Posts Tagged 'mortality'

Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification

Ocean acidification (OA) may potentially modify the responses of aquatic organisms to other environmental stressors including metals. In this study, we investigated the effects of near-future OA (pCO2 1000 μatm) and mercury (Hg) on the development and reproduction of marine copepod Tigriopus japonicus under multigenerational life-cycle exposure. Metal accumulation as well as seven life history traits (survival rate, sex ratio, developmental time from nauplius to copepodite, developmental time from nauplius to adult, number of clutches, number of nauplii/clutch and fecundity) was quantified for each generation. Hg exposure alone evidently suppressed the number of nauplii/clutch, whereas single OA exposure negligibly affected the seven traits of copepods. However, OA exposure significantly alleviated the Hg inhibitory effects on number of nauplii/clutch and fecundity, which could be explained by the reduced Hg accumulation under OA. Such combined exposure also significantly shortened the development time. Thus, in contrast to earlier findings for other toxic metals, this study demonstrated that OA potentially mitigated the Hg toxicity to some important life traits in marine copepods during multigenerational exposure.

Continue reading ‘Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification’

Marine fish intestine responds to ocean acidification producing more carbonate aggregates

Marine fish contribute to the carbon cycle by producing mineralized intestinal aggregates generated as by-products of their osmoregulation. Here we aimed at characterizing the control of intestinal aggregate production in the gilthead sea bream in response to near future increases of environmental CO2. Our results demonstrate that hypercapnia (800 and 1200 μatm CO2) elicits higher intestine epithelial HCO3- secretion and the subsequent parallel increase of intestinal aggregate production when compared to present values (400 μatm CO2). Intestinal gene expression analysis revealed the up-regulation of crucial transport mechanisms involved not only in the intestinal secretion cascade (Slc4a4, Slc26a3 and Slc26a6) of sea bream, but also in other mechanisms involved in intestinal ion uptake linked to water absorption such as NKCC2 and the Aquaporin 1b. These results highlight the important role of fish in the marine carbon cycle, and their potential growing impact of intestinal biomineralization processes in the scenario of ocean acidification.

Continue reading ‘Marine fish intestine responds to ocean acidification producing more carbonate aggregates’

Experimental impacts of climate warming and ocean carbonation on eelgrass Zostera marina

CO2 is a critical and potentially limiting substrate for photosynthesis of both terrestrial and aquatic ecosystems. In addition to being a climate-warming greenhouse gas, increasing concentrations of CO2 will dissolve in the oceans, eliciting both negative and positive responses among organisms in a process commonly known as ocean acidification. The dissolution of CO2 into ocean surface waters, however, also increases its availability for photosynthesis, to which the highly successful, and ecologically important, seagrasses respond positively. Thus, the process might be more accurately characterized as ocean carbonation. This experiment demonstrated that CO2 stimulation of primary production enhances the summertime survival, growth, and proliferation of perennial eelgrass Zostera marina from the Chesapeake region, which is regularly impacted by summer heat stress. The experiment also quantified the logarithmic response to CO2 in terms of shoot proliferation, size, growth and sugar accumulation that was fundamentally consistent with model predictions based on metabolic carbon balance derived from short-term laboratory experiments performed with other eelgrass populations from cool ocean climates and other seagrass species from tropical and temperate environments. Rather than acting in a neutral fashion or as an independent stressor, increased CO2 availability can serve as a quantitative antagonist to counter the negative impact of climate warming on seagrass growth and survival. These results reinforce the emerging paradigm that seagrasses are likely to benefit significantly from a high-CO2 world.

Continue reading ‘Experimental impacts of climate warming and ocean carbonation on eelgrass Zostera marina’

Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors

Parental effects passed from adults to their offspring have been identified as a source of rapid acclimation that may allow marine populations to persist as our surface oceans continue to decrease in pH. Little is known, however, whether parental effects are beneficial for offspring in the presence of multiple stressors. We exposed adults of the oyster Saccostrea glomerata to elevated CO2 and examined the impacts of elevated CO2 (control = 392; 856 µatm) combined with elevated temperature (control = 24; 28°C), reduced salinity (control = 35; 25) and reduced food concentration (control = full; half diet) on their larvae. Adult exposure to elevated CO2 had a positive impact on larvae reared at elevated CO2 as a sole stressor, which were 8% larger and developed faster at elevated CO2 compared with larvae from adults exposed to ambient CO2. These larvae, however, had significantly reduced survival in all multistressor treatments. This was particularly evident for larvae reared at elevated CO2 combined with elevated temperature or reduced food concentration, with no larvae surviving in some treatment combinations. Larvae from CO2-exposed adults had a higher standard metabolic rate. Our results provide evidence that parental exposure to ocean acidification may be maladaptive when larvae experience multiple stressors.

