Posts Tagged 'acclimation'

Long-term thermal acclimation drives adaptive physiological adjustments of a marine gastropod to reduce sensitivity to climate change

Highlights

  • The effects of thermal history on thermal threshold and physiology were assessed.
  • Gastropods acclimated to warmer environments had higher thermal threshold (CTmax).
  • Warm-acclimated gastropods were metabolically less active than cool-acclimated ones.
  • Energy conservation appeared to be a strategy for thermal acclimation.
  • Long-term thermal acclimation may allow marine organisms to adjust to climate change.

Abstract

Ocean warming is predicted to challenge the persistence of a variety of marine organisms, especially when combined with ocean acidification. Whilst temperature affects virtually all physiological processes, the extent to which thermal history mediates the adaptive capacity of marine organisms to climate change has been largely overlooked. Using populations of a marine gastropod (Turbo undulatus) with different thermal histories (cool vs. warm), we compared their physiological adjustments following exposure (8-week) to ocean acidification and warming. Compared to cool-acclimated counterparts, we found that warm-acclimated individuals had higher thermal threshold (i.e. increased CTmax by 2°C), which was unaffected by the exposure to ocean acidification and warming. Thermal history also strongly mediated physiological effects, where warm-acclimated individuals adjusted to warming by conserving energy, suggested by lower respiration and ingestion rates, energy budget (i.e. scope for growth) and O:N ratio. After exposure to warming, warm-acclimated individuals had higher metabolic rates and greater energy budget due to boosted ingestion rates, but such compensatory feeding disappeared when combined with ocean acidification. Overall, we suggest that thermal history can be a critical mediator of physiological performance under future climatic conditions. Given the relatively gradual rate of global warming, marine organisms may be better able to adaptively adjust their physiology to future climate than what short-term experiments currently convey.

Continue reading ‘Long-term thermal acclimation drives adaptive physiological adjustments of a marine gastropod to reduce sensitivity to climate change’

Acclimation potential to a future ocean acidification scenario in the key copepod species Calanus finmarchicus

Ocean acidification, as a result of the increased concentration of carbon dioxide in
the ocean, poses a threat towards marine ecosystems through lowered pH and altered seawater chemistry. The marine copepod Calanus finmarchicus is an ecologically and socioeconomically important species. In this study C. finmarchicus collected in Trondheimsfjorden was exposed to a CO2 concentration relevant for year 2300 (~2080 ppm) for two consecutive generations in the laboratory. The ability of C. finmarchicus to acclimate towards a pCO2 scenario relevant for year 2300, as well as the genetic contribution to this ability, was investigated in the study. Individuals exposed to elevated CO2 concentrations for two generations had significantly higher LC50 values than individuals kept under ambient CO2 concentrations, which indicates that C. finmarchicus has the ability to acclimate to a pCO2 scenario of 2080 ppm. Microsatellite analyses on the animals revealed a tendency of lower genetic diversity, measured as allelic richness and expected heterozygosity, in the populations exposed to high CO2 concentrations compared to the control populations, although the difference was not significant. The microsatellite analysis thus indicated that some of the observed increase in tolerance among the CO2 exposed animals may be due to genetic adaptation, but this needs to be further studied. The present study indicated that C. finmarchicus may be tolerant towards the direct effects of a pCO2 scenario relevant for year 2300.

Continue reading ‘Acclimation potential to a future ocean acidification scenario in the key copepod species Calanus finmarchicus’

Parental effects improve escape performance of juvenile reef fish in a high-CO2 world

Rising CO2 levels in the oceans are predicted to have serious consequences for many marine taxa. Recent studies suggest that non-genetic parental effects may reduce the impact of high CO2 on the growth, survival and routine metabolic rate of marine fishes, but whether the parental environment mitigates behavioural and sensory impairment associated with high CO2 remains unknown. Here, we tested the acute effects of elevated CO2 on the escape responses of juvenile fish and whether such effects were altered by exposure of parents to increased CO2 (transgenerational acclimation). Elevated CO2 negatively affected the reactivity and locomotor performance of juvenile fish, but parental exposure to high CO2 reduced the effects in some traits, indicating the potential for acclimation of behavioural impairment across generations. However, acclimation was not complete in some traits, and absent in others, suggesting that transgenerational acclimation does not completely compensate the effects of high CO2 on escape responses.
Continue reading ‘Parental effects improve escape performance of juvenile reef fish in a high-CO2 world’

Symbiodinium community composition in scleractinian corals is not affected by life-long exposure to elevated carbon dioxide

