One challenge in global change biology is to identify the mechanisms underpinning physiological sensitivities to environmental change and to predict their potential to adapt to future conditions. Using ocean acidification as the representative stressor, molecular pathways associated with abnormal larval development of a globally distributed marine mussel are identified. The targeted developmental stage was the trochophore stage, which is, for a few hours, pH sensitive and is the main driver of developmental success. RNA sequencing and in situ RNA hybridization were used to identify processes associated with abnormal development, and DNA sequencing was used to identify which processes evolve when larvae are exposed to low pH for the full duration of their larval stage. Trochophores exposed to low pH exhibited 43 differentially expressed genes. Thirteen genes, none of which have previously been identified in mussel trochophores, including three unknown genes, were expressed in the shell field. Gene annotation and in situ hybridization point to two core processes associated with the response to low pH: development of the trochophore shell field and the cellular stress response. Encompassing both of these processes, five genes demonstrated changes in allele frequency that are indicative of rapid adaptation. Thus, genes underpinning the most pH-sensitive developmental processes also exhibit scope to adapt via genetic variation currently maintained in the mussel population. These results provide evidence that protecting existing genetic diversity is a critical management action to maximize the potential for rapid adaptation under a changing environment.
Continue reading ‘Molecular basis of ocean acidification sensitivity and adaptation in Mytilus galloprovincialis’Posts Tagged 'adaptation'
Molecular basis of ocean acidification sensitivity and adaptation in Mytilus galloprovincialis
Published 26 October 2021 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, morphology, otherprocess, physiology, reproduction
Heritable variation and lack of tradeoffs suggest adaptive capacity in Acropora cervicornis despite negative synergism under climate change scenarios
Published 15 October 2021 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, community composition, corals, laboratory, molecular biology, mortality, multiple factors, North Atlantic, otherprocess, photosynthesis, physiology, protists, temperature
Knowledge of multi-stressor interactions and the potential for tradeoffs among tolerance traits is essential for developing intervention strategies for the conservation and restoration of reef ecosystems in a changing climate. Thermal extremes and acidification are two major co-occurring stresses predicted to limit the recovery of vital Caribbean reef-building corals. Here, we conducted an aquarium-based experiment to quantify the effects of increased water temperatures and pCO2 individually and in concert on 12 genotypes of the endangered branching coral Acropora cervicornis, currently being reared and outplanted for large-scale coral restoration. Quantification of 12 host, symbiont and holobiont traits throughout the two-month-long experiment showed several synergistic negative effects, where the combined stress treatment often caused a greater reduction in physiological function than the individual stressors alone. However, we found significant genetic variation for most traits and positive trait correlations among treatments indicating an apparent lack of tradeoffs, suggesting that adaptive evolution will not be constrained. Our results suggest that it may be possible to incorporate climate-resistant coral genotypes into restoration and selective breeding programmes, potentially accelerating adaptation.
Continue reading ‘Heritable variation and lack of tradeoffs suggest adaptive capacity in Acropora cervicornis despite negative synergism under climate change scenarios’Lipid remodeling reveals the adaptations of a marine diatom to ocean acidification
Published 14 October 2021 Science ClosedTags: adaptation, biological response, laboratory, otherprocess, physiology, phytoplankton
Ocean acidification is recognized as a major anthropogenic perturbation of the modern ocean. While extensive studies have been carried out to explore the short-term physiological responses of phytoplankton to ocean acidification, little is known about their lipidomic responses after a long-term ocean acidification adaptation. Here we perform the lipidomic analysis of a marine diatom Phaeodactylum tricornutum following long-term (∼400 days) selection to ocean acidification conditions. We identified a total of 476 lipid metabolites in long-term high CO2 (i.e., ocean acidification condition) and low CO2 (i.e., ambient condition) selected P. tricornutum cells. Our results further show that long-term high CO2 selection triggered substantial changes in lipid metabolites by down- and up-regulating 33 and 42 lipid metabolites. While monogalactosyldiacylglycerol (MGDG) was significantly down-regulated in the long-term high CO2 selected conditions, the majority (∼80%) of phosphatidylglycerol (PG) was up-regulated. The tightly coupled regulations (positively or negatively correlated) of significantly regulated lipid metabolites suggest that the lipid remodeling is an organismal adaptation strategy of marine diatoms to ongoing ocean acidification. Since the composition and content of lipids are crucial for marine food quality, and these changes can be transferred to high trophic levels, our results highlight the importance of determining the long-term adaptation of lipids in marine producers in predicting the ecological consequences of climate change.
