We have looked at oysters metabolism, and have found out that their respiration rate increases when they are exposed to cadmium at environmentally relevant levels, as the organism spends more energy on basal maintenance, Sokolova said.

Metabolism also increases when they are exposed to higher temperatures. At some point, when they are exposed to both cadmium and higher temperatures, their metabolism can not go up any more and they start dying because they have hit the maximum level.

In its native habitat on the east coast of North America, the eastern oyster lives in estuaries where the temperature ranges fluctuate seasonally -- from 0 to 4 degrees centigrade in the winter to temperatures as high as 35 degrees centigrade in the summer. According to Sokolova, past studies have shown that oysters stop growing at about 28 degrees centigrade, a temperature that can persist under normal summer conditions for several months in a row.

Through a series of studies examining the impact of cadmium concentrations and high temperatures at the environmental, organismal, cellular and biochemical levels, Sokolova and her team have narrowed the problem down to the effects of the two factors on a complicated series of chemical reactions that occur in the oysters mitochondria in the process of cellular metabolism.

The researchers found that cadmium affects mitochondrial function by reducing the efficiency of the metabolic cycle in producing adenosine triphosphate (ATP), the main molecule that cells use to transfer energy. The inefficiency is particularly pronounced as temperatures approach or exceed 30 degrees centigrade. The researchers suspected that the cadmium caused a mal
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Contact: James Hathaway
jbhathaw@email.uncc.edu
704-687-6675
University of North Carolina at Charlotte
13-Dec-2006