Mohr S, Feibicke M, Berghahn R, Schmiediche R, Schmidt R
Metazachlor, Herbicide, mesocosm, Ponds, Streams, plankton community, 15 m3, Germany
Metazachlor is a frequently used herbicide with concentrations in surface waters up to 100 mg L 1. A long-term mesocosm study was performedin order to investigate effects on stream and pond communities also regarding recovery. Single metazachlor doses of 5, 20, 80, 200, and500 mg L 1 were given and the aquatic communities monitored for 140 days. In this paper, special attention is paid to the plankton response andthe results of the entire study are summarised. Metazachlor strongly affected the stream and pond mesocosm communities at concentrationshigher than 5 mg L 1. Direct negative effects were most prominent for chlorophytes whereas diatoms and cryptophytes seemed insensitive.The effects on zooplankton were caused by changes in habitat structure due to the strong decline of macrophytes. The slow degradation of metazachlorcombined with the absence of recovery in both chlorophytes and macrophytes is likely to cause long-lasting effects on aquaticecosystems.