Solute specific scaling of inorganic nitrogen and phosphorus uptake in streams

Abstract

Stream ecosystem processes such as nutrient cycling may vary with stream position in the watershed. Using a scaling approach, we examined the relationship between stream size and nutrient uptake length, which represents the mean distance that a dissolved solute travels prior to removal from the water column. Ammonium uptake length increased proportionally with stream size measured as specific discharge (discharge/stream width) with a scaling exponent = 1.01. In contrast, the scaling exponent for nitrate (NO₃^−) was 1.19 and for soluble reactive phosphorus (SRP) was 1.35, suggesting that uptake lengths for these nutrients increased more rapidly than increases in specific discharge. Additionally, the ratio of nitrogen (N) uptake length to SRP uptake length declined with stream size; there was lower demand for SRP relative to N as stream size increased. Ammonium and NO₃^− uptake velocity positively related with stream metabolism, while SRP did not. Finally, we related the scaling of uptake length and specific discharge to that of stream length using Hack's law and downstream hydraulic geometry. Ammonium uptake length increased less than proportionally with distance from the headwaters, suggesting a strong role for larger streams and rivers in regulating nutrient transport

The potential of agricultural headwater streams to retain soluble reactive phosphorus

“…Sheibley et al (2014) did not measure any in-stream SRP uptake at all, as was also the case in some of the Weinviertel streams. In their review about 969 nutrient uptake experiments, Hall et al (2013) observed that SRP uptake lengths were generally longer in human-impacted streams than in pristine systems.…”

“…Comprising about two-third of the total river length in European countries and the U.S. (Kavanagh & Harrison, 2014;Kristensen & Globevnik, 2014), small headwater streams are important links between the catchment and downstream reaches (Reddy et al, 1999;Dodds & Oakes, 2008). Due to their usually diverse channel morphology and their low discharge, pristine headwater streams can retain and process large amounts of nutrients and organic carbon from the catchment, thereby controlling matter transport into the remaining river system (Hall et al, 2002;Alexander et al, 2007;Hall et al, 2013). This retention function has become increasingly important in the face of the expansion and intensification of agriculture during the twentieth century (Gordon et al, 2008;Withers & Jarvie, 2008).…”

The varying role of water column nutrient uptake along river continua in contrasting landscapes

“…By comparing our water column v f measurements to reach-scale v f from a recently compiled meta-analysis (Hall et al 2013), we find that water column demand is lower than reach-scale demand, but the ranges overlapped for each solute (Fig. By comparing our water column v f measurements to reach-scale v f from a recently compiled meta-analysis (Hall et al 2013), we find that water column demand is lower than reach-scale demand, but the ranges overlapped for each solute (Fig.…”

“…The relationship between suspended inorganic sediments and v f-SRP may reflect Fig. Reach-scale studies were compiled from Hall et al (2013) and included any non-isotope study which reported v f . Reach-scale studies were compiled from Hall et al (2013) and included any non-isotope study which reported v f .…”

“…Anthropogenic point and non-point sources have increased nitrogen (N) and P loads throughout river networks globally (Carpenter et al 1998;Seitzinger et al 2005). Although nutrient uptake occurs in larger downstream river segments, the effect of stream size on nutrient uptake is variable (Hall et al 2013). Although nutrient uptake occurs in larger downstream river segments, the effect of stream size on nutrient uptake is variable (Hall et al 2013).…”