PRIMARY RESEARCH PAPER Kinetic pathways for the anaerobic decomposition of Ludwigia inclinata F. Romeiro Æ I. Bianchini Jr. Received: 2 March 2007 / Revised: 7 March 2008 / Accepted: 18 March 2008 / Published online: 16 April 2008 Ó Springer Science+Business Media B.V. 2008 Abstract This study is aimed at using kinetic modeling to investigate the yield of mineralization products from anaerobic decomposition of the aquatic macrophyte Ludwigia inclinata. The initial hypothe- sis was that the decay of different fractions of detritus and the kinetics of gases productions are both positively correlated to temperature. The plants and water samples were collected from a tropical oxbow lake; the anaerobic decomposition was described using incubations maintained at controlled tempera- tures. The methane and carbon dioxide productions were determined daily by gas chromatography. The mass loss of detritus owing to leaching and chemical oxidation was also measured, with the results being used to develop a mathematical (kinetic) model considering the heterogeneity of the resource and three mineralization pathways: (i) oxidation of the labile particulate organic carbon; (ii) formation of dissolved organic carbon leached from the detritus, and subsequent oxidation of those compounds; and (iii) oxidation of refractory particulate organic carbon (RPOC). The temperature did not affect the leaching rate constant or the mineralization of labile and dissolved fractions. On the other hand, the mineral- ization of RPOC was improved with increasing temperatures. The yield of CO 2 formation was higher at 20.1°C and decreased with increasing tempera- tures. The methanogenesis was significantly affected by the temperature; it abbreviated the beginning of the process and increased the CH 4 yield. Conversely as hypothesized, the results suggest that the increase in temperature improved the decay rates of RPOC, but did not affect the leaching process and the subsequent leachate oxidation. Furthermore, the ris- ing temperatures had positive correlation with methanogenesis and negative with CO 2 production. Keywords Anaerobic decomposition  Kinetic model  Methanogenesis  Oxbow lakes  Aquatic macrophytes  Ludwigia inclinata Introduction Flooded areas are estimated as covering ca. 5% of the Earth’s surface (or 5.8 9 10 6 km 2 ), especially in tropical regions (Prigent et al., 2001). These Handling editor: S. M. Thomaz F. Romeiro Ecology and Natural Resources Graduation Program, Universidade Federal de Sa ˜o Carlos, Via Washington Luiz, km 235, P.O. Box 676, 13565-905 Sao Carlos, SP, Brazil e-mail: romeiro@rocketmail.com I. Bianchini Jr. (&) Hydrobiology Department and Ecology and Natural Resources Graduation Program, Universidade Federal de Sa ˜o Carlos, Via Washington Luiz, km 235, P.O. Box 676, 13565-905 Sao Carlos, SP, Brazil e-mail: irineu@power.ufscar.br 123 Hydrobiologia (2008) 607:103–111 DOI 10.1007/s10750-008-9370-8