Hydrocarbons in the water and bottom sediments of Sivash Bay (the Azov Sea) during its salinization.

Sivash Bay is a unique hypersaline lagoon located in the northern part of the Crimean Peninsula. In 2014, due to political events in connection with the closure of the North Crimean Canal, the inflow of fresh water to Sivash Bay has been significantly reduced. As a result, there has been a steady increase in salinity since 2014 to the present. The main purpose of this work was to determine the spatial distribution and qualitative composition of hydrocarbons (aliphatic hydrocarbons, n-alkanes, polycyclic aromatic hydrocarbons) in the water and bottom sediments of the hypersaline Sivash Bay under increasing water salinity. The analysis of the physico-chemical parameters of Sivash Bay in 2020 showed the continued salinization and change of physico-chemical conditions of the lagoon. At the same time, spatially, the change in salinity affected only the total content and qualitative composition of hydrocarbons in the water. The content of the studied classes of hydrocarbons in the bottom sediments did not demonstrate a reliable correlation with the concentration of salts. There was also no statistically significant dependence of Eh and pH of bottom sediments on salinity. In accordance with the composition of n-alkanes and polyaromatic hydrocarbons, as well as on the basis of PCA analysis, it is possible to make a conclusion on natural, mainly autochthonous, sources of this class of substances and low toxicity of bottom sediments of the bay. Low concentrations and composition of hydrocarbons indicate an insignificant input of pollutants of anthropogenic origin in Sivash Bay during its salinization.

Non-corresponding contaminants in marine surface sediments as a factor of ARGs spread in the Sea of Azov.

The present study aims to analyze the level and total toxicity of the most common pollutants in surface sediments and assess their impact on the occurrence of antibiotic resistance genes (ARGs) in the Sea of Azov. Biotesting using the whole-cell bacterial lux-biosensors showed high integral toxicity of surface sediments and the presence of genotoxicants and substances that cause oxidative stress and protein damage. Using cluster analysis, it was shown that the distribution of pollutants in the Sea of Azov depends on the type of surface sediments. The relative abundance and distribution of 14 ARGs in surface sediments were shown. Principle component analyses results suggest that non-corresponding contaminants do not exert direct influence on the ARGs abundance in the surface sediments of the Sea of Azov. Thus, the need to investigate the significance of non-corresponding pollutants in the selection and distribution of ARGs in the aquatic environment remains a pressing problem.