The effects of climate change are becoming more apparent, predominantly concerning the impacts of ocean acidification on calcifying species. Many marine organisms rely on chemical signals for processes such as foraging for food, predator avoidance, or locating mates. The process of how chemical cues in marine invertebrates function, and how this sensory mode is affected by pH levels, is less researched. We tested the impact of reduced pH (7.6), simulating end-of-the-century predicted average ocean pH, against current oceanic pH conditions (8.2), on the behavioural response of male shore crabs Carcinus maenas to the female sex pheromone bouquet consisting of Uridine–diphosphate (UDP) and Uridine–triphosphate (UTP). While in current pH conditions (8.2), there was a significant increase in sexual interactions in the presence of female pheromone, males showed reduced sexual behaviours at pH 7.6. The crab weight–pH relationship, in which larger individuals respond more intensely sexually in normal pH (8.2), is reversed for both the initial detection and time to locate the cue. These results indicate that lowered pH alters chemical signalling in C. maenas also outside the peak reproductive season, which may need to be taken into account when considering the future management of this globally invasive species.
Continue reading ‘Effects of pH on olfactory behaviours in male shore crabs, Carcinus maenas’Posts Tagged 'adaptation'
Effects of pH on olfactory behaviours in male shore crabs, Carcinus maenas
Published 11 April 2024 Science ClosedTags: adaptation, biological response, chemistry, crustaceans, laboratory, North Atlantic, otherprocess, physiology, reproduction
Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents
Published 22 March 2024 Science ClosedTags: adaptation, biogeochemistry, biological response, laboratory, Mediterranean, molecular biology, nitrogen fixation, otherprocess, phanerogams, physiology, prokaryotes, protists, vents
Seagrass meadows form highly productive and diverse ecosystems in coastal areas worldwide, where they are increasingly exposed to ocean acidification (OA). Efficient nitrogen (N) cycling and uptake are essential to maintain plant productivity, but the effects of OA on N transformations in these systems are poorly understood. Here we show that complete N cycling occurs on leaves of the Mediterranean seagrass Posidonia oceanica at a volcanic CO2 vent near Ischia Island (Italy), with OA affecting both N gain and loss while the epiphytic microbial community structure remains largely unaffected. Daily leaf-associated N2 fixation contributes to 35% of the plant’s N demand under ambient pH, while it contributes to 45% under OA. Nitrification potential is only detected under OA, and N-loss via N2 production increases, although the balance remains decisively in favor of enhanced N gain. Our work highlights the role of the N-cycling microbiome in seagrass adaptation to OA, with key N transformations accelerating towards increased N gain.
Continue reading ‘Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents’Marine benthic communities of the future: use of acidified natural systems
Published 5 March 2024 Science ClosedTags: adaptation, biological response, BRcommunity, chemistry, community composition, echinoderms, field, molecular biology, morphology, North Atlantic, otherprocess, vents
Ocean acidification (OA) is one of the most significant threats to marine organisms and is linked to climate change. It occurs when anthropogenic CO2 is absorbed by the oceans, resulting in a decrease in seawater pH and the dissolution of calcium carbonate. Projections indicate that OA will exacerbate in the future, highlighting the need to understand its impact on marine ecosystems. Much of our knowledge about the effects of OA comes from laboratory experiments, as predicting responses in natural conditions is challenging. Therefore, studies focusing on species living in naturally acidified systems, such as shallow CO2 seeps or vents, are becoming increasingly popular to obtain more realistic predictions.
This doctoral thesis, consisting of 5 chapters, explores the effects of ocean acidification on benthic communities in the subtropical Atlantic Ocean, using the naturally acidified CO2 vent system off the southern coast of La Palma Island in the Canary Islands, Spain, as a natural laboratory. Chapter 1 serves as an introduction to this thesis, explaining what naturally acidified systems are and discussing the research conducted in various locations worldwide where they have been discovered. Specifically, it focuses on studies that have utilized CO2 vents, which originate from volcanic activity. This chapter provides an overview of the importance, advantages, and disadvantages of using these acidified systems as natural laboratories to study OA in situ. It highlights that although there is no perfect analogue for future oceans, these systems help us to better understand the direct and indirect impacts of OA on different marine communities.
Among all the CO2 vents in the world, one of the few naturally acidified shallow systems in the Atlantic Ocean, and the only one with subtropical communities is located off the southern coast of Fuencaliente municipality in La Palma Island, Canary Islands. Chapter 2 of the thesis characterizes the chemical properties of this natural CO2 system in La Palma. It provides information about its volcanic and hydrological origins, as well as the different emission points along the Punta de Fuencaliente. Furthermore, it describes the carbon dynamics of the system, including variations in total inorganic carbon (CT) from 2120.10 to 10784.84 μmol kg-1, alkalinity (AT) from 2415.20 to 10817.12 μmol kg-1, pH from 7.12 to 8.07, aragonite saturation state (Ω) from 0.71 to 4.15, and calcite Ω from 1.09 to 6.49 units. A high CO2 emission flux ranging from 2.8 to 28 kg of CO2 d-1 has also been detected, making this zone an important natural carbon source. Due to its origins, this acidified system presents disadvantages as a natural laboratory for studying OA, such as natural fluctuations caused by tides or additional input of alkaline substances. Nevertheless, it creates a natural gradient of CO2 or pH along the coast with chemical characteristics very similar to those predicted for future scenarios, making it an exceptional location for studying the long-term and multi-level effects of acidification on marine ecosystems.
