The mean SOC values in three lakes are given in Figure 3. In the meso- 

 trophic waters of Lakes Naroch, the seston SOC was the highest averaging 

 0.062 mg 02/mg organic matter per day for the vegetation season. With an 

 increase in the trophic status, the SOC notably decreases, reaching a 

 level of 0.036 mg 02/mg/day in eutrophic Lake Myastro, and 0.016 mg 02/mg/ 

 day in ultra-eutrophic Lake Batorin. 



The SOC of seston with a greater fraction of allochtonous organic mat- 

 ter as a result of sewage pollution is demonstrated by studies of the 

 Svisloch River. In clean waters of this river, the SOC made up 0.08 mg 

 02/mg of organic matter per day. In polluted portions, the value 

 obtained was 0.147 mg 02/mg of organic matter per day. A similar SOC 

 value (0.13 mg 02/mg/day was observed for a polluted part of the Dnieper 

 River. 



In general, the data suggests that concentrations of SOC in unpolluted 

 waters range from 0.01 - 0.10 mg 02/mg of organic matter per day. In the 

 presence of easily degradable allochtonous materials, the SOC values asso- 



Figure 3. Specific Oxygen Consumption (SOC) by seston in three 



representative lakes. 



154 



