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A nutrient’s downstream fate: Assessing nutrient transport using TASCC
Citation:
Jicha, T., B. Hill, F. McCormick, K. Fritz, D. Woodruff, C. Schumacher, C. Hintz, T. Newcomer-Johnson, AND P. Kaufman. A nutrient’s downstream fate: Assessing nutrient transport using TASCC. International Association for Great Lakes Research, Brockport, NY, June 10 - 14, 2019.
Impact/Purpose:
Advances methodology in monitoring and assessing streams and rivers for ecosystem function in retaining nutrients to protect receiving water bodies.
Description:
Streams hydrologically connect watersheds to their respective Great Lake, playing a central role in the load and form of nutrients downstream waters receive. We used the Tracer Additions for Spiraling Curve Characterization (TASCC) to measure the uptake length, velocity and areal rate over a range of phosphate, nitrate, and ammonium concentrations. Our findings indicate that nutrient concentrations alone do not characterize how in-stream nutrient uptake responds to changes in watershed or habitat conditions (no significant correlations). Stream uptake lengths generally decreased with increasing nutrient concentrations from increased disturbance. Mean uptake length for phosphate (242.6 ± 25.1) was shorter than for nitrate (420.6 ± 45.3) or Ammonium (522.9 ± 72.6). In urban streams this uptake length decrease was a result of higher areal uptake likely from physical retention. While in agricultural streams, shortened uptake lengths were likely due to stimulated biological demand. Streams with relatively complex in-channel and riparian habitats and slow flows may have more capacity to remove nutrients than flashy streams with hardened banks. As streams get wider, shallower, and higher velocity uptake lengths increase for phosphates (R2= 0.28 p=0.03) and nitrates (R2= 0.21 p=0.04), respectively. Streams with deeper average thalweg significantly increase the biological uptake (U) for phosphates (R2= 0.43 p= 0.006) and ammonium (R2= 0.37 p= 0.009) at ambient conditions. This is because Streams with lower width to depth ratio have slower moving water (R2= 0.52, p<0.01), and have significantly higher percentage of sediments smaller than coarse gravel size (R2=0.32, p=0.02). Effective management of eutrophication requires an understanding of how streams transport and transform nutrients, such that watersheds can be prioritized, and in-stream habitat features can be restored or protected.