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EFFECTS OF A CANOPY COVER DISTURBANCE ON METABOLISM AND NUTRIENT RETENTION IN A SUBTROPICAL STREAM

Limited information is available on the effects of natural disturbance events on ecosystem functioning in subtropical streams. We examined the effects of a strong tropical storm on metabolism and nutrient retention in a first-order stream in Brazil. The study was conducted before and right after a 130 km.h-1-wind episode resulting in 76% to 40% removal of stream canopy cover. We performed additions of NH4Cl, NaNO3 and K2HPO4 using the TASCC method to estimate uptake metrics and metabolism was assessed with the one-station method. Metabolism was predominantly heterotrophic both before and after the storm, but GPP increased after the storm (0.11 and 0.35 mgO2.L-1.day-1). Ambient uptake was higher (i.e., shorter uptake lengths) after the storm, especially for NO3- (from 59.4 to 29.3 m) and PO43- (from 61.9 to 41.4 m). Despite a great increase in the uptake velocities for NO3- (15 to 50.7 mm.min-1) and PO43- (14.3 to 24.7mm.min-1), NH4+ uptake velocity did not differ significantly (30.1 to 35 mm.min-1; p>0.05, t-test) across months. Canopy disturbance may influence nutrient uptake and metabolism differentially suggesting different factors controlling them.

Nícolas Finkler (Primary Presenter/Author, Co-Presenter/Co-Author), University of São Paulo, nicolas.finkler@gmail.com;


Wesley Aparecido Saltarelli ( Co-Presenter/Co-Author), University of São Paulo, wesley.saltarelli@gmail.com;


Adriana Miwa ( Co-Presenter/Co-Author), University of São Paulo, adriana_miwa@yahoo.com.br;


Walter K. Dodds ( Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


Flavia Tromboni ( Co-Presenter/Co-Author), Universidade do Estado do Rio de Janeiro, flavia.tromboni@gmail.com;


Davi Gasparini Fernandes Cunha ( Co-Presenter/Co-Author), University of São Paulo, davig@sc.usp.br;