PARENT SESSION
19 - Pesticide Ecotoxicology
8:00 AM to 6:30 PM, Monday, 13 May 2002
Exhibition Area

(19-29) The effects of the herbicide metsulfuron methyl on the ecology of macrophyte-dominated experimental ecosystems.

Wendt-Rasch, Lina^*,1, Gustafsson, Kerstin², Woin, Per¹, Pirzadeh, Pardis¹, ¹ Dept. of Ecology/ecotoxicology, Lund University, Lund, Sweden² Dept. of Systems ecology, Stockholm University, Stockholm, Sweden

ABSTRACT- The effects of metsulfuron methyl, a sulfonylurea herbicide, were studied in macrophyte dominated indoor microcosms (approx. 1000 L) over a 2-month period. Four microcosms served as controls, four microcosms received a repeated (two applications) low dose of the herbicide (0.5 g/L) and the remaining four received one high dose (5 g/l). The high dose herbicide regime aimed to simulate a contamination due to an accidental spill while the low dose aimed to simulate contamination due to normal use of the herbicide. The growth of the Elodea canadensis decreased in the exposed microcosms both observed in a bioassay and as total biomass of macrophytes on the bottom sediments at the end of the experiment. The amount of periphytic algae on the leaves of E. canadensis increased in the microcosms exposed to metsulfuron methyl. In addition, the species composition of the algae changed as a result of the herbicide exposure. The proportion of water surface that were covered with filamentous algae increased from 0.05±01% in the controls to 10±5% in the high exposure. The effects of the herbicide on the macrophytes and algae were significant both in the high and in the low dose treatments and thus effects may occur at concentrations, which may occur in waterbodies adjacent to agricultural land.

Key words: herbicide, ecotoxicity, aquatic community, sulfonyl urea