Date of Award
Master of Science (MS) in Biology
Nitrogen and phosphorus are the most common limiting nutrients for biological activity in freshwater ecosystems. Applying inorganic nitrogen fertilizer has increased crop productivity but caused excess nitrogen inputs to the hydrosphere. Nitrate contamination is a worldwide environmental problem. The fate of nitrogen in ecosystems is variable based on land type and hydrogeological interactions. Excess nitrogen can be retained in soils, sequestered in stream organisms, denitrified or transported downstream. The goals of this study were to monitor nitrogen concentrations in Pine Draw, Turnbull National Wildlife Refuge (TNWR), Washington, U.S.A., and to determine the source of nitrogen loading. Pine Draw is unique because it’s located in the channeled scablands and has minimal anthropogenic impacts but has experienced excess nutrients for at least 20 years. Symptoms of nutrient loading observed on TNWR are an overabundance of primary producers, decreased biological diversity, extensive algal blooms, low dissolved oxygen, episodic anoxia, loss of vascular plant life and fish kills. I sampled nine surface water, three groundwater inputs on Pine Draw and three surface water sites on Philleo drainage monthly from October 2016 to October 2017. I documented nitrate+nitrite (NO3-N), ammonium (NH4+-N) and phosphate (PO43-) concentrations as well as specific conductance, conductivity, dissolved oxygen, temperature, pH and discharge in both watersheds for the duration of the sampling period. We used stable isotope ratios of oxygen and nitrogen in nitrate to determine that the source of nitrogen to Philleo drainage, groundwater and Pine Draw was a combination of ammonium fertilizer and soil nitrate varying seasonally based on water source.
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Price, Henry, "The source of excess nutrients to Pine Draw, Turnbull National Wildlife Refuge" (2018). EWU Masters Thesis Collection. 518.