SHALLOW LAKES FROM PAMPEAN PLAIN (ARGENTINA): SINK OR SOURCE OF GREENHOUSE GASES?

DEL GIORGIO P.; LOMBARDO R.; MORDENTE A.; SÁNCHEZ, ML; O'FARRELL I.; RODRIGO SINISTRO; IZAGUIRRE I.

Honolulu

Congreso; ASLO Meeting; 2017

Association for the Sciences of Limnology and Oceanography

Lakes and rivers are now recognized as key sites of chemical and biological processing of carbon and major players in regions thatcontain high densities of surface waters. The pampean Plain is a temperate region of Argentina that harbors thousands of eutrophicshallow lakes. The aim of this study was to determine if these shallow lakes are acting as source or sink of carbon dioxide and methane. We present measurements of carbon dioxide and methane concentrations in 7 shallow lakes belonging to pampean region. Samplings were done in July of 2014, July and November of 2015. Ambient carbon dioxide and methane concentrationswere measured using a portable gas sensor. Air/water fluxes were measured in situ using floating chambers. Environmental variables were measured to characterize each lake. The surface waters of the shallow lakes exhibited an extremely wide range in gas concentrations ranging from 185 to 20,079 ppm for carbon dioxide, and from 18.26 to 17,814 ppm for methane, although thevast majority of samples were supersaturated in both. Air/water fluxes were positive in almost all samples (ranging from -23 to 410 mmol m-2 d-1for carbon dioxide and from 0.04 to 42 mmol m-2 d -1for methane). GHG concentrations and fluxes registered were considerably high in comparison with values registered in lakes of the North hemisphere. The contribution of these water bodies to the atmosphere is considerable taking into account the magnitude of the registered values and also the high number of these lakes that are located in the region. Most of these waters were acting as source of GHG with positive fluxes of carbon dioxide and methane.