Development of Methods to Assess the Impact of Herbicide Use on the Benthos of Littoral Impoundments in Northeast Brazil

• Published in: Journal of aquatic ecosystem stress and recovery Vol. 8; no. 3; p. 67
• Main Authors: de Medeiros, Vania Maria, Watanabe, Takako, Coler, Reginald R, Coler, Robert Anthony
• Format: Journal Article
• Language: English
• Published: 01.01.2001
• ISSN: 1386-1980

Brazil's Northeast Region is characterized by chronic near-drought conditions and almost all water sources are impounded. The reservoirs, which supply water for municipal and agricultural uses and are also used for fishing, are subject to contamination with agrochemicals, particularly paraquat, a herbicide routinely applied to sugarcane fields. To assess potential impacts of paraquat on benthic communities, laboratory tests of acute and chronic toxicity were conducted with invertebrates from a reservoir in a sugarcane-dominated watershed. Two dominant benthic species (the prawn Macrobrachium amazonicum and the snail Pomacea lineata) and the zooplanktonic microcrustacean Daphnia similis were tested. The tests yielded LC sub(50) and EC sub(50) values orders of magnitude lower than literature-reported values from temperate latitudes, indicating an unsuspected sensitivity of the tropical species to paraquat. The effects of this herbicide on aquatic invertebrates may thus not be as benign as generally believed. Local farming practices and limnological conditions may further increase the problem. The findings emphasize the need for toxicity testing programs based on local species and local conditions.