SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 9:45:00 AM
Location: Carson B
 
FischerH, Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, fischer@igb-berlin.de
Kloep, F, , Technical University Dresden, Dresden, Germany, fkloep@web.de
Wilczek, S, , Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, wilczek@igb-berlin.de
Pusch, M, , Institute of Freshwater Ecology and Inland Fisheries, Berlin, GERMANY, pusch@igb-berlin.de
 
MICROBIAL TRANSFORMATIONS OF CARBON AND NITROGEN IN THE HYPORHEIC ZONE OF A LARGE LOWLAND RIVER (ELBE, GERMANY)
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Microbial activities in the sediments of large lowland rivers are largely unknown despite of their potential role for biogeochemical budgets. We used a diving bell to get access to the shifting sediments in the central channel of a lowland river, which enabled us to sample several depth layers down to 1 m sediment depth. Bacterial abundance, production, and potential activity of a set of extracellular enzymes were measured as well as potential nitrification and denitrification rates. Temperature logger recordings were used to estimate hydraulic exchange between river water and interstitial water. Interstitial oxygen content was measured using a reinforced microoptode. We found depth gradients of microbial activity which were controlled by sediment structure, hydraulic conditions, and supply with organic carbon, nitrogen, and algae. High bacterial production and extracellular enzyme activity were sometimes found down to the deepest sediment layers investigated. By its large inner surface area and its connectivity with the surface water, even the central part of a large river is microbially highly active and may influence carbon and nitrogen cycling in the running water system.