Posts Tagged 'echinoderms'

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Molecular response to CO2-driven ocean acidification in the larvae of the sea urchin Hemicentrotus pulcherrimus: evidence from comparative transcriptome analyses

Published 13 January 2025 Science Closed
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Highlights

  • Ocean acidification affects morphology of Hemicentrotus pulcherrimus larvae.
  • Comparative transcriptome analyses were performed.
  • Six key potential biomarkers correlated with low pH tolerance were identified.

Abstract

In order to explore the impact of CO2-driven ocean acidification (OA) on gene expression of sea urchins, gametes of Hemicentrotus pulcherrimus were fertilized and developed to the four-armed larvae in either seawater at current pH levels (pHNBS = 7.98) or in three laboratory-controlled OA conditions (ΔpHNBS = −0.3, −0.4, −0.5 units) based on the projections of the Intergovernmental Panel on Climate Change (IPCC) for 2100. Four-armed larval specimens were collected, and comparative transcriptome analysis was then performed. The results showed that 58 differentially expressed genes (DEGs) were identified in OA-treated groups as compared to the control. Moreover, more transition and transversion SNPs were observed in OA-treated groups than those in the control indicating a potential occurrence of adaption to OA in H. pulcherrimus larvae. Six candidate DEGs shared among OA-treated groups were identified as potential biomarkers correlated with low pH tolerance, mainly enriched in nine pathways associated with Notch signaling, dorso-ventral axis formation, oxidative phosphorylation, lysine degradation, valine, leucine and isoleucine degradation, lysosome, cell adhesion molecules, glutathione metabolism and PPAR signaling pathway. These results will not only enrich our knowledge of the impacts of OA on sea urchin larvae from the aspect of gene expression, provide a better understanding on larval forms coping with OA, but also offer more clues and biomarkers for developing protection or management strategies for sea urchins under near-future OA conditions.

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Dynamic responses during early development of the sea urchin Strongylocentrotus intermedius to CO2-driven ocean acidification: a microRNA-mRNA integrated analysis

Published 9 January 2025 Science Closed
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Highlights

  • Sea urchin blastula stage is the most sensitive stage to ocean acidification (OA).
  • The PI3K/Akt pathway may be a hub pathway responding to OA in sea urchin larvae.
  • MiR-1 may be a key regulator in the dynamic response of sea urchin larvae to OA.

Abstract

To explore the dynamic molecular responses to CO2-driven ocean acidification (OA) during the early developmental stages of sea urchins, gametes of Strongylocentrotus intermedius were fertilized and developed to the four-armed larva stage in either natural seawater (as a control; pHNBS = 7.99 ± 0.01) or acidified conditions (ΔpHNBS = −0.3, −0.4, and − 0.5 units) according to the prediction for ocean pH by the end of this century. Specimens from five developmental stages (fertilization, cleavage, blastula, prism, and four-armed larva) were collected and comparative microRNA (miRNA) and mRNA transcriptome analyses were performed. The results showed that 1) a total of 22,224 differentially expressed genes (DEGs) and 51 differentially expressed miRNAs (DEMs) were identified in the OA-treated groups compared with the control group. 2) The numbers of both DEGs and DEMs were the largest at the blastula stage, indicating dramatic changes in gene expression. 3) Five “miR-1/DEG” modules were identified as potential biomarkers reflecting the response of sea urchins to OA during the early developmental period. 4) The PI3K/Akt signaling pathway was a key pathway involved in the response of S. intermedius to OA in its early developmental stages. This study deepens our understanding of the dynamic molecular regulatory mechanisms underlying sea urchin responses to CO2-driven OA.

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Genomic signals of adaptation to a natural CO2 gradient over a striking microgeographic scale

Published 14 November 2024 Science Closed
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Highlights

  • Arbacia lixula populations near CO2 vents show tolerance to acidification despite their vulnerable calcified structure.
  • A. lixula population reveal genetic divergence and substructure in response to small-scale pH variation.
  • Acidification potentially affects specific genes linked to growth, development, and calcification.
  • lixula exhibits adaptability and plasticity to acidification, suggesting its potential resilience to cope with OA.

