A mesocosm study of aerobic mineralization of seven aquatic macrophytes

Decomposition experiments were performed using the closed bottles method and seven aquatic macrophytes: Cabombafurcata, Cyperusgiganteus, Egerianajas, Eichhorniaazurea, Salviniaauriculata, Oxycaryumcubense and Utriculariabreviscapa. Cultures with lagoon water and macrophytes detritus were incubated at 20 °C under aerobic conditions. Total particulate and dissolved organic carbon and dissolved oxygen concentrations were analyzed. The major findings were: (i) the maximum amount of consumed oxygen (OC_MAX) and deoxigenation rates (k_d) differ among macrophyte decays (OC_MAX: 165–700 mg g⁻¹ DW; k_d: 0.014–0.045 d⁻¹); these differences depends mainly on molecular and elemental composition of detritus; in short period, the cytoplasm fraction of detritus enhanced the catabolic activity; (ii) the kinetic model adopted to describe the oxygen consumption was shown appropriate; the parameter more affected by the chemical differences of detritus was OC_MAX; the constant rates of oxygen consumption (k_d) were relatively smaller in relation to obtained to oxidative decarboxylation processes (ca. 6 times) and presented minimum changes if compared with the detritus variations.