The Application Of Scaling Rules To Energy Flow In Stream Ecosystems

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Abstract Kaplan 0109122 The investigators propose to estimate the contribution of dissolved organic matter (DOM) in transport to the support of stream ecosystem metabolism. The specific objective of this project is to estimate the mass flux of DOM (e.g., the rate of flux from the water column to the streambed), to represent this as the sum of fluxes from several lability classes, and to characterize the respective concentration and uptake length coefficient of DOM in each lability class. Uptake length converts easily to mass transfer coefficient or turnover rate through scaling relationships involving depth and water velocity. Quantifying the uptake of natural DOM in the stream is analogous to describing the uptake (or spiraling) of phosphorus or ammonium, but is complicated by the diversity of natural DOM (i.e. it consists of an array of compounds of varying lability), and the fact that isotopically-labeled natural DOM is not available. This project will use 13C-labeled DOM generated by growing plants in a 13C atmosphere. The longitudinal uptake of 13C -DOm will be resolved into multiple uptake lengths (corresponding to multiple lability classes), estimated as the sum of exponential-curves. In addition, the uptake kinetics of natural (12C) DOM in laboratory bioreactors will be compared to those of the labeled 13C-DOM, and this comparison will be used to scale the results of the 13C-DOM injection, to appropriately describe the uptake of natural DOM in the stream.