Influence of Watershed Scale Atrazine Reduction Practices on Pesticides and Fishes within Channelized Agricultural Headwater Streams

Abstract

Application of pesticides within the watersheds of agricultural streams typically leads to increased instream pesticide concentrations that reduces water quality and threatens aquatic life. Pesticide reduction practices that reduce pesticide application within agricultural watersheds should reduce concentrations of pesticides within agricultural streams. Unfortunately, the 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 atrazine reduction practices on 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 (watershed size – 3.89 km2) that received atrazine reduction practices within 26 to 31% of its watershed during the first two years and then the watershed usage of these practices was reduced to less than 6% in the last four years. We also collected water samples and fishes during the same time from a control stream (watershed size 4.54 km2) that received atrazine reduction practices in 6% or less of its watershed during the study. Only three of 15 pesticide response variables and two of 15 fish community response variables indicated a potential effect of atrazine 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 atrazine reduction practices than the time period without atrazine reduction practices. Mean differences in trophic guild richness and fish species composition similarity between the control and treatment streams occurred between time periods with and without atrazine reduction practices only during the summer. Our results suggest that implementing atrazine reduction practices to reduce atrazine usage within small portions (30% or less) of the watersheds of channelized agricultural headwater streams may not influence pesticides, pesticide mixtures, and fish community structure during the spring and summer.

Conservation implications of fish–habitat relationships in channelized agricultural headwater streams

“…Meador and Frey's (2018) study was a regional one extending from eastern Nebraska to central Ohio, whereas our results and others were conducted in only one or two states. Previous studies within channelized agricultural headwater streams in the CC and UBWC have documented that the concentrations of nutrients and pesticides rarely exceed USEPA benchmarks of acute and chronic toxicity (Sanders, 2012;Smiley & Gillespie, 2010;Smiley, King, & Fausey, 2010;Smiley, King, Gillespie, & Fausey, 2012). Streamside bioassays conducted in conjunction with our fish community assessments found that exposure to water from three CC sites for 21 wk did not negatively influence fathead minnows (Sanders, 2012).…”

A decade of conservation effects assessment research by the USDA Agricultural Research Service: Progress overview and future outlook

“…In turn, the increase in primary producer biomass was followed by an increase in fish biomass for two sport fishes, largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) (Locke et al 2008). In contrast, despite widespread implementation of conservation practices in two Midwestern watersheds, Cedar Creek and Upper Big Walnut Creek, research showed improvements in physical and chemical water quality had only a minimal influence on stream fish communities (Smiley et al 2009(Smiley et al , 2012. Further research by Smiley et al (2011) indicated that along with improved water quality, improvements in physical habitat would be needed to enhance fish biodiversity in agricultural stream ecosystems.…”