503 Nutrient spiraling in streams: From concept to measurement and from comparisons to process understanding

Thursday, May 21, 2009: 8:15 AM
Ambassador West
Patrick J. Mulholland , Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN
Eugènia Martí , Limnology Group, Centre d'Estudis Avançats de Blanes (CSIC), Blanes (Girona), Spain
The nutrient spiraling concept was first proposed by Webster and Patten in the late 1970’s to describe nutrient cycling in streams and the concept has been a central tenant of stream ecology ever since.  Quantifiable metrics were developed by Newbold, Elwood and O’Neill in the early 1980’s and several advances in techniques have been proposed over the last two decades.  Nutrient uptake length (Sw), the most commonly measured spiraling metric, defines the effectiveness of uptake processes (primarily biological) in removing nutrients from stream water as water flows downstream.  Several studies have shown that Sw is best measured using nutrient tracer addition experiments, although it is often measured using nutrient additions that increase concentrations – measurements that must be treated with caution.  The nutrient spiraling concept and its metrics have proven valuable for comparison across streams and within the same stream over time, contributing to our understanding of general patterns and driving forces for nutrient cycling in streams.  In recent years the use of stable isotopes has allowed further understanding of the processes controlling nutrient spiraling in streams.  In this talk we will illustrate achievements from the use of different methodologies and present advances from comparative and process-level studies.