Abstract

Our study explores genomic signs of adaptation in A. lixula to different water pH conditions. To achieve this, we analysed the genomics variation of A. lixula individuals living across a natural pH gradient in Canary Islands, Spain. We use a 2b-RADseq protocol with 74 samples from sites with varying pH levels (from 7.3 to 7.9 during low tide) and included a control site. We identified 14,883 SNPs, with 432 identified as candidate SNPs under selection to pH variations through redundancy analysis. While all SNPs indicated genomic homogeneity, the 432 candidate SNPs under selection displayed genomic differences among sites and along the pH gradient. Out of these 432 loci, 17 were annotated using published A. lixula transcriptomes, involved in biological functions such as growth. Therefore, our findings suggest local adaptation in A. lixula populations to acidification in CO2 vents, even over short distances of 75 m, underscoring their potential resistance to future Ocean Acidification.

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Drivers of biological diversity and responses to global changes in marine invertebrates

Published 12 November 2024 Science Closed
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Human activities, in particular global changes (e.g., ocean warming – OW and ocean acidification – OA) are projected to drive some marine species to extinction within the coming decades. Marine invertebrates are amongst the most vulnerable to these changes due to the increased energetic cost to maintain intracellular pH homeostasis. To mitigate extinction, organisms may migrate, acclimate or adapt genetically. While these mechanisms are increasingly documented, they are not fully understood. This knowledge is critical for assessment of extinction risks, an important index for effective conservation and management of marine biodiversity. This thesis aims to increase our understanding on the drivers of biological diversity and sensitivity of marine invertebrates to OW and OA. Specifically, I assess (1) the quality of inferences on adaptive evolution in recent publications on responses of marine invertebrates to OW or OA and summarize the current knowledge and identify the gaps (Paper I); (2) the drivers of genetic diversity, structure, connectivity among Acropora austera populations across Mozambique coral reefs (Paper II); (3) the sensitivity to low pH in larvae of the sea urchin, Tripneustes gratilla, from subtidal and intertidal seagrass meadows with contrasting pH variability at Inhaca Island, Mozambique (Paper III); (4) the role of natural fluctuation in pH on the response of larvae of the sea urchin Echinus esculentus to low pH (Paper IV). Field genome scans surveys, laboratory experiments and systematic literature review were used. My systematic literature review (Paper I) highlights that publication on adaptive responses of marine invertebrates to OW or OA used more frequently strong methods for inferences of genetic change, such as common garden experiments and molecular genetic analysis. Methods for weaker inferences, such as comparison to model prediction, were less frequently used. On the other hand, reciprocal transplants, the stronger method for inferring adaptive change was less used in comparison with weaker methods such as phenotypic and genotypic selection. I also showed different levels of genetic variability and connectivity between populations of corals along the Mozambique coast. These geographic differences in levels of genetic diversity and connectivity may be explained by oceanographic factors and mode of reproduction of the corals (Paper II). Larvae of the sea urchin T. gratilla from Inhaca Island had reduced fitness when exposed to low pH. Moreover, larvae from adults collected in an intertidal habitat were more sensitive to low pH as compared to larvae from adults collected in a subtidal population. This result reveals population specific responses to low pH and challenges current theories that predict higher tolerance in individuals living in habitats with higher pH range (Paper III). Under present day natural variability in pH, the extreme low pH does not appear to be the main driver of biological responses in larvae of the sea urchin E. esculentus and adaptation to such conditions might be associated with a cost of plasticity but not a cost of canalization (Paper IV). Overall, this thesis shows that oceanographic factors and natural variability in pH influence the levels of genetic diversity and biological sensitivity in populations of marine invertebrates. These parameters should be considered to better evaluate the ability of marine invertebrates to withstand environmental changes and to sustain the provision of ecological functions, and guide conservation strategies.

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Benthic diatom response to short-term acidification and warming influenced by grazing and nutrients

Published 7 October 2024 Science Closed
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Highlights

  • Periphyton was not affected by acidification and warming as nutrients are replete.
  • Direct effects of acidification and warming on grazers indirectly affected periphyton.
  • Differences in fecal production of grazers affected rate of periphyton regeneration.
  • Complex multiple factor interactions are important considerations for future studies.

