SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 11:15:00 AM
Location: Carson B
Preisler, A, , MPI for marine microbiology, Bremen, Germany,
WieringaEB, MPI for marine microbiology, Bremen, Germany,
Lavik, G, , MPI for marine microbiology, Bremen, Germany,
Jorgensen, B, B, MPI for marine microbiology, Bremen, Germany,
Role of Beggiatoa spp. in the N-cycle of coastal sediments
Beggiatoa are filamentous colorless sulfur bacteria that are among the largest known bacteria (up to a centimeter long with 200 micrometer cell-width). They are able to glide through the sediment into their favored environment, consisting of opposing oxygen-sulfide gradients. A remarkable characteristic is their ability to store nitrate in vacuoles up to 10E5-fold the nitrate concentration of the overlying water. Until now it is unclear which role these bacteria play in the N-cycle of sediments. We determined Beggiatoa biomass in different marine intertidal sediments, ranging from 0.1 - 27 g/m2. We found that high Beggiatoa biomass correlates artificially with high pore-water nitrate concentrations when the sediment has been frozen for storage purpose. This procedure breaks the cells, thus releasing the internal stored nitrate. Sediment cores taken by scuba divers allowed sampling of adjacent sediments (within 0.25 m2) with differently colored surfaces. A sediment with a dark surface had almost a five-fold higher biomass than one with a lighter colored (probably oxidized) surface. On the other hand, we found that areas with visible white Beggiatoa mats must not compulsory have a higher biomass than other sulfidic sediments.