NITROGEN UPTAKE WITHIN AN URBAN STREAM ECOSYSTEM

Urban stream ecosystems are faced with high input levels of nitrogen (N) from anthropogenic activities. N is important to plant growth and stream health; however, high levels can lead to algal blooms and eutrophication—a harmful effect to both stream life and water quality. Common urban sources of N include fertilizer, atmospheric deposition, storm water outfall, and leaf litter decomposition. Urban stream syndrome features include a flashier hydrograph, altered channel stability and morphology, increase in nutrient output (such as N), and heat retention, all resulting in a decrease in stream biodiversity. High input levels of N are seen within the Mississippi River Basin (MRB) in the form of nitrate. Urban areas are responsible for 25% of N that is emitted into the MRB.

This study focuses on urban stream nutrient uptake along two types of stream beds: concrete and nonconcrete-lined. Sugar Creek located in Bloomington-Normal, IL, serves as the study area possessing both stream beds. We hypothesized N uptake would be greater in a nonconcrete stream reach due to biogeochemical processes within the hyporheic zone. In contrast, concrete-lined stream beds limit N uptake and maintain higher concentrations carrying N farther downstream. We measured nutrient uptake using short-term nitrogen additions. Samples tested for nitrate were analyzed on a Dionex Ion Chromatograph 1100. We found that N uptake rates were relatively higher in urban streams as compared to studies conducted in other settings such as deserts and some forested areas.

Many urban streams were modified to manage for hydrology, potentially altering nutrient processing by limiting interactions with the hyporheic zone. Thus, quantifying the influence of stream bed type on nutrient uptake will identify how N is retained within a stream ecosystem and have implications for stream system restoration.