Oxygen demand during mineralization of aquatic macrophytes from an oxbow lake.

This study presents a kinetic model of oxygen consumption during aerobic decomposition of detritus from seven species of aquatic macrophytes: Cabomba furcata, Cyperus giganteus, Egeria najas, Eichhornia azurea, Salvinia auriculata, Oxycaryum cubense and Utricularia breviscapa. The aquatic macrophytes were collected from Oleo Lagoon situated in the Mogi-Guaçu river floodplain (SP, Brazil). Mineralization experiments were performed using the closed bottles method. Incubations made with lake water and macrophytes detritus (500 mL and 200 mg.L(-1) (DM), respectively) were maintained during 45 to 80 days at 20 degrees C under aerobic conditions and darkness. Carbon content of leachates from aquatic macrophytes detritus and dissolved oxygen concentrations were analyzed. From the results we concluded that: i) the decomposition constants differ among macrophytes; these differences being dependent primarily on molecular and elemental composition of detritus and ii) in the short term, most of the oxygen demand seems to depend upon the demineralization of the dissolved carbon fraction.

Oxygen demand during mineralization of aquatic macrophytes from an oxbow lake

This study presents a kinetic model of oxygen consumption during aerobic decomposition of detritus from seven species of aquatic macrophytes: Cabomba furcata, Cyperus giganteus, Egeria najas, Eichhornia azurea, Salvinia auriculata, Oxycaryum cubense and Utricularia breviscapa. The aquatic macrophytes were collected from Óleo Lagoon situated in the Mogi-Guaçu river floodplain (SP, Brazil). Mineralization experiments were performed using the closed bottles method. Incubations made with lake water and macrophytes detritus (500 mL and 200 mg.L-1 (DM), respectively) were maintained during 45 to 80 days at 20 °C under aerobic conditions and darkness. Carbon content of leachates from aquatic macrophytes detritus and dissolved oxygen concentrations were analyzed. From the results we concluded that: i) the decomposition constants differ among macrophytes; these differences being dependent primarily on molecular and elemental composition of detritus and ii) in the short term, most of the oxygen demand seems to depend upon the demineralization of the dissolved carbon fraction.

Nesse estudo foi utilizado um modelo cinético para a descrição dos consumos de oxigênio durante a mineralização aeróbia de detritos de sete espécies de macrófitas aquáticas: Cabomba furcata, Cyperus giganteus, Egeria najas, Eichhornia azurea, Salvinia auriculata, Oxycaryum cubense e Utricularia breviscapa. As macrófitas aquáticas foram coletadas na Lagoa do Óleo, situada na planície de inundação do rio Mogi-Guaçu (SP, Brasil). Os experimentos foram realizados empregando-se incubações similares as de DBO. As incubações foram preparadas com água da lagoa e detritos das macrófitas aquáticas (500 mL e 200 mg.L-1 (PS), respectivamente) e foram mantidas durante 45 a 80 dias a 20 °C, sob condições aeróbias e no escuro. Foram determinados os conteúdos de carbono dos lixiviados dos detritos e os consumos de oxigênio dissolvido durante a mineralização. A partir dos resultados obtidos pôde-se concluir que: i) os coeficientes de mineralização das macrófitas aquáticas diferiram entre si, essas diferenças dependeram principalmente das composições moleculares e elementares dos detritos; e ii) a curto prazo, grande parte da demanda de oxigênio parece depender da mineralização das de carbono dissolvido provenientes da lixiviação.