Abstract

This study investigated differences in total biomass (ash-free dry weight) of the periphyton and autotrophic biomass (chlorophyll-a content) of benthic diatoms in the absence or presence (No Grazer vs With Grazer) of two invertebrate grazers (Stichopus cf. horrens and Trochus maculatus) under simulated ambient (PRESENT), independent ocean acidification (OA) and warming (OW), and their combination (FUTURE) over an eight-day period. In the absence of a grazer, there were no significant differences in the average of the total and autotrophic biomass among treatments for both experiments. Stichopus significantly reduced the total and autotrophic biomass after 1 day, except under OW. Trochus significantly reduced the total biomass in the OA and OW treatments after 5 days, and the autotrophic biomass in the OA treatment after 1 and 5 days of grazing. In treatments where total and autotrophic biomass were not reduced, nutrients from the fecal matter and metabolic wastes of grazers seemingly stimulated the regeneration of microalgal biomass. The amount of fecal matter produced also affected the rate of microalgal renewal. In addition, due to the unexpected difference in seawater nutrient concentration during the two experiments, comparison of primary production under PRESENT was done to tease out nutrient effects. In PRESENT, autotrophic biomass was higher in Experiment 1 than Experiment 2, which was likely influenced by differences in nutrient concentrations. Results of this study elucidate underlying mechanisms in microalgal interactions with biotic and abiotic factors in tropical systems under changing ocean conditions.

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Skeletal magnesium content in Antarctic echinoderms along a latitudinal gradient

Published 4 October 2024 Science Closed
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Highlights

  • Skeletal structures presented high Mg content, except in echinoid spines.
  • Asteroids had the highest Mg content, followed by ophiuroids, holothuroids, and echinoids.
  • No local variability in skeletal Mg content was observed in asteroids and holothuroids.
  • Environmental parameters may have influenced the skeletal Mg in ophiuroids and echinoids.

Abstract

Ocean warming and acidification driven by anthropogenic CO2 emissions may impact the mineral composition of marine calcifiers. Species with high skeletal Mg content could be more susceptible in polar regions due to the increased solubility of CO2 at lower temperatures. We aimed to assess the environmental influence on skeletal Mg content of Antarctic echinoderms belonging to Asteroidea, Ophiuroidea, Echinoidea and Holothuroidea classes, along a latitudinal gradient from the South Shetland Islands to Rothera (Adelaide Island). We found that all skeletal structures, except for echinoid spines, exhibited high Mg content, with asteroids showing the highest levels. Our results suggest that asteroids and holothuroids exert a higher biological capacity to regulate Mg incorporation into their skeletons. In contrast, the variability observed in the skeletal Mg content of ophiuroids and echinoids appears to be more influenced by local environmental conditions. Species-specific differences in how environmental factors affect the skeletal Mg content can thus be expected as a response to global climate change.

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Long-term study of the combined effects of ocean acidification and warming on the mottled brittle star Ophionereis fasciata

Published 27 September 2024 Science Closed
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The global ocean is rapidly changing, posing a substantial threat to the viability of marine populations due to the co-occurrence of multiple drivers, such as ocean warming (OW) and ocean acidification (OA). To persist, marine species must undergo some combination of acclimation and adaptation in response to these changes. Understanding such responses is essential to measure and project the magnitude and direction of current and future vulnerabilities in marine ecosystems. Echinoderms have been recognised as a model in studying of OW-OA effects on marine biota. However, despite their global diversity, vulnerability, and ecological importance in most marine habitats, brittle stars (ophiuroids) are poorly studied. A long-term mesocosm experiment was conducted on adult mottled brittle star (Ophionereis fasciata) as a case study to investigate the physiological response and trade-offs of marine organisms to ocean acidification, ocean warming and the combined effect of both drivers. Long-term exposure of O. fasciata to high temperature and low pH affected survival, respiration and regeneration rates, growth rate, calcification/dissolution, and righting response. Higher temperatures increased stress and respiration and decreased regeneration and growth rates as well as survival. Conversely, changes in pH had more subtle or no effect affecting only respiration and calcification. Our results indicate that exposure to a combination of high temperature and low pH produces complex responses for respiration, righting response and calcification. We address the knowledge gap of the impact of a changing ocean on ophiuroids in the context of echinoderm studies, proposing this class as an ideal alternative echinoderm for future research.

