Assessing Septic System Discharge to Lakes 2010 Report

Pharmaceuticals and endocrine active compounds, including estrogenic compounds, were found in water and sediment of 12 Minnesota lakes as part of a recent study by USGS and St. Cloud State University in cooperation with the Minnesota Pollution Control Agency. Lakes with a high density of septic systems had the most frequent detections of these chemicals. Low-levels of estrogenic compounds in lakes have caused the extinction of species of forage fish and are known to cause abnormal sexual development in bass and walleye in Minnesota Rivers. Given these results, there is a need to know how estrogenic and pharmaceutical compounds in Minnesota lakes affect fish populations. To answer this question, the USGS Minnesota Water Science Center, in partnership with St. Cloud State University and the MN Department of Health, will survey 24 additional Minnesota lakes with high densities of septic systems for water and sediment contamination from pharmaceuticals and estrogenic compounds. Each lake in the study will also be assessed for watershed and groundwater hydrology characteristics that may contribute to the observed patterns of water and sediment concentrations of estrogenic and pharmaceutical compounds. A subset of lakes with high contaminant concentrations will be chosen for detailed analysis of exposed fish populations, and native fish populations will be assessed during the spawning season for endocrine disruption and mating success. The project will provide details on what pharmaceutical and estrogenic compounds are present in lakes and whether these compounds affect the native fish populations in these same lakes.