Continue reading ‘Lipid remodeling reveals the adaptations of a marine diatom to ocean acidification’Two temperate corals are tolerant to low pH regardless of previous exposure to natural CO2 vents
Published 28 September 2021 Science ClosedTags: adaptation, biological response, calcification, corals, laboratory, Mediterranean, otherprocess, photosynthesis, vents
Ocean acidification is perceived to be a major threat for many calcifying organisms, including scleractinian corals. Here we investigate (1) whether past exposure to low pH environments associated with CO2 vents could increase corals tolerance to low pH and (2) whether zooxanthellate corals are more tolerant to low pH than azooxanthellate corals. To test these hypotheses, two Mediterranean colonial corals Cladocora caespitosa (zooxanthellate) and Astroides calycularis (azooxanthellate) were collected from CO2 vents and reference sites and incubated in the laboratory under present-day (pH on the total scale, pHT 8.07) and low pH conditions (pHT 7.70). Rates of net calcification, dark respiration and photosynthesis were monitored during a six-month experiment. Monthly net calcification was assessed every 27 to 35 d using the buoyant weight technique, whereas light and dark net calcification was estimated using the alkalinity anomaly technique during 1 h incubations. Neither species showed any change in net calcification rates, respiration, and photosynthesis regardless of their environmental history, pH treatment and trophic strategy. Our results indicate that C. caespitosa and A. calycularis could tolerate future ocean acidification conditions for at least 6 months. These results will aid in predicting species’ future responses to ocean acidification, and thus improve the management and conservation of Mediterranean corals.
Continue reading ‘Two temperate corals are tolerant to low pH regardless of previous exposure to natural CO2 vents’Integrated assessment of ocean acidification risks to pteropods in the Northern high latitudes: regional comparison of exposure, sensitivity and adaptive capacity
Published 13 September 2021 Science ClosedTags: adaptation, Antarctic, biological response, chemistry, field, globalmodeling, laboratory, modeling, molecular biology, mollusks, North Pacific, otherprocess, physiology, South Pacific, zooplankton
Exposure to the impact of ocean acidification (OA) is increasing in high-latitudinal productive habitats. Pelagic calcifying snails (pteropods), a significant component of the diet of economically important fish, are found in high abundance in these regions. Pteropods have thin shells that readily dissolve at low aragonite saturation state (Ωar), making them susceptible to OA. Here, we conducted a first integrated risk assessment for pteropods in the Eastern Pacific subpolar gyre, the Gulf of Alaska (GoA), Bering Sea, and Amundsen Gulf. We determined the risk for pteropod populations by integrating measures of OA exposure, biological sensitivity, and resilience. Exposure was based on physical-chemical hydrographic observations and regional biogeochemical model outputs, delineating seasonal and decadal changes in carbonate chemistry conditions. Biological sensitivity was based on pteropod morphometrics and shell-building processes, including shell dissolution, density and thickness. Resilience and adaptive capacity were based on species diversity and spatial connectivity, derived from the particle tracking modeling. Extensive shell dissolution was found in the central and western part of the subpolar gyre, parts of the Bering Sea, and Amundsen Gulf. We identified two distinct morphotypes: L. helicina helicina and L. helicina pacifica, with high-spired and flatter shells, respectively. Despite the presence of different morphotypes, genetic analyses based on mitochondrial haplotypes identified a single species, without differentiation between the morphological forms, coinciding with evidence of widespread spatial connectivity. We found that shell morphometric characteristics depends on omega saturation state (Ωar); under Ωar decline, pteropods build flatter and thicker shells, which is indicative of a certain level of phenotypic plasticity. An integrated risk evaluation based on multiple approaches assumes a high risk for pteropod population persistence with intensification of OA in the high latitude eastern North Pacific because of their known vulnerability, along with limited evidence of species diversity despite their connectivity and our current lack of sufficient knowledge of their adaptive capacity. Such a comprehensive understanding would permit improved prediction of ecosystem change relevant to effective fisheries resource management, as well as a more robust foundation for monitoring ecosystem health and investigating OA impacts in high-latitudinal habitats.