Chapter 3 explores rocky benthic communities along the natural pH gradient generated by the CO2 vent system in front of Punta de Fuencaliente. The objective of this chapter was to understand the direct and indirect effects of OA on the diversity and species composition of these subtropical marine communities. The study utilized a high-resolution molecular technique called DNA metabarcoding, which sequences fragments of the mitochondrial gene Cytochrome C Oxidase subunit I (COI) to detect the actual species diversity in each area. In this chapter, metabarcoding analysis reveals, for the first time, high levels of taxonomic diversity in a naturally acidified area. These high levels of diversity are attributed to the detection of small and cryptic species that are undetectable by traditional techniques and are tolerant to natural acidification. The results of this chapter unveil that future subtropical communities could maintain high taxonomic diversity values under an acidification scenario, although they will tend toward miniaturization due to the dominance of small algae and invertebrate species. This will have significant consequences for benthic subtropical communities, leading to important changes in ecosystem functions.
It is not the first time that an increase in species diversity related to environmental variations has been detected. In 1978, Connell first proposed the “Intermediate Disturbance Hypothesis” (IDH), which suggests that ecosystems are more diverse when disturbances occur at intermediate scales.
Chapter 4 investigates whether the IDH can be applied to a naturally acidified system at different biological organization levels (from organisms to communities) using molecular data. In La Palma’s acidified system, a fluctuating pH gradient caused by tides can act as a physical disturbance to marine ecosystems. This chapter utilizes sequenced fragments of the mitochondrial COI gene from two species of sea urchins (Arbacia lixula and Paracentrotus lividus) and metabarcoding analyses of benthic communities from the previous chapter. High levels of genetic and taxonomic diversity were detected at both biological organization levels under intermediate pH fluctuation, respectively. Therefore, the results of this chapter support the validity of the IDH in marine ecosystems affected by natural pH fluctuations and at different biological organization levels. Among the species living under natural acidification in the CO2 vents of La Palma, the sea urchin Arbacia lixula stands out. This is because sea urchins, like other calcareous organisms, should be susceptible to acidification due to their calcareous skeletons, however, this species has been found to live apparently unaffected in both Mediterranean and Atlantic CO2 vents.
The final chapter 5 explores the adaptation potential of A. lixula populations along the natural pH gradient of La Palma Island. Using the 2bRADseq molecular technique, a total of 14,883 SNPs (Single Nucleotide Polymorphisms) were detected in 74 individuals, of which 432 loci were correlated with the pH gradient of La Palma and are considered potential SNPs under selection. Analysis of these SNPs demonstrates that despite the short distance between the studied A. lixula populations, significant differences exist in the genomic structure of the populations correlated with the pH gradient. Additionally, these sequences are aligned and compared with available A. lixula transcriptomes, revealing 17 annotated genes involved in biological functions related to growth, development, membrane functions, and calcification. This chapter suggests that A. lixula can adapt to acidification and, therefore, able to withstand future changes anticipated for the oceans.
This thesis is the first to be developed at the Marine Observatory of Climate Change in Punta de Fuencaliente (OMaCC), where the naturally acidified system of La Palma is located. It emphasizes the importance of these natural laboratories in overcoming the experimental limitations of laboratory studies and contributes to understand how subtropical benthic ecosystems may change in the future. Moreover, it has uncovered evidence of local adaptation to ocean acidification in populations living in these natural laboratories. This thesis highlights the importance of these special environments and observatories for future research on the effects of OA.
Continue reading ‘Marine benthic communities of the future: use of acidified natural systems’Local scale extreme low pH conditions and genetic differences shape phenotypic variation in a broad dispersal copepod species
Published 24 January 2024 Science ClosedTags: adaptation, biological response, chemistry, crustaceans, field, molecular biology, morphology, otherprocess, reproduction, South Pacific
Extreme low pH events in estuaries and upwelling areas can modulate the phenotypic and genetic diversity of natural populations. To test this hypothesis, we explored the linkage between local scale extreme low pH events, genetic diversity, and variation in fecundity-related traits (body size, egg size, and egg production rate) in the broad-dispersal copepod Acartia tonsa. We assessed genetic and phenotypic characteristics of populations by contrasting extreme low pH environments (upwelling and temperate estuary) in the coastal Southeast Pacific, under natural and experimental conditions. These populations showed significant genetic differentiation with higher diversity in mitochondrial and nuclear loci (encoding mtCOI and 18S rRNA) in the estuarine population. Copepods from this population are exposed to more frequent extreme low pH events (< 7.7), and the adult females exhibit consistent phenotypic variation in body size, egg size, and egg production rate across different cohorts. Experimental acclimation to extreme low pH conditions revealed no significant differences in fecundity-related traits between A. tonsa populations. Although these results partially support our hypothesis, the experimental findings suggest other drivers might also influence phenotypic differences in the local environments.
