Some Ecological Effects of the Use of Paraquat for the Control of Weeds in Small Lakes

Abstract

The use of pesticides in water has always been regarded with suspicion because of the special possibilities of dangers to man, domestic animals, irrigated crops, wildlife and aquatic organisms. In addition to possible direct toxicity, secondary hazards may arise from the disappearance from the aquatic ecosystem of the bulk of the primary producers, together with other effects arising from the decomposition of plant material. With the increasing interest in diquat and paraquat as aquatic herbicides a collaborative experiment was made in which the Monks Wood Experimental Station (Nature Conservancy), Jealotts Hill Research Station (I.C.I. Ltd), the Water Pollution Research Laboratory (Ministry of Technology) and the Botany Department of the University of Nottingham studied the results of applications of paraquat to a series of small lakes. Physico-chemical effects and response of captive fish are reported by Owens and Maris (in preparation), whilst biological effects and paraquat residue determinations are described here.