Water Resources Research Act Program

Details for Project ID 2016DC176B

Influence of consistently high levels of ammonium on food web dynamics in the Anacostia River

Institute: District of Columbia
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $10,000 Total Non-Federal Funds: $24,900

Principal Investigators: Caroline Solomon

Abstract: The Anacostia River in Washington, D.C. is classified as an impaired river from pollution based on several indicators; however, it is not well known how nutrient pollution and the different nitrogen (N) forms (i.e., NO3-, NH4+, urea) vary temporally or spatially or which N forms are of greatest concern. Such shifts in N form often influence the physiology of phytoplankton that lead to shifts in algal species and harmful or disruptive algal blooms. Recent literature is starting to suggest that excessive concentrations of NH4+ can lead to suppression of phytoplankton growth, which may have implications for migratory anadromous fish species that are filter feeders. Shifts in both phytoplankton community composition and fish communities will impact which fish are present in the Anacostia River for recreational and subsistence fishing. In order to properly assess N and food web dynamics in the Anacostia River, it is necessary to determine the effects of changing N form and proportions on phytoplankton and fish community composition and productivity. This project aims to assess the impact of NH4+ on phytoplankton and fish productivity and community composition in the Anacostia River’s N-enriched waters by both sampling of the River and conducting bioassay experiments. Samples will be collected over the course of a year bi-weekly from eleven sampling sites for assessment of nutrients, chlorophyll, and bacteria and phytoplankton community composition. Bioassay experiments done over several days will involve samples from certain sites that will be variably enriched with NH4+ and NO3-, with and without supplemental additions of phosphate (P) to produce a range of nutrient supply ratios. Data from the two-prong approach will be analyzed along with fish community data from District Department of the Environment to understand the impact on fisheries. Currently, there are regulatory advisories against fishing and thousands of people fish along the river for sustenance. This project will directly contribute to monitoring the influence of the pre- and post-construction of green and gray infrastructure on local phytoplankton and fish populations and the resulting impacts on local residents who fish in the Anacostia River