Site 1149 is a deepwater site characterized by very low sedimentation rates and probably low organic matter concentrations. The lack of geochemical evidence for high levels of sulfate reduction supports the view that organic carbon arriving on the seafloor is of insufficient quantity or quality to fuel rapid sulfate depletion by bacterial sulfate reduction. This is in agreement with the consistently low bacterial populations. However, other geochemical evidence suggests some limited bacterial turnover of carbon is occurring throughout the sediment column, with increases in ammonium and the production of bioavailable acetate. These changes in the geochemical profiles occur with increases in reduced manganese in the interstitial water, demonstrating that active bacterial manganese reduction may be an important process, to considerable depths, at this site. It is interesting that manganese and sulfate reduction and limited methanogenesis seem to be occurring together at this low-organic matter site. This is in stark contrast to the predicted sequential separation of these bacterial activities on thermodynamic grounds, which are often observed in shallow-water sediments (Jørgensen, 1983). These bacterial activities together can provide energy to support the small deep bacterial population detected by direct microscopy at Site 1149.