Tuesday, May 27, 2008
243

Spatial and temporal differences in daphnia sensitivity to toxaphene

Zijia Li, Engineering, University of Michigan, Ann Arbor, MI 48109, Yuehan Lu, Oceanography, University of Michigan, Ann Arbor, MI 48109, and Donna R. Kashian, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48105.

Understanding how Daphnia vary in spatial and temporal sensitivity to contaminants is important in understanding the evolutionary response to contaminants and interpretation of toxicity test.  We evaluated temporal and spatial differences in daphnid mortality to toxaphene, a persistent pesticide commonly found in surface waters.  To examine spatial differences we exposed Daphnia isolated from five lakes to toxaphene exposure and monitored survivorship. To evaluate differences in sensitivity across time we resurrected ancient Daphnia clones from sediment cores by hatching resting eggs from various time periods over 150 years and exposed the hatched Daphnia to toxaphene.  For both spatial and temporal evaluations we exposed a single Daphnia (n=20) to toxaphene concentrations ranging between 900 and 0 µg/l at 100 µg/L increments, and recorded time of death.  There did not appear to be much spatial differences for survivorship among lakes.  Daphnia from four of the five lakes experienced 50% mortality within 48 hours of exposure to 500 µg/L toxaphene, whereas Daphnia from one lake exhibited 50% mortality at 900 µg/L.  We expect Daphnia collected from sediment prior to the manufacturing of toxaphene to be much more sensitive than modern Daphnia. Further experimentation is needed to evaluate the adaptability of Daphnia to contaminants.


Web Page: Daphnia, toxaphene, mortality

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