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A nutrient’s downstream spiral
Jicha, T., B. Hill, D. Woodruff, T. Hollenhorst, M. Moffett, Dave Bolgrien, AND J. Hoffman. A nutrient’s downstream spiral. Twin Ports Freshwater Folk, Duluth, MN, April 04, 2018.
This research adds to the basic knowledge on how streams function and their response to added nutrients. This information can be used by resource managers to make land development decisions and prioritize protection or restoration sites.
Indicators of a stream’s ability to remove nutrients provide insights on watershed integrity and stream habitat characteristics that are needed to help managers to restore stream ecosystem services. We used the Tracer Additon Spiraling Characterization Curve (TASCC) to measure the uptake length, velocity and rate over a range of nutrient concentrations (max=1629 ug/L N-NO3, 1240 ug/L N-NH4, 2182 ug/L P-PO4) in eighteen Twin Port streams. We found that nutrient concentrations alone do not account for how in-stream nutrient removal functions respond to changes in watershed or habitat conditions (no significant correlations). Streams with relatively complex in-channel and riparian habitats and low discharge may have more capacity to remove nutrients than flashy streams with hardened banks. Phosphorus uptake velocity was correlated with riffle-run-pool habitat (r=0.99, p=0.02). Ammonium uptake length and areal rate were correlated with stream velocity and discharge (r=0.63-0.94). Nitrate areal uptake rate and velocity were also correlated with velocity and discharge (r=0.71-0.82). Understanding features that promote in-stream nutrient removal can guide land use and habitat restoration decisions. Functional assessments help resource managers connect the restoration of habitat with the restoration of ecosystem services such as clean water and fisheries. Functional indicators, being developed under this project for Keene Creek and Kingsbury Creek are being integrated with the VELMA watershed model to aid in ecosystem decision support in the Great Lakes. VELMA is a land use visualization tool developed by EPA and used by resource managers for assessing the impacts on downstream water quality from watershed development. Our stream functional indicator research is helping identify and map streams in Twin Ports area for the types of in-stream habitat features needed to enhance processing and removing excessive loads of nutrients projected by VELMA.