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

(19-17) Does the use of sulfunylureas endanger the aquatic flora?

Cedergreen, Nina^*,1, Streibig, Jens¹, ¹ The Royal Veterinary and Agricultural University, Institute of Agricultural Sciences, Taastrup, Denmark, Denmark

ABSTRACT- The agricultural use of sulfunylureas is known to affect growth, morphology and reproduction of non-target terrestrial plants. Considering the high water solubility and low binding to soil of these herbicides they could also be expected to affect the aquatic vegetation of ponds and streams situated in proximity to cultivated land. Therefore in this study we investigated the sensitivity of 12 common Danish aquatic plants towards the sulfunylurea metsulfuron methyl. The plants were tested in a flow-through system at 7 herbicide concentrations ranging from 0.00 to 1000 g l^-1, and two light conditions: 180 and 300 mol m^-2 s^-1. After a two-week growth period, relative growth rates, specific leaf area (SLA) and morphological parameters as root, shoot and leaf growth were measured. For 9 out of the 12 species, the herbicide did not affect growth rates even at the highest concentrations whereas the morphological parameters were more sensitive. Thus for SLA seven species exhibited significant dose-response with estimated EC₅₀ values ranging from 0.14 to 1.5 g l^-1. The different light growth conditions did not affect the toxicity of the herbicide. A spray drift event with 1 to 10 % field dose of metsulfuron methyl on a 30 cm deep pond will give a water concentration of 0.01 to 0.13 g l^-1. A concentration range which could have an effect on the aquatic plants, but which we do not believe will cause major changes at the population level.

Key words: Aquatic plants, Ecotoxicology, Sulfunylurea, Metsulfuron methyl