Posts Tagged 'adaptation'

Large-scale interventions may delay decline of the Great Barrier Reef

On the iconic Great Barrier Reef (GBR), the cumulative impacts of tropical cyclones, marine heatwaves and regular outbreaks of coral-eating crown-of-thorns starfish (CoTS) have severely depleted coral cover. Climate change will further exacerbate this situation over the coming decades unless effective interventions are implemented. Evaluating the efficacy of alternative interventions in a complex system experiencing major cumulative impacts can only be achieved through a systems modelling approach. We have evaluated combinations of interventions using a coral reef meta-community model. The model consisted of a dynamic network of 3753 reefs supporting communities of corals and CoTS connected through ocean larval dispersal, and exposed to changing regimes of tropical cyclones, flood plumes, marine heatwaves and ocean acidification. Interventions included reducing flood plume impacts, expanding control of CoTS populations, stabilizing coral rubble, managing solar radiation and introducing heat-tolerant coral strains. Without intervention, all climate scenarios resulted in precipitous declines in GBR coral cover over the next 50 years. The most effective strategies in delaying decline were combinations that protected coral from both predation (CoTS control) and thermal stress (solar radiation management) deployed at large scale. Successful implementation could expand opportunities for climate action, natural adaptation and socioeconomic adjustment by at least one to two decades.

Continue reading ‘Large-scale interventions may delay decline of the Great Barrier Reef’

Geographical variation in phenotypic plasticity of intertidal sister limpet’s species under ocean acidification scenarios

Ocean Acidification (OA) can have pervasive effects in calcifying marine organisms, and a better understanding of how different populations respond at the physiological and evolutionary level could help to model the impacts of global change in marine ecosystems. Due to its natural geography and oceanographic processes, the Chilean coast provides a natural laboratory where benthic organisms are frequently exposed to diverse projected OA scenarios. The goal of this study was to assess whether a population of mollusks thriving in a more variable environment (Talcaruca) would present higher phenotypic plasticity in physiological and morphological traits in response to different pCO2 when compared to a population of the same species from a more stable environment (Los Molles). To achieve this, two benthic limpets (Scurria zebrina and Scurria viridula) inhabiting these two contrasting localities were exposed to ocean acidification experimental conditions representing the current pCO2 in the Chilean coast (500 μatm) and the levels predicted for the year 2100 in upwelling zones (1500 (μatm). Our results show that the responses to OA are species-specific, even in this related species. Interestingly, S. viridula showed better performance under OA than S. zebrina (i.e., similar sizes and carbonate content in individuals from both populations; lower effects of acidification on the growth rate combined with a reduction of metabolism at higher pCO2). Remarkably, these characteristics could explain this species’ success in overstepping the biogeographical break in the area of Talcaruca, which S. zebrina cannot achieve. Besides, the results show that the habitat factor has a strong influence on some traits. For instance, individuals from Talcaruca presented a higher growth rate plasticity index and lower shell dissolution rates in acidified conditions than those from Los Molles. These results show that limpets from the variable environment tend to display higher plasticity, buffering the physiological effects of OA compared with limpets from the more stable environment. Taken together, these findings highlight the key role of geographic variation in phenotypic plasticity to determine the vulnerability of calcifying organisms to future scenarios of OA.

Continue reading ‘Geographical variation in phenotypic plasticity of intertidal sister limpet’s species under ocean acidification scenarios’

Cross‐generational response of a tropical sea urchin to global change and a selection event in a 43‐month mesocosm study

