Nitrogen and Phosphorus Uptake Within an Urban Stream Ecosystem

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Geography, Geology and the Environment


Catherine O'Reilly

Mentor Department

Geography, Geology and the Environment


Urban stream ecosystems are faced with high input levels of nitrogen (N) and phosphorus (P) from anthropogenic activities. N and P are important to plant growth and stream health; however, at high levels they can lead to algal blooms and eutrophication-a harmful effect to both stream life and water quality. Common sources of N and P within an urban setting include fertilizers, atmospheric deposition, street runoff, storm water outfall, and leaf litter decomposition. Urban stream syndrome (USS) describes the degradation of an ecosystem within an urban setting. Features such as a flashier hydrograph, altered channel stability and morphology, increase in nutrient output (such as N and P), temperature surges, and heat retention all result in an overall decrease in stream biodiversity. Not only will the environment be affected, economic services may suffer as a result. High input levels of N are seen within the Mississippi watershed basin in the form of nitrate. Focusing just on urban area outputs, 40% of N and P are emitted into the Mississippi watershed. This study will focus on urban stream nutrient uptake through the process of nutrient spiraling along two types of stream beds: natural (possessing a defined hyporheic zone) and concrete-lined. We hypothesize that N and P uptake will be greater in a natural section of stream due to biogeochemical processes occurring in the hyporheic zone. In contrast, a concrete-lined stream bed will limit the uptake process and maintain higher concentrations, carrying N and P farther downstream. Many urban streams have been modified to manage for hydrology, which potentially alters nutrient processing by limiting interactions with the hyporheic zone. Thus, quantifying the influence of stream bed type on nutrient uptake will identify how N and P are retained within a stream ecosystem and have implications for stream system restoration.



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