Metabolism describes the energy fluxes that sustain life, in organisms and ecosystems.  In flowing waters, the metabolic fluxes of primary production (P) and respiration (R) can be estimated from the temporal variation in dissolved oxygen, a method pioneered in Florida’s spring-fed rivers.  Using modern high frequency sensors and modeling tools, we now can explore metabolism in far more places, and for far longer periods than ever before, enabling new insights about metabolic regimes, or the temporal and spatial patterns of metabolic variation.  One important aspect of metabolism research is understanding the role of nutrient supply in controlling energy fluxes.  Nutrients are enriched globally as a consequence of human activities (agriculture, wastewater disposal), with well known impacts on ecological processes and integrity.  We seek to better understand nutrient effects in flowing waters in an effort to guide restoration practices and regulatory interventions.