Estimation of stream nutrient uptake from nutrient addition experiments

Abstract

Nutrient uptake in streams is often quantified by determining nutrient uptake length. However, current methods for measuring nutrient uptake length are often impractical, expensive, or demonstrably incorrect. We have developed a new method to estimate ambient nutrient uptake lengths using field experiments involving several levels of nutrient addition. Data analysis involves plotting nutrient addition uptake lengths versus added concentration and extrapolating to the negative ambient concentration. This method is relatively easy, inexpensive, and based on sound theoretical development. It is more accurate than the commonly used method involving a single nutrient addition. The utility of the method is supported by field studies directly comparing our new method with isotopic tracer methods for determining uptake lengths of phosphorus, ammonium, and nitrate. Our method also provides parameters for comparing potential nutrient limitation among streams.

Nutrient Uptake and Mineralization during Leaf Decay in Streams – a Model Simulation

“…Second, there are very few measurements of Monod coefficients for nutrient uptake by heterotrophic microbes. The technique developed by PAYN et al (2005) may be useful for such measurements. Third, we found no actual measurements of dead microbial tissue in decaying leaves in streams.…”

Saturation of NO3−uptake in prairie streams as a function of acute and chronic N exposure

“…Uptake lengths measured with short-term nutrient addition techniques (S w9 ) overestimate the actual uptake length (S w ) at ambient conditions (Mulholland et al 1990, 2002, Earl et al 2006. Ambient U t estimates from S w9 will underestimate the actual ambient U t as measured with stable isotope tracers , and multiple additions are required to extrapolate ambient S w and U t (Payn et al 2005. We anchored ambient uptake parameters with published 15 N studies and reported U t of NO 3 2 at the elevated addition concentrations experienced during the addition.…”

“…Dodds et al (2002) reported a K s of 64 mg NH 4 + -N/L for a prairie reach of Kings Creek, whereas Kemp and Dodds (2002b) projected whole-stream K s of 12.3 mg/L for NO 3 2 and 6.7 mg/L and NH 4 + based on uptake kinetics of different substratum types within the stream. Payn et al (2005) reported K s in forested streams of 6 mg NH 4 + -N/L for Ball Creek, North Carolina (USA), and 14 mg NH 4 + -N/L for Walker Branch, Tennessee (USA). In both streams, reported K s was higher than ambient NH 4 + concentrations (3.0 and 2.7 mg/L, respectively), results suggesting these streams are N limited.…”

Inferring nitrogen removal in large rivers from high‐resolution longitudinal profiling

“…The principal reason for this constraint is methodological, specifically a strong reliance on two methods: 15 N isotopic tracer addition (Hall et al 1998;Dodds et al 2000;Peterson et al 2001) and nutrient enrichment (Mulholland et al 2002;Payn et al 2005), both of which create logistical and financial limitations when applied to larger rivers. Isotopic enrichment, which is desirable because it retains ambient concentrations and yields pathway-specific removal information, is particularly impractical in large rivers because of the costs of isotopically labeled solutes.…”

“…Isotopic enrichment, which is desirable because it retains ambient concentrations and yields pathway-specific removal information, is particularly impractical in large rivers because of the costs of isotopically labeled solutes. Unlabeled nutrient enrichment additions, despite not discriminating removal pathways, are more feasible at higher flows and longer residence times (Tank et al 2008), but may enhance removal rates (Mulholland et al 2002), requiring repeated dosing to varying plateau concentrations to backextrapolate removal at ambient conditions (Payn et al 2005). Pulse injection methods (Covino et al 2010) to estimate both ambient concentration removal rates and removal kinetics with increased concentration obviate constraints of repeated plateau additions, but retain substantial logistical constraints in large rivers, and in river networks.…”