Vol 12, No 2 (2019)

In recent decades, alongside the comparatively well-studied bloom caused by phytoplankton, a bloom of marine and fresh waters caused by littoral benthic macroalgae of three genera—Ulva, Cladophora, and Spirogyra—have become a global phenomenon. In the present review, an attempt is made to gain an understanding of why it is these taxa of green filamentous algae that start to grow rapidly in the spring in many water bodies and streams, including oligotrophic waters, and then float up from the bottom, forming floating mats (metaphyton); then their decaying masses are washed ashore and cause substantial ecological and economical losses. Peculiar and common ecological and physiological features of Ulva, Cladophora, and Spirogyra favorable for the formation of green tides are considered. Although eutrophication (the supply of nitrogen and phosphorus from agricultural lands, industrial and domestic wastewaters, and aquaculture) is the evident cause of the increase in algal biomass, it is suggested that the location of external fluxes of inorganic nutrients (surface runoff or groundwater discharge), as well as the biogenic redirection of internal fluxes of nitrogen and phosphorus from pelagial to littoral (benthification), play a key role in the formation of green tides. Measures for controlling green tides are discussed. The necessity for detailed studies of the metaphytonic form of vegetation of benthic macroalgae is emphasized. Obviously, a revision of the present concept of oligotrophic/eutrophic waters which considers only the pelagic compartments of aquatic ecosystems is required.

This article presents the results of research into autochthonous bacteriophages, a previously unknown element in the structure of the microbial loop in the ecosystem of deep oligotrophic Lake Baikal. Transmission electron microscopy was used to study the morphological diversity of phages in the water column, surface microlayer, and benthic biofilms formed at the interface between water and geological rocks (marble, granite, mica, quartz, amphibolite, gabbro, and urtite). This article presents data on the dimensional structure of autochthonous bacteriophages, as well as their quantity, seasonal dynamics, and vertical distribution from the surface to the maximum depth (1200 m) when compared with the content of bacteria. Several morphotypes of Baikal autochthonous bacteriophages affecting Pseudomonas aeruginosa have been isolated and characterized by molecular-genetic methods. The complete genomes of giant phage PaBG from the Myoviridae family and phage MD8 from the Siphoviridae family have been determined.

An algorithm of a dynamic mass-balance model emulating the biotic energy flow in a planktonic community with the involvement of microbial organisms has been developed. The abiotic input parameters of the model are the latitude, mean depth of the water body, total phosphorus content, and water color. The model makes it possible to forecast the biomass and production of key plankton groups. It is shown that the food-base production for fish and their growth are determined by the degree of protozoan plankton involvement in the trophic web.

Data on the species diversity of the genus Micrasterias C. Agardh ex Ralfs representatives from water bodies of West Siberia and their occurrence in zones and subzones are generalized. Twenty-three specific and intraspecific taxa from the order Desmidiales are now known. The representatives of the family occur in mosaic order in the entire area of West Siberia. The highest number of taxa (15) was revealed in the middle taiga; significantly fewer were determined in southern and northern taiga, 9 and 8 taxa, respectively; and 3’5 taxa were in other zones. No such species were discovered in the steppe zone. Thirteen species (18 taxa) of the genus were found in lakes of different types, 5 species (7 taxa) in watercourses, 4 (5 taxa) were found in swamps, and 4 species were detected in temporal water bodies. The analysis performed on the adaptation of the species to environmental conditions demonstrated that representatives of this genus might serve as indicators of acid and brackish water. In relation to mineralization, halophobes are predominant (11 taxa) and acidophilus plants (15 taxa) predominate as pH indicators.