PARENT SESSION
6B The use of ecological models and concepts in aquatic higher tier risk assessment
9:00 AM to 7:00 PM, Tuesday, 08 May 2001
Session Chair:

(T/FF230) The effects of metsulfuron methyl and cypermethrin exposure on aquatic ecosystems: Response of the zooplankton community.

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

ABSTRACT- Water bodies in the agricultural landscape regularly receive a mix of pesticides from the surrounding fields. This study aimed at assessing potential combined effects of two frequently used pesticides, the herbicide metsulfuron-methyl and the insecticide cypermethrin, on a zooplankton community. The experiment was performed in enclosures in an artificial freshwater pond with macrophytes. Two insecticide levels (0, 0.05 g/L) were crossed with four herbicide levels (0, 1, 5 and 20 g/L) in a factorial design. The experiment lasted for 14 days (16-30 June 2000) and samples were taken on day 1, prior to the pesticide addition, and after 5, 10 and 14 days. On day 5 the number of copepod nauplii was significantly lower in systems treated with the insecticide. The opposite conditions were found on day 10 and 14. There was no difference in rotifer biomass between the systems during the whole experiment. The Shannon-Weiner diversity index calculated from zooplankton community data was significantly lower in insecticide-exposed systems on day 10 and 14. However, this diversity decrease was caused by the increase in nauplii larvae alone as no change in the rotifer community diversity was observed. This indicates the weakness of using traditional biodiversity metrics as endpoints in ecotoxicity testing. The herbicide did not affect the zooplankton community and no combined effects were observed.

Key words: pesticides , zooplankton, metsulfuron methyl, cypermethrin