Formation features of phytoplankton of the Bolshaya river (Omsk region) in the zoo's influence zone

According to the results of processing phytoplankton samples taken in 2018–2019 on the Bolshaya River (Omsk Region), the taxonomic composition of phytoplankton, its number and biomass were established in the zone of influence of the Bolsherechensky Zoo. As part of the phytoplankton, 183 species and intraspecific taxa from 8 divisions were identified. Seasonal dynamics of abundance of river phytoplankton and its changes in zone of zoo influence were investigated. In summer, a high level of phytoplankton development and «flowering» of water caused by Aphanizomenon flos-aquae are observed in the river on the territory of the zoo. In the formation of the number and biomass of phytoplankton, a significant share belongs to Chrysophyta and Euglenophyta. The trophic status of the Bolshaya River corresponds to the category of eutrophic waters. In autumn and summer, water in the river corresponds to the 3rd quality class of «satisfactory purity».

Biology and current state of anchovy kilka (Clupeonella engrauliformis Borodin)

In the Caspian Sea sprats is the name of the numerous small fish of herring family (Clupeonella). One of Clupeonella representatives is anchovy sprat. It differs from other types of kilka not only in appearance, but also in its way of life. A brief biology of the species and the state of ecosystem of the Caspian pelagic zone has been described. Anchovy kilka has been a leading targeted fish for over 50 years. Invading the Caspian Sea by ctenophore-mnemiopsis has undermined the stocks of anchovy sprats and caused the crisis of anchovy kilka fishing. Recently, there has been observed a slight increase in the number of the species. The survey materials confirm the increase in the number of juveniles in the studied catches. There are presented the materials from the last six years (2014–2019) of observations (eight research runs), shown the dynamics of abundance, biomass, spawning females, and total fertility of the population. Spawning efficiency and survival rate in early ontogenesis are analyzed. The relationship between kilka survival rate and the number of emerging generations is stated. Recommendations on restoring the stock of anchovy kilka are given. To restore the ecosystem of the Caspian Sea there has been proposed the invasion of a new species – ctenophore-beroe (Beroe ovata), which, due to the structure of its mouthparts eats only jelly-skinned (ctenophore-mnemiopsis, exceptionally) and can significantly reduce the number of ctenophore-mnemiopsis

Phytoplankton of the cooling waterbody of the Lukoml state district power station under changing anthropogenic load

The paper presents the results of long-term research of phytoplankton of the cooling waterbody of the Lukoml state district power station (Belarus). The dynamics of abundance, biomass, community structure, and composition of the dominant phytoplankton species for the period of 1972 – 2019 were analyzed. The stages of development of the plankton algae community are determined, due to changes in the intensity and direction of anthropogenic factors. The response of phytoplankton to changes in heat load and dependence on the development of the population of Dreissena polymorpha Pallas is shown. The influence of the fish rearing complex on the developmental intensity and phytoplankton structure was revealed. Since 2004, the periods of intensive vegetation of algae alternate with a significant decrease in abundance and biomass, which indicates the unstable state of the ecosystem of the cooling waterbody. The succession of the dominant complex in 2019 was characterized by the loss of the species Aphanizomenon flos-aquae Ralfs ex Bornet & Flahault (family Nostocaceae) and the inclusion of the species Planktothrix agardhii (Gomont) Anagnostidis & Komárek (family Oscillatoriaceae).