Vertical Distribution of Bacterioplankton in Dolnoto Lake—Seven Rila Lakes

ABSTRACT

Temporal and vertical distribution of bacterial abundance (BA) was studied in the high mountain Dolnoto Lake (max depth 11.0 m), the lake at lowest elevation (2 095 m a.s.l.) from the system of the Seven Rila Lakes. The research was performed in July and September, both in 2006 and 2007. Bacteriological analysis was completed with measurements of selected physicochemical parameters such as temperature, oxygen, pH, and inorganic nitrogen and phosphorous concentrations. BA was higher in 2007 (on average 93.92 x 10⁵ cell ml⁻¹), especially in Julq (121.56 x 10⁵ cell ml⁻¹) than in 2006 (on average 17.48 x 10⁵ cell ml⁻¹). The vertical distribution of bacteria depended on temperature, pH and PO₄-P, and the most abundant was the subsurface layer of water column in most of the sampling occasions. Bacterial communities from the different vertical layers had different metabolic profiles (EcoPlates Biolog). The lowest physiological diversity was recoded for the subsurface bacterial community.

Keywords:

• bacterioplankton
• control of bacterial vertical distribution
• high mountain lake