Tracer Additions for Spiraling Curve Characterization (TASCC): Quantifying stream nutrient uptake kinetics from ambient to saturation

Timothy P. Covino, Brian L. McGlynn, and Rebecca A. McNamara

Limnol. Oceanogr. Methods 8:484-498 (2010) | DOI: 10.4319/lom.2010.8.484

ABSTRACT: Stream nutrient tracer additions and nutrient spiraling metrics are frequently used to quantify lotic ecosystem behavior. Of particular concern is the influence nutrient concentration exerts on nutrient retention and export. However, characterizing spiraling response curves across a range of concentrations has remained challenging, in part due to the large effort required to develop these curves using traditional (e.g., plateau or steadystate) approaches. Here we outline and demonstrate a new approach to quantify nutrient uptake kinetics from ambient to saturation using Tracer Additions for Spiraling Curve Characterization (TASCC). This approach provides a rapid and relatively easy technique for quantifying ambient-spiraling parameters, nutrient uptake kinetics and kinetic model parameterization, and assessment of stream proximity to saturation. We compare the results from TASCC to traditional breakthrough curve integrated and plateau approaches. We highlight the advantages of the TASCC approach for characterizing continuous spiraling response curves from ambient to saturation with a single tracer addition experiment, and its applicability to larger rivers where achieving plateau conditions (i.e., steady-state) is impractical.