Bioensaios de decomposição anaeróbia de macrófitas aquáticas da lagoa do Óleo (Estação Ecológica de Jataí, Luiz Antônio - SP).

Abstract

This study aimed at investigating: i) the influence of temperature on decomposition of macrophyte detritus; ii) the importance of leaching in the dynamics of the decomposition; iii) the decomposition of different structures of aquatic plants and iv) the enzyme activity of xylanase during the decomposition. The samples of water and aquatic macrophytes were collected in the Óleo lagoon (Ecological Station of Jataí; 21º 36 S and 47º 49 W). Bioassays were performance (during 140 to 200 days) with macrophytes fragments and water samples incubated under controlled conditions. Periodically the productions of carbon dioxide (CO2) and methane (CH4) were determinate by gas chromatography and the enzymatic activities were measured from reaction mixtures (aliquots of the incubations and xylan solution) followed by reducing sugars dosage (colorimetric method). It was observed a positive correlation with temperature and detritus decomposition; once were verified greater consumption at higher temperatures. Temperature was important in the detritus fibrous fraction consumption (Q10 = 1.61) and in methanogenesis (Q10 = 3.17). The fractionating of dissolved (DOM) and particulate organic matter (POM), due to the leaching process, conduced to a increase in the consumption efficiencies of these fraction. The xylanase activity was only registered when the dissolved sugars leached from the detritus decreased. The roots were the most easily degraded structure of Scirpus cubensis; this specie was the most easily degraded, followed by Cabomba furcata; the Ludwigia inclinata was the most refractory. Overall, this study suggests that S. cubensis is one of the most important aquatic plant to the carbon cycling in the Óleo lagoon, once this specie present higher productivity and intense mineralization.