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Species sensitivity distributions: understanding ocean acidification’s impact on marine biota

Published 30 July 2024 Science Closed
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This research paper investigates the repercussions of ocean acidification on marine ecosystems, focusing on the sensitivity of diverse taxa to changing pH stages. Drawing from recent research, we discover the complicated interaction among climate change, contaminant accumulation, and atmosphere dynamics, with a particular emphasis on coastal regions reliant on fisheries. Through a complete assessment, we recognize substantial differences in sensitivity amongst calcifying taxa, highlighting the implications for each polar and temperate/tropical region. Furthermore, we propose tailored management techniques relying on distinct climate zones and taxonomic groups to mitigate the destructive effects of ocean acidification. Our sensitivity analyses monitoring of capability shifts in Species Sensitivity Distributions (SSDs) under preindustrial pH situations, underscoring the importance of historic baselines in predicting future influences. This paper contributes to our understanding of how ocean acidification threatens marine biodiversity and underscores the urgency of implementing efficient conservation measures.

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From individual calcifiers to ecosystem dynamics: ocean acidification effects on urchins and abalone

Published 16 July 2024 Science Closed
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A central question in ecology is: to what extent do trophic interactions govern the structure and function of communities? This question is becoming more pressing as trophic interactions shift with rapid climate change. Sea urchins and abalone are key invertebrates in the habitats in which they reside. Sea urchins are critical members of exemplar trophic cascades in kelp forests due to their impact on kelp establishment and maintenance; yet their populations are controlled by predators, such as sea otters and sunflower sea stars. Abalone compete with urchins for macroalgal food resources and therefore can help regulate urchin populations in kelp forests. Given that both urchin tests and abalone shells used for predator defense are comprised of calcium carbonate, much research has been conducted on the impacts of ocean acidification (OA) on these calcified structures. A growing body of literature has shown that urchin tests are less calcified and break with less force under OA conditions. Less is known about abalone, but their shells also appear to respond negatively to OA. Using kelp forest communities as exemplar ecosystems, we discuss the morphological, biomechanical, and physiological responses to OA in urchins and abalone and consider how these individual level responses scale to trophic interactions and ultimately whole ecosystem processes. Although the impacts of OA on the calcified structures used for defense have been well studied, calcified mechanisms for food consumption, such as the Aristotle’s lantern of urchins, are much less understood. Thus, examining both the feeding and defense sides of trophic interactions would greatly improve our understanding of OA responses across individual to ecosystem level scales. More generally, measurements of morphological, biomechanical, and physiological responses to OA can be made in individuals to help predict higher level ecological responses, which would greatly contribute to broader predictions of whole ecosystem responses to OA.

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Ocean warming and acidification adjust inter- and intra-specific variability in the functional trait expression of polar invertebrates

Published 3 July 2024 Science Closed
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Climate change is known to affect the distribution and composition of species, but concomitant alterations to functionally important aspects of behaviour and species-environment relations are poorly constrained. Here, we examine the ecosystem ramifications of changes in sediment-dwelling invertebrate bioturbation behaviour—a key process mediating nutrient cycling—associated with near-future environmental conditions (+ 1.5 °C, 550 ppm [pCO2]) for species from polar regions experiencing rapid rates of climate change. We find that responses to warming and acidification vary between species and lead to a reduction in intra-specific variability in behavioural trait expression that adjusts the magnitude and direction of nutrient concentrations. Our analyses also indicate that species behaviour is not predetermined, but can be dependent on local variations in environmental history that set population capacities for phenotypic plasticity. We provide evidence that certain, but subtle, aspects of inter- and intra-specific variation in behavioural trait expression, rather than the presence or proportional representation of species per se, is an important and under-appreciated determinant of benthic biogeochemical responses to climate change. Such changes in species behaviour may act as an early warning for impending ecological transitions associated with progressive climate forcing.

