HR: 08:30h
AN: B51D-03    [Abstracts]
TI: Biogeochemical snapshot of an urban water system: The Anacostia River, Washington DC
AU: * MacAvoy, S
EM: macavoy@american.edu
AF: American University, 101 Hurst Hall Biology Department 4400 Mass. Ave. NW, Washington, DC 20016,
AU: Ewers, E
EM: ee0464a@american.edu
AF: American University, 101 Hurst Hall Biology Department 4400 Mass. Ave. NW, Washington, DC 20016,
AU: Bushaw-Newton, K
EM: bushaw@american.edu
AF: American University, 101 Hurst Hall Biology Department 4400 Mass. Ave. NW, Washington, DC 20016,
AB: Highly urbanized and contaminated with PAHs, heavy metals, and sewage, the Anacostia River flows through Maryland and Washington, DC into the tidal Potomac River. Efforts have been underway to assess the river's ecological integrity and to determine the extent of anthropogenic influences. This study examines the nutrients, bacterial biomarkers, organic material, and carbon, nitrogen and sulfur sources in the Anacostia. High biological oxygen demand and low nitrogen (0.33-0.56 mg /L)/phosphorus (0.014 - 0.021 mg/L) concentrations were observed in three areas of the river. Bacterial activity based on carbon source utilization was higher in sediment samples than in water column samples. While bacterial abundances were decreased in downstream areas of sediment; abundances increased in downstream areas in the water column. Downstream sites had higher nutrient concentrations and dissolved organic carbon (up to 13.7 mg/L). Odd-chain length and branched fatty acids (FAs) in the sediments indicated bacterial sources, but long chain FAs indicative of terrestrial primary production were also abundant in some sediments. Also dominant among methyl esters and ketones in some sediment and water column samples was methyl isobutyl ketone, a common industrial solvent and combustion by-product. Sediment carbon stable isotope analyses show a mix of autochthonous and allochthonous derived materials, but most carbon was derived from terrestrial sources (-23.3 to -31.7‰). Sediment nitrogen stable isotopes ranged from -5.4 to. 5.6, showing nitrate uptake by plants and also recycling of nitrogen within the river. Sulfur sources were generally between 3 and -5, reflecting local sulfate sources and anaerobic sulfate reduction.
DE: 0408 Benthic processes (4804)
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0493 Urban systems
DE: 0496 Water quality
SC: Biogeosciences [B]
MN: 2007 Fall Meeting