HR: 11:20h
AN: B12B-05    [Abstracts]
TI: Benthic Microbial Response to Varying Organic Matter Inputs: An In-Situ Labeling Study in the Deep Sea
AU: * Aspetsberger, F
EM: aspets@uni-bremen.de
AF: University of Bremen, Klagenfurter Strasse, Bremen, 28334 Germany
AU: Ferdelman, T
EM: tferdelm@mpi-bremen.de
AF: Max Planck Institute, Celsiusstrasse 1, Bremen, 28359 Germany
AU: Witte, U
EM: uwitte@mpi-bremen.de
AF: Max Planck Institute, Celsiusstrasse 1, Bremen, 28359 Germany
AU: Zabel, M
EM: mzabel@uni-bremen.de
AF: University of Bremen, Klagenfurter Strasse, Bremen, 28334 Germany
AB: Particulate organic carbon (POC) arriving at the sea floor has been altered during vertical transport from surface waters, lateral transport along the continental slope or resuspension in the benthic boundary layer. Both availability and quality (reactivity) of POC play key roles for microbially mediated organic carbon turnover, thereby being critical for carbon cycling and transfer through the ocean. The export rate of POC is not a continuous process but strongly pulsed. To investigate the influence of POC quality on the benthic turnover rates, a series of in situ-experiments was carried out in the Benguela Upwelling Region (SW-Africa). Using a benthic chamber lander, we investigated the response of the sediment community on pulsed supplies of fresh and degraded $^{13}$C-labeled phytodetritus. Sediment community oxygen consumption (SCOC) and bacterial secondary production (BSP) did not differ significantly between the experimental treatments, showing that the artificial input did not alter the biogeochemical station characteristics. However, clear differences in benthic response were observed when following the added $^{13}$C-label. The mineralisation of the added material was 1.8 to 12.8 times higher for fresh than for altered phytodetritus. Highest recovery of label occurred at the sediment surface, with single indication for non-local transport within the uppermost 4cm of sediment. Following evidence that macro- as well as microorganisms play a major role in the early diagenesis of POC, label incorporation into macrofauna and bacterial fatty acids (PLFAs) was investigated. PLFA data suggest the presence of considerable numbers of sulphate-reducing bacteria, which displayed lower incorporation rates of added label relative to aerobic bacteria in comparable studies. The pathways for carbon cycling as well as the involvement of different benthic compartments seem to depend on the quality of POC arriving at the seafloor, thereby closely coupling its sources and transport to its diagenetic degradation via a biological link.
UR: http://www.rcom-bremen.de
DE: 4804 Benthic processes/benthos
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
DE: 4870 Stable isotopes
DE: 4803 Bacteria
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting