Stream Ecosystem Metabolism

Total respiration provides a single, integrative measure of all metabolic activity within a stream ecosystem, but we also wish to know what fraction is supported by primary production within the stream versus C fixed on land; what fraction of total inputs are respired; and the magnitude of export to downstream ecosystems. Three main approaches have been employed to address these questions. Organic energy budgets, including energy inputs and losses, allow insightful cross-system comparisons and are the basis for calculation of the overall efficiency with which ecosystems use available energy (Webster and Meyer 1997). The P/R ratio and NEP indicate whether an ecosystem is reliant on internal production or requires organic matter subsidies to sustain respiration. The distance traveled by an atom of C in organic form until it is mineralized to CO2 provides a comparative measure of an ecosystem's efficiency in processing organic material (Newbold et al. 1982b).

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