Spatial and temporal variability of CO2 and CH4 gas transfer velocities and quantification of the CH4 microbubble flux in mangrove dominated estuaries. (2nd December 2016)

• Record Type: Journal Article
• Authors: Rosentreter, J. A.; Maher, D. T.; Ho, D. T.; Call, M.; Barr, J. G.; Eyre, B. D.
• Is Part Of: Limnology and oceanography. Volume 62:Number 2(2017)
• Page Start: 561
• Page End: 578
• Publication Date: 2016-12-02
• Subjects: Limnology -- Periodicals; Oceanography -- Periodicals; Océanographie; Limnologie; Limnology; Oceanography; Computer network resources; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); Periodicals; 551.4805
• DOI: 10.1002/lno.10444
• Languages: English
• ISSNs: 0024-3590

Abstract

Abstract: Gas transfer velocities ( k ) of CO2 and CH4 were determined from 209 deployments of a newly designed floating chamber in six mangrove dominated estuaries in Australia and the United States to estimate mangrove system specific k . k 600 ‐ CO2 and k 600 ‐ CH4 ( k normalized to the Schmidt number of 600) varied greatly within and between mangrove creeks, ranging from 0.9 cm h −1 to 28.3 cm h −1 . The gas transfer velocity correlated well with current velocity at all study sites suggesting current generated turbulence was the main driver controlling k . An empirical relationship that accounts for current velocity and a linearly additive contribution of wind speed and water depth was a good predictor of k 600 ‐CO2 ( R 2 = 0.67) and k 600 ‐CH4 ( R 2 = 0.57) in the mangrove creeks in Australia. In a side‐by‐side study, good agreement was found between k determined from this new floating chamber and a 3 He/SF6 dual tracer release experiment (∼5% discrepancy). k 600 ‐ CH4 correlated well with k 600 ‐ CO2 ( R 2 = 0.81), however, k 600 ‐ CH4 was on average 1.2 times higher than k 600 ‐ CO2, most likely reflecting a microbubble flux contribution. The microbubble flux contributed up to 73% of the total CH4 flux and was best predicted by a model that included CH4 supersaturation, temperature, and current velocity. A large overestimation was found for both CO2 and CH4 fluxes when calculated using empirically derived k models from previous studies in estuaries. The high temporal and spatial variabilities of k CO2 and k CH4 highlights the importance of site specific transfer velocity measurements in dynamic ecosystems such as mangrove estuaries.