Applying “R-Osmos” to Quantify Hot Moments in a High Mountain Watershed: Co-Development of Novel Methodology to Advance Terrestrial–Aquatic Interface Models
Authors
Andrew Thurber1* (andrew.thurber@oregonstate.edu), Laura Lapham2, Frederick Colwell1, Dipankar Dwivedi3, Kenneth Hurst Williams3
Institutions
1Oregon State University–Corvallis, OR; 2University of Maryland, Solomons, MD; 3Lawrence Berkeley National Laboratory, Berkeley, CA
Abstract
Watershed function is driven by habitat heterogeneity and microbial activity integrated over space and time. These habitats experience seasonal changes in redox zonation with water flow shifting biogeochemical cycles and perturbing the microbial communities that mediate biogeochemical processes. Features such as river meanders can create hot spots of biological activity; however, they must be directly sampled to be understood. This project will quantify the impact of hot spots and moments on microbial rates, focusing on two critical processes: methane (CH4) oxidation and nitrate reduction at DOE’s East River Watershed Function science focus area (SFA). Researchers will deploy novel, continuous, time-integrating, in situ microbial rate samplers to inform the magnitude and variation in biogeochemical processes across the terrestrial–aquatic interface, which, upon completion, will be used to refine a reactive transport model for this area. To accomplish this goal, the team will use uniquely configured osmotic samplers (OsmoSamplers) to continuously quantify the rate at which microbial communities transform methane and nitrate on either side of a meander. OsmoSamplers use a diffusion gradient to slowly pump water into tubes of such small diameter that sample mixing is negated. Multiple OsmoSamplers can be used together to continuously add solutes and preservatives or collect samples for later analysis, providing a record of hot moments in long-term datasets. In this work, researchers will use rate-osmotic samplers (R-osmos) to acquire spatially explicit rate measurements by adding nitrate and methane separately to discern transformation of these critical compounds. Rates will be coupled with quantifications of natural solute composition (both nitrate and CH4) and quantitative gene abundance for the relevant processes (i.e., genes responsible for nitrate reductase and methane monooxygenase), allowing researchers to connect solute, rate, and microbiome characteristics. During its first year, the project has focused on “bench testing” the R-osmo device in preparation for a planned year-long field deployment that will commence in summer 2023. Through this, the team uncovered small, yet critical modifications to the design, making the instruments ready for deployment. This presentation will cover the overall aims of the project, update progress to date, and highlight opportunities that this research framework may provide for collaboration with other SFA users.