R. Lajmanovich, E. Lorenzatti, P. de la Sierra, F. Marino & P. Peltzer
The impact of pesticides on amphibians has been clearly and effectively described in several regions of the world. However, in Latin America there is scarce information on the presence of residual insecticides in frogs and toads. Because of their long environmental persistence, continued toxicity and the potential for long distance atmospheric transport, the effects of organochlorine contaminants can be remote in both space and time. Our research determines concentrations of the principal organochlorine insecticides in amphibian species of the Mesopotamic region of Argentina. In addition, the biomagnification factors (BMF) in amphibian predators were calculated.
The specimens were collected from intensely agricultural regions of the Entre Ríos and Santa Fe provinces (Argentina) in 2002. We examined the fat and viscera of amphibian species (Leptodactylus ocellatus, L. chaquensis, Hyla pulchella, and Bufo paracnemis) found there. Moreover, fat and viscera of potential amphibian predators, snakes (Clelia rustica) and raptors (Parabuteo unicinctus,) were considered. Samples were later transferred to a commercial freezer and stored frozen until chemical analysis. Fat and viscera samples were analyzed for organochlorine compounds in the Institute of Technological Development for the Chemical Industry (INTEC). Samples were analyzed for a & d HCH, aldrin, p´p´DDT, p´p´DDE, p´p´DDD, heptachlor, heptachlor epoxide, a & d chlordane, a & b endosulfan, dieldrin, and endrin. The commercial standard was provided by Chemicals Service, USA (99% purity). For details of the methodology, please contact the authors.
The mean chlordane concentration in frog and toad tissue was 18.5 ng/g (minimum 13, maximum 24). The tissue residue concentrations were highest in snakes with a BMF of 166. In amphibian tissue, the mean endosulfan was 12.5 ng/g (minimum 6, maximum 19) and the BMF in raptors was 288. The other organochlorine residues were lower than the detection limits. Organochlorine levels reported in this study are generally low and suggest that wild fauna resident in the Mesopotamic regions are probably not affected by local organochlorine contamination. However studies on the biomagnification values should be continued. The evaluation of affected wild populations to minimize adverse impacts to wildlife resources should be considered.
Contact: Rafael Lajmanovich, National Institute of Limnology (INALI-CONICET), José Macias 1933 (3016), Santo Tomé (Santa Fe) Argentina. inali@ceride.gov.ar
Eduardo Lorenzatti, Institute of Technological Development for the Chemical Industry (INTEC-UNL-CONICET), Güemes 3450, (3000) Santa Fe, Argentina.