A nutrient’s travel through time
Citation:
Jicha, T., D. Woodruff, T. Hollenhorst, M. Moffett, J. Hoffman, Dave Bolgrien, AND B. Hill. A nutrient’s travel through time. St. Louis River Estuary Summit, Superior, WI, March 13 - 14, 2018.
Impact/Purpose:
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
Description:
Indicators of a stream’s ability to remove nutrients provide insights on watershed integrity and managers’ ability to restore ecosystem services based on specific characteristics of stream habitat. 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 Eight streams in the St Louis River AOC, including four streams in the Nemadji watershed. 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 have more capacity to remove nutrients than flashy streams with hardened banks. Phosphorus uptake velocity was correlated with riffle-run-pool habitat (r=abs0.99, 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 was also correlated with discharge and velocity (r=0.71-0.82). Streams with low watershed disturbance and low baseline nutrient concentrations were more sensitive to nutrient loads than some streams with much higher nutrient concentrations- yielding higher uptake lengths. 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. 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 used by state resource managers for assessing the impacts on downstream water quality from watershed development. Stream functional indicator research is helping identify and map the types of in-stream features needed to enhance processing and removing excessive loads of nutrients, sediments or contaminants projected by VELMA.