Continue reading ‘Integrated assessment of ocean acidification risks to pteropods in the Northern high latitudes: regional comparison of exposure, sensitivity and adaptive capacity’Individual and interactive effects of ocean warming and acidification on adult Favites colemani
Published 9 September 2021 Science ClosedTags: adaptation, biological response, corals, growth, laboratory, molecular biology, mortality, multiple factors, North Pacific, otherprocess, photosynthesis, physiology, temperature
Tropical coral reefs are threatened by local-scale stressors that are exacerbated by global ocean warming and acidification from the post-industrial increase of atmospheric CO2 levels. Despite their observed decline in the past four decades, little is known on how Philippine coral reefs will respond to ocean warming and acidification. This study explored individual and synergistic effects of present-day (pH 8.0, 28°C) and near-future (pH 7.7, 32°C) scenarios of ocean temperature and pH on the adult Favites colemani, a common massive reef-building coral in Bolinao-Anda, Philippines. Changes in seawater temperature drive the physiological responses of F. colemani, whereas changes in pH create an additive effect on survival, growth, and photosynthetic efficiency. Under near-future scenarios, F. colemani showed sustained photosynthetic competency despite the decline in growth rate and zooxanthellae density. F. colemani exhibited specificity with the Cladocopium clade C3u. This coral experienced lower growth rates but survived projected near-future ocean warming and acidification scenarios. Its pH-thermal stress threshold is possibly a consequence of acclimation and adaptation to local environmental conditions and past bleaching events. This research highlights the importance of examining the susceptibility and resilience of Philippine corals to climate-driven stressors for future conservation and restoration efforts in the changing ocean.
Continue reading ‘Individual and interactive effects of ocean warming and acidification on adult Favites colemani’Acute acidification stress weakens the head kidney immune function of juvenile Lates calcarifer
Published 7 September 2021 Science ClosedTags: adaptation, biological response, fish, laboratory, molecular biology, North Pacific, otherprocess, physiology
Highlights
- A comprehensive analysis of L. calcarifer head kidney acute acidification response.
- Acute adaptation strategies to different acidification levels were different.
- Acute acidification stress had the effect of weakening immune function.
Abstract
Acidized water environment can impact many physiological processes of aquatic animals. The response of the head kidney to acidification, especially the immune response, is of great significance to health. This study analyzed the histological and transcriptional changes under different acidification levels (C group, pH 8.1; P group, pH 7.4; E group, pH 3.5) in the short term (12 h, 36 h and 60 h) in the head kidney of juvenile L. calcarifer. The results showed that the acidification of the water environment caused tissue damage to the head kidney of L. calcarifer, and the damage appeared earlier and was stronger in the extreme pH group. The transcriptional response of L. calcarifer head kidney increased with the increase of acidification level. The two treatments transcriptional responses showed different trends in terms of time. After KEGG function enrichment, with the increase of stimulation time, the proportion of down-regulated pathways was increasing, and the types of pathway enrichment at different acidification levels were quite different at the initial stage. At 12 h, the first category in the P group with the most significant number of pathways was ‘Metabolism’, and the first category in the E group with the largest number of pathways was ‘Human Diseases’. At 60 h, the enrichment pathways of the two groups were highly overlapping in immune-related pathways, which contained 26 common DEGs. They had a dominant expression pattern. In the P group, the expression level decreased with time. In the E group, the down-regulation degree of expression level at 12 h reached the level of the P group at 60 h, and the expression level remained low until 60 h. Through the correlation network, interferon regulatory factor 7 (IRF7), Tripartite motif containing-21 (TRIM21), Signal transducer and activator of transcription 1 (STAT1) and Signal transducer and activator of transcription 3 (STAT3) were found to have the most correlation with other genes. In this study, juvenile L. calcarifer showed different coping strategies to different levels of acute acidification stress, but all of them resulted in the extensive weakening of head kidney immune function.