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Evaluating the time to detect biological effects of ocean acidification and warming: an example using simulations of purple sea urchin settlement

Published 2 July 2024 Science Closed
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 Ocean acidification (OA) and ocean warming driven by climate change are important stressors for marine species and systems, but documenting and detecting their long-term impacts on biological responses outside of laboratory settings are challenging due to natural variability caused by complex processes and interactions. We used settlement of purple sea urchins Strongylocentrotus purpuratus in the Southern California Bight (USA) over 6 yr as an example data set to parameterize a simulation model for exploring the time needed to detect environmental effects on a biological response. A generalized linear model was used to describe an index of urchin settlement as functions of pH, sea surface temperature (SST), sea surface salinity (SSS), and spatio-temporal factors, demonstrating that settlement was negatively associated with pH (i.e. lower settlement at higher pH) and positively associated with SST and SSS. Monte Carlo simulations were developed from this base model under a variety of alternative scenarios to estimate the time to detect: (1) annual trends in pH and SST time series, (2) pH and SST effects on urchin settlement, and (3) annual trends in urchin settlement. Time to detect pH and SST effects was predominantly influenced by the underlying strength of the relationships and the model uncertainty. Time to detect annual trends in settlement was more sensitive to the severity of long-term OA and warming trends, which had cumulative (at times opposing) effects. This study highlights the variable time scales (2-60+ yr) that may be necessary to detect biological responses to OA and ocean warming and the sensitivity to different assumptions of the study system.

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Revisiting 20 years of coral–algal interactions: global patterns and knowledge gaps

Published 1 July 2024 Science Closed
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Coral–algal interactions are pivotal in reef ecosystems globally as they can scale up ecosystem levels and lead to dominance shifts. In this study, we conducted a systematic review of global coral–algal interactions, identifying the most studied locations, species, and types of interactions. We then assessed how these interactions may be impacted by consumers and climate change. Over the past 20 years (2001–2020), coral and algae interactions were mostly explored in the Pacific, and the Caribbean and US East Coast, where branching and massive corals were the focus, while other coral growth forms received less attention, and effects on algae were often overlooked. Adult corals were generally reported to be damaged when directly interacting with algae through physical abrasion or allelopathy. Conversely, algae interactions were found to have a positive impact on juvenile corals by facilitating larval recruitment and settlement. As expected, coral–algal interactions and the type of coral–algal relationships vary globally, most likely due to differences in abiotic conditions, community composition and the number of studies performed in a region. Despite the large emphasis on the role of consumers in controlling coral–algal interactions, few studies directly explored the effects of herbivory on coral–algal interactions. Given the growing evidence that ocean warming and acidification can reduce the competitive ability of corals, understanding the dynamic relationships between coral, algae, and consumers under future climate change conditions is crucial in predicting future coral recruitment potential and reef composition patterns. Here, we highlight the main findings from coral–algal interaction studies performed in the last 20 year and point to future directions, such as: 1) diversifying location, coral species, growth forms and life phases; 2) considering effects on both sides of interaction, not neglecting effects on algae; and 3) taking a closer look into the role of consumers and microbiomes. Advancing our understanding of coral–algal interactions, as well as how these interactions shift under changing conditions, is critical in predicting how coral reef ecosystems may operate in the future.

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Neuromolecular mechanisms related to reflex behaviour in Aplysia are affected by ocean acidification

Published 25 June 2024 Science Closed
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While ocean acidification (OA) impacts the behaviour of marine organisms, the complexity of neurosystems makes linking behavioural impairments to environmental change difficult. Using a simple model, we exposed Aplysia to ambient or elevated CO2 conditions (approx. 1500 µatm) and tested how OA affected the neuromolecular response of the pleural–pedal ganglia and caused tail withdrawal reflex (TWR) impairment. Under OA, Aplysia relax their tails faster with increased sensorin-A expression, an inhibitor of mechanosensory neurons. We further investigate how OA affects habituation training output, which produced a ‘sensitization-like’ behaviour and affected vesicle transport and stress response gene expression, revealing an influence of OA on learning. Finally, gabazine did not restore normal behaviour and elicited little molecular response with OA, instead, vesicular transport and cellular signalling link other neurotransmitter processes with TWR impairment. Our study shows the effects of OA on neurological tissue parts that control for behaviour.

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Drivers of biological response to fluctuating seawater ph conditions in sea urchin echinus esculentus larvae

Published 22 May 2024 Science Closed
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Highlights

  • Low pH has a negative effect on sea urchin larval fitness.
  • Under fluctuating pH conditions, the minimum pH is not driving the biological response.
  • Larvae are pre-adapted to fluctuating conditions and inverting the pH diurnal cycle leads to negative effects on fitness.
  • Adaptation to variability in a coastal species is associated with a cost of plasticity but not cost of canalization.