Continue reading ‘Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors’

Seawater acidification induced immune function changes of haemocytes in Mytilus edulis: a comparative study of CO2 and HCl enrichment

The present study was performed to evaluate the effects of CO2− or HCl-induced seawater acidification (pH 7.7 or 7.1; control: pH 8.1) on haemocytes of Mytilus edulis, and the changes in the structure and immune function were investigated during a 21-day experiment. The results demonstrated that seawater acidification had little effect on the cellular mortality and granulocyte proportion but damaged the granulocyte ultrastructure. Phagocytosis of haemocytes was also significantly inhibited in a clearly concentration-dependent manner, demonstrating that the immune function was affected. Moreover, ROS production was significantly induced in both CO2 and HCl treatments, and four antioxidant components, GSH, GST, GR and GPx, had active responses to the acidification stress. Comparatively, CO2 had more severe destructive effects on haemocytes than HCl at the same pH level, indicating that CO2 stressed cells in other ways beyond the increasing H+ concentration. One possible explanation was that seawater acidification induced ROS overproduction, which damaged the ultrastructure of haemocytes and decreased phagocytosis.

Continue reading ‘Seawater acidification induced immune function changes of haemocytes in Mytilus edulis: a comparative study of CO2 and HCl enrichment’

Spatio-temporal environmental variation mediates geographical differences in phenotypic responses to ocean acidification

Phenotypic plasticity is expected to play a major adaptive role in the response of species to ocean acidification (OA), by providing broader tolerances to changes in pCO2 conditions. However, tolerances and sensitivities to future OA may differ among populations within a species because of their particular environmental context and genetic backgrounds. Here, using the climatic variability hypothesis (CVH), we explored this conceptual framework in populations of the sea urchin Loxechinus albus across natural fluctuating pCO2/pH environments. Although elevated pCO2 affected the morphology, physiology, development and survival of sea urchin larvae, the magnitude of these effects differed among populations. These differences were consistent with the predictions of the CVH showing greater tolerance to OA in populations experiencing greater local variation in seawater pCO2/pH. Considering geographical differences in plasticity, tolerances and sensitivities to increased pCO2 will provide more accurate predictions for species responses to future OA.

Continue reading ‘Spatio-temporal environmental variation mediates geographical differences in phenotypic responses to ocean acidification’

Intra-population variability of ocean acidification impacts on the physiology of Baltic blue mussels (Mytilus edulis): integrating tissue and organism response

Increased maintenance costs at cellular, and consequently organism level, are thought to be involved in shaping the sensitivity of marine calcifiers to ocean acidification (OA). Yet, knowledge of the capacity of marine calcifiers to undergo metabolic adaptation is sparse. In Kiel Fjord, blue mussels thrive despite periodically high seawater PCO2, making this population interesting for studying metabolic adaptation under OA. Consequently, we conducted a multi-generation experiment and compared physiological responses of F1 mussels from ‘tolerant’ and ‘sensitive’ families exposed to OA for 1 year. Family classifications were based on larval survival; tolerant families settled at all PCO2 levels (700, 1120, 2400 µatm) while sensitive families did not settle at the highest PCO2 (≥99.8% mortality). We found similar filtration rates between family types at the control and intermediate PCO2 level. However, at 2400 µatm, filtration and metabolic scope of gill tissue decreased in tolerant families, indicating functional limitations at the tissue level. Routine metabolic rates (RMR) and summed tissue respiration (gill and outer mantle tissue) of tolerant families were increased at intermediate PCO2, indicating elevated cellular homeostatic costs in various tissues. By contrast, OA did not affect tissue and routine metabolism of sensitive families. However, tolerant mussels were characterised by lower RMR at control PCO2 than sensitive families, which had variable RMR. This might provide the energetic scope to cover increased energetic demands under OA, highlighting the importance of analysing intra-population variability. The mechanisms shaping such difference in RMR and scope, and thus species’ adaptation potential, remain to be identified.

Continue reading ‘Intra-population variability of ocean acidification impacts on the physiology of Baltic blue mussels (Mytilus edulis): integrating tissue and organism response’


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Ocean acidification in the IPCC AR5 WG II

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