Regulating factors of methane (CH4) emission in depositional environments of the Rivers Negro, Tapajos, Xingu and Amazonas

Abstract

The concern about increasing greenhouse gases emission and its consequences has been the subject of numerous studies in different environments, from Polar Regions to the Tropics, with the main focus on quantification and understanding of the role of natural and anthropogenic emissions. Studies about biogeochemistry of the Amazon River and its major tributaries have been developed in the last three decades. However, many processes are still unknown in this region, particularly regarding to emissions of greenhouse gases from rivers and the role of microorganisms in biogeochemical cycles. Microorganisms are responsible for oxidation and reduction of organic matter regulating the biogeochemical cycles. The quantification of the microorganisms related to CH4 production and the concentration of this gas in the sediment give us a clue of methanogenesis processes in different rivers and are essential for a more accurate assessment of the emission of greenhouse gases. The hypothesis of this study is that methane emission is bigger in sectors with physiographic and hydrodynamic characteristics favorable to the suspended sediment deposition, forming anoxic zones suitable for CH4 production. The joint assessment of CH4 concentration and abundance of methanogenic and methanotrofic microorganisms(bacteria and archaea) in sediment and water provides important information on the C cycling in these environments. For this, we analyze the concentrations of gas (CH4) dissolved in the sediment and water column, as well as the abundance of microorganisms involved in the production and consumption of gas. This project is housed within the project theme "The role of rivers on the regional carbon cycle" (Proc. N. 2008/58089-9) the FAPESP research on global climate change (PFPMCG). (AU)