Bacterial Populations in Deepwater Low-Sedimentation-Rate Marine Sediments and Evidence for Subsurface Bacterial Manganese Reduction (ODP Site 1149, Izu-Bonin Trench)

摘要: Bacterial distributions were determined at Site 1149 in the Izu-Bonin Trench, which is a deepwater (5818 m) low-sedimentation-rate area. This was first Ocean Drilling Program (ODP) leg where contamination checks conducted for microbiology. These demonstrated that inner portion of cores, microbiological samples taken, free from any potential sampling contamination. populations present all (deepest 171.2 meters below seafloor [mbsf]). The highest numbers near surface (1.4 mbsf; 7.2 °— 106 cells/cm3), but these declined rapidly within upper 10 mbsf. Below this, decreased more gradual rate to 105 cells/cm3 172 mbsf, 10-fold reduction. two-stage bacterial depth distribution has been observed several other ODP sites (e.g., Amazon Fan and Santa Barbara Basin). this site well those predicted by general equation global deep-sediment bacteria predominantly lower 95% prediction limits. low thought reflect sedimentation rates input bioavailable organic matter characteristic sites. Consistent with trend there only limited removal pore water sulfate and, thus, Most top ~5 coinciding populations, presence small amounts methane, an increase manganese ammonia. In deeper sediments, however, still indirect evidence continuing activity, increases ammonia, soluble manganese, acetate, decreasing sulfate. Interestingly, reduction, amount methanogenesis seemed be occurring simultaneously low–organic site, coincident detection provides further support universal deep biosphere marine sediments.