Chapter 36 



Distribution and Ecology of Azotobacter 

 in the Black Sea 



L. N. PSHENIN 



A he study of the productivity of a sea inckides the quantitative 

 calculation of organisms and the revealing of the dominant forms 

 playing an important role in those or other processes of the cycle 

 of substances (10). Nitrogen fixation in a sea, one of the most 

 important processes, has been studied little from the quantitative 

 and qualitative points of view. The aim of the present investiga- 

 tion (1955-1960) was to characterize the distribution and ecology 

 (in their principal features) of Azotobacter and Clostridium in 

 different regions of the Black Sea. In this article the materials 

 on Azotobacter are mainly examined. At the same time nitrogen- 

 fixing ability was studied in some other forms of microorganisms 

 which usually developed in the elective (for Azotobacter) media 

 inoculated by sea water. 



MATERIALS AND METHODS 



Our observations for the distribution of Azotobacter were 

 carried out at 90 stations in different regions of the Black Sea, 

 and in the west half of the sea in Februaiy 1956 they were 

 carried out synchronously with the observations for the distri- 

 bution of phytoplankton (3) at the same stations and depths. 

 In shallow-water and in the surface layer, samples of the water 

 were collected by a sampler supplied with sterile flasks; but in 

 the deep-water regions 10 to 2000 m, they were collected by a 

 batliometer. One hundred sixty samples of water taken at 30 

 stations were examined. Samples of the sediment were collected 

 by a bottomgrab or by a corer at 44 stations. Thallus {PhyUo- 

 phora) was collected from industrial trawls at 16 stations in the 

 Zernov Phyllophora field. Coastal algae (Uha, Cistoseira and 

 Enteromorpha ) were also examined. The number of bacteria was 



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