engleski

Vertical structure of microbial community in eutrophic meromictic saline lake

Vertical variations of autotrophic picoplankton (cyanobacteria), heterotrophic bacteria, pigmented and non-pigmented nanoflagellates, bacterial activity, and their relationships with the vertical gradients of temperature, salinity and oxygen were studied in a small, intensely eutrophicated sea-lake Rogoznica (eastern Adriatic Sea) in April and May 2004. It was noted that vertical patterns of the microbial components of the lake food web were strongly influenced by the gradients of physical and chemical factors. The pattern of cyanobacterial vertical distribution tightly followed the distribution pattern of oxygen concentration. The variations of heterotrophic filamentous cells exhibited similar patterns to that of HNAN distribution, pointing to the ecological importance of the elongated cells. High values of heterotrophic bacteria numbers, as well as high numbers of flagellates were always found in the picnocline zone. Numbers of high DNA-content cells and the bacterial production coincided with the chemocline layer, where high concentrations of dissolved organic carbon were present. Bacterial community in the chemocline layer was represented by higher proportions of high DNA-content cells, but with a rather low bacterial production per cell. In the surface layers, bacteria were less abundant but had a very high production per cell.

Bacteria; flagellates; cyanobacteria; bacterial production; Rogoznica Lake; vertical distribution

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