Virioplankton as an important component of plankton in the Volga Reservoirs

Abstract

The distribution of virioplankton, abundance and production, frequency of visibly infected cells of heterotrophic bacteria and autotrophic picocyanobacteria and their virus-induced mortality have been studied in mesotrophic and eutrophic reservoirs of the Upper and Middle Volga (Ivankovo, Uglich, Rybinsk, Gorky, Cheboksary, and Sheksna reservoirs). The abundance of planktonic viruses (VA) is on average by 4.6 ± 1.2 times greater than the abundance of bacterioplankton (BA). The distribution of VA in the Volga reservoirs was largely determined by the distribution of BA and heterotrophic bacterioplankton production (PB). There was a positive correlation between VA and BA and between VA and PB. In addition, BA and VA were both positively correlated with primary production of phytoplankton. Viral particles of 60 to 100 µm in size dominated in the phytoplankton composition. A large number of bacteria and picocyanobacteria with viruses attached to the surface of their cells were found in the reservoirs. Viruses as the most numerous component of plankton make a significant contribution to the formation of the planktonic microbial community biomass. The number of phages inside infected cells of bacteria and picocyanobacteria reached 74‒109 phages/cell. Easily digestible organic matter, which entered the aquatic environment as a result of viral lysis of bacteria and picocyanobacteria, could be an additional source of carbon for living bacteria. The results of long-term studies indicate a significant role of viruses in functioning of planktonic microbial communities in the Volga reservoirs.

Effect of increased ambient temperature on seasonal generation number in Lucilia sericata (Diptera, Calliphoridae)

“…Global warming affects plant and animal communities across all climatic zones (Burda and Koniakin, 2019;Baranovski et al, 2020). Insect species with southern ranges move northward, where they find themselves in unsuitable climatic conditions at certain stages of their ontogenesis, although the average annual temperatures do not necessarily differ from those of their original range (Avtaeva et al, 2019;2021). Inconsistencies with the habitat conditions in a new FOLIA OECOLOGICA -vol.…”

Differential Effects of Viruses on the Growth Efficiency of Freshwater Bacterioplankton in Eutrophic Relative to Non-Eutrophic Lakes

“…Flow cytometry analysis which revealed 3-fold higher standing stock of viruses and bacteria in the eutrophic than non-eutrophic lakes, was largely explained by the differences in the dissolved organic carbon and chlorophyll concentration [ 13 , 36 , 37 ]. A strong positive correlation of viral abundance with bacteria rather than with chlorophyll concentration pointed out the dominance of bacteriophages (viruses which infect bacteria) in the viral population.…”

“…Lytic infection, as evaluated from FVIC estimates (range: 1.0–4.1%) using the TEM approach, was comparable with literature reports from freshwater systems [ 40 , 41 , 42 ]. Our interpretation of viral-mediated bacterial mortality from FVIC by using the empirical models of Weinbauer et al [ 31 ] and Binder [ 32 ], which essentially relates to the bacteriophage infection cycle, suggested that between 7% and 76% of bacterial production was destroyed among the investigated lakes [ 12 , 13 , 43 ]. Two-fold higher estimates of viral lysis in the eutrophic compared with non-eutrophic lakes are suggestive of their relative importance in influencing bacterial communities, which are known to increase with trophic status [ 23 , 44 , 45 ].…”

“…In recent years, aquatic viruses have been recognized as important and potential top-down agents which play vital roles in regulating carbon and nutrient fluxes, food-web dynamics, and microbial diversity [ 10 , 11 ]. Viral infection is known to vary systematically together with their principal hosts, bacteria along the lake trophic gradient, with reports of higher lysis in eutrophic compared with oligotrophic environments [ 12 , 13 ]. Viruses, through their host-specificity mechanism and density-dependent regulation, can transiently remove 20–60% of the daily bacterial population in lake ecosystems of varying trophic states [ 14 ].…”

Viruses may facilitate the cyanobacterial blooming during summer bloom succession in Xiangxi Bay of Three Gorges Reservoir, China

“…It also has been revealed that nutrients, temperature, light, and hydrodynamic regimes are the key environmental factors affecting the outbreaking and succession of blooms ( Fang et al, 2013 ; Yang et al, 2022 ). As for viruses in reservoirs, Kopylov and Zabotkina (2021) investigated the distribution of viruses, the frequency of visibly infected cells of heterotrophic bacteria and autotrophic picocyanobacteria and their virus-induced mortality in six reservoirs along the Volga. The viral infection rate of picocyanobacteria in mesoeutrophic reservoir was higher than that in mesotrophic reservoir ( Kopylov et al, 2010 ).…”