Nutrient Uptake in a Large Urban River¹

Abstract

Small streams have been shown to be efficient in retaining nutrients and regulating downstream nutrient fluxes, but less is known about nutrient retention in larger rivers. We quantified nutrient uptake length and uptake velocity in a regulated urban river to determine the river’s ability to retain nutrients associated with wastewater treatment plant (WWTP) effluent. We measured net uptake of soluble reactive phosphorus (SRP), dissolved organic phosphorus, ammonium (NH4), nitrate, and dissolved organic nitrogen in the Chattahoochee River, Atlanta, GA by following the downstream decline of nutrients and fluoride from WWTP effluent on 10 dates under low flow conditions. Uptake of all nutrients was sporadic. On many dates, there was no evidence of measurable nutrient uptake lengths within the reach; indeed, on several dates release of inorganic N and P within the sample reach led to increased nutrient export downstream. When uptake occurred, SRP uptake length was negatively correlated with total suspended solids and temperature. Uptake velocities of SRP and NH4 in the Chattahoochee River were lower than velocities in less‐modified systems, but they were similar to those measured in other WWTP impacted systems. Lower uptake velocities indicate a diminished capacity for nutrient uptake.

Annual mass drownings of the Serengeti wildebeest migration influence nutrient cycling and storage in the Mara River

“…We were only able to estimate nutrient uptake for one drowning, because carcasses needed to be located sufficiently upstream of the Kenya-Tanzania border to enable the necessary measurements. However, these uptake lengths are on the order of the uptake lengths documented for other rivers of similar size with high background nutrient concentrations (27)(28)(29).…”

“…We measured nutrient uptake length (S w ), uptake velocity (v f ), and aerial uptake (U) for NH 4 + and SRP after a mass drowning of 5,000 wildebeest in 2011, using the carcasses as a high-input nutrient source and declines in concentration downstream as an indication of nutrient uptake in the river (27,28,47,48) (Table S3). We calculated minimum U (U min ; based on upstream nutrient concentrations) and maximum U (U max ; based on the highest nutrient concentrations during the sampling period) for NH 4 + and SRP on days 8, 16, and 26 after the drowning.…”

“…The decomposing carcasses in the river represent a large nutrient source, and we used the declines in ammonium (NH 4 + ) and soluble reactive phosphorus (SRP) concentration downstream to estimate nutrient uptake length (the mean distance a solute travels before being removed by biological assimilation or uptake), uptake velocity (the speed at which a nutrient molecule moves from the water column to an uptake compartment), and total aerial uptake (total flux of nutrients from the water column to the stream bottom) at three time points from 1 to 4 wk after the drowning occurred (27,28). Total aerial uptake over this time accounted for between 149 and 879 kg of N (based on minimum and maximum estimations, as described in Materials and Methods), or 1-6% of soft tissue N loading, and between 109 and 136 kg of P, or 24-30% of soft tissue P loading.…”

Nutrient flux, uptake, and transformation in a spring-fed stream in the Missouri Ozarks, USA

“…Our study of Mill Creek shows that net uptake of DIN and SRP can significantly reduce stream fluxes of nutrients during baseflow. Compared to other large systems where nutrient uptake has been studied (e.g., Haggard et al 2005;Gibson and Meyer 2007), Mill Creek still had high uptake and a measurable uptake length of DIN. The characteristics of Mill Creek account for this high retention.…”

“…Measurement of nutrient budgets or fluxes in watersheds also provides a view of nutrient uptake. In cases where hydrology is well-characterized, one can estimate rates of net nutrient uptake (gross uptake minus remineralization) from such synoptic studies (Mulholland 1992;Sjodin et al 1997;Martí et al 1997;Haggard et al 2005;Gibson and Meyer 2007;Roberts and Mulholland 2007;Ruehl et al 2007). Net uptake may be a better indicator of the role of a stream in influencing nutrient fluxes across the landscape than gross uptake rates because it represents true nutrient retention by a stream, at least over the time frame of observation (Martí et al 1997;Roberts and Mulholland 2007;Brookshire et al 2009).…”