Abstract

A large body of evidence is documenting the impact of reduced pH on marine species and ecosystems. This information is used to infer the present and future impacts of ocean acidification. However, a vast majority of the studies were performed using constant pH and the high level of pH variability experienced by marine organisms on the coastal zone was often overlooked. Recent studies highlight the key role of this variability in driving biological response to pH as well as species sensitivity to ocean acidification. For example, it was hypothesized that because of local adaptation, the extreme of the present range of pH variability is a good predictor for local biological thresholds. Using a complex experimental design, we investigated what part of the pH variability is driving the biological response of the sea urchin Echinus esculentus larvae. Comparing stable (pH 8.13, 7.82, 7.53) and fluctuating treatments (12 h at pH 8.13 and 12 h at pH 7.53) following natural or inverted diurnal cycles, we were able to show that (i) under constant conditions, low pH deviating from the present range of natural variability had a negative effect on larval growth rate and calcification; (ii) under fluctuating conditions, a desynchronization of the pH variation with the photoperiod led to decreased larval growth rate and calcification; (iii) overall, larval fitness (survival, growth and calcification) was higher under fluctuating conditions as compared to constant. While these data do not support the hypothesis that the minimum pH is the main driver of the biological response, they provide evidence of adaptation to variability in a coastal species with associated a cost of plasticity but not a cost of canalization.

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Simultaneous ocean acidification and warming do not alter the lipid-associated biochemistry but induce enzyme activities in an asterinid starfish

Published 6 May 2024 Science Closed
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Highlights

  • Ocean acidification and warming impacts on tropical-subtropical asterinid starfish were investigated.
  • Combined stressors did not affect starfish lipid and fatty acids.
  • Ocean warming increased starfish total lipid, SFAs, and PUFAs but reduced MUFAs concentration.
  • Elevated temperature allowed starfish to cope with the negative effect of increased pCO2 on enzyme activities.

Abstract

Ocean acidification and warming affect marine ecosystems from the molecular scale in organismal physiology to broad alterations of ecosystem functions. However, knowledge of their combined effects on tropical-subtropical intertidal species remains limited. Pushing the environmental range of marine species away from the optimum initiates stress impacting biochemical metabolic characteristics, with consequences on lipid-associated and enzyme biochemistry. This study investigates lipid-associated fatty acids (FAs) and enzyme activities involved in biomineralization of the tropical-subtropical starfish Aquilonastra yairi in response to projected near-future global change. The starfish were acclimatized to two temperature levels (27 °C, 32 °C) crossed with three pCO2 concentrations (455 μatm, 1052 μatm, 2066 μatm). Total lipid (ΣLC) and FAs composition were unaffected by combined elevated temperature and pCO2, but at elevated temperature, there was an increase in ΣLC, SFAs (saturated FAs) and PUFAs (polyunsaturated FAs), and a decrease in MUFAs (monounsaturated FAs). However, temperature was the sole factor to significantly alter SFAs composition. Positive parabolic responses of Ca-ATPase and Mg-ATPase enzyme activities were detected at 27 °C with elevated pCO2, while stable enzyme activities were observed at 32 °C with elevated pCO2. Our results indicate that the lipid-associated biochemistry of A. yairi is resilient and capable of coping with near-future ocean acidification and warming. However, the calcification-related enzymes Ca-ATPase and Mg-ATPase activity appear to be more sensitive to pCO2/pH changes, leading to vulnerability concerning the skeletal structure.

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Developmental and biochemical markers of the impact of pollutant mixtures under the effect of global climate change

Published 3 May 2024 Science Closed
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Highlights

  • Complex interactions of MP, CPF on sea urchin larvae under OA & OW were revealed
  • Provides a comprehensive evaluation of CPF, MP, OA, OW effects on sea urchin larvae
  • Oxidative stress, detox impairment induced in sea urchin larvae by combined stressors
  • Unexpected stress induced by temperature rise impacts larval growth
  • Holistic approach integrating growth and biomarkers is vital for effective mitigation

