The Accumulation of 36 Cl Ring-Labeled DDT in a Freshwater Marsh

Abstract

An enclosed 4-acre marsh at the southwestern edge of Lake Erie was treated by helicopter with 3.9 millicuries of chlorine-36 ring-labeled DDT at a rate of 0.2 lb technical DDT per acre. Radiolabeled DDT residues were traced until 15 months after the application. Whole body residues were of major concern, although tissues were assayed from vertebrates too large to assay entire. DDT residues were detected in sago pondweed (Potamogeton pectinatus), duckweed (Lemna minor), bladderwort (Utricularia vulgaris), crayfish (Orconectes immunis), tadpoles (Rana pipiens), and carp (Cyprinus carpio) when first assayed 4 hours after the application. The alga Cladophora averaged 96 ppm DDT, or 3,125 times the environmental level, 3 days after the application. A northern water snake (Natrix sipedon) accumulated 36 ppm 13 months after the application. The maximum level in carp was 19 ppm in the soft palate, also after 13 months. Plants and most invertebrates accumulated their highest residues during the first week; vertebrates required longer periods. Algae, the pondweeds (Potamogeton spp.), duckweed, crayfish, and small carp should make good indicator species of environmental DDT residues. This study was initiated to increase our knowledge of natural DDT accumulation in wetland organisms. Serious doubts have been raised when the results of laboratory toxicity studies are projected to the field (Stickel et al. 1965). Although a single large insecticide dose is often administered to an organism in the laboratory, small frequent doses are ingested in the field through the food web. Since the amount of an ingested toxicant that is assimilated by an organism varies with the rate and form of intake, long-term toxicity studies must be conducted under near environmen1 Financed by U. S. Atomic Energy Commission Grant AT (11-1)-1358 and the Winous Point Research Committee in cooperation with the North American Wildlife Foundation and the Ohio Cooperative Wildlife Research Unit. 2 Present address: 3500 Lattimore Road, Port Clinton, Ohio. tal conditions to obtain accurate information. Such studies cannot be soundly designed until more is known about natural insecticide accumulation in food-chain organisms. The main concern of the project was with food-chain aspects of DDT accumulation. The total quantity of DDT was usually determined irrespective of its actual location within or on individual species. However, organs and tissues from vertebrates were also analyzed at intervals to supplement the whole body assay data or to obtain information on animals too large to assay whole. No attempt was made to determine the effect of the DDT on animal populations. Our current use of persistent chemicals to control nuisance and vector insects poses a threat to this country's wetland environments that cannot be fully assessed with our existing knowledge of wetland-insectiThis content downloaded from 157.55.39.92 on Wed, 22 Jun 2016 06:56:54 UTC All use subject to http://about.jstor.org/terms ACCUMULATION OF DDT IN A FRESHWATER MARSH Meeks 377 cide dynamics. As many as 2.5 million acres are treated annually for mosquito control at an average rate of 1 lb of chemical per acre (Hall 1962). Some wetlands are sprayed a dozen or more times a year (Springer 1956). These same lands maintain diverse endemic wildlife populations, exceeding all other land types in wildlife productivity (DeVos and Mosby 1963:87). I thank Dr. Tony J. Peterle, John M. Anderson, Charles W. Kellenbarger, Robert Orr, and David Guest for special services they freely offered. Achem Corporation, Ambler, Pennsylvania, supplied the granular applicator, and the Minerals and Chemicals Corporation of America, Menlo Park, New Jersey, furnished the granules.