Ocean acidification (OA) is expected to negatively affect coral reefs, however little is known about how OA will change the coral-algal symbiosis on which reefs ultimately depend. This study investigated whether there would be differences in coral Symbiodinium types in response to OA, potentially improving coral performance. We used denaturing gradient gel electrophoresis (DGGE) of the internal transcribed spacer 2 (ITS2) region of ribosomal DNA to investigate the dominant types of Symbiodinium associating with six species of scleractinian coral that were exposed to elevated partial pressures of carbon dioxide (pCO2) in situ from settlement and throughout their lives. The study was conducted at three naturally occurring volcanic CO2 seeps (pCO2 ~500 to 900 ppm, pHTotal 7.8 – 7.9) and adjacent control areas (pCO2 ~390 ppm, pHTotal ~8.0 – 8.05) in Papua New Guinea. The Symbiodinium associated with corals living in an extreme seep site (pCO2 >1000 ppm) were also examined. Ten clade C types and three clade D types dominated the 443 coral samples. Symbiodinium types strongly contrasted between coral species, however, no differences were observed due to CO2 exposure. Within five species, 85 – 95% of samples exhibited the same Symbiodinium type across all sites, with remaining rare types having no patterns attributable to CO2 exposure. The sixth species of coral displayed site specific differences in Symbiodinium types, unrelated to CO2 exposure. Symbiodinium types from the coral inhabiting the extreme CO2 seep site were found commonly throughout the moderate seeps and control areas. Our finding that symbiotic associations did not change in response to CO2 exposure suggest that, within the six coral hosts, none of the investigated 13 clade C and D Symbiodinium types had a selective advantage at high pCO2. Acclimatisation through changing symbiotic association therefore does not seem to be an option for Indo-Pacific corals to deal with future OA.

Continue reading ‘Symbiodinium community composition in scleractinian corals is not affected by life-long exposure to elevated carbon dioxide’

The role of preconditioning in ocean acidification experiments: a test with the intertidal isopod Paradella dianae

Environmental alterations are accelerating worldwide and the rate of change in ocean chemistry is predicted to happen so rapidly that it is unclear how marine ecosystems will respond. It is hypothesized that the phenotypic plasticity or acclimation capacity of an individual provides a buffer against environmental change; however, this plasticity depends on the speed at which the change occurs. Ocean acidification studies have found direct and acute responses from organisms exposed to elevated CO2 levels. Now, the challenge lies in integrating acclimation into experimental design in short-term studies, requiring proper preconditioning setups. Here we experimentally show that different preconditioning approaches produce different physiological and behavioral responses in the intertidal isopod Paradella dianae. Isopods were impaired when immediately exposed to elevated CO2 levels relative to individuals that were gradually acclimated to high CO2 concentrations. Abruptly introducing organisms to severe changes in CO2 conditions can produce confounding effects of short-term stress with acclimated responses to long-term shifts in ocean chemistry. By exposing organisms to sudden changes in CO2 concentrations, we are forcing immediate physiological stress reactions that could be independent of exposure to specific CO2 levels. We discuss how integrating acclimation in experimental design can help provide more accurate predictions about the impact of ocean acidification on marine ecosystems.

Continue reading ‘The role of preconditioning in ocean acidification experiments: a test with the intertidal isopod Paradella dianae’

Responses of the Emiliania huxleyi proteome to ocean acidification

Ocean acidification due to rising atmospheric CO2 is expected to affect the physiology of important calcifying marine organisms, but the nature and magnitude of change is yet to be established. In coccolithophores, different species and strains display varying calcification responses to ocean acidification, but the underlying biochemical properties remain unknown. We employed an approach combining tandem mass-spectrometry with isobaric tagging (iTRAQ) and multiple database searching to identify proteins that were differentially expressed in cells of the marine coccolithophore species Emiliania huxleyi (strain NZEH) between two CO2 conditions: 395 (~current day) and ~1340 p.p.m.v. CO2. Cells exposed to the higher CO2 condition contained more cellular particulate inorganic carbon (CaCO3) and particulate organic nitrogen and carbon than those maintained in present-day conditions. These results are linked with the observation that cells grew slower under elevated CO2, indicating cell cycle disruption. Under high CO2 conditions, coccospheres were larger and cells possessed bigger coccoliths that did not show any signs of malformation compared to those from cells grown under present-day CO2 levels. No differences in calcification rate, particulate organic carbon production or cellular organic carbon: nitrogen ratios were observed. Results were not related to nutrient limitation or acclimation status of cells. At least 46 homologous protein groups from a variety of functional processes were quantified in these experiments, of which four (histones H2A, H3, H4 and a chloroplastic 30S ribosomal protein S7) showed down-regulation in all replicates exposed to high CO2, perhaps reflecting the decrease in growth rate. We present evidence of cellular stress responses but proteins associated with many key metabolic processes remained unaltered. Our results therefore suggest that this E. huxleyi strain possesses some acclimation mechanisms to tolerate future CO2 scenarios, although the observed decline in growth rate may be an overriding factor affecting the success of this ecotype in future oceans.

