DYNAMICS OF MICROBIAL GROUP' ABUNDANCES IN LAKE SEVAN: A COMPARISON OF CYANOBACTERIAL ASSEMBLAGE TO HETEROTROPHIC BACTERIA.

The modern state of microbiological community of Lake Sevan pelagic water is characterized. We analyzed the data using methods accepted in hydrobiology. The tendencies of saprophytes and cyanobacteria total amount correlation changes within the water column of the lake were studied. Decreasing bacterial number over last years (2009-2010) in Lake Sevan waters was established. The comparatively high bacteria consist within surface and bottom layers of lake water column were noticed. Cyanobacterial community structure was examined. The dominance of certain cyanobacterial taxa was shown over the entire period of investigations. The highest values of cyanobacterial abundances were observed for surface or bottom layers mainly in late summer season. The possible impact of cyaonobacterial blooms on saprophytes development was assessed over the last years (2005-2010) in Lake Sevan waters. Our investigations have revealed no significant relationship between saprophytes and cyanobacterial composition over the entire period of study. Neither seasonal no depths relation was observed, except for some months and depths when observed certain positive or negative interaction was not considered as a relationship existence. In conclusion, negative or positive relationship observed between those microbial groups, at least in midsummer, those interactions seemed to be associated with either sufficient nutrition upload or temperature gradient. [ABSTRACT FROM AUTHOR]