Long‐term experimental investigations of transgenerational plasticity (TGP) and transgenerational acclimatization to global change are sparse in marine invertebrates. Here, we test the effect of ocean warming and acidification over a 25‐month period of Echinometra sp. A sea urchins whose parents were acclimatized at ambient or one of two near‐future (projected mid‐ and end‐ of the 21st century) climate scenarios for 18 months. Several parameters linked to performance exhibited strong effects of future ocean conditions at 9 months of age. The Ambient‐Ambient group (A‐A, both F0 and F1 at ambient conditions) was significantly larger (21%) and faster in righting response (31%) compared to other groups. A second set of contrasts revealed near‐future scenarios caused significant negative parental carryover effects. Respiration at 9 months was depressed by 59% when parents were from near‐future climate conditions, and righting response was slowed by 28%. At ten months, a selective pathogenic mortality event lead to significantly higher survival rates of A‐A urchins. Differences in size and respiration measured prior to the mortality were absent after the event, while a negative parental effect on righting (29% reduction) remained. The capacity to spawn at the end of the experiment was higher in individuals with ambient parents (50%) compared to other groups (21%) suggesting persistent parental effects. Obtaining different results at different points in time illustrates the importance of longer‐term and multi‐generation studies to investigate effects of climate change. Given some animals in all groups survived the pathogenic event and that effects on physiology (but not behavior) among groups were eliminated after the mortality, we suggest that similar events could constitute selective sweeps, allowing genetic adaptation. However, given the observed negative parental effects and reduced potential for population replenishment it remains to be determined if selection would be sufficiently rapid to rescue this species from climate change effects.

Continue reading ‘Cross‐generational response of a tropical sea urchin to global change and a selection event in a 43‐month mesocosm study’

Projected near-future ocean acidification decreases mercury toxicity in marine copepods

Highlights

  • Copepods were subjected to OA and Hg pollution under multigenerational exposure.
  • OA reduced Hg accumulation and its toxicity to the growth/reproduction in copepods.
  • Copepod proteome enabled its physiological resilience to decreasing pH.
  • Proteomics indicated many toxic events, ensuring Hg toxicity to the copepod’s traits.
  • Proteome compensation was accounting for the alleviative effect of OA on Hg toxicity.

Abstract

Here, we examined the combinational effect of ocean acidification (OA) and mercury (Hg) in the planktonic copepod Pseudodiaptomus annandalei in cross-factored response to different pCO2 (400, 800 μatm) and Hg (control, 1.0 and 2.5 μg/L) exposures for three generations (F0-F2), followed by single-generation recovery (F3) under clean condition. Several phenotypic traits and Hg accumulation were analyzed for F0-F3. Furthermore, shotgun-based quantitative proteomics was performed for F0 and F2. Our results showed that OA insignificantly influenced the traits. During F0-F2, combined exposure reduced Hg accumulation as compared with the counterpart Hg treatment, supporting the mitigating effect of OA on Hg toxicity in copepods. Proteomics analysis indicated that the copepods probably increased energy production/storage and stress response to ensure physiological resilience against OA. However, Hg induced many toxic events (e.g., energy depletion and degenerated organomorphogenesis/embryogenesis for F0; cell cycle arrest and detrimental stress-defense for F2), which were translated to the population-level adverse outcome, i.e., compromised growth/reproduction. Particularly, compensatory proteome response was identified (e.g., increased immune defense for F0; energetic compensation and enhanced embryogenesis for F2), accounting for a negative interaction between OA and Hg. Together, this study provides the molecular mechanisms behind the effects of OA and Hg pollution in marine copepods.

Continue reading ‘Projected near-future ocean acidification decreases mercury toxicity in marine copepods’

Epiphytic hydroids on Posidonia oceanica seagrass meadows are winner organisms under future ocean acidification conditions: evidence from a CO2 vent system (Ischia Island, Italy)

Effects of ocean acidification (OA) on the plant phenology and colonization/settlement pattern of the hydrozoan epibiont community of the leaves of the seagrass Posidonia oceanica have been studied at volcanic CO2 vents off Ischia (Italy). The study was conducted in shallow Posidonia stands (2.5–3.5 m depth), in three stations on the north and three on the south sides of the vent’s area (Castello Aragonese vents), distributed along a pH gradient. At each station, 10–15 P. oceanica shoots were collected every three months for one-year cycle (Sept 2009–2010). The shoot density of Posidonia beds in the most acidified stations along the gradient (pH < 7.4) was significantly higher than that in the control area (pH = 8.10). On the other hand, we recorded lower leaf lengths and widths in the acidified stations in the whole year of observations, compared to those in the control stations. However, the overall leaf surface (Leaf Area Index) available for epiphytes under ocean acidification conditions was higher on the south side and on both the most acidified stations because of the higher shoot density under OA conditions. The hydrozoan epibiont community on the leaf canopy accounted for seven species, three of which were relatively abundant and occurring all year around (Sertularia perpusilla, Plumularia obliqua, Clytia hemisphaerica). All hydroids species showed a clear tolerance to low pH levels, including chitinous and non-calcifying forms, likely favoured also by the absence of competition for substratum with the calcareous forms of epiphytes selected against OA.

