Abstract
Dissolved organic carbon (DOC) is nowadays recognized as the main substrate and source of energy for aquatic microbial community. The great part of available organic carbon for bacterioplankton might be formed after photolytic degradation of humic material, which constitutes the major part of DOC in almost all natural waters. The effects of DOC photo-degradation were evaluated, as was its utilization by bacterioplankton, through a two-step experiment, one involving photo-degradation of DOC and the other bacterial growth on the photo-degraded substrate. Photo-degradation was responsible for the consumption of 19% of DOC, reduced SUVA254, an increase in the E2/E3 and E3/E4 ratios, in addition to modifications in the fluorescence spectra that indicated a rise in the labile fraction of DOC. However, these alterations on DOC were not reflected in differences in bacterioplankton growth, as shown by the fact that there were no significant differences in density, biomass, bacterial production, bacterial respiration and bacterial growth efficiency between treatment and control.
Highlights
The importance of organic carbon in aquatic environments was for a long time restricted to its interactions with metals and its relationship with ecosystem stability (AZAM et al, 1983; STEINBERG, 2003), being considered biologically inert
The role of bacteria in this route is to turn dissolved organic matter lost from the herbivorous food web into particulate organic matter, which can be assimilated by protozooplankton (AZAM et al, 1983)
This study aimed to evaluate the effects of photo-degradation on dissolved organic carbon (DOC), and bacterioplankton growth utilizing photo-chemically degraded DOC as a substrate, in a humic lake from the upper Paraná river floodplain
Summary
The importance of organic carbon in aquatic environments was for a long time restricted to its interactions with metals and its relationship with ecosystem stability (AZAM et al, 1983; STEINBERG, 2003), being considered biologically inert. The role of bacteria in this route is to turn dissolved organic matter lost from the herbivorous food web into particulate organic matter, which can be assimilated by protozooplankton (AZAM et al, 1983). In this way, the bacterial community plays a fundamental role in the aquatic trophic chains and has great importance in the biogeochemical processes, even on a biosphere level (COTNER; BIDDANDA, 2002)
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