Posts Tagged 'biological response'



Sex differences in oxidative stress responses of tropical topshells (Trochus histrio) to increased temperature and high pCO2

Highlights

• Sex differences in oxidative stress of topshells were investigated under climate change.
• Males undergo cellular damage under high pCO2, counter-balanced by increased temperature.
• Heat shock response was thermo- and sex-regulated, most predominant in males.
• Catalase and GSTs activities were maximum under high temperature and hypercapnia.
• Sexes have distinct physiological strategies to cope oxidative stress, more efficient in females.

Abstract

Given scarcity of knowledge on gender ecophysiological responses of tropical marine organisms to global climate change, the major aim of this research was to investigate potential sex differences in oxidative status of topshell Trochus histrio, after a combined exposure to increased temperature and pCO2. Lipid peroxidation, heat-shock response and antioxidant enzymatic activities were evaluated. Lipid peroxidation varied differently between sexes, with males undergoing cellular damage under high pCO2, which was elevated temperature-counteracted. Heat shock response was thermo- and sex-regulated, with males exhibiting significantly higher heat shock proteins production than females. Catalase activity increased with temperature and was exacerbated in combination with hypercapnia, being highest in females, while glutathione S-transferases activity peaked in males. These results clearly support the existence of distinct physiological strategies to cope oxidative stress between sexes, apparently more efficient in females, and also reinforce for the need of encompassing sex as meaningful variable in future biomarker studies.

Continue reading ‘Sex differences in oxidative stress responses of tropical topshells (Trochus histrio) to increased temperature and high pCO2’

Behavioural responses of Antarctic krill (Euphausia superba) to CO2-induced ocean acidification: would krill really notice?

The Southern Ocean is expected to be significantly affected by future ocean acidification. Antarctic krill (Euphausia superba) is the key species of the Southern Ocean ecosystem. Understanding their behavioural responses to acidification is critical for assessing the impacts of ocean acidification on the ecosystem. Adult Antarctic krill reared in different holding tanks with various CO2 levels for 6 months prior to the experiments were tested for their behavioural responses to different carbon dioxide partial pressures (pCO2) (400, 1000, 1500, 2000, and 4000 μatm pCO2) in a two-channel flume. The time krill occupied either of the flume channels (with high or ambient CO2 levels) was highly variable in all tests. In most cases no significant preference to either side of the flume was found. The krill did not display any systematic discrimination to the sea water with different CO2 levels regardless of the CO2 levels that krill were acclimated for in the 6 months prior to the experiment. Poor ability to discriminate high CO2 waters may have an important implication to their life history in the future as ocean acidification rapidly progresses in parts of Southern Ocean.

Continue reading ‘Behavioural responses of Antarctic krill (Euphausia superba) to CO2-induced ocean acidification: would krill really notice?’

Inorganic carbon and pH dependency of Trichodesmium’s photosynthetic rates

We established the relationship between photosynthetic carbon fixation rates and pH, CO2 and HCO3 concentrations in the diazotroph Trichodesmium erythraeum IMS101. Inorganic 14C-assimilation was measured in TRIS-buffered ASW medium where the absolute and relative concentrations of CO2, pH and HCO3 were manipulated. First, we varied the total dissolved inorganic carbon concentration (TIC) (< 0 to ~ 5 mM) at constant pH, so ratios of CO2 and HCO3 remained relatively constant. Second, we varied pH (~ 8.54 to 7.52) at constant TIC, so CO2 increased whilst HCO3 declined. We found that 14C-assimilation could be described by the same function of CO2 for both approaches but showed different dependencies on HCO3 when pH was varied at constant TIC than when TIC was varied at constant pH. A numerical model of Trichodesmium’s CCM showed carboxylation rates are modulated by HCO3 and pH. The decrease in Ci assimilation at low CO2, when TIC was varied, is due to HCO3 uptake limitation of the carboxylation rate. Conversely, when pH was varied, Ci assimilation declined due to a high-pH mediated increase in HCO3 and CO2 leakage rates, potentially coupled to other processes (uncharacterised within the CCM model) that restrict Ci assimilation rates under high-pH conditions.

