caa a22 4500 605517061 CHVBK 20210128100717.0 cr unu---uuuuu 210128e20150401xx s 000 0 eng 10.1007/s10533-015-0085-4 doi (NATIONALLICENCE)springer-10.1007/s10533-015-0085-4 Spatial and temporal variability in carbon dioxide and methane exchange at three coastal marshes along a salinity gradient in a northern Gulf of Mexico estuary [Elektronische Daten] [Benjamin Wilson, Behzad Mortazavi, Ronald Kiene] Carbon gas fluxes in tidal marshes vary spatially and temporally because of vegetation cover, subsurface biogeochemical processes, and environmental forcing. The objective of this study was to examine how ecosystem carbon gas exchange changes along an estuarine salinity gradient. We measured carbon dioxide (CO2) and methane (CH4) gas fluxes from three marshes representing a salinity gradient (0-32ppt) in the Mobile Bay estuary, Alabama, USA. CH4 flux was relatively small with no significant differences across sites despite salinity differences. Interestingly, sediment porewater CH4 concentrations were significantly higher at the high salinity salt marsh and decreased with decreasing salinity. Midday net ecosystem exchange (where a positive rate indicates net carbon assimilated through photosynthesis) was greatest at the most fresh site (4.8±0.3µmol CO2 m−2s−1), followed by the saline (2.8±1.0µmol CO2 m−2s−1) and brackish (1.4±0.6µmol CO2 m−2s−1) sites. However, net ecosystem exchange integrated diurnally revealed each marsh to be a net CO2 source to the atmosphere as a result of high ecosystem respiration with the freshwater marsh emitting more CO2 (−893.4±187.9g C m−2year−1) than the brackish (−517.8±85.2g C m−2year−1) and salt marsh (−410.2±98.2g C m−2year−1). This finding leads to the conclusion that either the marshes are losing carbon or that they receive a subsidy of respirable carbon, possibly via tidal deposition. The extent to which sedimentation from tidal deposition contributes carbon to these ecosystems, however, remains unknown. Without such a subsidy, marshes in the study area will not be able to keep up with sea level rise. Springer International Publishing Switzerland, 2015 Carbon dioxide nationallicence Methane nationallicence Climate change nationallicence Primary production nationallicence Ecosystem respiration nationallicence Mobile Bay Alabama nationallicence Wilson Benjamin Department of Biological Sciences, University of Alabama, Box 870344, 35487, Tuscaloosa, AL, USA aut Mortazavi Behzad Department of Biological Sciences, University of Alabama, Box 870344, 35487, Tuscaloosa, AL, USA aut Kiene Ronald Department of Marine Sciences, University of South Alabama, 36688, Mobile, AL, USA aut Biogeochemistry Springer International Publishing 123/3(2015-04-01), 329-347 0168-2563 123:3<329 2015 123 10533 https://doi.org/10.1007/s10533-015-0085-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10533-015-0085-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Wilson Benjamin Department of Biological Sciences, University of Alabama, Box 870344, 35487, Tuscaloosa, AL, USA aut NATIONALLICENCE 700 1- Mortazavi Behzad Department of Biological Sciences, University of Alabama, Box 870344, 35487, Tuscaloosa, AL, USA aut NATIONALLICENCE 700 1- Kiene Ronald Department of Marine Sciences, University of South Alabama, 36688, Mobile, AL, USA aut NATIONALLICENCE 773 0- Biogeochemistry Springer International Publishing 123/3(2015-04-01), 329-347 0168-2563 123:3<329 2015 123 10533