W8 PM Ecotoxicology of Agrochemicals and Pharmaceuticals
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 337-338

(WAI-1118-091236) Effects of sulfonylurea herbicides on the biomass and production of microbial communities in prairie wetlands.

Waiser, M¹, Donald, D², Glozier, N², Cessna, A³, Holm, J¹, Froese, J², Bailey, J¹, Syrgiannis, J², Mollison, J¹, ¹ National Water Research Institute, Environment Canada, Saskatoon, SK, Canada² Prairie and Northern Region, Environment Canada, Regina and Saskatoon, SK, Canada³ Agriculture and Agri-food Canada, Saskatoon, SK, Canada

ABSTRACT- Five shallow prairie dugouts south of Regina, SK, CAN, were chosen as the study sites for this sulfonylurea herbicide effects experiment. During the last week in May, 2004, 5 enclosures were installed in each dugout (25 enclosures total). On June 8, after a one week acclimation period, enclosures were treated with expected environmental concentrations of herbicides. Of the 5 enclosures installed in each dugout, one was treated with thifensulfuron-methyl, one with metsulfuron-methyl, one with sulfosulfuron-methyl, one with ethametsulfuron-methyl, while the fifth was untreated and served as the control. Bacterial production (³H thymidine uptake), bacterial numbers (counts using epifluorescent microscopy) algal biomass (as Chlorophyll a) algal primary production (using ¹⁴C labelled bicarbonate) and water chemistry parameters (major nutrients and ions, oxygen, temperature, conductivity, pH) as well as herbicide concentrations were measured in each enclosure and in the surrounding dugout water at timed intervals (before and after treatment) over a 30 day period. Results from repeated measures analysis of variance suggest no chronic or acute effect of any of the tested herbicides on any of the microbial variables tested. Examination of trends within each individual enclosure, however, indicated the potential for a negative effect of sulfonylurea herbicides on bacterial numbers and production which may have been missed due to the high variation between replicate treatments.

Key words: sulfonylurea herbicide effects, prairie wetlands, aquatic microbial communities, enclosures