Detritus age on aerobic mineralization of Salvinia auriculata Aubl.
SCIESSERE1, L.; CUNHA-SANTINO1,2, M. B. & BIANCHINI1,2, JR., I .
1 Programa de Pós-Graduação em Ecologia e Recursos Naturais, Universidade Federal de São Carlos. Via Washington Luiz, km 235. Cx. Postal 676. 13565-905. São Carlos, SP, Brasil.
lusciessere@gmail.com pmbc@iris.ufscar.br
2 Departamento de Hidrobiologia, Universidade Federal de São Carlos. Via Washington Luiz, km 235. Cx. Postal 676. 13565-905. São Carlos, SP, Brasil.
ABSTRACT: Considering the essential role of the aquatic macrophytes decomposition to aquatic ecosystems, this study evaluated the oxygen consumption of Salvinia auriculata detritus with 10 and 180 days, in the presence or absence of sediment; the detritus were previously decomposed under aerobic and anaerobic conditions. The plant, water and sediment samples were colleted on Óleo Lagoon (21º 36'S and 47º 49' W; Jataí Ecologic Station; Luiz Antônio, SP, Brazil). It was set up 20 mineralization chambers (10 with and 10 without sediment), they were prepared with detritus and water from the lagoon (0.70 g detritus DW L- 1) and maintained in the dark, under aerobic conditions and at 20oC. The DO concentrations were measured during 177 days. The results of the accumulated consumption of oxygen were adjusted to a first order kinetic model. In general, the treatments without sediment presented higher values of maximum consumption of oxygen (COmax). The incubations of the younger detritus (10 days) presented higher values of COmax (mean: 213 mg g-1 DW) when compared with the older detritus (180 days, mean: 107 mg g-1 DW). The deoxygenation coefficients varied from 0.0088 day- 1 to 0.0436 day- 1; it was not possible to establish a tendency between them, related to the age or presence of sediment. The results indicated that, in the Óleo Lagoon, during aerobic decomposition within the upper layers of sediment, the benthonic oxygen demand did not necessarily increase by the higher presence of microorganisms and nutrient availability. The oxygen consumption rate constants from mineralization of S. auriculata detritus were similar, regardless of the presence of sediment, but younger detritus consumed more dissolved oxygen than older detritus.
Key-words: aerobic process, aquatic macrophytes, decomposition, fibers.
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