[Microbiological processes in the mromictic lake Vae de San Juan in Cuba]

The lake was studied in April and July of 1973. Gleothece prevailed in mixolimnion and green sulphur bacterium Pelodyction phaeum in the layer of pink water down to 10 m. The production of photosynthetic suphlur bacteria comprises 3% of the production of algae. Sulphate reduction takes place mainly in water beyond the layer of sulphur bacteria. The content of hydrogen sulphide in monimolimnion is 104 mg/litre. Bacteria utilize, at the account of photosynthesis, 40% of produced hydrogen sulphide. Three maxima in the bacterial content in water have been registered: (a) at a depth of 7 m; (b) in the layer of pink water, at a depth of 10 m; (c) at the bottom. Total mineralization and electroconductance of water at the bottom are higher by a factor of 6 than those at the surface. Destruction of organic substance is higher than its production a little.