Continue reading ‘Epiphytic hydroids on Posidonia oceanica seagrass meadows are winner organisms under future ocean acidification conditions: evidence from a CO2 vent system (Ischia Island, Italy)’

Parental whole life cycle exposure modulates progeny responses to ocean acidification in slipper limpets

Multigenerational exposure is needed to assess the evolutionary potential of organisms in the rapidly changing seascape. Here, we investigate if there is a transgenerational effect of ocean acidification exposure on a calyptraeid gastropod such that long‐term exposure elevates offspring resilience. Larvae from wild type Crepidula onyx adults were reared from hatching until sexual maturity for over 36 months under three pH conditions (pH 7.3, 7.7, and 8.0). While the survivorship, growth, and respiration rate of F1 larvae were unaffected by acute ocean acidification (OA), long‐term and whole life‐cycle exposure significantly compromised adult survivorship, growth, and reproductive output of the slipper limpets. When kept under low pH throughout their life cycle, only 6% of the F1 slipper limpets survived pH 7.3 conditions after ~2.5 years and the number of larvae they released was ~10% of those released by the control. However, the F2 progeny from adults kept under the long‐term low pH condition hatched at a comparable size to those in medium and control pH conditions. More importantly, these F2 progeny from low pH adults outperformed F2 slipper limpets from control conditions; they had higher larval survivorship and growth, and reduced respiration rate across pH conditions, even at the extreme low pH of 7.0. The intragenerational negative consequences of OA during long‐term acclimation highlights potential carryover effects and ontogenetic shifts in stress vulnerability, especially prior to and during reproduction. Yet, the presence of a transgenerational effect implies that this slipper limpet, which has been widely introduced along the West Pacific coasts, has the potential to adapt to rapid acidification.

Continue reading ‘Parental whole life cycle exposure modulates progeny responses to ocean acidification in slipper limpets’

Natural CO2 seeps reveal adaptive potential to ocean acidification in fish

Volcanic CO2 seeps are natural laboratories that can provide insights into the adaptation of species to ocean acidification. Whilst many species are challenged by reduced pH levels, some species benefit from the altered environment and thrive. Here, we explore the molecular mechanisms of adaptation to ocean acidification in a population of a temperate fish species that experiences increased population sizes under elevated CO2. Fish from CO2 seeps exhibited an overall increased gene expression in gonad tissue compared to those from ambient CO2 sites. Up‐regulated genes at CO2 seeps are possible targets of adaptive selection as they can directly influence the physiological performance of fishes exposed to ocean acidification. Most of the up‐regulated genes at seeps were functionally involved in the maintenance of pH homeostasis and increased metabolism, and presented a deviation from neutral evolution expectations in their patterns of DNA polymorphisms, providing evidence for adaptive selection to ocean acidification. The targets of this adaptive selection are likely regulatory sequences responsible for the increased expression of these genes which would allow a fine‐tuned physiological regulation to maintain homeostasis and thrive at CO2 seeps. Our findings reveal that standing genetic variation in DNA sequences regulating the expression of genes in response to a reduced pH environment could provide for adaptive potential to near‐future ocean acidification in fishes. Moreover, with this study we provide a forthright methodology combining transcriptomics and genomics which can be applied to infer the adaptive potential to different environmental conditions in wild marine populations.

Continue reading ‘Natural CO2 seeps reveal adaptive potential to ocean acidification in fish’

Microalgal photosynthesis induces alkalization of aquatic environment as a result of H+ uptake independently from CO2 concentration – new perspectives for environmental applications

Highlights

  • Microalgae photosynthesis induces strongly H+ uptake reversing ocean acidification.
  • Water alkalization through algal H+ uptake is independent from CO2 concentration.
  • New management approaches for reversing ocean acidification using algal H+ uptake.
  • Algal H+ uptake depends on essential nutrients, cell density and light intensity.
  • Acidification of aquatic environment induces microalgal photosynthesis and growth.

