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2497947 
Journal Article 
Using the aquatic macrophyte Vallisneria americana (wild celery) as a nutrient bioindicator 
Benson, ER; O'Neil, JM; Dennison, WC 
2008 
Yes 
Hydrobiologia
ISSN: 0018-8158
EISSN: 1573-5117 
596 
187-196 
WOS:000251729800016 
Human sewage and septic waste are significant sources of nutrient loading to many aquatic ecosystems. Ecologically relevant nitrogen sources can be traced by analyzing nitrogen stable isotope ratios (delta N-15 signatures) in aquatic plants. Elevated delta N-15 signatures can suggest increased uptake of nitrogen derived from human and/or animal waste. In the current study, Vallisneria americana, a freshwater angiosperm, was collected from several locations in Upper Saranac Lake, NY, USA. Samples were also collected from Lake George, NY and the Sassafras River, MD, USA. Plant material was analyzed for delta N-15 and % N; some samples were also analyzed for delta C-13, % C, and % P. Results suggest that there is variation in septic inputs to Upper Saranac Lake, with some areas of the lake receiving more input than others. Results also show that increased watershed population density is correlated with elevated delta N-15 signatures of Vallisneria americana. Taken together, these results suggest that nitrogen stable isotope analysis of aquatic plant tissue is an effective method for assessing and monitoring septic inputs to freshwater ecosystems. 
nitrogen stable isotope; Upper Saranac Lake NY; Lake George NY; Sassafras River MD; Adirondack Park; Chesapeake Bay