Optode-based method for measuring in-situ aerobic respiration

Terrestrial-Aquatic Interfaces (TAIs) are hotspots for microbial diversity and play a key role in the carbon cycle. River and streambed sediments contain a community of aerobic microbes that are currently sampled via excavation and transported to laboratory settings for testing. This approach changes the biochemical signature, losing potential information contained in the samples. Resazurin, a tracer that transforms to resorufin in the presence of aerobic respiration, can be used as a proxy for microbial activity and biological function of watersheds and natural systems, but it is currently technologically unattainable to continuously monitor the Raz/Rru transformations in-situ . Therefore, we are designing and building a fiber optic sensing technology capable of measuring Raz/Rru and oxygen in river and streambed soils. The continuous, semi-distributed sensing capabilities of fiber optics coupled with the Raz/Rru system will provide an indicator of redox potential via sub-centimeter resolution oxygen and aerobic respiration rate profiles of hyporheic soils. This technique will provide immediate data on hyporheic soils without disturbing the microbial community, expanding knowledge on the relationship between hydrologic flow and microbial activity.