HR: 0830h
AN: B41C-0893    [PDF]
TI: Methane Emissions from Tropical Coastal Lagoons, Yucatan, Mexico
AU: * Young, M
EM: megyoung@pangea.stanford.edu
AF: Dept. of Geological and Environmental Sciences, Stanford University, Braun Hall/ Bldg 320, Stanford, CA 94305 United States
AU: Paytan, A
EM: apaytan@pangea.stanford.edu
AF: Dept. of Geological and Environmental Sciences, Stanford University, Braun Hall/ Bldg 320, Stanford, CA 94305 United States
AU: Herrera-Silveira, J
EM: jherrera@kin.mda.cinvestav.mx
AF: Laboratorio de Produccion Primaria, Centro de Investigaciones y Estudios Avanzados, Carr. Ant. Progresso, Km 6, Merida, YUC 97310 Mexico
AB: Tropical and sub-tropical wetlands are thought to be the dominant natural source of methane to the atmosphere, and the majority of tropical methane flux research has been carried out in freshwater environments. In order to obtain better estimates of methane emissions from tropical coastal environments, we are currently conducting a multi-year study of methane cycling and flux in three tropical coastal lagoons and associated mangrove ecosystems located on the Yucatan Peninsula in Mexico. Previous studies have shown that methane emissions from tropical coastal ecosystems are widely variable, and that these emissions can be quite high despite the presence of moderate to marine salinities. We measured surface water methane concentrations in two lagoons (Celestun and Chelem) during different seasons, as well as in a third, heavily polluted lagoon (Terminos), during the rainy season. Celestun lagoon has a distinct year-round salinity gradient (7-35 ppt) due to groundwater input, Terminos lagoon ranges from fresh water at the river entrances to marine in most of the lagoon area, and Chelem has a salinity range from marine to slightly hyper-saline (30-40 ppt). Diffusive methane flux to the atmosphere was calculated from surface water methane concentrations, using both sample-specific and average area wind speed measurements. Additionally, flux chambers were used to measure methane emissions from each of the lagoons during the rainy season. Calculated diffusive fluxes ranged from less than 1 mg CH4/m2/day up to 100 mg CH4/m2/day in all three lagoons, with the highest fluxes occurring in both areas of lower salinity and areas with known waste water discharge. However, measurements of bubble flux made using flux chambers were between 20 and 150 times greater than the diffusive flux calculated for the same locations. During the course of this study, it appears that the most significant bubble flux occurs in these lagoons during the rainy season. Observations and flux chamber measurements indicate that bubble flux even over a relatively short portion of the year could account for a significant amount of the total methane emissions from these systems. Therefore, additional research is needed to better quantify bubble flux emissions from tropical coastal lagoons and mangrove ecosystems, and estimates based on diffusive methane flux represent only the minimum average methane flux from the lagoons.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting