Composition and structure of phytoplankton in the coastal and central parts of Arakhley lake (Zabaikalsky territory) in spring and summer 2017

Shallow coastal areas are exposed by human influence to the greatest extent and act as a barrier between the catchment area and pelagic areas of reservoirs. Hydrobiological examination of Lake Arakhley was carried out in spring and summer 2017. As a result, taxonomic structure that dominates the complex, ecological characteristics and quantity of phytoplankton of the coastal and central part of the lake were studied. It was established that phytoplankton of the lake has 97 taxa below genus. The representatives of four divisions: Bacillariophyta, Chlorophyta, Chrysophyta and Cyanobacteria form its basis (86.6 %). 12 species, half of which were constant for spring and summer 2017 plankton, are the most frequent types of coastal waters and the open part of the lake. Comparative analysis of the floral composition of algae plankton in pelagic and littoral parts found their similarity (similarity coefficient 41–65 %). Cluster analysis revealed algocenosis similar in biotope: reservoirs of splash zone (the largest number of Cyanobacteria), a group of shallow stations (low taxonomic diversity, preponderance of benthic forms of diatoms), a group of stations with higher aquatic vegetation (high diversity of Chrysophyta, low one of Chlorococcales; the presence of the facultative planktonic species in the plankton) and deep zone stations (high diversity of green algae of Chlorococcales). The uneven distribution of quantitative characteristics is due to the location of vegetation belts in the studied parts of the lake. The tendency of increasing number and biomass of phytoplankton from stations without higher aquatic vegetation to those with plants was noted. High index values of Shannon and Pielou specifies a complex structure and high biodiversity of phytoplankton community, and their seasonal distribution demonstrates the response of phytoplanktons to the climat change of environment.