Long-term trends in lake metabolism: Heterogeneity and variance

Lakes are often described in terms of their metabolic status: eutrophic, oligotrophic, or dystrophic. These labels hint that trophic state is a steady, persistent condition. In contrast, long-term studies of metabolism highlight substantial spatial and temporal heterogeneity in rates and controls. Indeed, insights can be gained from both long-term trends in lake productivity and from changes in heterogeneity over time and within and among lakes.  The combination of multiple systems of varying trophic state in close proximity and the short generation time of primary producers make lakes ideal laboratories for examining concepts dealing with ecosystem variance and heterogeneity.