Bacterioplankton of the Gdansk Basin, Baltic Sea

The numbers, biomass, and production of bacterioplankton were determined in the Russian Sector of the Gdansk Basin (Baltic Sea) in 2007–2009. Significant spatial and temporal variations were determined. During the year, bacterial activity increased with increasing water temperature and higher availability of organic substrates. The lowest bacterial production (0.01–31.63 mg C m−3 day−1) was observed in late winter and late autumn, while the highest (0.17–341.70 mg C m−3 day−1) occurred in spring and summer. Since bacterial numbers and biomass were found to depend on the weather conditions and the terrigenous inflow, significant variations were observed from year to year. The highest and lowest numbers and biomass of bacterioplankton determined in summer were 0.09–1.10 × 106 cells mL−1 and 2–22 mg C m−3 for July 2007 and 1.96–11.23 × 106 cells mL−1 and 23–123 mg C m–3 for July 2009. The values of these parameters were the highest along the coast and decreased towards the open sea.