Abstract

This study investigates the combined impact of microplastics (MP) and Chlorpyriphos (CPF) on sea urchin larvae (Paracentrotus lividus) under the backdrop of ocean warming and acidification. While the individual toxic effects of these pollutants have been previously reported, their combined effects remain poorly understood. Two experiments were conducted using different concentrations of CPF (EC10 and EC50) based on previous studies from our group. MP were adsorbed in CPF to simulate realistic environmental conditions. Additionally, water acidification and warming protocols were implemented to mimic future ocean conditions. Sea urchin embryo toxicity tests were conducted to assess larval development under various treatment combinations of CPF, MP, ocean acidification (OA), and temperature (OW). Morphometric measurements and biochemical analyses were performed to evaluate the effects comprehensively. Results indicate that combined stressors lead to significant morphological alterations, such as increased larval width and reduced stomach volume. Furthermore, biochemical biomarkers like acetylcholinesterase (AChE), glutathione S-transferase (GST), and glutathione reductase (GRx) activities were affected, indicating oxidative stress and impaired detoxification capacity. Interestingly, while temperature increase was expected to enhance larval growth, it instead induced thermal stress, resulting in lower growth rates. This underscores the importance of considering multiple stressors in ecological assessments. Biochemical biomarkers provided early indications of stress responses, complementing traditional growth measurements. The study highlights the necessity of holistic approaches when assessing environmental impacts on marine ecosystems. Understanding interactions between pollutants and environmental stressors is crucial for effective conservation strategies. Future research should delve deeper into the impacts at lower biological levels and explore adaptive mechanisms in marine organisms facing multiple stressors. By doing so, we can better anticipate and mitigate the adverse effects of anthropogenic pollutants on marine biodiversity and ecosystem health.

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Functional diversity and metabolic response in benthic communities along an ocean acidification gradient

Published 1 May 2024 Science Closed
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Highlights

  • Ocean acidification (OA) affect the distribution of traits within a community leading to the selection of specific functional traits.
  • Along with the selection of traits, OA led to differences in oxygen consumption between benthic communities following acidification gradient.
  • Altered acidified condition have a negative effect on the stability of the community resulting from changes in functional evennes of benthic communities.

Abstract

Altered ocean chemistry caused by ocean acidification (OA) is expected to have negative repercussions at different levels of the ecological hierarchy, starting from the individual and scaling up to the community and ultimately to the ecosystem level. Understanding the effects of OA on benthic organisms is of primary importance given their relevant ecological role in maintaining marine ecosystem functioning. The use of functional traits represents an effective technique to investigate how species adapt to altered environmental conditions and can be used to predict changes in the resilience of communities faced with stresses associated with climate change. Artificial supports were deployed for 1-y along a natural pH gradient in the shallow hydrothermal systems of the Bottaro crater near Panarea (Aeolian Archipelago, southern Tyrrhenian Sea), to explore changes in functional traits and metabolic rates of benthic communities and the repercussions in terms of functional diversity. Changes in community composition due to OA were accompanied by modifications in functional diversity. Altered conditions led to higher oxygen consumption in the acidified site and the selection of species with the functional traits needed to withstand OA. Calcification rate and reproduction were found to be the traits most affected by pH variations. A reduction in a community’s functional evenness could potentially reduce its resilience to further environmental or anthropogenic stressors. These findings highlight the ability of the ecosystem to respond to climate change and provide insights into the modifications that can be expected given the predicted future pCO2 scenarios. Understanding the impact of climate change on functional diversity and thus on community functioning and stability is crucial if we are to predict changes in ecosystem vulnerability, especially in a context where OA occurs in combination with other environmental changes and anthropogenic stressors.

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Transgenerational acclimation to acidified seawater and gene expression patterns in a sea urchin

Published 26 April 2024 Science Closed
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Highlights

  • Transgenerational response to ocean acidification reduces prediction uncertainty.
  • Two-generations experiment with mature sea urchin was conducted in acidified seawater.
  • Acclimated parent larvae showed higher survival, less size reduction in acidified water.
  • Different gene expressions were observed in larvae from acclimated/non-acclimated parents.

Abstract

Transgenerational responses of susceptible calcifying organisms to progressive ocean acidification are an important issue in reducing uncertainty of future predictions. In this study, a two-generation rearing experiment was conducted using mature Mesocentrotus nudus, a major edible sea urchin that occurs along the coasts of northern Japan. Morphological observations and comprehensive gene expression analysis (RNA-seq) of resulting larvae were performed to examine transgenerational acclimation to acidified seawater. Two generations of rearing experiments showed that larvae derived from parents acclimated to acidified seawater tended to have higher survival and show less reduction in body size when exposed to acidified seawater of the same pH, suggesting that a positive carry-over effect occurred. RNA-seq analysis showed that gene expression patterns of larvae originated from both acclimated and non-acclimated parents to acidified seawater tended to be different than control condition, and the gene expression pattern of larvae originated from acclimated parents was substantially different than that of larvae of non-acclimated and control parents.

