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Methane dynamics in the subsaline ponds of the Chihuahuan Desert: A first assessment

Aguirrezabala-Campano, Teresa, Gerardo-Nieto, Oscar, Gonzalez-Valencia, Rodrigo, Souza, Valeria, Thalasso, Frederic
The Science of the total environment 2019 v.666 pp. 1255-1264
aquatic ecosystems, basins, carbon dioxide, carbon dioxide production, greenhouse gas emissions, marine environment, methane, methane production, methanotrophs, ponds, salt lakes, sulfates, summer, Chihuahuan Desert
The Cuatro Cienegas Basin (CCB) in the Chihuahuan desert is characterized by the presence of over 500 ponds located in an endorheic basin. These ponds are subsaline ecosystems characterized by a low productivity and a particularly high sulfate concentration, comparable to marine environments. This study focused on assessing the main physicochemical parameters in these ponds along with the characterization of the CH4 dynamics through the determination of fluxes, dissolved CH4 concentrations, and net methanotrophic and methanogenic activity. Despite a sulfate concentration ranging from 1.06 to 4.73 g L−1, the studied ponds showed moderate but clear CH4 production and emission, which suggests that methanogenesis is not completely outcompeted by sulfate reduction. CH4 fluxes ranged from 0.12 to 0.98 mg m−2 d−1, which falls within the higher range of marine emissions and within the lower range reported for coastal saline lagoons and saline ponds. During summer, significant CH4 production in the oxic water column was observed. In addition to CH4, CO2 fluxes were determined at levels from 0.2 to 53 g m−2 d−1, which is within the range recorded for saline lakes in other parts of the world. Our results provide additional evidence that subsaline/saline aquatic ecosystems play an important role in the emission of greenhouse gases to the atmosphere.