A comparison of spatial and temporal drivers of stream metabolism

Abstract Stream metabolism provides insight into the functional processes that regulate trophic status, biomass, and nutrient cycling in streams. Comparative (spatial) analyses of streams generally do not account for shifting at‐site controls on stream over time and, thus, may identify primary cross‐site differences longer scales. The spatial component included assessing environmental factors controlling (daily values) during a summer low‐flow period (August) at 17 wadable sites four regions United States. Explanatory variables analysis discrete nutrients physical parameters. temporal 12 with more than 90 days values, continuous nitrate, photosynthetically active radiation (PAR), turbidity, maximum water temperature (°C) stage (water surface elevation). Spatial August (31 days) found average gross production (GPP) ranged from 0.1 to 4 g O 2 m −2 day −1 ecosystem respiration (ER) 0.37 6.4 . Sites were primarily heterotrophic; however, some varied autotrophic heterotrophic daily. Multiple regression indicated GPP was function orthophosphate, percent canopy cover, number since high flow ( R = 0.51), whereas ER 0.40). Temporal patterns daily evaluated using autoregressive models relatively complete, records. PAR, nitrate dominant influencing GPP, depth most common explanatory models. components (i.e., or previous day) had strong influence both except after spates, indicating biomass be control rather variability stable‐flow periods. We two regimes: seasonal pattern elevated spring followed by low stable temporally disturbed which tended occur frequent spates. These among conditions. Because are only limited periods when high, comparative must estimate scale representing adequately characterise between