Author: Ruby N Ghosh,   (Opti O2, LLC)

Description:
Dissolved oxygen (DO) dynamics in rivers and throughout the watershed play a critical role in catalyzing biogeochemical reactions and are affected by in-situ biological processes. Quantifying the impacts of DO dynamics on biogeochemistry, as well as the influence of biology on DO dynamics, requires continuous in-situ measurements at both high enough frequency to capture details such as changes in microbial respiration and long enough duration to observe annual scale effects/mechanisms. Fine grain temporal data is especially important in systems involving exchange between surface, stream and ground water. Our novel optical oxygen sensing technology provides real-time (∆t=5min) DO data from streams as well as in-situ deployments in saturated and unsaturated soils. These continuous measurements are obtained without removal or recalibration of the probe over multiple seasons (currently up to 18 months). We report on our insights from 3 case studies: (i) groundwater-surface water interactions within the hyporheic zone of an alpine stream from a 15 month record of spatially resolved DO measurements directly within the stream-bed, (ii) snowmelt driven biogeochemical processes in the hillslope to floodplain continuum and (iii) observation of tidally driven DO pulses followed by direct measurements of consumption by microbial respiration in a coastal watershed. Our high frequency measurements provide insights into ecosystem scale processes from the effects of snow drought in an alpine watershed to how rapid shifts in redox state influence carbon cycling in a tidal river-floodplain.

Category: Scientific Program Abstract > Special Session > SS22 A Report Card on the Sensor Revolution: contribution of high Frequency Sensors to fulfil knowledge gaps in Aquatic Ecosystem Science