EFFECT OF CADMIUM AND SEASONALITY ON CRITICAL TEMPERATURES OF AEROBIC METABOLISM IN EASTERN OYSTERS, Crassostrea virginica Gmelin 1791
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University of North Carolina at Charlotte
Cadmium (Cd) and elevated temperatures are common stressors in estuarine and coastal environments affecting intertidal mollusks such as oysters. Cd and elevated temperature can raise the metabolic demands of oysters due to the increase cost of detoxification and damage repair and induce tissue-wide hypoxemia. According to the concept of the oxygen- and capacity-limited thermal tolerance (OCLTT), this is expected to lead to the shift of the critical temperature (Tc) of aerobic metabolism (indicated by the onset of partial anaerobiosis) restricting the thermal tolerance limits of the organism. We tested this hypothesis by determining the onset of anaerobic metabolism, changes in the cellular energy budget and the extent of oxidative damage during acute temperature rise (from 20°C to 36°C) in eastern oysters Crassostrea virginica under control conditions and after prolonged Cd exposure (50 µg Cd l-1 for 30 days). In summer and winter control oysters, levels of anaerobic end products increased at 28°C and 24°C, respectively, indicating an earlier onset of tissue hypoxemia in winter-acclimated oysters. Cd exposure shifted Tc to lower levels in summer oysters (from 28 to 24°C) oysters Tc was 24°C in summer However, in winter there was no temperature-induced accumulation of anaerobic end products in Cd-exposed oysters suggesting that the effect of Cd exposure on Tc varies between the seasons and/or that the studied range of temperatures was insufficient to detect Tc in the winter Cd-exposed group. Acute warming had no negative effects on tissue and cellular energy status of oysters in summer or winter but led to an increase of oxidative damage to proteins in winter control oysters. This suggests that oysters are well adapted to acute temperature fluctuations in the intertidal zone and maintain energy balance despite the limitations of aerobic metabolism and partial transition to anaerobiosis.
Schneider, StanleyParrow, MatthewCurran, KentRingwood, Amy
Thesis (Ph.D.)--University of North Carolina at Charlotte, 2012.
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