2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

5/22/2018 | 3:00 PM - 3:15 PM | WITHIN VERSUS AMONG RIVER VARIATION IN GAS EXCHANGE RATE | 330 B

WITHIN VERSUS AMONG RIVER VARIATION IN GAS EXCHANGE RATE

Knowledge of air-water gas exchange is needed to estimate ecosystem metabolism and greenhouse gas evasion in rivers. Ecologists assume a single value for gas exchange for a given river. Yet rates of gas exchange should vary with time as a function of discharge, but in an unknown way. Here we estimated gas exchange rate (K, 1/d) as parameters in a metabolism model for 237 rivers measured through time. We pooled information on gas exchange as a piecewise linear function of discharge allowing any possible shape between gas exchange and discharge. Median rates of $K$ among rivers fell within published values based on gas tracers; slope and velocity predicted variation in K. Within rivers, K tended to decline with increasing discharge, likely because depth (z) increased faster than variation in turbulence. The degree of decline depended upon the hydraulic geometry of the channel with K declining more quickly with discharge in rivers with high bank slopes Gas exchange velocity (k=z*K, m/d), increased with increasing discharge; however, the relationships varied strongly among rivers suggesting much unexplained variation in how gas exchange respond to changing discharge.

Oxygen
New Methods
Biodiversity

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Presenters/Authors

Robert O. Hall (), Flathead Lake Biological Station, University of Montana, bob.hall@flbs.umt.edu;