Biopolymers from marine microorganisms offer numerous new materials, which can be used in commercial applications. Marine enviroment proved to be a promising field to discover new natural products. The aim of this thesis was to check mechanical characteristics of selected bacterial suspensions based on their production of extracellular polymers that increase viscosity of the medium. Among 76 examinated bacterial isolates we chose two most promising ones (Loktanella sp. BF5_0537 and Halomonas sp. BF5_0027). In further studies we checked the effect of added carbon, temperature and salinity on viscosity. Peptone and yeast extract had the strongest effect on viscosity of bacterial suspensions, among simple carbon sources glycerol increased viscosity the most. The isolate Loktanella sp. BF5_0537 had the highest viscosity at the room temperature 21 °C and 0,5 M NaCl concentration, isolate Halomonas sp. BF5_0027 had the highest viscosity at 8 °C and 2 M NaCl concentration. There was no correlation between the month of isolation of Halomonas sp. or Loktanella sp. and viscosity. In order to determine the conditions that could potentially lead to increased viscosity in marine ecosystem, we tried to induce blooming of phytoplankton under controlled laboratory conditions, but we were unsuccessful.