Treydte, Sandra (2010) Impact of ocean acidification and warming on the energy metabolism of the Greenland smoothcockle Serripes groenlandicus. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 76 pp.

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Abstract

Anthropogenic C02 emissions, mainly attributable to fossil-fuel combustion, lead to ocean acidification and warming which may impact on marine animals and, in case of temperature, have already caused alterations in marine ecosystems. Following the Intergovernmental Panel on Climate Change (IPCC, 2007; "business as usual" scenario) atmospheric C02 concentrations could be as high as 800 μatm (0.08 kPa) by the end of the present century and annual mean air temperature in the Arctic will increase by 4-5°C according to the Arctic Climate Impact Assessment (ACIA, 2004). A number of studies revealed a high degree of tolerance in various taxa characterized by high metabolic rates and a high level of activity. In contrast, most marine invertebrates have low metabolic rates and low capacities of ion-regulation, which are indicative for enhanced susceptibility towards ocean acidification. The synergistic impact of both elevated partial pressure of C02 (hypercapnia) and increased temperature was addressed by studying the short to medium-term effects on energy metabolism and acid-base status of an Arctic invertebrate, the Greenland smoothcockle (Serripes groenlandicus), under present day normocapnia (380 μatm), C02 expected towards 2100 (750 μatm) and beyond (1120 μatm) combined with an acute temperature rise from 1 to 7°C. Extracellular pH was negatively correlated with ambient water Pco2 and remained uncompensated throughout the whole ten days experimental period. Changes in haemolymph bicarbonate concentrations followed the non-bicarbonate buffer line. In contrast, intracellular acid-base status did not show any effect with the exception of a slight decrement in pH following the alphastat pattern. Aerobic energy metabolism was maintained during ten days of exposure as arterial haemolymph oxygen partial pressure remained constant and accumulation of anaerobic end products did not occur in foot muscle tissue. Whole animal oxygen consumption increased with temperature during both normo- and hypercapnia. Lower Arrhenius activation energies and Q10 values under hypercapnia could be indicative for a reduction in temperature responsiveness and metabolic depression under elevated Pco2 levels. A final control revealed strong seasonality and thus serves as a correction for seasonal shifts during the experimental period. The results of the present study suggest that the Greenland smoothcockle is susceptible to future ocean acidification as extracellular acid-base disturbances remained uncompensated. A temperature change assumed for the end of the resent century is probably not limiting the individual aerobic scope of the investigated species. Future research is needed to evaluate seasonal shifts in thermal tolerance limits without and with the impact of ocean acidification.

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