Redox-Conditions and Precipitation of Iron and Copper 189 



Fig. 1. Bacterial plate (about ^2 natural size). 1) surface of the sediment. 



2) purple sulfurmicrobes from an earlier niveau of the plate, now adhering 



to the wall of the aquarium. 3) bacterial plate, floating in the water. 



MUD- LAYER 



WATER- COLUMN 



Fig. 



2. Redox-conditions and bacterial plate (Aquarium no. 1/marine), 