Continue reading ‘Acute acidification stress weakens the head kidney immune function of juvenile Lates calcarifer’The marine gastropod Crepidula fornicata remains resilient to ocean acidification across two life history stages
Published 1 September 2021 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, morphology, North Pacific, otherprocess
Rising atmospheric CO2 reduces seawater pH causing ocean acidification (OA). Understanding how resilient marine organisms respond to OA may help predict how community dynamics will shift as CO2 continues rising. The common slipper shell snail Crepidula fornicata is a marine gastropod native to eastern North America that has been a successful invader along the western European coastline and elsewhere. It has also been previously shown to be resilient to global change stressors. To examine the mechanisms underlying C. fornicata’s resilience to OA, we conducted two controlled laboratory experiments. First, we examined several phenotypes and genome-wide gene expression of C. fornicata in response to pH treatments (7.5, 7.6, and 8.0) throughout the larval stage and then tested how conditions experienced as larvae influenced juvenile stages (i.e., carry-over effects). Second, we examined genome-wide gene expression patterns of C. fornicata larvae in response to acute (4, 10, 24, and 48 h) pH treatment (7.5 and 8.0). Both C. fornicata larvae and juveniles exhibited resilience to OA and their gene expression responses highlight the role of transcriptome plasticity in this resilience. Larvae did not exhibit reduced growth under OA until they were at least 8 days old. These phenotypic effects were preceded by broad transcriptomic changes, which likely served as an acclimation mechanism for combating reduced pH conditions frequently experienced in littoral zones. Larvae reared in reduced pH conditions also took longer to become competent to metamorphose. In addition, while juvenile sizes at metamorphosis reflected larval rearing pH conditions, no carry-over effects on juvenile growth rates were observed. Transcriptomic analyses suggest increased metabolism under OA, which may indicate compensation in reduced pH environments. Transcriptomic analyses through time suggest that these energetic burdens experienced under OA eventually dissipate, allowing C. fornicata to reduce metabolic demands and acclimate to reduced pH. Carry-over effects from larval OA conditions were observed in juveniles; however, these effects were larger for more severe OA conditions and larvae reared in those conditions also demonstrated less transcriptome elasticity. This study highlights the importance of assessing the effects of OA across life history stages and demonstrates how transcriptomic plasticity may allow highly resilient organisms, like C. fornicata, to acclimate to reduced pH environments.
Continue reading ‘The marine gastropod Crepidula fornicata remains resilient to ocean acidification across two life history stages’Acidification can directly affect olfaction in marine organisms
Published 30 July 2021 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, otherprocess, photosynthesis, physiology, protists
In the past decade, many studies have investigated the effects of low pH/high CO2 as a proxy for ocean acidification on olfactory-mediated behaviours of marine organisms. The effects of ocean acidification on the behaviour of fish vary from very large to none at all, and most of the maladaptive behaviours observed have been attributed to changes in acid–base regulation, leading to changes in ion distribution over neural membranes, and consequently affecting the functioning of gamma-aminobutyric acid-mediated (GABAergic) neurotransmission. Here, we highlight a possible additional mechanism by which ocean acidification might directly affect olfaction in marine fish and invertebrates. We propose that a decrease in pH can directly affect the protonation, and thereby, 3D conformation and charge distribution of odorants and/or their receptors in the olfactory organs of aquatic animals. This can sometimes enhance signalling, but most of the time the affinity of odorants for their receptors is reduced in high CO2/low pH; therefore, the activity of olfactory receptor neurons decreases as measured using electrophysiology. The reduced signal reception would translate into reduced activation of the olfactory bulb neurons, which are responsible for processing olfactory information in the brain. Over longer exposures of days to weeks, changes in gene expression in the olfactory receptors and olfactory bulb neurons cause these neurons to become less active, exacerbating the problem. A change in olfactory system functioning leads to inappropriate behavioural responses to odorants. We discuss gaps in the literature and suggest some changes to experimental design in order to improve our understanding of the underlying mechanisms and their effects on the associated behaviours to resolve some current controversy in the field regarding the extent of the effects of ocean acidification on marine fish.
Continue reading ‘Acidification can directly affect olfaction in marine organisms’Genetic and physiological traits conferring tolerance to ocean acidification in mesophotic corals
Published 29 July 2021 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, otherprocess, photosynthesis, physiology, protists
The integrity of coral reefs worldwide is jeopardized by ocean acidification (OA). Most studies conducted so far have focused on the vulnerability to OA of corals inhabiting shallow reefs, while nothing is currently known about the response of mesophotic scleractinian corals. In this study we assessed the susceptibility to OA of corals, together with their algal partners, inhabiting a wide depth range. We exposed fragments of the depth generalist coral Stylophora pistillata collected from either 5 or 45 meters to simulated future OA conditions, and assessed key molecular, physiological and photosynthetic processes influenced by the lowered pH. Our comparative analysis reveals that mesophotic and shallow S. pistillata corals are genetically distinct and possess different symbiont types. Under the exposure to acidification conditions, we observed a 50% drop of metabolic rate in shallow corals, whereas mesophotic corals were able to maintain unaltered metabolic rates. Overall, our gene expression and physiological analyses show that mesophotic corals possess a greater capacity to cope with the effects of OA compared to their shallow counterparts. Such capability stems from physiological characteristics (i.e. biomass and lipids energetics), a greater capacity to regulate cellular acid-base parameters, and a higher baseline expression of cell-adhesion and extracellular matrix genes. Moreover, our gene expression analysis suggests that the enhanced symbiont photochemical efficiency under high pCO₂ levels could prevent acidosis of the host cells and it could support a greater translocation of photosynthates, increasing the energy pool available to the host. With this work, we provide new insights on the response to OA of corals living at mesophotic depths. Our investigation discloses key genetic and physiological traits underlying the potential for corals to cope with future OA conditions.
