Intensity of mineralization in the hyporheic zone of the prealpine river Ba?a (West Slovenia) |
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Authors: | Tatjana Sim?i? Nata?a Mori |
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Institution: | (1) National Institute of Biology, Večna pot 111, 1001 Ljubljana, Slovenia |
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Abstract: | Respiratory electron transport system (ETS) activity and oxygen consumption in the interstitial water, and in the fine (i.e.
silt) and coarse (sand) sediment fractions from the hyporheic zone of the prealpine river Bača (W Slovenia) have been measured
in order to estimate the intensity of potential and actual carbon mineralization through microbial communities. Hyporheic
samples from the river bed (RB) and gravel bars (GB) were compared. ETS activity and oxygen consumption of all fractions from
the RB did not differ significantly from those from the GB. ETS activity and oxygen consumption of biofilm attached to 1 g
of the silt were higher than of that attached to the same mass of the sand. A significant correlation between ETS activity
and oxygen consumption indicated that the former should be a good indicator of intensity of bioactivity in hyporheic sediments.
The ratio of ETS activity to oxygen consumption (ETS/R ratio) revealed that the oxygen consumption of microorganisms is responsible
for approximately 60% of the metabolic potential in the hyporheic sediments. The contributions of different fractions of sediment
to the total ETS activity differed between RB and GB. The contribution of microorganisms in the interstitial water and silt
was higher in GB than in the RB, but the sand fraction contributed less to potential carbon loss in GB than in the RB. Average
total respiratory carbon loss per volume through the hyporheic zone was higher in the RB than in GB. The main reasons suggested
are the different intensity of exchange of surface water with the hyporheic zone, and the rate of consolidation of sediments,
which is primarily a function of river hydrology and geomorphology.
Handling editor: J. Padisak |
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Keywords: | Hyporheic sediments ETS activity Oxygen consumption ETS/R ratio |
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