PARENT SESSION

1H a/b/c - Pesticides, pharmaceuticals, perfluoroalkylated substances, antibiotics
Poster Hall
8:30 AM - Wednesday, 30 April 2003
Chair: de Voogt, P.¹, ¹
Co-chair: Purdy, R.², Pluecken, U.³, Koerdel, W.⁴, Tolls, J.⁵, Kümmerer, K.⁶, ^{2 3 4 5 6}

(WEP/24) The effect of photosynthetic inhibitors on aquatic plants.

Cedergreen, Nina¹, Streibig, Jens Carl¹, ¹ The Royal Veterinary and Agricultural University, Frederiksberg, Copenhagen, Denmark

ABSTRACT- The effect of photosynthetic inhibitors on aquatic plants. Cedergreen N. and Streibig J.C., The Royal Veterinary and Agricultural University, Copenhagen, Denmark. Terbuthylazine and bentazon are herbicides found in high concentrations in Danish surface waters with reported values of up to 4 g terbuthylazine l^-1 and 8 g bentazon l^-1. Both herbicides block the electron transport of the PS II system, and thus they could be potential harmful to the aquatic flora. In the present study we investigated the sensitivity of the aquatic plant species: Lemna minor, L. trisulca, Spirodela polyrrhiza, Callitriche platycarpa, Myriophyllum spicatum, Elodea canadensis, Potamogeton crispus, Ceratophyllum submerseum, C. demersum and Sparganium erectum to terbuthylazine and bentazon. Two independent experiments were performed in flow-through microcosms at a day/night water temperature of 18 C°/15 C° and a photoperiod of 16 hours with either 207±50 mol m^-2 s^-1 (PAR) or 544±75 mol m^-2 s^-1 (PAR). Terbuthylazine was tested at seven concentrations ranging from 8 to 1500 g l^-1 and bentazone was tested at 500 and 1000 g l^-1, with the concentrations based upon standard OECD Lemna-test. After a two-week growth period plants were harvested and relative growth rates measured. For terbuthylazine, all species except Sparganium showed a significant dose-response relationship with EC50-values ranging from 48±28 to 698±246 g l^-1. For bentazon growth was not affected in any of the species at 500 g l^-1, whereas at 1000 g l^-1 a growth decrease of approximately 40% was observed for Lemna trisulca. Thus, despite the same mode of action, the two herbicides affect the aquatic plants differently, probably due to differences in the physiochemical properties of the two herbicides. Common for both herbicides, however, is that growth is not significantly affected at environmentally relevant concentrations.

Key words: Macrophytes, Ecotoxicology, Herbicides, Growth