Continue reading ‘Local scale extreme low pH conditions and genetic differences shape phenotypic variation in a broad dispersal copepod species’The vulnerability of World Heritage seagrass habitats to climate change
Published 23 January 2024 Science ClosedTags: adaptation, biological response, otherprocess, performance, phanerogams
Seagrass is an important natural attribute of 28 World Heritage (WH) properties. These WH seagrass habitats provide a wide range of services to adjacent ecosystems and human communities, and are one of the largest natural carbon sinks on the planet. Climate change is considered the greatest and fastest-growing threat to natural WH properties and evidence of climate-related impacts on seagrass habitats has been growing. The main objective of this study was to assess the vulnerability of WH seagrass habitats to location-specific key climate stressors. Quantitative surveys of seagrass experts and site managers were used to assess exposure, sensitivity and adaptive capacity of WH seagrass habitats to climate stressors, following the Climate Vulnerability Index approach. Over half of WH seagrass habitats have high vulnerability to climate change, mainly from the long-term increase in sea-surface temperature and short-term marine heatwaves. Potential impacts from climate change and certainty scores associated with them were higher than reported by a similar survey-based study from 10 years prior, indicating a shift in stakeholder perspectives during the past decade. Additionally, seagrass experts’ opinions on the cumulative impacts of climate and direct-anthropogenic stressors revealed that high temperature in combination with high suspended sediments, eutrophication and hypoxia is likely to provoke a synergistic cumulative (negative) impact (p < .05). A key component contributing to the high vulnerability assessments was the low adaptive capacity; however, discrepancies between adaptive capacity scores and qualitative responses suggest that managers of WH seagrass habitats might not be adequately equipped to respond to climate change impacts. This thematic assessment provides valuable information to help prioritize conservation actions, monitoring activities and research in WH seagrass habitats. It also demonstrates the utility of a systematic framework to evaluate the vulnerability of thematic groups of protected areas that share a specific attribute.
Continue reading ‘The vulnerability of World Heritage seagrass habitats to climate change’Biochemical adaptability of the relationship between tropical hard corals and photosynthetic symbiotic algae under climate change
Published 23 January 2024 Science ClosedTags: adaptation, algae, BRcommunity, corals, otherprocess, performance, review
Tropical coral reefs, a vital component of the global marine ecosystem, are currently under threat from climate change factors such as rising temperatures, ocean acidification, and extreme weather events. High temperatures induce coral bleaching, resulting in the loss of their energy supply and an acceleration of metabolic rates, rendering them more vulnerable. Ocean acidification affects the formation of calcium carbonate skeletons in symbiotic algae and decreases photosynthetic efficiency, further exacerbating the risk of damage to the symbiotic algae in high-temperature conditions. Extreme weather events directly cause physical damage to corals and alter marine environments, reducing their chances of survival. This review focuses on the impact of climate change on the biochemical adaptability between tropical hard corals and photosynthetic symbiotic algae, exploring their ecological relationship, the influence of climate change on this relationship, and the adaptive mechanisms. Understanding the adaptive mechanisms between hard corals and symbiotic algae is crucial for developing conservation strategies and management plans to maintain the functionality and biodiversity of coral reef ecosystems. It also aids in ensuring the survival and prosperity of this delicate relationship under the challenges posed by climate change, allowing future generations to continue enjoying the magnificence of tropical coral reefs.
Continue reading ‘Biochemical adaptability of the relationship between tropical hard corals and photosynthetic symbiotic algae under climate change ‘Within- and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival
Published 4 December 2023 Science ClosedTags: adaptation, biological response, growth, laboratory, mollusks, mortality, otherprocess, reproduction
Understanding the mechanisms by which individual organisms respond and populations adapt to global climate change is a critical challenge. The role of plasticity and acclimation, within and across generations, may be essential given the pace of change. We investigated plasticity across generations and life stages in response to ocean acidification (OA), which poses a growing threat to both wild populations and the sustainable aquaculture of shellfish. Most studies of OA on shellfish focus on acute effects, and less is known regarding the longer term carryover effects that may manifest within or across generations. We assessed these longer term effects in red abalone (Haliotis rufescens) using a multi-generational split-brood experiment. We spawned adults raised in ambient conditions to create offspring that we then exposed to high pCO2 (1180 μatm; simulating OA) or low pCO2 (450 μatm; control or ambient conditions) during the first 3 months of life. We then allowed these animals to reach maturity in ambient common garden conditions for 4 years before returning the adults into high or low pCO2 treatments for 11 months and measuring growth and reproductive potential. Early-life exposure to OA in the F1 generation decreased adult growth rate even after 5 years especially when abalone were re-exposed to OA as adults. Adult but not early-life exposure to OA negatively impacted fecundity. We then exposed the F2 offspring to high or low pCO2 treatments for the first 3 months of life in a fully factorial, split-brood design. We found negative transgenerational effects of parental OA exposure on survival and growth of F2 offspring, in addition to significant direct effects of OA on F2 survival. These results show that the negative impacts of OA can last within and across generations, but that buffering against OA conditions at critical life-history windows can mitigate these effects.
