Abstract
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.
Highlights
In tropical aquatic systems, the growth of aquatic macrophytes is usually favored by high temperatures and intense solar radiation (Silva and Esteves, 1993; Camargo and Esteves, 1995)
The tissues of aquatic macrophytes are constituted of fibers (i.e. corresponding mainly to particulate organic matter (POM), soluble organic
This study aimed at describing the kinetic from oxygen uptake and carbon mineralized during aerobic decomposition of detritus; it compares the decomposition rates and their relationship with the molecular and elemental composition of the detritus by assessing the consumed oxygen from seven aquatic macrophytes (Cabomba furcata Schult. and Schult. f. (1830), Cyperus giganteus Vahl (1805), Egeria najas, Planchon (1849) Eichhornia azurea (Swartz) Kunth (1843), Salvinia auriculata Aubl. (1775), Oxycaryum cubense (Poepp. and Kunth) Lye (1971) and Utricularia breviscapa Wright ex Griseb. (1866))
Summary
The growth of aquatic macrophytes is usually favored by high temperatures and intense solar radiation (Silva and Esteves, 1993; Camargo and Esteves, 1995). Under these conditions, high rates of primary production of macrophytes support trophic food chains and the energy flow of several aquatic ecosystems (Schlickeisen et al, 2003). When an imbalance between primary production and herbivory exist, most of the photosynthetic production is channeled through the detritus food web. The decomposition of macrophyte detritus depends upon molecular composition (e.g. cellulose, lignin and hemicellulose) and the microbial metabolism food web interactions are relevant. The tissues of aquatic macrophytes are constituted of fibers (i.e. corresponding mainly to particulate organic matter (POM), soluble organic
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