Organic matter (OM) decomposition is one of the key processes in all ecosystems, including aquatic ones. Every year, earth’s primary producers fix about 100 gigatons of organic carbon and every year, virtually the same amount of OM is decomposed back completing the global carbon cycle. However, although decomposition is an ecosystem process as important as primary production, much more is known about this latter one and about the role that autotroph organisms play in comparison to decomposition and, specially, the role of microorganisms in this process. There are several reasons for this asymmetry. The most important one is that decomposition is a complex process that emerges only at community level, involving many organisms at different spacial and temporal scales, whereas primary production is a process resident in each individual autotroph, and limited to a smaller fraction of biodiversity. Besides, it is difficult to study microorganisms, that play a central role in decomposition process, under in situ conditions and only very recently there are available techniques to undertake functional studies. For all these reasons, functional studies about the OM decomposition role are very scarce, in spite of the implications of this process in global carbon cycle and related aspects, as climate change, and exchange mechanisms of carbon between the atmosphere and aquatic and terrestrial ecosystems. This is specially true for wetlands, thar are among the most productive ecosystems on earth and where most of the carbon is stored as OM that goes through detritic pathways.