R8 PM Pesticide Mixtures
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in 331-332

(GRU-1117-925040) Response of juvenile rainbow trout to pesticides in urban streams in western Washington.

Curran, Catherine¹, Bogard, Sara¹, Bricker, Jacki¹, Lowery, Erin¹, Menard, Cara¹, Shavey, Christie¹, Grassley, James¹, grue, christian¹, ¹ University of Washington, seattle, WA, USA

ABSTRACT- Recent efforts to document pesticide concentrations within surface waters have generated a significant amount of information. Unfortunately, these reports uniformly suffer from a lack of adequate biological interpretation. Although levels reported are low (most <1.0 ppb), the presence of these chemicals has generated concerns, particularly their potential effects on salmonids. We exposed juvenile (ca. 10 g) rainbow trout (Oncorhynchus mykiss) to a chemical cocktail representative of urban streams in western Washington. Nominal concentrations (ppb active ingredient) of 9 herbicides, 3 insecticides, an insecticide breakdown product, and a fungicide were the maximum reported during peak storm flow events (hereafter 1X). With the exception of the fungicide and the breakdown product, formulated products (single ai) were used and if possible were selected from those available at retail outlets. Two experiments were conducted. In the first, 20 trout were individually exposed to the 1 X cocktail or clean dechlorinated water for 96-h under static conditions at 12 C. In the second, 10 trout were individually exposed to a 1X, 3.3X or 10X cocktail or clean dechlorinated water under the same conditions. Behavior and water quality were assessed at 6, 24, 48, 72 and 96 h. Survivors were euthanized and frozen (-40C) for subsequent brain acetylcholinesterase assays. All fish survived, except for 1 fish exposed to the 10X cocktail. Fish exposed to the chemical cocktails were more lethargic than controls, particularly those exposed to the 10X cocktail. Brain AChE activity was not inhibited in fish exposed to the 1X cocktail in either experiment, but was in the 3.3X (23%) and 10X (84%) cocktails. Concentrations tested are >2 orders of magnitude greater than mean (geometric) concentrations of the pesticides reported during storm events.

Key words: rainbow trout, pesticide mixtures, urban streams, AChE activity