Isolating stream metabolism and nitrate processing at point-scales, and controls on heterogeneity

Abstract

AbstractStream solute signals arise from the convolution of catchment delivery, hydraulic transport, and biogeochemical processing. Drawing inference from such signals requires analytical or experimental tools to isolate the signal attributable to stream processing. We used Lexan® chambers open to the air and inserted into the sediment (benthic chambers) and high-frequency in situ sensors to measure metabolism and nutrient processing rates for a small (0.36 m2) footprint across a variety of benthic cover types. We estimated gross primary production (GPP) and ecosystem respiration (ER) based on high-resolution dissolved O2 measurements, and we estimated N retention via both autotrophic assimilation (UA) and dissimilatory removal (UD) from high-resolution NO3− measurements. We observed marked spatial variation in metabolism and nutrient retention, principally in response to autotroph cover and light during thirty-three 1-wk deployments in Gum Slough, a spring-fed river (discharge ≈ 1.5 m3/s) in northern Flo...