The present study examined the hydrochemical and biological parameters influencing the spatial distribution of bacterioplankton in the Laptev Sea and the East Siberian Sea shelf regions affected by the Khatanga, Indigirka and Kolyma rivers runoff during September 2017. The highest bacterial abundance and the amount of actively respiring bacteria were determined in rivers delta and in surface water along the edge of continental shelf. Despite the expectations based on previous studies salinity was not the determining factor affecting spatial distribution and activity of bacterioplankton. Bacterial abundance and biomass were significantly and positively correlated with chlorophyll “a” and pheophytin content.

Analysis of the distribution of abundance and activity of bacterioplankton in the estuary area of the Ob River in July 2016 and September 2013, as well as environmental factors, made it possible to distinguish between riverine, brackish water, and marine zones. In summer, the abundance of bacterioplankton varied from 2604 ± 436 × 10³ cells/mL in brackish waters to 468 ± 91 × 10³ cells/mL in seawater. The average values of bacterial production in waters with a salinity of less than 8 and more than 22 PSU were 17.43 and 4.91 mgC m^–3 day^–1, respectively. In autumn, the bacterial abundance decreased towards the sea from 1289 ± 385 × 10³ cells/mL in freshwaters to 85 ± 37 × 10³ cells/mL in the offshore part; the value of production decreased by more than an order of magnitude. With an increase in salinity, the proportion of cells with active electron transport chain in the abundance of bacterioplankton decreased from 5.8 to 0.6%. Thus, the distribution of river runoff, marked by salinity, proved to be the main factor affecting the spatial distribution and activity of bacterioplankton. However, the mechanism of such regulation remains unclear.

The present work aimed to study the influence of mercuric chloride (HgCl2) on pigment content (chlorophyll aand pheophytin) in sediment traps on the basis of experimental data. The marine microalgal...

The biogeochemical role of zooplankton in the ocean is determined not only by life-long accumulation of chemical elements from the environment, but also by post-mortal transformation of carcasses chemical composition. The contribution of zooplankton carcasses to vertical flux of major and trace elements depends on sedimentation and remineralization rates of detrital particles. Carcasses decomposition rate during sinking from the upper to the deeper water layers determines the rapid recycling of chemical elements and depends on ambient temperature and microbial activity. This data set summarizes 21-day experiment in microcosms that simulates temperature conditions in the Arctic environment. The data show slow decomposition of copepod carcasses compared with initial material on days 14-21 of the experiment. In addition to visual evidence, we provide data on changes in bacterial abundance and biomass during the whole experimental period.