Production Characteristics of Bacterio- and Phytoplankton of the Avacha Bay and the Southern region of the Far Eastern State Marine Biosphere Reserve in the summer and autumn of 2017

A study and comparative analysis of production characteristics of bacterio- and phytoplankton in Avacha Bay and in the southern region of the Far Eastern State Marine Biosphere Reserve (FEMBR) in Posyet Bay was carried out in summer, 2017. Bacterial production in the surface samples from these basins was similar, varying from 0.28 to 2.3 mg C/(day m 3 ) for Avacha Bay and from 0.22 to 2.0 mg C/(day m 3 ) for FEMBR, while the number of bacterioplankton cells was significantly higher at the FEMBR site, reaching 2.1 ×10 6 cells/mL. Evidence of hypoxia in the relief depressions of both water areas was noted. Bacterial oxygen consumption was found to be one of the main factors in development of hypoxia in Avacha Bay. Primary production in the surface samples and in the water column in both basins was comparable, but the concentration of chlorophyll a in the FEMBR southern region was more than an order of magnitude lower. This ratio resulted from absorption by other organisms of most of the produced microalgae biomass in the water column and a higher assimilation number, which increases from high to low latitudes. On the contrary, in Avacha Bay both high levels of primary production and a high concentration of chlorophyll a were noted, which indicated an intensive terrigenous influx of biogenic elements of a natural and anthropogenic nature.