Comment on "Solute-specific scaling of inorganic nitrogen and phosphorus uptake in streams" by Hall et al. (2013)

Abstract. Hall et al. (2013) presented a synthesis on 969 nutrient tracer experiments conducted primarily in headwater streams (generally < fourth-order streams), with discharges < 200 L s⁻¹ for ~90 % of the experiments, and used a scaling method to test the hypothesis that nutrient demand is constant with increasing stream size (i.e., along a river continuum). In this comment we present a reanalysis of a subset of the data used by Hall et al. (2013) and propose that their correlations between nutrient uptake lengths of ecologically important solutes and specific discharge are inadvertently spurious. Therefore, the conclusions derived from such correlations are debatable. We conclude the comment by highlighting some of the uncertainties associated with using modeling frameworks for scaling nutrient uptake in stream ecosystems.