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Grantee Research Project Results

Nitrogen-Related Ecosystem Services Along a Nitrogen Saturation Gradient in the Klamath Hydroelectric Project Reservoirs

EPA Grant Number: FP917450
Title: Nitrogen-Related Ecosystem Services Along a Nitrogen Saturation Gradient in the Klamath Hydroelectric Project Reservoirs
Investigators: Deemer, Bridget R
Institution: Washington State University
EPA Project Officer: Jones, Brandon
Project Period: August 1, 2012 through July 31, 2015
Project Amount: $126,000
RFA: STAR Graduate Fellowships (2012)
Research Category: Academic Fellowships , Fellowship - Aquatic Ecology and Ecosystems

Description:

Objective:

The goal of this study is to quantify summertime denitrification, N sedimentation and nitrous oxide production in the Klamath Hydroelectric Project Reservoirs. Specifically, this research will examine how background N concentrations affect the proportion of N that is removed permanently via denitrification versus the proportion of N buried within more temporary storage pools in the sediment. The study also will examine how background N concentrations affect denitrification efficiency, or the proportion of N converted to dinitrogen versus nitrous oxide.

Approach:

This study will focus on five reservoirs within the Klamath River basin that experience a range of background N concentrations. Denitrification rates and nitrous oxide production rates will be estimated in each reservoir by quantifying the accumulation of dinitrogen and nitrous oxide within the hypolimnion over the course of the summer. Potential denitrification as a function of depth also will be quantified in each system using the acetylene block technique. N sedimentation rates will be quantified by deploying a series of in situ sedimentation traps in each reservoir and analyzing sediments for total N content. Background nitrogen concentrations (total nitrogen, dissolved organic nitrogen, nitrate and ammonium) also will be measured several times throughout the summer by sampling along a vertical profile at the deepest part of each reservoir.

Expected Results:

Denitrification rates are not expected to scale linearly with system N-status, supporting the notion that Klamath reservoirs are N-saturated. Elevated N concentrations are expected to result in lower rates of denitrification relative to N sedimentation and higher rates of nitrous oxide production relative to dinitrogen production. Overall, it is expected that elevated background N concentrations reduce the ecosystem services provided by reservoir ecosystems.

Potential to Further Environmental/Human Health Protection

Anthropogenically fixed excess nitrogen is associated with a number of serious aquatic and atmospheric pollution issues, including an increase in the frequency and severity of harmful algal blooms, the proliferation of coastal hypoxic zones, the contamination of drinking water wells, and increased fluxes of nitrous oxide to the atmosphere. This study will describe how anthropogenic N loading affects N removal processes in reservoirs. This will represent a significant contribution to the understanding of the controls on N-related ecosystem services.

Supplemental Keywords:

denitrification, sedimentation, nitrogen saturation

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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