Seventy-seven composite samples composed of largemouth bass (Micropterus salmoides), channel catfish (Ictaluras punctatus), threadfin shad (Dorosoma petenense), Asiatic clam (Corbicula fluminea), burrowing mayfly (Hexagenia sp.), water snake (Natrix spp.), and little green heron (Butorides virescens) were collected from upper and lower reaches of the Apalachicola River, Florida, in 1978 for residue analysis of organochlorine insecticides, PCBs (polychlorinated biphenyls), and metals. Compared with data from the National Pesticide Monitoring Program and criteria recommended for the protection of aquatic life, residue concentrations were moderately high in the Apalachicola River. Biota from the upper river generally had higher organic and lower metal residues than those from the lower river. Highest residues in the biota were total DDT, total PCBs, and toxaphene. Although individual mean concentrations were below 2 μg/g and total organic contaminant residues never exceeded 5 μg/g, residue concentrations of DDT, PCBs, and toxaphene (particularly from the upper river) exceeded recommended permissible levels for the protection of aquatic life. Metal residues were generally below 1 μg/g. Exceptions were arsenic residues in threadfin shad (1.07 μg/g) and Asiatic clams (1.75 μg/g), and selenium in eggs of channel catfish (1.39 μg/g). The residues observed in the biota, particularly from the upper station, indicated moderate contamination of the Apalachicola River system at the time samples were collected.
