DAY-TO-NIGHT ACTIVITY OF BACTERIA IN THE SURFACEMICROLAYER OF EUTROPHIC LAKE

摘要

This study examined changesof bacteria numbers in the surface microlayer(SM) and subsurface water (SW) of a lake duringa day- and night-time. The research also address-es the synthesis of DNA and cell protein as well asthe activity of cellular dehydrogenases dependingon time of the day. Results demonstrated that inspring and summer the numbers of bacteria (percm') in the SM was significantly greater duringnight-time than day-time (average: May, day-time - 30.058 x 10~6, night-time - 71.343 x 10~6;July, day-time - 10.801 x 106, night-time - 40.353x 10~6). In October, numbers of bacteria in day-and night-time were not statistically different (re-spectively: 5.841 x 10~6and 3.664 x 10~6). Results indicated also that the rate of DNAsynthesis by SM bacteria was much higher in thenight-time (average: May - 2.049 x 10-6 pg h-'cell-'; July - 1.363 x 10~(-6)pg h~(-1)cell~(-1)), than in theday-time (average: May - 0.7263 x 10~(-6)pg h~(-1)cell~(-1); July - 0.3404 x10-6pg h~(-1)1)). In con-trast, in October the values of DNA synthesis bySM bacteria were higher in night-time. These changes are significantly smaller in SWat a depth of several dozen centimetres. However,no significant impact was observed of a time ofthe day on the activity of protein synthesis andactivity of cellular dehydrogenases by bacteria in-habiting SM and SW.