Continue reading ‘Within- and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival’The interactive effects of ocean acidification and warming on bioeroding sponge Spheciospongia vesparium microbiome indicated by metatranscriptomics
Published 16 November 2023 Science ClosedTags: adaptation, biological response, BRcommunity, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, physiology, porifera, prokaryotes, temperature
Global climate change will cause coral reefs decline and is expected to increase the reef erosion potential of bioeroding sponges. Microbial symbionts are essential for the overall fitness and survival of sponge holobionts in changing ocean environments. However, we rarely know about the impacts of ocean warming and acidification on bioeroding sponge microbiome. Here, the structural and functional changes of the bioeroding sponge Spheciospongia vesparium microbiome, as well as its recovery potential, were investigated at the RNA level in a laboratory system simulating 32 °C and pH 7.7. Based on metatranscriptome analysis, acidification showed no significant impact, while warming or simultaneous warming and acidification disrupted the sponge microbiome. Warming caused microbial dysbiosis and recruited potentially opportunistic and pathogenic members of Nesiotobacter, Oceanospirillaceae, Deltaproteobacteria, Epsilonproteobacteria, Bacteroidetes and Firmicutes. Moreover, warming disrupted nutrient exchange and molecular interactions in the sponge holobiont, accompanied by stimulation of virulence activity and anaerobic metabolism including denitrification and dissimilatory reduction of nitrate and sulfate to promote sponge necrosis. Particularly, the interaction between acidification and warming alleviated the negative effects of warming and enhanced the Rhodobacteraceae-driven ethylmalonyl-CoA pathway and sulfur-oxidizing multienzyme system. The microbiome could not recover during the experiment period after warming or combined stress was removed. This study suggests that warming or combined warming and acidification will irreversibly destabilize the S. vesparium microbial community structure and function, and provides insight into the molecular mechanisms of the interactive effects of acidification and warming on the sponge microbiome.
Continue reading ‘The interactive effects of ocean acidification and warming on bioeroding sponge Spheciospongia vesparium microbiome indicated by metatranscriptomics’Complex dynamics of coral gene expression responses to low pH across species
Published 15 November 2023 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, chemistry, community composition, corals, laboratory, molecular biology, morphology, mortality, North Atlantic, otherprocess, performance, physiology, protists
Coral capacity to tolerate low pH affects coral community composition and, ultimately, reef ecosystem function. Low pH submarine discharges (‘Ojo’; Yucatán, México) represent a natural laboratory to study plasticity and acclimatization to low pH in relation to ocean acidification. A previous >2-year coral transplant experiment to ambient and low pH common garden sites revealed differential survivorship across species and sites, providing a framework to compare mechanistic responses to differential pH exposures. Here, we examined gene expression responses of transplants of three species of reef-building corals (Porites astreoides, Porites porites and Siderastrea siderea) and their algal endosymbiont communities (Symbiodiniaceae) originating from low pH (Ojo) and ambient pH native origins (Lagoon or Reef). Transplant pH environment had the greatest effect on gene expression of Porites astreoides hosts and symbionts and P. porites hosts. Host P. astreoides Ojo natives transplanted to ambient pH showed a similar gene expression profile to Lagoon natives remaining in ambient pH, providing evidence of plasticity in response to ambient pH conditions. Although origin had a larger effect on host S. siderea gene expression due to differences in symbiont genera within Reef and Lagoon/Ojo natives, subtle effects of low pH on all origins demonstrated acclimatization potential. All corals responded to low pH by differentially expressing genes related to pH regulation, ion transport, calcification, cell adhesion and stress/immune response. This study demonstrates that the magnitude of coral gene expression responses to pH varies considerably among populations, species and holobionts, which could differentially affect acclimatization to and impacts of ocean acidification.
