on the metabolism and behavior of tropical sea cucumbers’

Subscribe

Search

  • Reset

OA-ICC Highlights

Resources