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Managing Nutrients in Two New England Estuaries: The Feasibility of Using Stable Isotopes To Monitor Nitrate SourcesEPA Grant Number: FP916375
Title: Managing Nutrients in Two New England Estuaries: The Feasibility of Using Stable Isotopes To Monitor Nitrate Sources
Investigators: Barnes, Rebecca T.
Institution: Yale University
EPA Project Officer: Zambrana, Jose
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems
The objectives of this research project are to enhance the current understanding of the nitrogen loading in two estuaries and explore the temporal and spatial variation of isotopic source signatures. Nitrogen is the limiting nutrient in many estuaries and increasing the availability of this nutrient often leads to increased eutrophication in these coastal systems. Estuarine eutrophication is associated with higher rates of algal net primary production, seasonal hypoxia, decreases in the amount of sea grasses, fish kills, and changes to the plant and animal communities. The National Estuarine Eutrophication Assessment estimated that 40 percent of U.S. estuaries are impaired as a result of eutrophication. To reduce nitrogen loading to coastal waters it is necessary to know the relative importance of the various sources. Recent studies have shown that sources of NO3‾ can be differentiated based on their isotopic signature using both δ15N and δ18O. Currently, the range of isotopic values in the literature for the various nitrate sources (sewage, atmospheric deposition, microbial nitrification, fertilizer, etc.) is too large to clearly differentiate between sources. For this method to be successful in determining the relative contribution of each nitrate source to a particular estuary, local source values are needed.
I propose parallel studies in two New England estuaries (Narragansett Bay, RI, and Great Bay, NH) to increase the spatial and temporal resolution of the isotopic signatures for the following sources of NO3‾: agricultural runoff, atmospheric deposition, sewage, microbial nitrification, urban runoff, and septic. The relative importance of the various NO3‾ sources to both Narragansett Bay and Great Bay will be determined monthly to assess the changing impact of different sources throughout the study period. The geographic variability of this study will allow for the analysis of small (within a single estuarine watershed) and regional (between two estuarine watersheds) differences and trends in isotopic source signatures. The proposed project will enhance the current understanding of the nitrogen loading to these two estuaries, explore the temporal and spatial variation of isotopic source signatures, and ultimately support the development of future nitrogen management plans.