Dynamics of the Sivash Bay (the Sea of Azov) water balance under the conditions of varying natural and climatic (precipitation, water exchange with the Sea of Azov, river flow and evaporation), and anthropogenic factors (overlap of the North-Crimean Canal in 2014 and change of nature management) is studied. The basic water balance components in the Sivash Bay are assessed for three periods: the first one (1939-1971)-before the North-Crimean Canal was put into operation (conditionally natural mode of the Sivash Bay waters)-is studied using historical data; the second one (1972-2013)-during active exploitation of the canal under various functioning regimes of the irrigation systems, and the third period (2014-2016)-after the Canal was overlapped-are studied using the in situ data obtained by Marine Hydrophysical Institute and allowing for the modified natural and climatic factors. Intensity of water exchange between the Sivash Bay and the Sea of Azov after the canal was overlapped and the Sivash or the Azov currents became predominant is assessed using the calculation of the water level variations in the indicated areas and taking into account the wind conditions in summer, 2014. It is shown that the eastern winds promote intensification of the Azov water inflow to the Sivash Bay, hence, increasing salinity of its waters. Thus, overlap of the North-Crimean Canal in 2014 makes for a complete reconstruction of the hydrological water regime in the bay and its gradual transition to the conditionally natural state.

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Dynamics of the Sivash Bay (the Sea of Azov) water balance under the conditions of varying natural and climatic (precipitation, water exchange with the Sea of Azov, river flow and evaporation), and anthropogenic factors (overlap of the North-Crimean Canal in 2014 and change of nature management) is studied. The basic water balance components in the Sivash Bay are assessed for three periods: the first one (1939-1971)before the North-Crimean Canal was put into operation (conditionally natural mode of the Sivash Bay waters)is studied using historical data; the second one (1972-2013)during active exploitation of the canal under various functioning regimes of the irrigation systems, and the third period (2014-2016)after the Canal was overlappedare studied using in situ data obtained by Marine Hydrophysical Institute and allowing for the modified natural and climatic factors. Intensity of water exchange between the Sivash Bay and the Sea of Azov after the Canal was overlapped and the Sivash or the Azov currents became predominant is assessed using the calculation of the water level variations in the indicated areas and taking into account the wind conditions in summer, 2014. It is shown that the eastern winds promote intensification of the Azov water inflow to the Sivash Bay, hence, increasing salinity of its waters. It is revealed that overlap of the North-Crimean Canal in 2014 makes for a complete reconstruction of the hydrological water regime in the bay and its gradual transition to the conditionally natural state.

The ability of a bay and gulf ecosystems to self-purification was estimated and the current ecological state of the Sevastopol Bay in whole and the separated parts of the bay was given as an example. A zoning by type of anthropogenic impact subject to the water exchange with the open sea and an influence of the Chernaya River run-off were taken into account. A comparative analysis of assimilation capacity of the most environmentally disadvantaged part of the Sevastopol Bay (the Southern Bay) and the clean water area, bordering on the open sea, was carried out. The hydrodynamic regime of the Sevastopol Bay was described using numerical modelling. The prospect, opportunity and examples of the methodology for assessing the assimilation capacity of marine ecosystems are demonstrated.