Continue reading ‘Complex dynamics of coral gene expression responses to low pH across species’Linking physiological effects of environmental stressors from cellular to whole-organismal levels in the early-life history stages of Crassostrea virginica (eastern oyster)
Published 2 November 2023 Science ClosedTags: adaptation, biological response, laboratory, mollusks, morphology, mortality, North Atlantic, otherprocess, performance
The Eastern oyster, Crassostrea virginica (Gmelin, 1791), is an ecologically and economically important species that resides in dynamic coastal ecosystems along the East and Gulf coasts of the United States. The success of oyster populations depends on the recruitment of their early life stages, which are especially vulnerable to environmental stress due to high developmental energy demands. As climate change continues, it is necessary to anticipate how the early life stages of the Eastern oyster will respond to environmental stressors under ecologically relevant scenarios. Therefore, the goal of this dissertation was to understand how the early life stages of C. virginica are physiologically affected by multiple global climate change stressors from a holistic perspective by incorporating local environmental data, observations across three life stages (i.e., carryover effects), responses from two important types of Eastern oysters, and physiological metrics from the cellular to whole-organism levels. To achieve this goal, chapter two observes the relative importance of three environmental tolerance mechanisms (selective mortality, carryover effects, and phenotypic plasticity) in shaping the performance of juvenile oysters in response to salinity exposures during the larval stage. Findings from this chapter indicate that typical differences in salinity among successive larval cultures in shellfish hatcheries likely do not impact performance as juveniles; rather, phenotypic plasticity likely underpins juvenile oyster performance as their physiology correlated with environmental conditions during the juvenile phase, not the larval exposures. Chapter three investigates carryover effects in more detail to explore how multiple global climate change stressors, ocean acidification and ocean warming, might affect the physiology of larval C. virginica, if those effects carry over to impact the performance of juvenile oysters and lastly, if those carryover effects change under different future environmental scenarios. Conditions of ocean acidification and ocean warming did affect the larval stage of the Eastern oyster and carry over into the juvenile stage, though these effects were nuanced and context dependent. Specifically, carryover effects from conditions of acidification were more persistent and negative, whereas warming had more fleeting carryover, and cross-tolerant, effects that were generally positive. Continuing to observe the effects of ocean acidification and ocean warming on the Eastern oyster, chapter four compares the larval responses of wild and selectively bred oysters. C. virginica larvae from wild and selectively bred oysters responded differently to conditions of acidification, but not warming. Furthermore, wild oyster larvae may be more resilient in the face of ongoing climate change. Despite exhibiting more lethal and negative effects of acidified conditions early in the larval stage, wild oyster larvae compensated for these earlier negative effects, while larvae from selectively bred oysters began showing signs of stress towards the end of the experiment. Lastly, exploring the development of carryover effects, chapter five observes how conditions of acidification during the settlement stage (i.e., settlement and metamorphosis) carried over to impact the juvenile stage. No detectable carryover effects were found, even though conditions of acidification negatively affected tissue growth at the beginning of the settlement stage. Overall, while Eastern oysters are able to withstand environmental stress to some degree, there were sub-lethal and carryover effects from multiple global climate change stressors identified in this dissertation that could have consequences for both wild and selectively bred populations in the future. The results from this dissertation will support subsequent studies to accurately predict the future success of wild oyster populations (e.g., effects to recruitment) and aquaculture production based on their physiological performances in the face of ongoing climate change.
Continue reading ‘Linking physiological effects of environmental stressors from cellular to whole-organismal levels in the early-life history stages of Crassostrea virginica (eastern oyster)’Effect of elevated temperature, sea water acidification, and phenanthrene on the expression of genes involved in the shell and pearl formation of economic pearl oyster (Pinctada radiata)
Published 13 October 2023 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, multiple factors, otherprocess, physiology, temperature, toxicants
Highlights
- Increasing PCO2 and temperature in presence of PAH influence pearl oysters’ status.
- Barely examined multi-stressor impacts were conducted through full-factorial design.
- Ocean warming and acidification increase Phe bioaccumulation in oyster soft tissue.
- All stressors downregulated the studied shell formation-related genes expression.
Abstract
Our study aims to examine the effect of some stressors on the gene expression levels of shell matrix proteins in a pearl oyster. Oysters were exposed to the different combinations of the temperature, pH, and phenanthrene concentration is currently measured in the Persian Gulf and the predicted ocean warming and acidification for 28 days. The expression of all the studied genes was significantly downregulated. Time and temperature had the greatest effects on the decreases in n19 and n16 genes expression, respectively. Aspein and msi60 genes expression were highly influenced by pH. Pearlin was affected by double interaction temperature and phenanthrene. Moreover, a correlation was observed among the expression levels of studied genes. This study represents basic data on the relationship between mRNA transcription genes involved in the shell and pearl formation and climate changes in pollutant presence conditions and acclimatizing mechanism of the oyster to the future scenario as well.
Continue reading ‘Effect of elevated temperature, sea water acidification, and phenanthrene on the expression of genes involved in the shell and pearl formation of economic pearl oyster (Pinctada radiata)’Long-term coral microbial community acclimatization is associated with coral survival in a changing climate
Published 4 October 2023 Science ClosedTags: abundance, adaptation, biological response, BRcommunity, community composition, corals, laboratory, mesocosms, mortality, North Pacific, otherprocess, prokaryotes
The plasticity of some coral-associated microbial communities under stressors like warming and ocean acidification suggests the microbiome has a role in the acclimatization of corals to future ocean conditions. Here, we evaluated the acclimatization potential of coral-associated microbial communities of four Hawaiian coral species (Porites compressa, Porites lobata, Montipora capitata, and Pocillopora acuta) over 22-month mesocosm experiment. The corals were exposed to one of four treatments: control, ocean acidification, ocean warming, or combined future ocean conditions. Over the 22-month study, 33–67% of corals died or experienced a loss of most live tissue coverage in the ocean warming and future ocean treatments while only 0–10% died in the ocean acidification and control. Among the survivors, coral-associated microbial communities responded to the chronic future ocean treatment in one of two ways: (1) microbial communities differed between the control and future ocean treatment, suggesting the potential capacity for acclimatization, or (2) microbial communities did not significantly differ between the control and future ocean treatment. The first strategy was observed in both Porites species and was associated with higher survivorship compared to M. capitata and P. acuta which exhibited the second strategy. Interestingly, the microbial community responses to chronic stressors were independent of coral physiology. These findings indicate acclimatization of microbial communities may confer resilience in some species of corals to chronic warming associated with climate change. However, M. capitata genets that survived the future ocean treatment hosted significantly different microbial communities from those that died, suggesting the microbial communities of the survivors conferred some resilience. Thus, even among coral species with inflexible microbial communities, some individuals may already be tolerant to future ocean conditions. These findings suggest that coral-associated microbial communities could play an important role in the persistence of some corals and underlie climate change-driven shifts in coral community composition.
