The interactions of a chlorinated hydrocarbon insecticide among the water sediments and biota in an estuarine system.

Water, sediment and biota collected from the San Antonio Bay estuarine system were analyzed for residues of the chlorinated hydrocarbon insecticides dieldrin, DDT, DDD and DDE by electron- capture gas-liquid chromatography. Analyses indicated a relatively low level of contamination, in the parts per billion range, of this area. Of the residues detected, those of DDE were the most common in biological samples. Blue crabs, as a group, had a greater incidence of contamination (dieldrin, 32%; DDTs, 94%) than any of the other organisms sampled. The incidence of insecticide residues in oysters (dieldrin, 25%; DDTs, 60%) and clams (dieldrin, 31%; DDTs 68%) were comparable. Penaeid shrimp showed a lesser incidence of contamination than the other groups (dieldrin, 26%; DDTs, 13%).