Особливості трансформації фітопланктону Житомирського водосховища (р. Тетерів, басейн Дніпра, Україна)

Abstract

Stable functioning of the ecosystem of the Zhytomir reservoir, which is indicated by the absence of directed changes in the primary production over a long period, is pro­bably supported by the alterations of the algae groups at the level of their structure, by the high speed of incorporation of organic matter into the bio-water cycle, and by large areas of water levels. Over the last 10 years, the role of blue-green algae has decreased in the taxonomic composition of the phytoplankton of the Zhytomir reservoir, while the species richness of green, euglenic and golden ones has increased; there were minor alterations to the phytoplankton structure at the class level and more noticeable changes at the order, family, and birth levels. Over a period of almost ten years the species saturation of the genus Chlamydomonas Ehrenb., Euglena Ehrenb., Cyclotella Kützing., Peridinium Ehrenb. Generally, the generic coefficients and the saturation of species with intraspecific taxa increased (which was also observed for the small Denyshivske reservoir), whereas for large reservoirs of the Dnipro and Volga there is a tendency to simplify the taxonomic structure of phytoplankton with their age. Phytoplankton biomass indicators remained unchanged for almost ten years, however, there was a shift in biomass peaks from summer to autumn. The number of algae cells decreased. Phytoplankton alignment decreased. Inadequacy has been established in the trophic status of the Zhytomir Reservoir, determined by biomass and primary phytoplankton production. The higher trophic level, determined by the intensity of photosynthesis, is probably due to the predominance in the dominant complexes of small-cell highly productive species that support the high trophic status of aquatic ecosystems with relatively low phytoplankton biomass. At the present stage, there is a tendency to improve the water quality of the reservoir according to the saprobiological indicators of phytoplankton development in comparison with 2003–2007.