Formation of sulfur bacteria (probably Beggiatoa) in the top of column 2 (column that was placed in the dark).
Patchy formation of purple and green sulfur bacteria. It is uncertain why this column developed such patches, and it is interesting that this column also exhibited low concentrations of H2S and CH4 as compared to the
other columns.
Column 5, which received glucose, developed a hard mat or biopolymer at the air-water surface. The water in this column became anaerobic and stayed that way during all sampling.
The formation of iron sulfides (FeS) in Column 6 causes the sediments in this column to be black. Only this column was amended with Fe (see
Treatments).
Purple and green sulfur bacteria are evident in several columns, but are most pronounced in Column 7, shown here. These anaerobic bacteria are phototrophic, but use H2S as an electron donor instead of H2O.