%0 Journal Article
%T Dynamics of the Methanogenic Archaea in Tropical Estuarine Sediments
%A Mar¨ªa del Roc¨ªo Torres-Alvarado
%A Francisco Jos¨¦ Fern¨¢ndez
%A Florina Ram¨ªrez Vives
%A Francisco Varona-Cordero
%J Archaea
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/582646
%X Methanogenesis may represent a key process in the terminal phases of anaerobic organic matter mineralization in sediments of coastal lagoons. The aim of the present work was to study the temporal and spatial dynamics of methanogenic archaea in sediments of tropical coastal lagoons and their relationship with environmental changes in order to determine how these influence methanogenic community. Sediment samples were collected during the dry (February, May, and early June) and rainy seasons (July, October, and November). Microbiological analysis included the quantification of viable methanogenic archaea (MA) with three substrates and the evaluation of kinetic activity from acetate in the presence and absence of sulfate. The environmental variables assessed were temperature, pH, Eh, salinity, sulfate, solids content, organic carbon, and carbohydrates. MA abundance was significantly higher in the rainy season (106¨C107£¿cells/g) compared with the dry season (104¨C106£¿cells/g), with methanol as an important substrate. At spatial level, MA were detected in the two layers analyzed, and no important variations were observed either in MA abundance or activity. Salinity, sulfate, solids, organic carbon, and Eh were the environmental variables related to methanogenic community. A conceptual model is proposed to explain the dynamics of the MA. 1. Introduction Coastal and marine environments, including estuaries and coastal lagoons, are characterized by large amounts of organic matter, which is mineralized primarily in sediments through anaerobic processes, sulfate reduction being the dominant metabolic pathway [1, 2]. However, although these ecosystems are the typical habitat of sulfate-reducing prokaryotes (SRP), methanogenic archaea (MA) and methane production have also been detected [3, 4]. MA are strict anaerobes that produce methane as end-product of their metabolism. These organisms are common in anoxic environments in which electron acceptors such as nitrate and sulfate are either absents or present at low concentrations and are usually dominant in freshwater environments. In the presence of these electron acceptors, methanogenesis is outcompeted by anaerobic respiration, mainly for thermodynamic reasons [5]. MA distribution patterns and its number, as well as physical, chemical, and nutritional parameters controlling their abundance and distribution have been studied in lacustrine sediments [6] and in coastal environments [7, 8]. Most of the ecological studies assessing the structure of methanogenic communities in estuarine systems have been performed in
%U http://www.hindawi.com/journals/archaea/2013/582646/