Toxicity Associated with Urban and Agricultural Land Use in Southeast Wisconsin Streams

Abstract

Urban and agricultural land uses negatively influence fish and invertebrate community health and water quality in Wisconsin's streams. Urban and agricultural development within a watershed affects streams by decreasing riparian vegetation which increases surface runoff in the form of high flow events, that changes channel morphology and increases the loading of toxins and nutrients, and ultimately lowers water quality altering biotic communities. The objective of this research was use a modified in situ testing system to determine the toxicological responses including mortality, biomass, and reproduction of the fathead minnow (Pimephales promelas) and Daphnia magna to a gradient of urban and agricultural land uses found at five streams in the greater Milwaukee metropolitan area, southeast Wisconsin. Stream-exposed P. promelas 14-day mortality and 14-day biomass and D. magna 14-day and 48-hr mortality were adversely affected compared to the experimental control at all streams. Stream-exposed D. magna 14-day reproduction was significantly elevated above the control at three of five streams suggesting stimulatory effects possibly related to nutrient enrichment and increased food resources provided by stream water. There were no significant correlations between the gradients of urbanization and of agricultural land uses to toxic responses, which may be the result of a limited sample size and the inherent variability of biological responses to toxic events. The modified in situ method was shown to be viable for testing responses of stream biota to land use. Future studies should include sampling high flow events, concurrent testing with other bioassessment methods, and the inclusion of additional study sites.