Continue reading ‘Genetic and physiological traits conferring tolerance to ocean acidification in mesophotic corals’Chapter six – A brief summary of what we know and what we do not know about the impacts of ocean acidification on marine animals
Published 20 July 2021 Science ClosedTags: adaptation, biological response, methods, morphology, otherprocess, performance, physiology, reproduction, review
In the past decades, the impacts of ocean acidification (OA) on marine animals have gained much attention. To date, numerous works in the literature have shown that OA can affect a variety of biological processes of marine animals, and our knowledge about its effects on marine organisms is mainly focused on the following aspects: (1) fertilization and early development; (2) biomineralization, metabolism, and growth; and (3) immunity and behaviors. However, there are still some limitations that currently exist in research on OA, which include (1) performing experiments with “constant acidification” rather than natural pH fluctuations that may not fully reflect their future true living conditions; (2) using pCO2 levels that were predicted to be reached in a hundred years in the future for experiments with relatively short exposure times, thus overlooking marine organisms’ potential for genetic adaptation or acclimation to the acidified seawater; (3) large amounts of experiments examining OA’s physiological impacts while leaving the potential affecting mechanisms largely unstudied; and (4) a lack of experiments investigating indirect effects of OA on marine organisms and the whole ecosystem. After providing a summary of the current knowledge of OA’s impacts on marine animals, this review aims to highlight potential directions for future studies.
Continue reading ‘Chapter six – A brief summary of what we know and what we do not know about the impacts of ocean acidification on marine animals’Adaptation to simultaneous warming and acidification carries a thermal tolerance cost in a marine copepod
Published 16 July 2021 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, otherprocess, physiology, zooplankton
The ocean is undergoing warming and acidification. Thermal tolerance is affected both by evolutionary adaptation and developmental plasticity. Yet, thermal tolerance in animals adapted to simultaneous warming and acidification is unknown. We experimentally evolved the ubiquitous copepod Acartia tonsa to future combined ocean warming and acidification conditions (OWA approx. 22°C, 2000 µatm CO2) and then compared its thermal tolerance relative to ambient conditions (AM approx. 18°C, 400 µatm CO2). The OWA and AM treatments were reciprocally transplanted after 65 generations to assess effects of developmental conditions on thermal tolerance and potential costs of adaptation. Treatments transplanted from OWA to AM conditions were assessed at the F1 and F9 generations following transplant. Adaptation to warming and acidification, paradoxically, reduces both thermal tolerance and phenotypic plasticity. These costs of adaptation to combined warming and acidification may limit future population resilience.
Continue reading ‘Adaptation to simultaneous warming and acidification carries a thermal tolerance cost in a marine copepod’Environmental legacy effects and acclimatization of a crustose coralline alga to ocean acidification
Published 15 July 2021 Science ClosedTags: adaptation, algae, biological response, calcification, chemistry, field, individualmodeling, laboratory, modeling, morphology, North Pacific, otherprocess
Prior exposure to variable environmental conditions is predicted to influence the resilience of marine organisms to global change. We conducted complementary 4-month field and laboratory experiments to understand how a dynamic, and sometimes extreme, environment influences growth rates of a tropical reef-building crustose coralline alga and its responses to ocean acidification (OA). Using a reciprocal transplant design, we quantified calcification rates of the Caribbean coralline Lithophyllum sp. at sites with a history of either extreme or moderate oxygen, temperature, and pH regimes. Calcification rates of in situ corallines at the extreme site were 90% lower than those at the moderate site, regardless of origin. Negative effects of corallines originating from the extreme site persisted even after transplanting to more optimal conditions for 20 weeks. In the laboratory, we tested the separate and combined effects of stress and variability by exposing corallines from the same sites to either ambient (Amb: pH 8.04) or acidified (OA: pH 7.70) stable conditions or variable (Var: pH 7.80-8.10) or acidified variable (OA-Var: pH 7.45-7.75) conditions. There was a negative effect of all pH treatments on Lithophyllum sp. calcification rates relative to the control, with lower calcification rates in corallines from the extreme site than from the moderate site in each treatment, indicative of a legacy effect of site origin on subsequent response to laboratory treatment. Our study provides ecologically relevant context to understanding the nuanced effects of OA on crustose coralline algae, and illustrates how local environmental regimes may influence the effects of global change.
