Bacterioplankton in a subarctic estuary: the Gulf of Bothnia (Baltic Sea)

Abstract

Cell numbers averaged 0.8 × 106 cells ml-1 in winter, 1.66 × 106 cells ml-1 in June and 1.60 × 106 cells ml-1 in August. Thymidine incorporation rates were 0.17, 5.0 and 7.8 pmol l-1 h-1 respectively (all depths included). Mean cell volumes were 0.026-0.090 ‰m3 in winter, 0.029-0.129 μm3 in June and 0.018-0.051 μm3 in August. The shortest turnover time was c1 mo in winter and c5 d in June and August. Bacterial numbers and thymidine incorporation rate showed a positive correlation with temperature. Part of the bacterioplankton production in the Bothnian Bay was supported by allochthonous sources. Bacterial cell volumes in August were probably also controlled by predators. In the Gulf of Bothnia the available resources apparently control bacterioplankton. -from Author