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SFS Annual Meeting

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Ecosystem metabolism is almost always calculated from changes in oxygen concentrations, but determining the equivalent carbon flux necessitates a stoichiometric conversion factor. For respiration, this conversion factor, or respiratory quotient (RQ = moles CO2 produced/moles O2 consumed), is often assumed to be 1 based on the complete oxidation of glucose. However, empirical studies of RQ are few and far between: Marine studies suggest an RQ <1 while a pelagic lakes study found RQ converges >1 due to organic matter substrate control of RQ. We hypothesize that in lotic systems with much greater benthic influence, the prevalence of anaerobic respiration in sediments also controls RQ. We present the results of a benthic chamber experiment designed to determine the relative contribution of anaerobic respiration versus organic matter quality to ecosystem RQ. We also interrogate nighttime paired CO2 and O2 data to determine the variation in RQ found in lotic systems over space and time. Even slight RQ deviations from 1 can have large consequences for calculated carbon fluxes.

Lily Kirk (Primary Presenter/Author), University of Florida,;

Matthew Cohen (Co-Presenter/Co-Author), University of Florida,;