We include this paper (from 2005) in our collection of Crucial papers because it now assumes great importance in view of the findings of the group led by Prof Andres Carrasco in Argentina. It is also significant in that it attracted a vigorous response from the Monsanto hired guns, who were intent, as ever, in demonstrating that a highly toxic chemical is not really toxic at all to non-target organisms. That of course is biological nonsense, and Prof Relyea gave these people pretty short shrift in his response posted under our "Further Reading" heading.
Ecological Applications, 15(2), 2005, pp. 618–627 q 2005 by the Ecological Society of America
by RICK A. RELYEA
Department of Biological Sciences, 101 Clapp Hall, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA
Pesticides constitute a major anthropogenic addition to natural communities. In aquatic communities, a great majority of pesticide impacts are determined from singlespecies experiments conducted under laboratory conditions. Although this is an essential protocol to rapidly identify the direct impacts of pesticides on organisms, it prevents an assessment of direct and indirect pesticide effects on organisms embedded in their natural ecological contexts. In this study, I examined the impact of four globally common pesticides (two insecticides, carbaryl [Sevin] and malathion; two herbicides, glyphosate [Roundup] and 2,4-D) on the biodiversity of aquatic communities containing algae and 25 species of animals. Species richness was reduced by 15% with Sevin, 30% with malathion, and 22% with Roundup, whereas 2,4-D had no effect. Both insecticides reduced zooplankton diversity by eliminating cladocerans but not copepods (the latter increased in abundance). The insecticides also reduced the diversity and biomass of predatory insects and had an apparent indirect positive effect on several species of tadpoles, but had no effect on snails. The two herbicides had no effects on zooplankton, insect predators, or snails. Moreover, the herbicide 2,4-D had no effect on tadpoles. However, Roundup completely eliminated two species of tadpoles and nearly exterminated a third species, resulting in a 70% decline in the species richness of tadpoles. This study represents one of the most extensive experimental investigations of pesticide effects on aquatic communities and offers a comprehensive perspective on the impacts of pesticides when nontarget organisms are examined under ecologically relevant conditions.