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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Urban Ecology I
EFFECTS OF WASTE WATER TREATMENT PLANT INPUTS ON THE METABOLISM OF A MEDITERRANEAN STREAM.
G. Canals1, E. Marti2, F. Sabater1, J. Ortiz2, and M.A. Puig2. 1Departament d'Ecologia, Universitat de Barcelona, Barcelona, Spain, 2Centre d'Estudis Avancats de Blanes (CSIC), Blanes, Spain
Inputs from waste water treatment plants (WWTP) increase stream nutrients and organic matter loads especially in semiarid regions where water is scarce. This study aimed to examine how stream function, in particular its metabolism, is affected by these inputs. Research was conducted in La Tordera, a 3rd order stream (NE of Barcelona, Spain). We selected two reaches with similar geomorphology and riparian vegetation coverage located upstream and downstream of a WWTP. On June and November 2001 we measured whole-stream metabolism at the two reaches using the upstream-downstream dissolved oxygen (DO) change technique. Concentrations of DIN, SRP and DOC were one order of magnitude larger in the downstream than in the upstream reach. Metabolism patterns were similar for the two dates. The diurnal profile of instantaneous DO change rates at the upstream reach had positive rates of net ecosystem production (NEP) around noon; whereas, NEP rates remained negative throughout the day at the downstream reach. Daily metabolism was dominated by respiration in both reaches. However, rates of respiration and gross primary production were higher and the P:R ratio was lower in the downstream than in the upstream reach. Therefore, inputs from WWTP affect this stream by mostly enhancing the heterotrophic metabolism.
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