712 Marine Microbiology 



— 35% c ) . Taking into account the fact that the density of water in 

 the Azov and North Caspian Seas is much less than that for wliich 

 the above calcuhitions were made, it is easily understood that 

 plankton particles will sink much more quickly. At the shallower 

 depths which are observed in the North Caspian and Azov Seas 

 (maximum 15 m, average 5-6 m) plankton particles reach the 

 bottom with three to four days under ideal conditions of calm. 



Despite the fact that a certain part of the dead organic sub- 

 stance decomposes, as has already been said, in the water column, 

 not only hard-to-decompose compounds are found on the sedi- 

 ment surface, but also labile organic molecules, the latter mainly 

 from benthic organisms. 



Table 1 shows the initial decomposition of the components 

 of plankton. 



TABLE 1 



Composition of Organic Matter of Plankton and the Surface Sediments 



OF Bei.oye Lake (From the Data of Speranskaya [14]) 



Quantity of Quantity of 



Decomposed Stable 



Substance Substance 



ni I , jj^iQuj of Plank- which 

 rlankton Upper iiilt Layer ' 



p^. n^^t -Til nil 4„j ton in Per Passed 

 Per Lent I otal Calculated 



Dry Percent as Plank- Cent of the into 



Weight ton Ash ^"'''«' Sediments 



Quantity in Per Cent 



Hemicellulose decomposes most rapidly; lignin-liumus com- 

 plex-most slowly. 



According to the data of Gorshkova ( 6 ) on the total amount 

 of carbon in sediments of the Azov Sea and Taganrog Ba\', the 

 carbon of sugars and hemicellulose constitutes up to 5-10 per 

 cent; the carbon of cellulose: 4.6-14 per cent; the carbon of 



