Bacterioplankton in the Western Kara Sea

This paper reports data on the structural and production characteristics of bacterioplankton in the western Kara Sea at the beginning and middle of summer. On the slope of the St. Anna Trough, the average prokaryote abundance in the water column was 594–708 × 10³ cells mL⁻¹ (26.4–36.5 mgC m^–3) in June and 247–517 × 10³ cells mL⁻¹ (12–28 mgC m^–3) at the beginning of August. On the transect along the Novaya Zemlya archipelago, the average bacterioplankton abundance in the water column was 186–554 × 10³ cells mL⁻¹ (8.5–30 mgC m^–3) within a week after the seasonal ice retreat and 169–443 × 10³ cells mL⁻¹ (8–21 mgC m^–3) in midsummer. The specific bacterial growth rate did not exceed 1.28 day^–1; high values were observed in the upper warm water layer, above the halocline, and also in near-bottom water. At the beginning of summer, the bacterioplankton production tended to decrease in the northeast direction. The prokaryote abundance distribution was associated with water temperature and oxygen saturation possibly as an indirect indicator of the past phytoplankton bloom.