Pesticide Influence on the Desmid Flora of a Reservoir in an Agricultural Region at Campo Verde, Mato Grosso, Brazil

Abstract

The objective of the research was to investigate the influence of pesticides on the desmid flora. Five series of samples were taken between July 5, 2005, and April 6, 2006, for analysis of pesticide content and algal community structure in the Sao Lourenco River springs on the Pirassununga Ranch, Campo Verde, Mato Grosso. The greatest amounts of pesticides were detected in July, when the abundance of algae was also greatest. Positive correlations were determined between the concentrations of endosulfan ( r = 0.94; p = 0.051), cyhalothrin ( r = 0.96; p = 0.037) and endrin ( r = 0.96; p = 0.037) and the biomass of desmids. Insecticides, such as endosulfan, inhibit the activity of ATPase, contributing considerably to the mortality of the biota, since ATP is of fundamental importance in the energy metabolism of all organisms. This suggests that the pesticides promote algal growth both by removing the small herbivores that feed on the algae and increasing the release of inorganic nutrients from decomposing animals in the water. Algae were least abundance in January, possibly due to the presence of the herbicide atrazine ( r = -0.63; p > 0.05).