Structure of virioplankton and viral lysis of prokaryotes on the shelf of Siberian Arctic seas: impact of large river runoff

A small amount of information about the composition and functioning of prokaryotes and viruses in the Kara, Laptev and East Siberian seas makes it impossible to provide a quantitative assessment of all parameters of the carbon cycle which is necessary to analyze and predict the impact of climate change on the entire Arctic biota. Of particular interest are the areas of the inner and outer shelf of the Arctic seas which are, on the one hand, a zone of mixing of river and sea waters of the Ob, Yenisei, Lena, Indigirka and Kolyma rivers with a large amount of the smallest detrital particles; on the other hand, it is a zone of highly saline marine areas, which determined the task of our study. The modern methods of studying the structural and functional characteristics of microorganisms are used in the work: epifluorescence microscopy and transmission electron microscopy; the growth rate and production of plankton heterotrophic prokaryotes were determined by dilution method in situ and the method involving application of antibiotics, modified for natural habitats. On the shelf of the Siberian Arctic seas, the abundance of free viruses, frequency of visibly infected prokaryotic cells and viral-mediated mortality of prokaryotes values varied within 0.1–13.6 × 10 6 viruses mL −1 , 0.2–5.6% abundance of prokaryotes, 1.4–64.4% production of heterotrophic prokaryotes, respectively. We suggest that the input of a large amount of the smallest organic particles on which a significant amount of viruses is absorbed into the coastal waters of the Siberian seas (including riverine–marine water mixing zone) leads to a decrease in viral infection and mortality of prokaryotes.