THE BLACK SEA 413 



Table 163. Biomass of micro-organisms, phytoplankton 

 and zooplankton in the eastern part of the Black Sea 



Mean biomass 

 Location throughout the Sea, mg 



Mean biomass per 1 m 3 in the to 

 200 m layer 20 



Mean biomass per 1 m 3 in the 200 

 to 2,000 m layer 40 



Total biomass of micro-organisms 



beneath 1 m 2 of the sea surface 74,050 



Same for phytoplankton 11,600 



Same for zooplankton 36,800 



method of lowering glass slides to different depths and counting the number 

 of bacterial cells at definite time intervals. The average daily PjB coefficient 

 (ratio of production to biomass daily) is determined on the basis of these 

 observations. For the daily exposure of slides in the open part of the Sea an 

 average PjB coefficient of 0-2 to 0-7 was obtained. Similar indices have been 

 found for the Caspian Sea and the Arctic Ocean. The highest average daily 

 PI В coefficients have been recorded in the Pacific Ocean (the daily gain in 

 weight being about 80 per cent). Kriss gives the annual PjB ratio for the active 

 photosynthetic layer (0 to 50 m) in the Black Sea as 58-4, and for the hydrogen 

 sulphide zone — 29-2. 



A. Kriss (1958) has also attempted to determine the total mass of micro- 

 organisms in the water of the Black Sea and the order of magnitude for the 

 mineralization of the organic matter resulting from their activity. For the 

 active photosynthetic layer (0 to 50 m) this value is 6-5 mg/m 3 , approximately 

 0- 1 per cent of the average content of organic matter in the Black Sea waters. 

 Deeper down, at 50 to 125 m, the concentration of micro-organisms is more 

 or less constant and equal to about 7 mg/m 3 , while the value for organic 

 matter mineralization at this depth is about 1 mg/m 3 . 



A. Kriss (1958) comes to the following conclusion as a result of his com- 

 prehensive analysis: 'The synthesis of organic matter in the form of micro- 

 bial cells proceeds on a large scale in the Black Sea at the price of carbon 

 dioxide assimilation ; the amount of organic matter formed as a result of 

 autotrophic nutrition of micro-organisms is greater than that produced 

 through photosynthesis by the organisms of the oxygen zone. If the amount 

 of organic matter produced by phytoplankton throughout the whole Black 

 Sea comprises 4,000,000 tons (59 mg/m 3 x 67,594 km 3 of the oxygenated zone), 

 then the total mass of organic matter in the form of autotrophic (filamentary) 

 micro-organisms is more than 15 million tons (33 mg/m 3 x 462,360 km 3 of 

 water in the hydrogen sulphide zone). Thus, the complete mineralization of 

 dead organic matter, the regeneration of biogenic compounds in the form 

 required for aquatic plant nutrition, the synthesis of organic matter from 

 inorganic compounds and direct participation in nutrient chains constitute 

 the manifold activities of micro-organisms in the creation of biological and 

 in particular commercial productivity of seas and oceans.' 



