11:30 AM - 11:45 AM
[BBG02-09] Mn(II) oxidation processes at the surface of microbially colonized manganese deposits
At Sambe hot spring, manganese oxides (ca. 1 cm thick crust) develop at about 150-200 m downstream from the vent site, and exhibit 1) an alternation of manganese and iron oxides (site 10.5), 2) a mixture of manganese oxide and calcite (site 11), and 3) a two-layer structure of manganese oxide and calcite (site 12.5). 16S rDNA analyses detected clones closely related with known manganese-oxidizing bacteria from all sites, and cyanobacteria from sites 11 and 12.5. To also taking the results of microelectrode measurements (pH, O2, Mn(II), and Ca2+) into account, the manganese oxides are primarily formed by microbial direct process at site 10.5, and by microbial direct and indirect processes at sites 11 and 12.5. Microelectrode measurements of formaldehyde-treated samples also demonstrated that the contribution of inorganic process was negligible.