Assessing the Effects of Endocrine Disrupters (EDCs) from a St. Paul Sewage Treatment Plant on Sperm Viability and Testicular Development in Fish: Adding a New Dimension to an Existing Project Peter W. Sorensen, Ph.D., Heiko L. Schoenfuss, Ph.D., Ira R. Adelman, Ph.D., Department of Fisheries, Wildlife & Conservation Biology, College of Natural Resources; Deborah L. Swackhamer, Ph.D., Division of Environmental and Occupational Health, School of Public Health, University of Minnesota Research Introduction: The objective of this study is to determine whether fish exposed to compounds found in the effluent of the St. Paul (Minnesota) Sewage Treatment Plant (STP) experience sex reversal and suffer from reduced sperm viability as a result of exposure to endocrine disrupting compounds (EDCs). This study was part of a larger effort to identify the effects of endocrine disrupters on the reproductive health of fish populations. EDCs are man-made or naturally occurring compounds that are found in the environment and disrupt hormonal pathways causing harm to the exposed organisms or their offspring. Previous studies in the United Kingdom have demonstrated that STP effluent is resulting in feminized male fish with abnormal reproductive organs. One defining characteristic of male fish exposed to STP effluent in the UK, as well as wild carp and walleye captured below the St. Paul STP (our study site), is that they contain high concentrations of vitellogenin (VTG: female egg-yolk protein) in their blood. However, no study has examined whether there might be a correlation between endocrine disruption, as indicated by the presence of VTG in male fish caught in STP, and adverse effects on the fertility of these fish. Our study seeks to examine this by examining the effects of exposing male goldfish to STP effluent under laboratory conditions. We have been assessing fertility by examining milt (sperm and seminal fluids) volume and sperm motility (a function of swimming speed). Sperm motility is an especially important parameter to examine in fish for most are external fertilizers. Goldfish were utilized for this study as they have been studied extensively and constitute the best understood endocrine vertebrate model. An apparatus for goldfish exposure to EDCs and sewage effluent was built and a protocol for assessing sperm quality was established. Three experiments were completed and are described below. Experiment I: This experiment was designed to determine whether exposure to EDCs has adverse effects on milt quantity and sperm motility. Fish were exposed for eight weeks to estradiol or estrone, two known EDCs at relevant concentrations. Fish exposed to 50ng/L estradiol were found to have a milt volume decrease by 76% while total motile sperm count decreased by 84%. 100ng/L estradiol caused milt volume decrease by 90% and total motile sperm decrease by 95%. Fifty ng/L estrone exposure resulted in a complete loss of milt after eight weeks. Experiment II and III: These experiments were designed to determine whether exposure to STP effluent results in decreased milt volume and sperm motility. Male goldfish were exposed under laboratory conditions for ten weeks to a well water control, 25μl/l ethanol carrier control, 50ng/l estradiol, or effluent collected daily from the St. Paul STP. Besides small adjustments of the experimental design, only the time of the year in which effluent was collected varied between the two experiments. Winter effluent (“winter