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Interactive effects of chronic ocean acidification and warming on the growth, survival, and physiological responses of adults of the temperate sea urchin Strongylocentrotus intermedius

Published 19 April 2024 Science Closed
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Highlights

  • Ocean acidification and warming (OAW) repressed the survival and growth of Strongylocentrotus intermedius.
  • OAW altered the relative expression and activities of key metabolic enzymes of S. intermedius.
  • OAW attenuated the ATP production and antioxidant capability of S. intermedius.
  • Interactive effects of OAW on S. intermedius were analyzed in detail.

Abstract

To investigate the interactive effects of chronic ocean acidification and warming (OAW) on the growth, survival, and physiological responses of sea urchins, adults of the temperate sea urchin Strongylocentrotus intermedius were incubated separately/jointly in acidic (ΔpHNBS = −0.5 units) and thermal (ΔT = +3.0 °C) seawater for 120 days under lab-controlled conditions based on the projected ocean pH and temperature for 2100 put forward by the Intergovernmental Panel on Climate Change (IPCC). Survival rate (SR), average food consumption rate (FCR), gut index (GuI), specific growth rate (SGR), digestive capability, energy production, and antioxidant capability were subsequently determined. The results showed that 1) the SR, FCR, GuI and SGR decreased sharply under OAW conditions. Significant interactive effects of OAW on SR and SGR were observed at 120 days post-incubation (dpi), and on FCR this occurred at 90 dpi. 2) OAW altered the activities of both digestive and antioxidant enzymes. There were significant interaction effects of OAW on the activities of amylase, trehalase, and superoxide dismutase. 3) The relative gene expression levels and activities of key enzymes involved in glycometabolism pathways (i.e., glycolysis and the tricarboxylic acid cycle) were significantly affected by OAW, resulting in an alteration of the total ATP content in the sea urchins. Interaction effects of OAW were observed in both relative gene expression and the activity of enzymes involved in glycolysis (hexokinase), the transformation of glycolysis end-products (lactate dehydrogenase), the tricarboxylic acid cycle (citrate synthetase), and ATP production (Na+/K+-ATPase). The data from this study will enrich our knowledge concerning the combined effects of global climate change on the survival, growth, and physiological responses of echinoderms.

Continue reading ‘Interactive effects of chronic ocean acidification and warming on the growth, survival, and physiological responses of adults of the temperate sea urchin Strongylocentrotus intermedius’

Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers and limits poleward range shifts

Published 21 March 2024 Science Closed
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Ongoing climate change has caused rapidly increasing temperatures and an unprecedented decline in seawater pH, known as ocean acidification. Increasing temperatures are redistributing species toward higher and cooler latitudes that are most affected by ocean acidification. While the persistence of intertidal species in cold environments is related to their capacity to resist sub-zero air temperatures, studies have never considered the interacting impacts of ocean acidification and freeze stress on species survival and distribution. Here, a full-factorial experiment was used to study whether ocean acidification increases mortality in subtidal Mytilus trossulus and subtidal M. galloprovincialis, and intertidal M. trossulus following sub-zero air temperature exposure. We examined physiological processes behind variation in freeze tolerance using 1H NMR metabolomics, analyses of fatty acids, and amino acid composition. We show that low pH conditions (pH = 7.5) significantly decrease freeze tolerance in both intertidal and subtidal populations of Mytilus spp. Under current day pH conditions (pH = 7.9), intertidal M. trossulus was more freeze tolerant than subtidal M. trossulus and subtidal M. galloprovincialis. Conversely, under low pH conditions, subtidal M. trossulus was more freeze tolerant than the other mussel categories. Differences in the concentration of various metabolites (cryoprotectants) or in the composition of amino acids and fatty acids could not explain the decrease in survival. These results suggest that ocean acidification can offset the poleward range expansions facilitated by warming and that reduced freeze tolerance could result in a range contraction if temperatures become lethal at the equatorward edge.

Continue reading ‘Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers and limits poleward range shifts’

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