Hydroecological characteristics of Malooleksandrivskogo reservoir of r. Inhulets in relating to the restoration of the mini-HES operation

Abstract

The ecological status of the river Inhulets within the borders of the village Mala Oleksandrivka in the Kherson region was investigated in connection with the resumption of activity of mini-HES. Sulfate and chloride ions predominate in the water. As for mineralization – water is brackish. Phytoplankton is represented by 39-48 species of algae of 5 divisions: Cyanophyta, Dinophyta, Euglenophyta, Chlorophyta, Bacillariophyta. The dinophyte algae dominate, particularly Ceratium hirundinella, which is traditionally considered to be pond-lake specie. Exactly it gives high indexes of biomass. The domination of dinophyte grows from the first to the eighth points. The chlorococcal and centric diatoms are also widely presented, from which Stephanodiscus hantzschii should be pointed out. In zooplankton samples from 17 to 32 kinds are registered, from three groups: (Rotatoria) –20 species, (Cladocera) – 8 species, (Copepoda) – 4 species. The random species, which were met in considerable amount in all the samples, were rotifers of the kind Brachionus (B. budapestinensis, B. calyciflorus, B. аngularis) and of the kind Keratella (K. сochlearis, K. valga, K. quadrata). Macrozoobenthos is represented by 12 species: Oligochaeta – 2 species, Gammaridea – 1 species, Chironomidae – 2 species and larvae of the Diptera – 2 species, Mollusca – 5 species. Secondary water (insect larvae) dominate quantitatively and qualitatively. Among oligochaetes dominates Tubifex tubifex by biomass, and among chironomid larvae – Chironomus plumosus, that is 66,4 % of the total biomass of zoobenthos. The average number and biomass of macrozoobenthos in the reservoir was 650 ind / m² and 13,1 g / m². At the same time, maximum indicators of the quantitative development of zoobenthos were observed on the muddy sand in the middle and adjoining sections of the reservoir (in accordance 6,61 g / m² and 18,96 g / m²). Despite doing researches in the fall, indicates of benthos biomass were quite high. Before the dam was built (early last century), 30 species of fish lived in the river Inhulets, among which 53,3 % are industrially significant fish species. After the dams has appeared (30–50 years of the last century) the number of species decreases to 22. Significant species such as Vimba vimba, Aspius aspius, Pelecus cultratus, Misgurnus fossilis disappear. At the beginning of this century, the number of species has increased to 27. The increase of the species number occurs with the help of adventitious species: Pseudorasbora parva, Pungitius platigaster, Perccottus glenii, Gasterosteus aculeatus, Ponticola kessleri, Babka gymnotrachelus, Proterorhinus semilunaris, Syngnathus nigrolineatus. It is necessary to create a special commercial fishery to improve fish production.