Significance of Microorganisms of Upper Sediment Layer 1\1 



rivers) the stratification is still more stable; this causes continuous 

 oxygen impoverishment in nearbottom layers. On the basis of 

 these observations an experiment was developed on the regenera- 

 tion of biogen microelements under inhibited oxygen conditions 

 near the silt surface. 



The Taganrog Bay argilaceous silt was taken as a sample. 

 The salinity of the initial water samples was 6.5%c. The volume of 

 samples was about 5 liters, the silt layer— 5-10 cm. The experi- 

 ment lasted 10 days under tlie conditions of artificial depletion of 

 oxygen. The samples were analysed for the content of O^, NO 2, 

 NH4'^, NO3", PO"4 and pH. The total number of bacteria and the 

 number of putrefactive bacteria on the mud-water interface were 

 determined. Some samples were kept without silt to reveal its 

 significance in providing the nearbottom water with bio-micro- 

 elements. The results of the experiment showed that bottom silt 

 brings about a more even distribution of microorganisms in time 

 (in the course of 10 days experiment); silt contributes to a 

 "buffering ability" of the bacterial medium. The presence of silt 

 leads to the increase of the content of phosphates in water be- 

 cause of the regeneration of phosphates from the compounds 

 contained in bottom silt. The pH, in the silt - containing samples, 

 was 0.2-0.5 lower than in those without silt owing to an extra 

 elimination of CO-. Saprophytic bacteria did not differ in number 

 eitlier in silt- devoid or silt- containing samples. The increase in 

 the content of NH4^ is in parallel with the increase in the total 

 number of bacteria. This fact and the one cited above on the 

 number of saprophytic bacteria not increasing in silt- containing 

 samples, gWe some reason to think that along with the processes 

 of nitrification an active process of dentrification takes place re- 

 sulting in the elimination of NIL, the later being bound by anions. 



On the third and sixth days of the experiment the number 

 of bacteria and NH4" showed a marked increase. After that the 

 content of NH4^ begins to fall, simultaneously accompanied by a 

 reduction of the total number of bacterial cells and an increase in 

 amount of oxygen. 



At this time, the oxidation of tlie organic substance is gener- 

 ally terminated and replaced by the beginning of the nitrification 

 of ammonium. This regularity is clearly seen in Figiu'e 1. 



