STAR Grant R833418: Transport/Fate/Ecological Effects of Steroids from Poultry Litter & Evaluations of Existing/Novel Management Strategies 2007 - 2010
This study seeks to determine the abundance and fate of steroids associated with poultry litter and their impacts on ecological systems, and to evaluate current management practices in this context.
Proposed research address all three areas of interest presented in this EPA STAR RFP: fate of poultry litter-associated hormones, impacts of exposure on ecological systems, and evaluation of various management strategies. Given that fecal sex steroids persist at high concentrations in poultry litter, we hypothesize that runoff from fields treated with litter will exert a direct steroidal effect on aquatic organisms within receiving waters. Previous studies at our laboratory have demonstrated that: (1) fecal steroids in poultry litter reach receiving waters via rain-induced runoff; (2) this runoff is sufficiently estrogenic to feminize male fish; and (3) differences in agricultural management strategies can affect steroid concentrations in runoff and receiving waters. Proposed research will address remaining questions concerning environmental persistence and bioactivity of steroids upon reaching surface waters and further investigate affects of agronomic practices on mitigating resultant environmental steroid loads.
Objectives will be accomplished in laboratory, controlled research field, and in situ watershed investigations. Multiple litter sources (broilers, laying hens, etc) will be screened for steroidal constituents to determine inherent variability. Steroids in aqueous litter mixtures (lab-generated and field-collected) will be monitored over time to determine degradation rates and pathways. Particular attention will be given to ratios of free vs. conjugated steroidal constituents. Fish will be exposed to aqueous litter mixtures in laboratory assays to determine the affects of steroid degradation on bioactivity. Influences of agricultural management practices on steroid transport to surface waters (via rain-induced runoff and/or groundwater migration) will be investigated using adjacent 33 acre research fields cropped variously under existing no-till practices of direct surface litter application, or by a novel sub-surface litter application technique. Finally, Maryland Biological Stream Survey protocols will be applied to agriculturally impaired watersheds to assess possible community and population level disturbances resulting from fecal steroid exposure.
Laboratory assays will clarify exposure criteria required to induce previously observed steroid effects. Controlled field runoff studies will determine the abundance, chemical nature, and environmental fate of litter-associated steroids transported under various cropping strategies. Biological stream sampling (MBSS) will assess links between environmental degradation and regional agricultural practices. Proposed project elements, coupled with previous research, should provide regulators with sufficient information to assess the actual risks that poultry litter-associated steroids pose to aquatic ecosystems and thus improve environmental protection. The Delmarva Peninsula is the most densely concentrated poultry producing area in the U.S. generating over generating over 600 million birds and 730,000 metric tons of litter annually. Since the primary disposal method is land application, this represents an enormous source of nutrients and other contaminants, including steroids, to aquatic systems. If subsurface application of poultry litter proves effective at reducing contaminant runoff and becomes widely used as a management option in the region, it could dramatically reduce the impact of poultry litter-associated contaminants, including fecal steroids and nutrients, on the Chesapeake Bay watershed.
Susan Laessig at email@example.com