Results of the hydrological, hydrochemical, biological and medico-hydrobiological studies of the Kuialnyk Estuary
Authors: Tuchkovenko Yu. S. , Garkusha О. P. , Gryb О. M. , Gushcha S. G. , Denha Yu. М. , Kalashnik K. S. , Koieva Kh. О. , Komorin V. N. , Koshelev О. V. , Minicheva G. G. , Loboda N. S. , Pohrebnyi А. L. , Oleynik Yu. V. , Stepanenko S. М. , Tsurcan О. І. 
Published: January 2023

The Kuialnyk Estuary belongs to the group of closed estuaries of the Northwestern Black Sea coast and is a unique water body of national importance with therapeutic properties. The natural territories of the Kuialnyk Estuary were declared as a resort of national importance and form a part of the Kuialnyk National Nature Park.
The purpose of the research is to introduce the results of the hydrological, hydrochemical, hydrobiological and medico-biological studies of the condition of the Kuialnyk Estuary and seawater in the Odesa Bay that were conducted in 2021 and to compare them with the results of previous years. This would help to determine the conditions under which the estuary’s natural system is functioning, to ensure preservation and restoration of its natural resources, to prevent their pollution, clogging and depletion, as well as to identify changes of the natural resources of the Kuialnyk Estuary in the context of its artificial replenishment with seawater from the Odesa Bay and varying hydro-ecological factors.
The general conclusion is as follows: replenishment of the estuary with seawater during the cold period of 2020-2021, increasing amount of atmospheric precipitation and decreasing rate of evaporation from the estuary’s water surface in 2021 raised the Kuialnyk Estuary’s water level. This led to significant improvement of the estuary’s hydro-ecological condition compared to 2020, however, because of its contamination with petroleum hydrocarbons, some toxic and polycyclic aromatic hydrocarbons, the water quality in 2021 is still assessed as satisfactory. The quality of the bottom sediments of the Kuialnyk Estuary from the environmental perspective is assessed as very poor because of their contamination with petroleum hydrocarbons, organochlorine pesticides and polycyclic aromatic hydrocarbons. The physicochemical composition of colloidal dispersions of the Kuialnyk Estuary’s peloids is barely different as compared to previous years. As per indicators of Eh (2017-2021) and pH (2020-2021), the quality of the peloids within the area used by the sanatorium did not meet the established conditions and the Medical (Balneological) Conclusion. Compared to 2020, the sanitary and microbiological condition of peloids improved in 2021, however, was still unsatisfactory. The characteristics of peloids’ biological activity during different periods of studies correlate with general mineralization fluctuations. Maintaining oil mineralization at a level not higher than 250 g/dm3 is quite important in order to preserve the unique deposit of natural healing resources of the Kuialnyk Estuary.
Therefore, solving the following problems remains a priority: reducing the mineralization of the estuary’s water via increase of the rate of clean fresh water supply from various sources instead of using salty seawater; preventing the pollution from anthropogenic sources from entering the estuary (through water runoff from the watercourses flowing into the Kuialnyk Estuary such as the chute from the sandbar, Korsuntsivska and Hildendorfska gullies and others).