Kolar, I. E. University of Vienna, a8305211@unet.univie.ac.at
Brugger, A. E. University of Vienna, a8940639@unet.univie.ac.at
Reitner, B. University of Vienna, a8756796@unet.univie.ac.at
Qučric, N. V. University of Vienna, a8902172@unet.univie.ac.at
Herndl, G. J. Netherlands Institute For Sea Research, herndl@nioz.nl

 
TEMPORAL AND SPATIAL DISTRIBUTION OF BIODEGRADABLE DOC IN THE HYPORHEIC ZONE OF AN OLIGOTROPHIC RIVER AND ITS ADJACENT GROUNDWATER
 
In bio-assay experiments, bacterial utilization of hyporheic and groundwater DOC was investigated over an annual cycle. Bioavailability of DOC was operationally defined as the DOC-fraction removed (BDOC) by bacteria within 30 d. Total DOC and BDOC concentrations were highest during winter. The contribution of BDOC to the total DOC pool decreased with increasing temperature and was lowest in April. This distribution pattern of BDOC and data from incubations performed at in situ temperature (4 C) and at 20 C, respectively, indicate an accumulation of BDOC during the winter due to temperature-limited activity of the subsurface bacterial community. On a spatial scale, most of the BDOC entering the river bank was removed within the first few centimenters while the recalcitrant fraction of the DOC pool decreased only slightly with depth. On average, the BDOC contributed 10-25 % to the total DOC in the surface layers of the sediment and declined to 0-3 % of the total DOC in deeper layers. This indicates efficient removal of BDOC by the bacterial community close to the surface while the observed bacterial actvity in the deeper layers cannot be explained by the utilization of the low concentration of the BDOC present. In deeper layers, we suggest that bacteria-mediated hydrolysis of POC is the main source for bacterial metabolism.
 
Day: Tuesday, Feb. 2
Time: 09:15 - 09:30am
Location: Eldorado Hotel
 
Code: CS56TU0915E