CORRELATING NUTRIENT UPTAKE AND STREAM METABOLISM IN URBAN CEMENT-LINED STREAMS

In order to improve anthropogenic efficiency, streams found in urban regions are often altered with a cement-lined bed. These cement-lined streams however, are responsible for highly nutrient rich waters causing eutrophication and poor water quality in downstream environments. The excess nutrient is unable to penetrate the cement surfaces and contact the hyporheic zone that aids in much of the nutrient retention. However, nutrient retention in cement-lined streams is still possible through uptake by the algae and microbes growing on the stream bed. The demand of nutrient by the algae and microbes can be monitored by identifying trends in the rate of retention or uptake velocity (Vf). Previous studies suggest that the uptake velocity can be affected by the productivity or metabolism of the algae and microbes, meaning that more productivity will result in more nutrient removal. Yet these studies have been restricted to environments other than cement-lined streams. Therefore, the purpose of this study is to understand the connection between the algal and microbial activity and the nutrient removal in a cement-lined stream setting. This will be done by measuring ammonia (NH4+) and phosphate (PO43-) removal rates as well as stream productivity in various cement lined streams in Normal/Bloomington, Illinois. The removal rates will be measured by conducting in situ uptake analyses and testing collected samples for NH4+ and PO43-. The activity of the algae and microbes will be measured by deploying dissolved oxygen data recorders at stream sites. From this, the dominant activity, either algal gross primary production (GPP) or microbial community respiration (CR), can be calculated. It is expected that for a cement-lined stream in comparison to other environments that uptake velocities will be high (based on previously collected data), and most of the stream metabolism will be in the form of GPP due to the high exposure to sunlight cement lined streams experience