Studies on the distribution and flux of pesticides in waterways associated with a ricefield - marshland ecosystem.

On coastal prairie and marshland in Chambers County, Texas (USA), the distribution and flux of chlorinated hydrocarbon pesticides in waterways associate with a ricefield - marsh land ecosystem were studied. Aldrin applied with seed rice entered the aquatic ecosystem through drainage of flooded ricefields. Chemical alteration of the pesticide was observed; dieldrin was the primary breakdown product. All insecticides were distributed unevenly, exhibiting a predilection for biotic components of the ecosystem. Residue analyses of representative species of the aquatic biota indicated significant biological accumulation and passage of these refractory compounds along the food chain. Rapid localization and concentration of pesticides in living organisms was observed. Reproductive tissues exhibited a marked affinity for the pesticides. Decline of assimilated residues in both biotic and abiotic components appeared to follow a 1st-order reaction curve. Contamination of the aquatic environment with toxaphene during the study period resulted in a massive kill of aquatic organisms. Neither long-term effects nor significant biological magnification of toxaphene was observed. Other chlorinated hydrocarbon pesticides of unknown origin were detected, including DDE, DDD and DDT.