Ecological Archives A021-090-A1

Solange Filoso and Margaret A. Palmer. 2011. Assessing stream restoration effectiveness at reducing nitrogen export to downstream waters. Ecological Applications 21:1989–2006.

Appendix A (TABLE A1). A table containing NO3-N uptake rates in restored lowland streams calculated from N addition experiments conducted during average flow conditions.

  HBR WIL SPA
Average N concentrations
Uptake length (m) 298 117 58
Uptake velocity (mg/min) 0.0014 0.001 0.002
Areal uptake (mg N/m2/min) 0.16 0.27 0.51
Elevated N concentrations
Uptake length (m) 374 232 82
Uptake velocity (mg/min) 0.0010 0.0005 0.0014
Areal uptake (mg N/m2/min) 0.12 0.18 0.36

The experiments were conducted only in the restored lowland streams, where we observed a consistent decrease in N fluxes along the restored reach during average-flow conditions. The objective of the experiments was to determine whole-reach uptake rates for the different streams and also to determine if uptake rates varied with increasing N concentrations. The experiments were done by continuously dripping a concentrated NO3- solution (using bromide (Br-) as a conservative tracer) into the stream to temporarily elevate NO3- concentrations above background levels. When the Br- concentration reached a plateau, water samples were collected at stations downstream of the injection point. The experiments were first performed by increasing concentrations by about 10 to 15% above the observed background concentrations and later by doubling these concentrations. Nitrate uptake rates were calculated using the method described in the Stream Solute Workshop (1990).

LITERATURE CITED

Stream solute workshop. 1990. Concepts and methods for assessing solute dynamics in stream ecosystems. Journal of North American Benthological Society 9:95–119.


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