Continue reading ‘Long-term coral microbial community acclimatization is associated with coral survival in a changing climate’Vulnerability to climate change of United States marine mammal stocks in the western North Atlantic, Gulf of Mexico, and Caribbean
Published 3 October 2023 Science ClosedTags: adaptation, biological response, mammals, methods, otherprocess, performance, review
Climate change and climate variability are affecting marine mammal species and these impacts are projected to continue in the coming decades. Vulnerability assessments provide a framework for evaluating climate impacts over a broad range of species using currently available information. We conducted a trait-based climate vulnerability assessment using expert elicitation for 108 marine mammal stocks and stock groups in the western North Atlantic, Gulf of Mexico, and Caribbean Sea. Our approach combined the exposure (projected change in environmental conditions) and sensitivity (ability to tolerate and adapt to changing conditions) of marine mammal stocks to estimate vulnerability to climate change, and categorize stocks with a vulnerability index. The climate vulnerability score was very high for 44% (n = 47) of these stocks, high for 29% (n = 31), moderate for 20% (n = 22), and low for 7% (n = 8). The majority of stocks (n = 78; 72%) scored very high exposure, whereas 24% (n = 26) scored high, and 4% (n = 4) scored moderate. The sensitivity score was very high for 33% (n = 36) of these stocks, high for 18% (n = 19), moderate for 34% (n = 37), and low for 15% (n = 16). Vulnerability results were summarized for stocks in five taxonomic groups: pinnipeds (n = 4; 25% high, 75% moderate), mysticetes (n = 7; 29% very high, 57% high, 14% moderate), ziphiids (n = 8; 13% very high, 50% high, 38% moderate), delphinids (n = 84; 52% very high, 23% high, 15% moderate, 10% low), and other odontocetes (n = 5; 60% high, 40% moderate). Factors including temperature, ocean pH, and dissolved oxygen were the primary drivers of high climate exposure, with effects mediated through prey and habitat parameters. We quantified sources of uncertainty by bootstrapping vulnerability scores, conducting leave-one-out analyses of individual attributes and individual scorers, and through scoring data quality for each attribute. These results provide information for researchers, managers, and the public on marine mammal responses to climate change to enhance the development of more effective marine mammal management, restoration, and conservation activities that address current and future environmental variation and biological responses due to climate change.
Continue reading ‘Vulnerability to climate change of United States marine mammal stocks in the western North Atlantic, Gulf of Mexico, and Caribbean’Influence of seagrass on juvenile Pacific oyster growth in two US west coast estuaries with different environmental gradients
Published 25 September 2023 Science ClosedTags: adaptation, biological response, BRcommunity, chemistry, field, growth, mollusks, morphology, North Pacific, otherprocess, performance, photosynthesis, physiology
Ocean acidification threatens many marine organisms, including oysters. Seagrass habitat has been suggested as a potential refuge for oysters because it may ameliorate stressful carbonate chemistry and augment food availability. We conducted an in situ study to investigate whether eelgrass Zostera marina habitat affects the growth of juvenile Pacific oysters Crassostrea gigas and influences local carbonate chemistry or food quantity at sites where we expected contrasting conditions in two US west coast estuaries. Juvenile oysters were out-planted in typical intertidal on-bottom (just above sediment) and off-bottom (45 cm above sediment) culture positions and in adjacent eelgrass and unvegetated habitats from June to September 2019. Water quality was measured with sondes for 24 h periods each month, and discrete water samples were collected in conjuncture. Results show that eelgrass habitat did not alter average local carbonate chemistry (pH, pCO2, Ωcalcite), but consistently reduced available food (relative chlorophyll a). Eelgrass habitat had little to no effect on the shell or tissue growth of juvenile oysters but may have influenced their energy allocation; oysters displayed a 16% higher ratio of shell to tissue growth in eelgrass compared to unvegetated habitat when cultured on-bottom. At the seascape scale, average site-level pH was negatively correlated with shell to tissue growth but not with shell growth alone. Overall, these findings suggest that juvenile oysters may display a compensatory response and allocate more energy to shell than tissue growth under stressful conditions like acidic water and/or altered food supply due to reduced immersion or eelgrass presence.
