Pesticide contamination and aquatic macroinvertebrates in rural basins (Buenos Aires, Argentina).

JERGENTZ, S.; MUGNI, H.; SCHULZ, R.; BONETTO, C.

Buenos Aires.22-25 Octubre 2001.

Congreso; 4ta Reunión Anual SETAC Latinoamericana.; 2001

The objective of the present work was to study the eventual toxicity of pesticides in streams of basins which undergone intense agriculture activity, mainly related with the soy bean culture. Four streams close to Arrecifes city were chosen (Maguire, Helves, Luna and Horqueta), and studied during the period of maximum application: Feb-Apr. 2001. Acute toxicity tests with Daphnia magna were carried out weekly in water samples from each stream. Water chemistry and the macroinvertebrate composition were determined in four occasions. Sampling devices were installed to trap the drifted organisms, stream suspended matter, runoff and flood water plus sediment. Pesticides (endosulfan, chlorpyrifos and cypermethrin) in the sediment samples trapped in the above mentioned devices were determined. No acute toxicity was detected in the water throughout the studied period. However, the fact that e.g. Smicridae (Trichoptera) were absent from the stream community but captured in comparatively high numbers on the drift samplers of Feb. 20-28, suggest the occurrence of upstream toxicity episodes. Analytical determinations of insecticides in sediments and the dynamic of the macroinvertebrate fauna are discussed in relation to each other.