Chapter 66 



Significance of Microorganisms of Upper 



Sediment Layer of Shallow Water Basin 



in Transformation of Organic Matter 



A. I. Zhukova and M. V. Fedosov 



A he chemical conditions of shallow water basins are detemiined 

 to a considerable degree by the biochemical processes which take 

 place in the upper sediment layer. 



Our southern basins, such as the Azov and North Caspian 

 Seas, are characterized by a rapid turnover of organic substance, 

 i.e., its production in the form of phytoplankton during "bloom- 

 ing," and then dying off and rapid decomposition under high 

 temperature conditions in summer. 



The intensity of the process of photosynthesis in these basins 

 is very great. According to previously obtained data (3) phyto- 

 plankton in the Azov Sea in spring, summer and autumn periods 

 produces on the average from 280 to 340 mg of organic substance 

 per twenty-four hours. 



As is known from the work of Gorshkova (6), the organic 

 substance produced by phytoplankton is very unstable and 

 rapidly decomposes. The experimental investigation of the de- 

 composition rate of blue green algae showed that one day after 

 death of the vegetable cells, the water gets about 20 per cent of 

 their phosphorus and 30 per cent of their nitrogen, the decomposi- 

 tion of the phytoplankton being completed on the whole within 

 five days. Similar data were previously obtained by Skopintsev 

 (10) in the course of an experiment with fresh water plankton. 

 Dead planktonic organisms sinking slowly to the bottom begin 

 to decompose in the water column. 



According to the calculations made by Skopintsev (10) the 

 nannoplankton, with an average diameter of 50 /x (m = micron), 

 sink on to the bottom at the rate of 1.9m per day at t° = 22 C (S 



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