Continue reading ‘Environmental legacy effects and acclimatization of a crustose coralline alga to ocean acidification’Calcifying phytoplankton in natural laboratories for understanding ocean acidification
Published 15 July 2021 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, chemistry, community composition, field, laboratory, molecular biology, morphology, otherprocess, phytoplankton, South Pacific
Coccolithophores are unicellular phytoplanktonic organisms characterized by a covering of calcite plates, the coccoliths, which are produced intracellularly. These calcifiers, as one of the main planktonic functional groups, play an important role in the inorganic carbon cycle and possibly as ballast that sinks organic carbon to the deep-sea. Most efforts to understanding coccolithophore response to ocean acidification (OA) –or the raise in atmospheric CO2 reduces ocean pH and saturation states (Ω) of CaCO3– have been through lab experiments, mostly using a small set of strains of the cosmopolitan, easily cultivated species Emiliania huxleyi. This species is especially interesting because it is young (~ 291,000 years) and has adapted to a wide range of marine environments. However, it is not the only coccolithophore and even within that species there is a lot of phenotypic and genetic diversity and diverse responses to OA in the lab. Despite the efforts made it is unclear how the physiological effects under controlled conditions translate to community-level responses in the field. This thesis aimed to contribute to understanding this issue by studying the distribution, composition and realized niches of coccolithophore assemblages and E. huxleyi morphotypes in contrasting pCO2/pH/Ωcalcite environments of the Eastern South Pacific, and to evaluate the responses of different E. huxleyi23 morphotypes to targeted pCO2/pH levels set in the lab. For this, the coccolithophores were surveyed in a coastal-oceanic section, mesotrophic waters, upwelling systems, and fjords-channels of Patagonia. From a total of 40 species, E. huxleyi was the most prevalent (30-100 % relative abundance). Within this taxon, several morphotypes has been described as stable in culture and genetically differentiated (e.g., the A and R morphotypes). The moderately-calcified A morphotype dominated the E. huxleyi populations being only surpassed by the R hyper-calcified morphotype in upwelling systems with high pCO2/low pH. This abrupt shift in the composition of E. huxleyi populations suggested that these coastal environments hold genetic reservoirs for their adaptation to OA. Therefore, the hypothesis was tested that these forms are adapted to resist high pCO2/low pH conditions. Unexpectedly, the morphotypes from the Eastern South Pacific were not more sensitive than the R hyper-calcified strains from neighboring high pCO2/low pH waters (lowering growth rates and PIC/POC ratios). On the other hand, realized-niche analysis showed that the A morphotype has a broader niche that is more tolerant to environmental-change (i.e., generalist) than the R morphotype’s niche, specialized to high pCO2/low pH waters. The lack of evidence for local adaptation to high pCO2/low pH conditions in E. huxleyi, might be explained by a narrow unimodal niche response to Ωcalcite revealed by niche analysis that was not tested experimentally. Alternatively, the R hyper-calcified morphotype might be selected by an unidentified condition particular to the Eastern South Pacific that correlates with temperature, salinity, and Ωcalcite of its realized-niche. Overall, despite their rapid turnover and large population sizes, oceanic planktonic microorganisms do not necessarily exhibit adaptations to high-pCO2 upwelled waters, and this ubiquitous coccolithophore may be near the limit of its capacity to adapt to ongoing OA.