Continue reading ‘Influence of seagrass on juvenile Pacific oyster growth in two US west coast estuaries with different environmental gradients’Simultaneous warming and acidification limit population fitness and reveal phenotype costs for a marine copepod
Published 8 September 2023 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, morphology, mortality, multiple factors, otherprocess, reproduction, temperature, zooplankton
Phenotypic plasticity and evolutionary adaptation allow populations to cope with global change, but limits and costs to adaptation under multiple stressors are insufficiently understood. We reared a foundational copepod species, Acartia hudsonica, under ambient (AM), ocean warming (OW), ocean acidification (OA), and combined ocean warming and acidification (OWA) conditions for 11 generations (approx. 1 year) and measured population fitness (net reproductive rate) derived from six life-history traits (egg production, hatching success, survival, development time, body size and sex ratio). Copepods under OW and OWA exhibited an initial approximately 40% fitness decline relative to AM, but fully recovered within four generations, consistent with an adaptive response and demonstrating synergy between stressors. At generation 11, however, fitness was approximately 24% lower for OWA compared with the AM lineage, consistent with the cost of producing OWA-adapted phenotypes. Fitness of the OWA lineage was not affected by reversal to AM or low food environments, indicating sustained phenotypic plasticity. These results mimic those of a congener, Acartia tonsa, while additionally suggesting that synergistic effects of simultaneous stressors exert costs that limit fitness recovery but can sustain plasticity. Thus, even when closely related species experience similar stressors, species-specific costs shape their unique adaptive responses.
Continue reading ‘Simultaneous warming and acidification limit population fitness and reveal phenotype costs for a marine copepod’Differential reaction norms to ocean acidification in two oyster species from contrasting habitats
Published 6 September 2023 Science ClosedTags: adaptation, biological response, growth, laboratory, mollusks, morphology, mortality, North Atlantic, otherprocess, physiology
Ocean acidification (OA), a consequence of the increase in anthropogenic emissions of carbon dioxide, causes major changes in the chemistry of carbonates in the ocean with deleterious effects on calcifying organisms. The pH/pCO2 range to which species are exposed in nature is important to consider when interpreting the response of coastal organisms to OA. In this context, emerging approaches, which assess the reaction norms of organisms to a wide pH gradient, are improving our understanding of tolerance thresholds and acclimation potential to OA. In this study, we decipher the reaction norms of two oyster species living in contrasting habitats: the intertidal oyster Crassostrea gigas and the subtidal flat oyster Ostrea edulis, which are two economically and ecologically valuable species in temperate ecosystems. Six-month-old oysters of each species were exposed in common garden for 48 days to a pH gradient ranging from 7.7 to 6.4 (total scale). Both species are tolerant down to a pH of 6.6 with high plasticity in fitness-related traits such as survival and growth. However, oysters undergo remodelling of membrane fatty acids to cope with decreasing pH along with shell bleaching impairing shell integrity and consequently animal fitness. Finally, our work reveals species-specific physiological responses and highlights that intertidal C. gigas seems to have a better acclimation potential to rapid and extreme OA changes than O. edulis. Overall, our study provides important data about the phenotypic plasticity and its limits in two oyster species, which is essential for assessing the challenges posed to marine organisms by OA.
Continue reading ‘Differential reaction norms to ocean acidification in two oyster species from contrasting habitats’Physiological responses of scallops and mussels to environmental variability: implications for future shellfish aquaculture
Published 25 August 2023 Science ClosedTags: adaptation, biological response, chemistry, field, growth, mollusks, morphology, North Pacific, otherprocess
Highlights
- High acclimatization capability in mussels and scallops
- Growth rates, δ13C, δ15N, and shell strength differed between seasons and depths.
- Mussels and scallops had higher growth rates at 5 m than 30 m.
- Shell strength changed with depth in mussels but not in the scallops.
- Differences in nutritional sources between depths are higher in winter than spring.
Abstract
Puget Sound (Washington, USA) is a large estuary, known for its profitable shellfish aquaculture industry. However, in the past decade, scientists have observed strong acidification, hypoxia, and temperature anomalies in Puget Sound. These co-occurring environmental stressors are a threat to marine ecosystems and shellfish aquaculture. Our research assesses how environmental variability in Puget Sound impacts two ecologically and economically important bivalves, the purple-hinge rock scallop (Crassodoma gigantea) and Mediterranean mussel (Mytilus galloprovincialis). Our study examines the effect of depth and seasonality on the physiology of these two important bivalves to gain insight into ideal grow-out conditions in an aquaculture setting, improving the yield and quality of this sustainable protein source. To do this, we used Hood Canal (located in Puget Sound) as a natural multiple-stressor laboratory, which allowed us to study acclimatization capacity of shellfish in their natural habitat and provide the aquaculture industry information about differences in growth rate, shell strength, and nutritional sources across depths and seasons. Bivalves were outplanted at two depths (5 and 30 m) and collected after 3.5 and 7.5 months. To maximize mussel and scallop growth potential in an aquaculture setting, our results suggest outplanting at 5 m depth, with more favorable oxygen and pH levels. Mussel shell integrity can be improved by placing out at 5 m, regardless of season, however, there were no notable differences in shell strength between depths in scallops. For both species, δ13C values were lowest at 5 m in the winter and δ15N was highest at 30 m regardless of season. Puget Sound’s combination of naturally and anthropogenically acidified conditions is already proving to be a challenge for shellfish farmers. Our study provides crucial information to farmers to optimize aquaculture grow-out as we begin to navigate the impacts of climate change.
