Dissolved methane concentrations and fluxes to the atmosphere from a tropical floodplain lake

Large uncertainties in estimates of methane (CH₄) emissions from tropical inland waters reflect the paucity of information at appropriate temporal and spatial scales. CH₄ concentrations, diffusive and ebullitive fluxes, and environmental parameters in contrasting aquatic habitats of Lake Janauacá, a...

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Bibliographic Details
Published in:	Biogeochemistry 2020-03, Vol.148 (2), p.129-151
Main Authors:	Barbosa, Pedro M., Melack, John M., Amaral, João H. F., MacIntyre, Sally, Kasper, Daniele, Cortés, Alicia, Farjalla, Vinicius F., Forsberg, Bruce R.
Format:	Article
Language:	eng
Subjects:	Aquatic habitats Atmosphere Atmospheric models Biogeochemistry Biogeosciences Detection Dissolved organic carbon Earth and Environmental Science Earth Sciences Ecosystems Emission measurements Emissions Environmental Chemistry Environmental conditions Environmental factors Environmental Sciences & Ecology Floodplains Fluxes Geology Habitats Hydrology Inland waters Lakes Life Sciences Mathematical models Methane ORIGINAL PAPERS Rivers Sediments Spatial variations Statistical analysis Statistical models Surface water Tropical climate Water circulation Water column Water depth Water levels Wetlands
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Summary:	Large uncertainties in estimates of methane (CH₄) emissions from tropical inland waters reflect the paucity of information at appropriate temporal and spatial scales. CH₄ concentrations, diffusive and ebullitive fluxes, and environmental parameters in contrasting aquatic habitats of Lake Janauacá, an Amazon floodplain lake, measured for two years revealed patterns in temporal and spatial variability related to different aquatic habitats and environmental conditions. CH₄ concentrations ranged from below detection to 96 µM, CH₄ diffusive fluxes from below detection to 2342 µmol m⁻² h⁻¹, and CH₄ ebullitive fluxes from 0 to 190 mmol m⁻² d⁻¹. Vegetated aquatic habitats had higher surface CH₄ concentrations than open water habitats, and no significant differences in diffusive CH₄ fluxes, likely due to higher k values measured in open water habitats. CH₄ emissions were enhanced after a prolonged low water period, when the exposed sediments were colonized by herbaceous plants that decomposed after water levels rose, possibly fueling CH₄ production. Statistical models indicated the importance of variables related to CH₄ production (temperature, dissolved organic carbon) and consumption (dissolved nitrogen, oxygenated water column), as well as maximum depth, in controlling surface water CH₄ concentrations.
ISSN:	0168-2563 1573-515X