Abstract
This study aimed at describing the kinetic aspects of glucose aerobic mineralization by different types of microorganisms selected by filtration membranes of different pore sizes: 0.22, 0.45, 2.2 and 7.4 μm, and also in glass wool. Water samples were collected from Oleo Lagoon (21o36´ S and 47o49´ W). About 30 mg of glucose was added into filtered water, and the samples were incubated in the dark at 21oC under aerobic conditions. The dissolved oxygen consumption was determined periodically during 59 days (polarographic method; DOmeter YSI model 58). The data were fitted into a first-order kinetic model. The maximum values of consumed oxygen varied from 2.10 mg L -1 (pore size 0.22 μm treatment) to 32.83 mg L -1 (pore size 0.45 μm treatment). The glucose mineralization on the 0.22 μm treatment showed the lowest oxygen consumption coefficient k d = 0.03 day -1 and half time (t 1/2 ) = 23 days) and the highest value was observed on the 0.45 μm treatment and 2.2 μm treatment (k d = 0.08 day -1 and t 1/2 = 9 days). Oxygen consumption was higher in the sample filtered into 0.45 μm, suggesting that bacterivory occurred in treatments with glass wool, 2.2 and 7.4 μm. The filtration into 0.22 μm pore size membranes favored chemical oxidation.
Highlights
Detritus can be defined as any form of nonliving organic matter found as particulate (POM) and dissolved organic matter (DOM) (Moore et al, 2004)
The kinetics of oxygen consumption from the aerobic mineralization of glucose submitted to fractionation in distinct pore size membranes and glass wool are shown in Figure 1, from which the oxygen uptake deriving from water samples from Óleo Lagoon was subtracted
COmax for all 59 days of experiments ranged from 2.10 mg L-1 to 32.83 mg L-1
Summary
Detritus can be defined as any form of nonliving organic matter found as particulate (POM) and dissolved organic matter (DOM) (Moore et al, 2004). The detritus stabilizes both energy flux and transfer efficiencies across trophic levels (Azam, 1998). DOM consists of various fractions such as humic and non-humic compounds and low and. High molecular weight components (Benner, 2002; Hansell, 2002) whose dynamics and characteristics influence a number of key processes, including the control of nutrient availability and element and energy cycling (Currie et al, 1996; Williamson et al, 1999). In aquatic ecosystems the dissolved organic matter is composed of two fractions: (i) the readily utilizable DOM or labile pool and (ii) the refractory DOM that are not utilized (Geller, 1986)
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