Continue reading ‘Inorganic carbon and pH dependency of Trichodesmium’s photosynthetic rates’

Impacts of ocean acidification on sea urchin growth across the juvenile to mature adult life-stage transition is mitigated by warming

Understanding how growth trajectories of calcifying invertebrates are affected by changing climate requires acclimation experiments that follow development across life-history transitions. In a long-term acclimation study, the effects of increased acidification and temperature on survival and growth of the tropical sea urchin Tripneustes gratilla from the early juvenile (5 mm test diameter—TD) through the developmental transition to the mature adult (60 mm TD) were investigated. Juveniles were reared in a combination of three temperature and three pH/pCO2 treatments, including treatments commensurate with global change projections. Elevated temperature and pCO2/pH both affected growth, but there was no interaction between these factors. The urchins grew more slowly at pH 7.6, but not at pH 7.8. Slow growth may be influenced by the inability to compensate coelomic fluid acid–base balance at pH 7.6. Growth was faster at +3 and +6°C compared to that in ambient temperature. Acidification and warming had strong and interactive effects on reproductive potential. Warming increased the gonad index, but acidification decreased it. At pH 7.6 there were virtually no gonads in any urchins regardless of temperature. The T. gratilla were larger at maturity under combined near-future warming and acidification scenarios (+3°C/pH 7.8). Although the juveniles grew and survived in near-future warming and acidification conditions, chronic exposure to these stressors from an early stage altered allocation to somatic and gonad growth. In the absence of phenotypic adjustment, the interactive effects of warming and acidification on the benthic life phases of sea urchins may compromise reproductive fitness and population maintenance as global climatic change unfolds.

Continue reading ‘Impacts of ocean acidification on sea urchin growth across the juvenile to mature adult life-stage transition is mitigated by warming’

Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)

Elevated concentrations of dissolved carbon dioxide (CO2) and reduced pH levels are observed during the culture and transportation of aquatic organisms. Studies on the toxicity effects of CO2 in penaeid shrimp are scarce when compared to the amount of research in fish. The objective of the present study was to determine the lethal concentration and safety levels of CO2 for juvenile white shrimp Litopenaeus vannamei. Juveniles (1.76 ± 0.36 g) were exposed for 96 h to one of six concentrations of dissolved CO2 (14.5, 23.8, 59.0, 88.0, 115.0, and 175.0 mg/L) or a control condition (without the addition of CO2), and their survival was monitored for 96 h. The LC50 values with 95% confidence limits at 24, 48, 72, and 96 h were 130.05 (104.2–162.1), 77.2 (73.8–80.02), 69.65 (65.47–74.32), and 59.12 (53.08–66.07) mg/L of CO2, respectively. The calculated safety level was 5.9 mg/L of CO2, and the highest concentration that did not induce significantly higher mortality than that observed in controls (NOEC) was 23.8 mg/L of CO2. We recommend that CO2 levels should be kept below the safety level obtained in this study.

Continue reading ‘Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)’

The interactive effects of elevated CO2 and ammonium enrichment on the physiological performances of Saccharina japonica (Laminariales, Phaeophyta)

Environmental challenges such as ocean acidification and eutrophication influence the physiology of kelp species. We investigated their interactive effects on Saccharina japonica (Laminariales, Phaeophyta) under two pH conditions [Low, 7.50; High (control), 8.10] and three NH 4 + concentrations (Low, 4; Medium, 60; High, 120 μM). The degree of variation of pH values in the culture medium and inhibition rate of photosynthetic oxygen evolution by acetazolamide were affected by pH treatments. Relative growth rates, carbon, nitrogen, and the C:N ratio in tissue samples were influenced by higher concentrations of NH 4 + . Rates of photosynthetic oxygen evolution were enhanced under elevated CO2 or NH 4 + conditions, independently, but these two factors did not show an interactive effect. However, rates of NH 4 + uptake were influenced by the interactive effect of increased CO2 under elevated NH 4 + treatment. Although ocean acidification and eutrophication states had an impact on physiological performance, chlorophyll fluorescence was not affected by those conditions. Our results indicated that the physiological reactions by this alga were influenced to some extent by a rise in the levels of CO2 and NH 4 + . Therefore, we expect that the biomass accumulation of S. japonica may well increase under future scenarios of ocean acidification and eutrophication.

Continue reading ‘The interactive effects of elevated CO2 and ammonium enrichment on the physiological performances of Saccharina japonica (Laminariales, Phaeophyta)’

Larval ecology in the face of changing climate – impacts of ocean warming and ocean acidification

Ocean warming and acidification are major climate change stressors for marine invertebrate larvae, and their impacts differ between habitats and regions. In many regions species with pelagic propagules are on the move, exhibiting poleward trends as temperatures rise and ocean currents change. Larval sensitivity to warming varies among species, influencing their invasive potential. Broadly distributed species with wide developmental thermotolerances appear best able to avail of the new opportunities provided by warming. Ocean acidification is a multi-stressor in itself and the impacts of its covarying stressors differ among taxa. Increased pCO2 is the key stressor impairing calcification in echinoid larvae while decreased mineral saturation is more important for calcification in bivalve larvae. Non-feeding, non-calcifying larvae appear more resilient to warming and acidification. Some species may be able to persist through acclimatization/adaptation to produce resilient offspring. Understanding the capacity for adaptation/acclimatization across generations is important to predicting the future species composition of marine communities.

Continue reading ‘Larval ecology in the face of changing climate – impacts of ocean warming and ocean acidification’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,076,084 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book