Continue reading ‘Physiological responses of scallops and mussels to environmental variability: implications for future shellfish aquaculture’Genomic signatures suggesting adaptation to ocean acidification in a coral holobiont from volcanic CO2 seeps
Published 25 July 2023 Science ClosedTags: adaptation, biological response, BRcommunity, corals, field, molecular biology, otherprocess, physiology, phytoplankton, prokaryotes, South Pacific, vents
Ocean acidification, caused by anthropogenic CO2 emissions, is predicted to have major consequences for reef-building corals, jeopardizing the scaffolding of the most biodiverse marine habitats. However, whether corals can adapt to ocean acidification and how remains unclear. We addressed these questions by re-examining transcriptome and genome data of Acropora millepora coral holobionts from volcanic CO2 seeps with end-of-century pH levels. We show that adaptation to ocean acidification is a wholistic process involving the three main compartments of the coral holobiont. We identified 441 coral host candidate adaptive genes involved in calcification, response to acidification, and symbiosis; population genetic differentiation in dinoflagellate photosymbionts; and consistent transcriptional microbiome activity despite microbial community shifts. Coral holobionts from natural analogues to future ocean conditions harbor beneficial genetic variants with far-reaching rapid adaptation potential. In the face of climate change, these populations require immediate conservation strategies as they could become key to coral reef survival.
Continue reading ‘Genomic signatures suggesting adaptation to ocean acidification in a coral holobiont from volcanic CO2 seeps’Differences in carbonate chemistry up-regulation of long-lived reef-building corals
Published 24 July 2023 Science ClosedTags: adaptation, biological response, calcification, chemistry, corals, field, morphology, otherprocess, physiology, South Pacific
With climate projections questioning the future survival of stony corals and their dominance as tropical reef builders, it is critical to understand the adaptive capacity of corals to ongoing climate change. Biological mediation of the carbonate chemistry of the coral calcifying fluid is a fundamental component for assessing the response of corals to global threats. The Tara Pacific expedition (2016–2018) provided an opportunity to investigate calcification patterns in extant corals throughout the Pacific Ocean. Cores from colonies of the massive Porites and Diploastrea genera were collected from different environments to assess calcification parameters of long-lived reef-building corals. At the basin scale of the Pacific Ocean, we show that both genera systematically up-regulate their calcifying fluid pH and dissolved inorganic carbon to achieve efficient skeletal precipitation. However, while Porites corals increase the aragonite saturation state of the calcifying fluid (Ωcf) at higher temperatures to enhance their calcification capacity, Diploastrea show a steady homeostatic Ωcf across the Pacific temperature gradient. Thus, the extent to which Diploastrea responds to ocean warming and/or acidification is unclear, and it deserves further attention whether this is beneficial or detrimental to future survival of this coral genus.
Continue reading ‘Differences in carbonate chemistry up-regulation of long-lived reef-building corals’Brain transcriptome of gobies inhabiting natural CO2 seeps reveal acclimation strategies to long-term acidification
Published 11 July 2023 Science ClosedTags: adaptation, biological response, field, fish, Mediterranean, molecular biology, otherprocess, vents
Ocean acidification (OA) is known to affect the physiology, survival, behaviour and fitness of various fish species with repercussions at the population, community and ecosystem levels. Some fish species, however, seem to acclimate rapidly to OA conditions and even thrive in acidified environments. The molecular mechanisms that enable species to successfully inhabit high CO2 environments have not been fully elucidated especially in wild fish populations. Here, we used the natural CO2 seep in Vulcano Island, Italy to study the effects of elevated CO2 exposure on the brain transcriptome of the anemone goby, a species with high population density in the CO2 seep and investigate their potential for acclimation. Compared to fish from environments with ambient CO2, gobies living in the CO2 seep showed differences in the expression of transcripts involved in ion transport and pH homeostasis, cellular stress, immune response, circadian rhythm and metabolism. We also found evidence of potential adaptive mechanisms to restore the functioning of GABAergic pathways, whose activity can be affected by exposure to elevated CO2 levels. Our findings indicate that gobies living in the CO2 seep may be capable of mitigating CO2-induced oxidative stress and maintaining physiological pH while meeting the consequent increased energetic costs. The conspicuous difference in the expression of core circadian rhythm transcripts could provide an adaptive advantage by increasing the flexibility of physiological processes in elevated CO2 conditions thereby facilitating acclimation. Our results show potential molecular processes of acclimation to elevated CO2 in gobies enabling them to thrive in the acidified waters of Vulcano Island.
Continue reading ‘Brain transcriptome of gobies inhabiting natural CO2 seeps reveal acclimation strategies to long-term acidification’