Abstract

The photosynthetic process in microalgae and the extracellular proton environment interact with each other. The photosynthetic process in microalgae induces a pH increase in the aquatic environment as a result of cellular protons uptake rather than as an effect of CO2 consumption. The photosynthetic water photolysis and the reduction/oxidation cycle of the plastoquinone pool provide lumen with protons. Weak bases act as “permeant buffers” in lumen during the photosynthetic procedure, converting the ΔpH to Δψ. This is possibly the main reason for continuous light-driven proton uptake from the aquatic environment through cytosol and stroma, into the lumen. The proton uptake rate and, therefore, the microalgal growth is proportional to the light intensity, cell concentration, and extracellular proton concentration. The low pH in microalgae cultures, without limitation factors related to light and nutrients, strongly induces photosynthesis (and proton uptake) and, consequently, growth. In contrast, the mitochondrial respiratory process, in the absence of photosynthetic activity, does not substantially alter the culture pH. Only after intensification of the respiratory process, using exogenous glucose supply leads to significantly reduced pH values in the culture medium, almost exclusively through proton output. Enhanced dissolution of atmospheric CO2 in water causes the phenomenon of ocean acidification, which prevents the process of calcification, a significant process for numerous phytoplankton and zooplankton organisms, as well for corals. The proposed interaction between microalgal photosynthetic activity and proton concentration in the aquatic environment, independently from the CO2 concentration, paves the way for new innovative management strategies for reversing the ocean acidification.

Continue reading ‘Microalgal photosynthesis induces alkalization of aquatic environment as a result of H+ uptake independently from CO2 concentration – new perspectives for environmental applications’

Transgenerational plasticity responses of oysters to ocean acidification differ with habitat

Transgenerational plasticity (TGP) has been identified as a critical mechanism of acclimation which may buffer marine organisms against climate change, yet whether the TGP response of marine organisms is altered depending on their habitat is unknown. Many marine organisms are found in intertidal zones where they experience episodes of emersion daily as the tide rises and recedes. During episodes of emersion, the accumulation of metabolic carbon dioxide (CO2) leads to hypercapnia for many species. How this metabolic hypercapnia impacts the TGP response of marine organisms to climate change is unknown as all previous transgenerational studies have been done under subtidal conditions, where parents are constantly immersed. Herein, we assess the capacity of the ecologically and economically important oyster, Saccostrea glomerata to acclimate to elevated CO2 dependent on habitat, across its vertical distribution, from the subtidal to intertidal zone. Tidal habitat altered both the existing tolerance and transgenerational response of S. glomerata to elevated CO2. Overall, larvae from parents conditioned in an intertidal habitat had a greater existing tolerance to elevated CO2 than larvae from parents conditioned in a subtidal habitat but had a lower capacity for beneficial TGP following parental exposure to elevated CO2. Our results suggest that the transgenerational plasticity responses of marine species will not be uniform across their distribution and highlights the need to consider the habitat of a species when assessing TGP responses to climate change stressors.

Continue reading ‘Transgenerational plasticity responses of oysters to ocean acidification differ with habitat’

Tissue comparison of transcriptional response to acute acidification stress of barramundi Lates calcarifer in coastal and estuarine areas

Highlights

  • Assessed tissues response of barramundi in acidification stress by RNA-seq analysis
  • Acidification inhibited the immune function of barramundi in different tissues.
  • Provided insights for susceptible physiological processes to acidification stress

Abstract

In order to explore the common and unique physiological changes in tissues of juvenile barramundi Lates calcarifer in acidified water environment, RNA sequence analysis was used to analyze the molecular responses of liver, head kidney, and gill of juvenile barramundi in pH 7.4 and pH 8.1 seawater environment. The number of differential expression genes identified in liver, head kidney and gill were 860, 388 and 1792, respectively. Through functional enrichment analysis, the differential expression genes common to the three tissues were all related to immunity. Among the unique differential genes in the liver, pathways related to digestion, endocrine, and metabolism were enriched. Among the unique differential expression genes in gill, pathways related to genetic information processing, immunity and metabolism were enriched. The findings of the present study uncover the transcriptional changes in fish correspond to environmental pH change, and provide a better understanding on the biological process at molecular level to environmental pH adapting. This work highlights that assessments for the potential of estuarine fishes to cope with environmental pH change to develop the future conservation strategies.

Continue reading ‘Tissue comparison of transcriptional response to acute acidification stress of barramundi Lates calcarifer in coastal and estuarine areas’

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