Rock Creek

Objectives

1. To determine the presence and levels of contaminants found in Rock Creek in bed sediment and in fish tissues.

2. To assess the effects of these urban contaminants on fish health.

3. To examine the trophic interactions between invertebrate and fish communities. This will provide Rock Creek park managers an understanding of the community structure and biological health within Rock Creek, as well as the pathways for bioaccumulation of chemical contaminants.

Statement of Problem

Urban development has had a dramatic effect on many of the parks and natural areas within the National Capital Region and across the United States. Numerous chemical contaminants are delivered to the park areas in streams and by atmospheric deposition. In Rock Creek, Washington D.C., and particularly in the sediments in the streambed, there is a complex mixture of chemical contaminants, many at concentrations above known criteria for the protection of aquatic life. These compounds include polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalates, metals, and organochlorine pesticides. To assess the degree to which aquatic organisms have been affected by chemical contaminants found within Rock Creek, we propose to examine whole tissue (filet) and gut samples from white suckers (Catostomus commersoni), to conduct histopathological analysis of white sucker tissue samples for the presence of disease, and to assess the trophic structure of the fish and invertebrate communities by analyzing fish stomachs for diet.

Strategy and Approach

Sampling for white suckers will occur 3 times per year (late spring, summer and late fall). Three stream reaches will be selected and will be coordinated with sampling efforts from the Washington D.C. Department of Health, the Montgomery County Department of Environmental Policy and Compliance, and USGS-BRD Leetown Science Center. Contact has already been made with these agencies and they have expressed interest in USGS collaboration. Fifteen fish per reach per season will be collected using backpack electrofishers (total of 45 fish per season and 135 fish for the year). Organ, blood, and skin samples will be removed from each fish and sent to Leetown Science Center for the analysis of histopathology by Dr. Vicki Blazer (USGS-BRD). To assess the trophic structure of the fish and invertebrate communities, fish stomachs will be removed from each fish and analyzed for diet by Dr. Mary Freeman (USGS-BRD Patuxent field station, University of Georgia). Filets will be removed, composited by reach (for a total of 1 sample per reach, 3 samples per season, and 9 samples per year) and sent to the Severn Trent Laboratory in Denver, Colorado, for analysis of selected metals, PAHs, PCBs, and organochlorine pesticides. In addition, a replicate filet sample (15 additional fish) will be collected from one selected reach during the summer season and analyzed for a total of 10 samples analyzed by the Severn Trent Laboratory.

Fish and chemical data will analyzed within the context of other studies being conducted within Rock Creek by federal, state, and local agencies. These will include macroinvertebrate species richness and community structure by the Montgomery County Department of Environmental Policy and Compliance, fish surveys by the Washington D.C. Department of Health, and mercury sampling by the USGS NAWQA program.