Characterizing Zones of High Potential Nutrient Cycling in Agricultural Streams and their Relation to Agricultural Best Management Practices
Nitrogen and phosphorus flux from agricultural basins are contributing to intense outbreaks of harmful algal blooms in the Great Lakes with resulting impaired water quality and limits on human water consumption. While management of agricultural catchments focuses heavily on land-based strategies, natural in-stream processes (e.g., denitrification, sediment-P burial) are ongoing and could be enhanced if spatial extent and intensity were identified and managed. Land-use effects on in-stream processes are poorly understood, and linkages to adaptive management and terrestrial Best Management Practices (BMP) may prove critical to enhance nutrient retention. To promote potential decrease in phosphorus and nitrogen flux to the Great Lakes, we propose to identify “hotspots” of nitrogen and phosphorus cycling and to 1) characterize rates of specific biogeochemical mechanisms (ambient and potential denitrification, sediment phosphorus release); 2) characterize supporting processes (e.g., sediment oxygen demand, sediment carbon content, dissolved carbon optical characteristics); and 3) model landscape-scale geologic and geomorphic characteristics, to predict locations of “functional process zones” containing biogeochemical hotspots in measured and unmeasured catchments. Spatial coverage will be expanded through the use of sediment measurements predictive of biogeochemical processes (e.g., sediment C, N, P, and particle size). We will conduct these characterizations in Priority Watersheds, sampling processes in catchments with both high and low implementation (in consultation with NRCS). Sampling and modeling will focus on all stream orders, with increased weight given to more numerous low-order streams.