نبذة مختصرة : Aerobic respiration of organic matter is a key metabolic process influencing carbon (C) biogeochemistry in aquatic ecosystems. Anthropogenic and environmental perturbations to stream ecosystem metabolism can have deleterious effects on downstream water quality. Various environmental features of rivers also influence stream metabolism, including physical (e.g., discharge, light, flow regimes) and chemical factors (nutrients, organic matter) and watershed characteristics (e.g., stream size or drainage area, land use). The relative proportion of surface water contact with benthic sediments has been considered the primary driver of ecosystem processes, including ecosystem respiration (ER). While aquatic ecosystem respiration occurs in the water column (ER wc ) and in benthic sediments—including surficial and subsurface sediments (ER sed )—ER sed has long been assumed to be the primary contributor to whole-river ecosystem respiration (ER tot ). Recent studies show, however, that somewhere along the river continuum (e.g., 5 th –9 th order), rivers transition from being dominated by benthic processes to being dominated by water column processes. Yet few metabolism studies have parsed contributions from the water column (ER wc ) to ER tot , making it difficult to evaluate the relative magnitude and importance of ER wc across the river continuum and across biomes. In this study, we used the Yakima River basin, Washington, USA, to increase our understanding of basin-scale variation in ER wc . We collected ER wc data and water chemistry samples in triplicate at 47 sites in the Yakima River basin distributed across Strahler stream orders 2–7 and different hydrological and biophysical settings during summer baseflow conditions in 2021. We found that observed ER wc rates were consistently slow throughout the basin during baseflow conditions, ranging from −0.11–0.03 mg O 2 L⁻ 1 d⁻ 1 , and were generally at the very slow end of the range of published ER wc literature ...
Processing Request
No Comments.