Continue reading ‘Calcifying phytoplankton in natural laboratories for understanding ocean acidification’Contribution of maternal mRNA provisioning to embryonic stress response in a reef-building coral
Published 8 July 2021 Science ClosedTags: adaptation, biological response, BRcommunity, corals, laboratory, molecular biology, morphology, otherprocess, physiology, protists, reproduction
Prior to fertilization, mothers provision their oocytes with mRNA that regulates the early stages of development and may additionally include transcripts for proteins that support embryonic stress response early on. At some point during embryogenesis, however, these maternal transcripts are degraded as zygotic transcription activates and intensifies during a phenomenon known as the maternal-to-zygotic transition (MZT). Some evidence suggests that as the MZT progresses, and the effects of maternal transcripts are waning while the zygotic expression is being established, offspring of marine broadcast spawners become more vulnerable to environmental perturbations. In light of escalating threats to marine broadcast spawners, it is critical to understand their reproduction and development, which are essential processes for species resilience by repopulating and replenishing existing populations. Reef building corals, in particular, are under threat from multiple stressors at the local and global scales. Mass mortality has occurred in recent years due to a series of marine heatwaves. In addition, there is chronic stress occurring in the form of ocean acidification, or the decline in pH in surface waters due to the uptake of atmospheric carbon dioxide of anthropogenic origin. Here, we characterize the function of maternal mRNAs, the timeline of the MZT, and sensitivity of gene expression to ocean acidification (OA) in the reef- building coral, Montipora capitata to investigate role of the MZT in embryonic stress response in reef-building corals.
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Continue reading ‘Contribution of maternal mRNA provisioning to embryonic stress response in a reef-building coral’Selection experiments in the sea: what can experimental evolution tell us about how marine life will respond to climate change?
Published 2 July 2021 Science ClosedTags: adaptation, algae, biological response, corals, crustaceans, echinoderms, molecular biology, mollusks, mortality, otherprocess, physiology, phytoplankton, prokaryotes, reproduction, review
Rapid evolution may provide a buffer against extinction risk for some species threatened by climate change; however, the capacity to evolve rapidly enough to keep pace with changing environments is unknown for most taxa. The ecosystem-level consequences of climate adaptation are likely to be the largest in marine ecosystems, where short-lived phytoplankton with large effective population sizes make up the bulk of primary production. However, there are substantial challenges to predicting climate-driven evolution in marine systems, including multiple simultaneous axes of change and considerable heterogeneity in rates of change, as well as the biphasic life cycles of many marine metazoans, which expose different life stages to disparate sources of selection. A critical tool for addressing these challenges is experimental evolution, where populations of organisms are directly exposed to controlled sources of selection to test evolutionary responses. We review the use of experimental evolution to test the capacity to adapt to climate change stressors in marine species. The application of experimental evolution in this context has grown dramatically in the past decade, shedding light on the capacity for evolution, associated trade-offs, and the genetic architecture of stress-tolerance traits. Our goal is to highlight the utility of this approach for investigating potential responses to climate change and point a way forward for future studies.
Continue reading ‘Selection experiments in the sea: what can experimental evolution tell us about how marine life will respond to climate change?’Adult exposure to ocean acidification and warming leads to limited beneficial responses for oyster larvae
Published 30 June 2021 Science ClosedTags: adaptation, biological response, laboratory, mollusks, mortality, multiple factors, physiology, reproduction, temperature
There is a need to understand the responses of marine molluscs in this era of rapid climate change. Transgenerational plasticity that results in resilient offspring provides a mechanism for rapid acclimation of marine organisms to climate change. This study tested the hypothesis that adult parental exposure to elevated pCO2 and warming will have transgenerational benefits for offspring in the oysters Saccostrea glomerata and Crassostrea gigas. Adult S. glomerata and C. gigas were exposed to orthogonal treatments of ambient and elevated pCO2, and ambient and elevated temperature for 8 weeks. Gametes were collected and fertilized, larvae were then reared for 9 days under ambient and elevated pCO2. Egg lipidome and larval morphology and lipidome were measured. Parental exposure to warming and elevated pCO2 led to limited beneficial transgenerational responses for eggs and larvae of S. glomerata and C. gigas. Overall, larvae of S. glomerata were more sensitive than C. gigas, and both species had some capacity for transgenerational plasticity. This study supports the idea that transgenerational plasticity acts as an acclimatory mechanism for marine organisms to cope with the stress of climate change, but there are limitations, and it may not be a panacea or act equally in different species.
