Biological Consequences of Urban Stormwater Runoff on Reproduction and Survival of Aquatic Organisms

ü Best Management Practices storm water ponds (BMPs) are ways of controlling and filtering storm water and storm sewer effluent. Urbanized areas are increasingly turning to the use of these BMPs as a means to mitigate the affect of storm water runoff on aquatic environments. However, the effectiveness of BMPs is not well understood and there have been few studies that look at the biological efficacy of these filtration systems. This study looked at the effectiveness of three BMPs in the cities of St. Paul and Minneapolis, MN. The BMPs being studied used iron filings blended with sand as a filtration substrate. Water was collected at winter snow melt, spring rain event, and summer rain event. Collected water was used to expose Daphnia magna and Pimephales promelas. D. magna exposure endpoints were survival and reproduction. Daphnia were exposed for 16-day periods to establish adult survival and neonate production. P. promelas exposure endpoints were larval c-start performance, growth, and feeding assays. Larval P. promelas were exposed to stormwater for 21-days before assessing their endpoints. Water chemistry indicates that there is an improvement in water quality from the Inflow to Outflow in each BMP. However, there were few significant differences in larval minnow or Daphnia performance results between the Inflow and Outflow of the BMPs for all three storm water sampling events. The only area that showed marked improvement was larval performance over time, with minnows exposed to water collected later in the year performing better on predator escape assays than minnows exposed to winter snow melt. The design of the BMP filtration system may need to be improved or more filtration may be needed to achieve improvements in biological outcomes