PARENT SESSION
6A Current developments in risk assessment for pesticides
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/FF218) The effects of metsulfuron methyl and cypermethrin exposure on aquatic ecosystems: Response of primary producers.

Wendt-Raush, L.¹, Woin, P.¹, Pirzadeh, P.¹, ¹

ABSTRACT- The combined and separate short term effects of metsulfuron methyl (herbicide) and cypermethrin (insecticide) were investigated in small freshwater enclosures (80 L) in an artificial pond, using a factorial design where two insecticide levels (0, 0.05 g/L) were crossed with four herbicide levels (0, 1, 5 and 20 g/L). Metsulfuron methyl exposure of the aquatic enclosures resulted in a decreased pH and increased conductivity at the lowest concentration tested (1 g/L). The root growth of the macrophyte species Elodea canadensis and Myriophyllum spicatum were drastically decreased following exposure to 1 g metsulfuron methyl/L and higher. The biomass of periphytic algae growing on the leaves of M. spicatum increased in the enclosures exposed to metsulfuron methyl. The species composition of the periphytic algae significantly diverged from the controls in the enclosures exposed to 20 g metsulfuron methyl*l-1. The phytoplankton community in the exposed enclosures remained similar to the controls both regarding biomass and species composition. A laboratory single species assay indicated that the shoot elongation of E. canadensis was decreased at concentrations of 0.1 g metsulfuron methyl/L. No clear combinatory effects of the herbicide and insecticide exposure were observed.

Key words: pesticides, phytoplankton, periphytic algae, macrophytes