Studying the state of the habitat of water biological resources of the Northern Caspian on microbiological indicators

Abstract

In the spring of 2020, in most of the water area of the northern Caspian, the prevalence of saprotrophic floras did not exceed 50000 cells/ml, which microbiota level in summer. The number of oligotrophs in most of the water area was inferior to saprotrophs, which indicated an mbalance in the heterotrophic microbial community. In summer, in the northern part of the Caspian Sea, a decrease in the average heterotrophic group of bacterioplankton and bacteriobenthos was recorded, which indicated the process of self-purification of the marine environment from allochthonous elements. Viewing in the summer period in the waters of the Northern Caspian Sea, the zone of the zone with water saprobicity corresponding to the “polluted” category, the process of self-cleaning of the reservoir after the spring flood was not completed. In the autumn of 2020, the distribution of heterotrophic bacterioplankton and bacteriobenthos reached its lowest levels for all periods of research. In water, the number of saprotrophs was inferior to oligotrophs, which indicated the presence of a heterotrophic microbiota in the water, but they remained in the zone of increased saprobicity. An analysis of the taxonomic structure microbiota showed that heterotrophic communities of bacterioplankton and bacteriobenthos form representatives of the 6th family of gram-negative bacteria (Alsaligenaceae,Enterobacteriaceae, Flavobacteriaceae, Moraxellaceae, Pseudomonadaceae and Vibrionaceae), as well as gram-positive microorganisms. Gram-positive bacteria are most often found in enrichment cultures, mainly of the listed families. Some of the isolated bacteria belong to the group of opportunistic pathogens, which led to the identification of a potential danger to aquatic organisms. However, most of the identified representatives are true saprophytes, covering the inhabitants of water and bottom sediments. The predominance of indigenous microbiocenosis tends to reduce the bacterial pressure of the ecosystem in the water area and improve the state of the habitat of aquatic biological resources in terms of biological micro-characteristics.