Continue reading ‘Responses of the Emiliania huxleyi proteome to ocean acidification’

Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic

Cyanobacteria make significant contributions to global carbon and nitrogen cycling, particularly in the oligotrophic subtropical and tropical gyres. The present study examined short-term (days) physiological and acclimation responses of natural cyanobacterial populations to changes in pH/pCO2 spanning the last glacial minimum, ~8.4/~150 ppm, to projected year 2100 values of ~7.8/~800 ppm. Fe- and P-replete colonies of Trichodesmium increased N2-fixation rates (nmol N colony−1 h−1) at pH 7.8 by 54% (range 6 to 156%) over ambient pH/pCO2 conditions, while N2-fixation at pH/pCO2 8.4 was 21% (range 6 to 65%) lower than at ambient pH/pCO2; a similar pattern was observed when the rates were normalized to colony C. C-fixation rates were on average 13% (range −72 to 112%) greater at low pH than at ambient pH and 37% (−53 to 23%) greater than at high pH. Whole community assemblages dominated by Prochlorococcus and Synechococcus (47 to 95% of autotrophic biomass), whether nutrient-replete or P-limited, did not show a clear response of C-fixation rates to changes in pH/pCO2. Comparison of initial and final C-fixation responses across pH/pCO2 treatments suggests rapid acclimation of cellular physiology to new pH/pCO2 conditions. Changes in cell size and pigment content for Prochlorococcus and Synechococcus were minor and did not vary in a consistent manner with changes in pH/pCO2. These results for natural populations of all 3 cyanobacteria concur with previous research and suggest that one important response to changes in ocean pH and pCO2 might be an increase in N2 and C fixation by Trichodesmium under nutrient-replete conditions. The response of single-cell cyanobacteria to changes in pH/pCO2 will likely be indirect and controlled by the response to other variables, such as nutrients.

Continue reading ‘Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic’

High latitude fish in a high CO2 world: synergistic effects of elevated temperature and carbon dioxide on the metabolic rates of Antarctic notothenioids

Although the physiological response of teleost fishes to increased temperature has been well documented, there is only a small body of literature that examines the effects of ocean acidification on fish under ecologically relevant scenarios. Furthermore, little data exists which examines the possible synergistic effects of increased sea surface temperatures and pCO2 levels, although it is well established that both will co-committedly change in the coming centuries. In this study we examined the effects of increased temperature, increased pCO2, and a combination of these treatments on the resting metabolic rate (RMR) of four species of notothenioid fish, Trematomus bernacchii, T. hansoni, T. newnesi, and Pagothenia borchgrevinki, acclimated to treatment conditions for 7, 14 or 28 days. While most species appear capable of rapidly acclimating to increased pCO2, temperature continues to impact RMR’s for up to 28 days. One species in particular, T. newnesi, displayed no acclimatory response to any of the treatments regardless of acclimation time and may have a reduced capacity to respond to environmental change. Furthermore, we present evidence that temperature and pCO2 act synergistically to further elevate the RMR and slow acclimation when compared to temperature or pCO2 increases alone.

Continue reading ‘High latitude fish in a high CO2 world: synergistic effects of elevated temperature and carbon dioxide on the metabolic rates of Antarctic notothenioids’

Parental environment mediates impacts of increased carbon dioxide on a coral reef fish

Carbon dioxide concentrations in the surface ocean are increasing owing to rising CO2 concentrations in the atmosphere1. Higher CO2 levels are predicted to affect essential physiological processes of many aquatic organisms2, 3, leading to widespread impacts on marine diversity and ecosystem function, especially when combined with the effects of global warming4, 5, 6. Yet the ability for marine species to adjust to increasing CO2 levels over many generations is an unresolved issue. Here we show that ocean conditions projected for the end of the century (approximately 1,000 μatm CO2 and a temperature rise of 1.5–3.0 °C) cause an increase in metabolic rate and decreases in length, weight, condition and survival of juvenile fish. However, these effects are absent or reversed when parents also experience high CO2 concentrations. Our results show that non-genetic parental effects can dramatically alter the response of marine organisms to increasing CO2 and demonstrate that some species have more capacity to acclimate to ocean acidification than previously thought.

Continue reading ‘Parental environment mediates impacts of increased carbon dioxide on a coral reef fish’


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Ocean acidification in the IPCC AR5 WG II

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