Investigating the Influence of on Phytoplankton! Assemblages in the , D.C. Anna McCall1, Kody Schouten1,2, and Caroline M. Solomon1! 1Gallaudet University, Washington, D.C. 20002; 2Tarleton State University, Stephenville, TX 76402!

Abstract Methods Results

The Anacostia River watershed Study Site! covers two counties Chlorophyll and Phytoplankton Assemblages! ! (Montgomery and Prince George’s) and the District of Columbia. The ! 6-19-13 bloom 7-17-13 bloom portion of the Anacostia River in ! Washington DC, the area of our ! study, is one of the most densely Washington DC ! Cyptomonas ovata Scrippsiella sp. populated areas near a river in the ! (identified by Steve (identified by Steve . Potential sources of ! Morton, NOAA) Morton, NOAA) nutrients that influence the ! phytoplankton community come ! from the upper watershed as well ! as combined sewer outfalls that flank both sides of the river. We ! hypothesized that rainfall would be correlated with nutrient Bloom observed Bloom observed concentrations and the appearance of specific phytoplankton ! near site 4 near site 1 blooms. The river was sampled bi-weekly from March to July ! + ! Sampling sites on the Anacostia River Chlorophyll concentrations at all sites! 2013. Samples were analyzed for ammonium (NH4 ), urea, total phosphorous (TP), chlorophyll as well as physiological rates ! + such as NH4 uptake and urease activity. Natural abundance + Laboratory analyses! Nutrients! samples were also collected to help identify sources of NH4 . Over the course of the summer, we observed two blooms of ! different phytoplankton species that utilized different nutrients ! that originated from sewage after periods of heavy rainfall.

Introduction & Hypothesis

The Anacostia River watershed, which is located in Maryland and DC, contains over 600,000 residents, making it one of + the most densely populated areas near a NH4 concentrations at all sites Urea concentrations at all sites TP concentrations at all sites river in the United States (US EPA, (note difference in scale) 2012). The city of DC uses a combined 15N-NH + Natural Abundance, NH + uptake, and urease activity! sewer overflow (CSO) system (see figure 4 4 on the right to meet the standards for a healthy river in 2010 and 2011 (Anacostia Watershed Society, 2011; see Environmental Data figure below). CSOs may be the major source for both nitrogen and phosphorus compounds whose high levels may lead to frequent The CSO tunnel locations algal blooms. For instance, historical on the Anacostia River (DC + Water and Sewage monthly NH4 concentrations during the Authority 2013) years of 2002 to 2011 varied from 0 to 28 μM while total phosphorus (TP) ranged from 0.48 to 7.39 μM during 2002 to + + 2006 (2002-2011; DC DOE, 2013). δ 15N-NH4 at all sites on 7-17-13! NH4 uptake and concentrations at all sites Urease activity at all sites until 6-19-13! Concentrations of organic nitrogen and Annual total precipitation, 2002-2013; dark blue bars on 7-17-13! rates of related enzymatic activity (e.g. represent higher precipitation levels than the yearly urease activity, and nitrogen uptake) average (National Weather Service, 2013) have not yet been measured in the Anacostia. Conclusions The focus of the water quality monitoring efforts by others have been on the There were two blooms observed during our study: the 6-19-13 bloom with Cyptomonas ovata, and the 7-17-13 bloom with Scrippsiella sp. These + presence of industrial chemicals, fecal blooms happened shortly after a period of high rainfall. The C. ovata bloom occurred when NH4 concentrations were high while TP concentrations + bacteria, and the health of fish, but not were low. On the other hand, the Scrippsiella sp. bloom was present when the TP concentrations were high and the NH4 concentrations were low. so much on nutrient pollution and its These blooms occurred under completely different nutrient regimes. impacts. We hypothesize that human 15 + and other waste that enter the Anacostia The N-NH4 natural abundance data shows a sewage signal for 2 or 3 different water regions. The first water region extends from site 1 to site 4 during periods of high rainfall and and the source may be upstream of site 1. The second water region involves sites 5 to 9, but may be divided into two regions depending on various warmer months may cause high levels of data. The sewage signal that begins to increase at site 5 may be coming from two streams, Hickey Run and Watts Branch, which meet the Report Card of the Monthly total precipitation, March-July 2013; dark blue Anacostia south of site 4. nitrogen and phosphorus concentrations, Anacostia River in 2011 bars represent higher precipitation levels than the and subsequently result in algal blooms, provided by the Anacostia some of which may be harmful. Watershed Society (2011) monthly average (National Weather Service, 2013) Our results support our hypothesis that human and other waste that enter the Anacostia during periods of high rainfall and warmer months may + cause increases in NH4 and TP concentrations that result in different algal blooms. References Acknowledgements National Weather Service. 2013. National Weather Service Database. th American Public Health Association (APHA). 2006. Standard Methods. 20 edition. http://www.nws.noaa.gov/climate/index.php?wfo=lwx. Accessed 25 July 2013. Anacostia Watershed Society. 2011. 2011 State of the River Report. Parsons, T.R., Maita, Y., Lalli, C.M. 1984. A manual of chemical and biological methods for seawater analysis. We are appreciative of the support from the Gordon Brown Endowment Foundation and NASA for our summer internships. We want to thank http://www.anacostiaws.org/programs/publicaffairs/2011-state-river-report. Accessed 12 June 2013. New York: Pergamon Press. Elizabeth Craft who provided advice and technical support. We also want to thank Dr. Patricia Glibert and Jeff Alexander at UMCES-Horn Point DC Water and Sewage Authority.. 2013. Combined sewer system. Revilla, M., Alexander, J., Glibert, P.M. 2005. Urea analysis in coastal waters: Comparison of enzymatic http://www.dcwater.com/wastewater_collection/css/. Accessed 21 June 2013. and direct methods. Limnol. Oceanogr.: Methods 3:290-299. Laboratory for processing and analyzing the natural abundance and nitrogen uptake samples and Steve Morton at NOAA for identifying unknown District Department of the Environment. 2013. Anacostia and monitoring program. Solomon, C.M., Alexander, J.A., Glibert, P.M. 2007. Measuring urease activity in aquatic environmental phytoplankton species. Many thanks goes to the Anacostia Riverkeeper for taking us out on the boat to collect samples. This research study is http://ddoe.dc.gov/service/anacostia-and-potomac-river-monitoring-program. Accessed 21 June 2013 samples. Limnol Oceanogr: Methods. 5:280-288. supported by grants from the D.C. Water Resources Research Institute and Maryland Sea Grant. Glibert PM, Capone DG. 1993. Mineralization and assimilation in aquatic, sediment, and wetland systems. In Knowles United States Environmental Protection Agency. 2012. Anacostia River watershed District of Columbia. United R., Blackburn TH (eds). Nitrogen isotope techniques. Academic Press, New York. Pp. 243-272. States Environmental Protection Agency archive. http://water.epa.gov/type/watersheds/archives/chap6ana.cfm. Accessed 18 July 2013.