Continue reading ‘Adult exposure to ocean acidification and warming leads to limited beneficial responses for oyster larvae’Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance
Published 2 June 2021 Science ClosedTags: adaptation, algae, biological response, BRcommunity, community composition, echinoderms, laboratory, mesocosms, morphology, mortality, multiple factors, otherprocess, oxygen, performance, temperature
Globally, kelp forests are threatened by multiple stressors, including increasing grazing by sea urchins. With coastal upwelling predicted to increase in intensity and duration in the future, understanding whether kelp forest and urchin barren urchins are differentially affected by upwelling-related stressors will give insight into how future conditions may affect the transition between kelp forests and barrens. We assessed how current and future-predicted changes in the duration and magnitude of upwelling-associated stressors (low pH, dissolved oxygen, and temperature) affected the performance of purple sea urchins (Strongylocentrotus purpuratus) sourced from rapidly-declining bull kelp (Nereocystis leutkeana) forests and nearby barrens and maintained on habitat-specific diets. Kelp forest urchins were of superior condition to barrens urchins, with ~ 6–9 times more gonad per body mass. Grazing and condition in kelp forest urchins were more negatively affected by distant-future and extreme upwelling conditions, whereas grazing and survival in urchins from barrens were sensitive to both current-day and all future-predicted upwelling, and to increases in acidity, hypoxia, and temperature regardless of upwelling. We conclude that urchin barren urchins are more susceptible to increases in the magnitude and duration of upwelling-related stressors than kelp forest urchins. These findings have important implications for urchin population dynamics and their interaction with kelp.
Continue reading ‘Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance’Coral reefs in the Anthropocene ocean: novel insights from skeletal proxies of climate change, impacts, and resilience
Published 1 June 2021 Science ClosedTags: adaptation, biological response, corals, field, growth, morphology, North Pacific, South Pacific
Anthropogenic emissions of greenhouse gases are driving rapid changes in ocean conditions. Shallow-water coral reefs are experiencing the brunt of these changes, including intensifying marine heatwaves (MHWs) and rapid ocean acidification (OA). Consequently, coral reefs are in broad-scale decline, threatening the livelihoods of hundreds of millions of people. Ensuring survival of coral reefs in the 21st century will thus require a new management approach that incorporates robust understanding of reef-scale climate change, the mechanisms by which these changes impact corals, and their potential for adaptation. In this thesis, I extract information from within coral skeletons to 1) Quantify the climate changes occurring on coral reefs and the effects on coral growth, 2) Identify differences in the sensitivity of coral reefs to these changes, and 3) Evaluate the adaptation potential of the keystone reef-building coral, Porites. First, I develop a mechanistic Porites growth model and reveal the physicochemical link between OA and skeletal formation. Ishow that the thickening (densification) of coralskeletal framework is most vulnerable to OA and that, under 21st century climate model projections, OA will reduce Porites skeletal density globally, with greatest impact in the Coral Triangle. Second, I develop an improved metric of thermal stress, and use a skeletal bleaching proxy to quantify coral responses to intensifying heatwaves in the central equatorial Pacific (CEP) since 1982. My work reveals a long history of bleaching in the CEP, and reef-specific differences in thermal tolerance linked to past heatwave exposure implying that, over time, reef communities have adapted to tolerate their unique thermal regimes. Third, I refine the Sr-U paleo-thermometer to enable monthly-resolved sea surface temperatures (SST) generation using laser ablation ICPMS. I show that laser Sr-U accurately captures CEP SST, including the frequency and amplitude of MHWs. Finally, I apply laser Sr-U to reconstruct the past 100 years of SST at Jarvis Island in the CEP, and evaluate my proxy record of bleaching severity in this context. I determine that Porites coral populations on Jarvis Island have not yet adapted to the pace of anthropogenic climate change.
Continue reading ‘Coral reefs in the Anthropocene ocean: novel insights from skeletal proxies of climate change, impacts, and resilience’The effect of climate change on the predatory success of sharks
Published 26 May 2021 Science ClosedTags: adaptation, biological response, chordata, otherprocess, performance, physiology, respiration, review
This literature overview focuses on how shark species, are faring with the anthropogenically induced climatic changes. The ocean is drastically affected by this, which has major implications on the aquatic life. Some effects include increasing temperature, carbon dioxide and acidity levels. This has led to shifts in the predatory success in sharks, which will only increase in severity as climate change intensifies, because changes in climate induce other changes in most aspects of the shark’s life. These can be grouped into three categories: shifts in body functions, behaviors and habitat. Some changes in body function include difficulty integrating sensory cues through reduced neuron receptor function, decreased brain/muscle aerobic potential and changes in growth/development. Behavioral changes include shifted swimming patterns, interacting with different species assemblages and prey behaviors. Lastly, habitat changes affect the shark’s ability to capture prey through increases in salinity, degradation of critical habitat and reduction in dissolved oxygen.
Continue reading ‘The effect of climate change on the predatory success of sharks’
