Evaluation of the water quality in the different regions of the Baltic Sea and the Curonian Lagoon of the Baltic Sea

The task of the work was to study changes of bacterioplankton abundance in the Baltic Sea and the Curonian Lagoon of the Baltic Sea and evaluate the water quality according to microbiological parameters in the different regions under research. The bacterioplankton data of the Baltic Sea and the Curonian Lagoon were obtained during the period of 2000-2005 at 14 ecological monitoring stations once a season from the surface and near bottom layers. The investigation included determination of bacterial concentration (total bacterial number) and saprophytic bacteria. The highest concentrations of the total bacterial number and saprophytic bacteria are always observed in the Klaipeda Strait of the Curonian Lagoon, as the rivers decisively influence it. During the period of investigations a tendency of the increase in total bacterial number was observed in the Klaipeda Strait region. The lowest concentrations of the total bacterial number and saprophytic bacteria are observed in the open region of the Baltic Sea. Calculations of correlation indices between the total bacterial number and concentrations of saprophytic bacteria were made to characterize water quality. The received material made it possible to evaluate the quality of water in the area under investigation according to the microbiological indices.