Prokaryotic Plankton and Viruses in the Waters of the Fram Strait in the Winter Period

Abstract

New data have been obtained on the distribution of prokaryotic plankton and pelagic viruses in the Fram Strait (the Greenland Sea) during the polar night (late November). Three main types of water masses were present in the study area: surface polar, Atlantic, and transformed Atlantic. The content of mineral biogenic elements increased with depth. The concentration of chlorophyll a had low values (0.07–0.13 mg/m³). The abundance and biomass of prokaryotes varied from 286 000 to 675 000 cells/mL and from 2.7 to 11.7 mg C/m³, respectively. The composition of prokaryotic plankton was dominated by single small cells (more than 97% of the abundance and more than 68% of the biomass). The average cell volume was 0.034–0.096 μm³. The number of viruses varied from 724 000 to 3 920 000 particles/mL, and the biomass varied from 0.040 to 0.216 μg C/m³. Against the background of local maxima in the abundance of prokaryotic plankton in the 0–25 m layer, the highest concentrations of viruses were noted in the surface layer. In the latitudinal distribution (from south to north), an increase in the number of viruses and prokaryotes was revealed. A close relationship between their abundance and biomass with hydrological parameters and phosphate content was established; the role of certain water masses in the vertical distribution of microbes was insignificant. The relatively high abundance of viruses and prokaryotes indicated their significant activity during the polar night.