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Uptake of nutrients and organic C in streams in New York City drinking-water-supply watersheds

350 210 Stroud Water Research Center

Newbold, J.D., T.L. Bott, L.A. Kaplan, C.L. Dow, J.K. Jackson, A.K. Aufdenkampe, L.A. Martin, D.J. Van Horn, and A.A. Long. 2006. Journal of the North American Benthological Society 25(4):998–1017.

doi:10.1899/0887-3593(2006)025[0998:UONAOC]2.0.CO;2

Abstract

Uptake of nutrients and organic C was measured once annually between 2000 and 2002 in each of 10 streams within the water-supply source areas for New York City. Nutrients (PO43– and NH4+) and organic C (glucose and arabinose) were injected into the streams for 1 to 2 h, and uptake lengths were estimated from the longitudinal declines in downstream concentration relative to that of a conservative tracer. Uptake lengths increased with stream size and were converted to uptake velocities, Vf, to remove scaling effects. Vf s of PO43– and NH4+ varied inversely with the ambient concentration of total dissolved P (TDP) and total dissolved N (TDN), respectively, and were described by a model based on Michaelis–Menten kinetics. However, Vf s of glucose and arabinose were unrelated to the concentrations of any solute. Vf s of PO43–, NH4+, arabinose, and (with less certainty) glucose varied positively with measures of ecosystem metabolism (24-h community respiration and gross primary productivity). Uptake flux (U) of NH4+ also varied positively with ecosystem metabolism, but Us of PO43–, glucose, and arabinose did not. The Vf s of PO43– and NH4+ were positively related to invertebrate species richness and % forest cover, and negatively related to molecular tracer concentrations (polyaromatic hydrocarbons and fecal steroids [PO43–-Vf], fragrance materials [NH4+-Vf]) and population density. Spiraling, as a measure of ecosystem function, was sensitive to human impacts, most clearly through responses to nutrient loadings, but very probably through responses to other impacts as well.

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