Uptake and accumulation of an organochlorine insecticide (dieldrin) by an estuarine mollusc, Rangia cuneata
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Clams (Rangia cuneata) were collected from Trinity Bay in Texas to study uptake and accumulation of dieldrin from dilute solution. The clams were acclimated for 1 to 2 weeks in holding tanks at 25 C, 8.2 pH, and 15.6% salinity. They were then transferred to experiment tanks with water having like properties and a dieldrin concentration maintained at about 0.55 microgram/liter. Samples of clams and water were removed after 12, 24, 36, 48, 60, and 72 hours and after freezing and cleanup of the meat samples were analyzed for pesticide residue by gas-liquid chromatography. The result indicated that Rangia is capable of absorbing and concentrating dieldrin in its tissue to levels far above ambient. The smallest dieldrin residue in experimental clams was 38.2 micrograms/liter after 12 hours exposure and the largest 1226 micrograms/liter after 60 hours. Apparently the dieldrin is not noxious enough in the concentration used to affect siphoning and thus it is accumulated in quantities that may become a threat to the estuarine food web.