190 Marine Microbiology 



TABLE 1 

 pH- and rHj- Values in Relation to the Bacterial Plate 



10 cm Above U'ithin the Plate 10 cm Below the 



General the Plate Surface of the Mud 



Conditions pH rHt pH rH. pH rHt 



Limnic 6.7-7.6 25-32 6.6-7.2 10-22 6.3-6.8 6.1-6.3 



Marine 7.5 25-32 7.2 21 6.6 5.2 



The contents of H2S above the plate were ± and in water 

 below the plate 3-27 mg/L. The highest concentrations, up to 

 80 mg/L, have been found within the sediment. In aquaria with- 

 out a bacterial plate, we have observed only a small shift of the 

 values near the mud-surface, and the waterbody remained under 

 reducing conditions (compare Fig. 3, Eh, pH and rH2 before 

 adding iron and copper salts). In other aquaria the shifting at 

 the surface of the sediment was higher and the conditions within 

 the water were aerobic. 



Sulphureta may have a geomicrobiological importance at 

 least for two geological processes, (a) sulfur deposition and 

 genesis of sedimentary sulfur beds, (b) precipitation of iron, 

 copper and other heavy metals as sulfides and genesis of sedi- 

 mentary sulfidic ores. An example for (b) are the copper shales 

 of Mansfeld westward of Halle and southward of the Harz 

 mountains, Gennany. Pyrite, Bornite and other minerals are 

 embedded in dark bituminous shales of the Zechstein fomiation. 

 The sediments have been settled in a shallow basin of salt water, 

 the Zechstein Sea. 



In relation to this process, we have studied the influence 

 of iron and copper salts upon the biotope and the biocenosis, 

 both under marine and limnic conditions. We have added (over 

 four days) to the surface of the water, drop by drop, 1 per 

 cent solutions, of 3gm CuSO--5 H2O and 4gm FeCb-6 H.O to 

 each volume of 20 L water (a) undisturbed bacterial plate, 

 and (b) with slowly stirring so that the waterbody has been 

 mixed and the bacterial plate disappeared. The store of H2S 

 in the water was consumed, and important modifications took 

 place within a short time. 



