Watershed scale influence of pesticide reduction practices on pesticides and fishes within channelized agricultural headwater streams

Authors: Smiley, Peter - Rocky; King, Kevin; GILLESPIE, ROBERT - Indiana University-Purdue University; Fausey, Norman

Submitted to: Journal of Sustainable Watershed Science & Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/29/2012
Publication Date: 5/12/2012
Citation: Smiley, P.C., King, K.W., Gillespie, R.B., Fausey, N.R. 2012. Watershed scale influence of pesticide reduction practices on pesticides and fishes within channelized agricultural headwater streams. Journal of Sustainable Watershed Science & Management. 1:61-75.

Interpretive Summary: Watershed management and conservation practices that lead to the reduction of pesticide usage within agricultural watersheds have the potential to reduce pesticide concentrations and assist with protecting aquatic life within agricultural streams. Unfortunately, the watershed scale impacts of practices that lead to the reduction of pesticide usage have not been quantified. Understanding the effects of reducing pesticide usage at the watershed scale will assist with developing watershed management guidelines for headwater streams within the Midwestern United States. Watershed management practices intended to reduce atrazine usage did not influence atrazine concentrations, pesticide mixtures, or fish communities within channelized agricultural headwater streams during the spring and summer. The results suggest that implementation of watershed management practices on 30% or less of the watershed area of channelized agricultural headwater streams may not influence the amount of pesticides or fishes in these small streams. This information can be used by state, federal, and private agencies responsible for managing agricultural watersheds and restoring streams.

Technical Abstract: Implementation of pesticide reduction practices to reduce pesticide usage within agricultural watersheds has the potential to reduce pesticide concentrations within agricultural streams. The watershed scale influence of pesticide reduction practices on pesticides and the biota within agricultural headwater streams has not been empirically evaluated. We evaluated the watershed scale influence of pesticide reduction practices for reducing atrazine usage on the pesticides, pesticide mixtures, and fish communities within channelized agricultural headwater streams in central Ohio.Water samples for pesticide measurements and fishes were collected in the spring and summer from a treatment stream that received pesticide reduction practices during the first two years and then did not in the last four years. We also sampled a control stream that did not receive pesticide reduction practices. Only three of 15 pesticide response variables and three of 15 fish community response variables differed between time periods with and without pesticide reduction practices. Mean differences in atrazine desethyl concentration, atrazine desethyl percent occurrence, and the number of pesticides between the control and treatment streams were greater during the time period with pesticide reduction practices than the time period without pesticide reduction practices. Mean differences in fish species richness, trophic guild richness, and species composition similarity between the control and treatment streams only occurred in the summer. Our results suggest that implementing pesticide reduction practices to reduce atrazine usage within small portions of the watersheds of channelized agricultural headwater streams may not influence pesticides, pesticide mixtures, and fish community structure during the spring and summer.