Purpose. The purpose of the study is to analyze the features of spatial-temporal and vertical distribution of oxygen, hydrogen sulfide and main nutrients (phosphates, nitrates, ammonium and silica acid), as well as the characteristics of carbonate system in the Black Sea in the modern period.

Methods and Results. The data used in the study were obtained by the scientists of Marine Hydrophysical Institute in the scientific cruises in the Black Sea in 2013–2021 within the economic zone of Russia. During these cruises, more than 200 deep-sea stations were carried out, samples were taken using a cassette of 12 bathometers of the Sea-Bird 911 plus CTD Seabird-Electronics INC device at certain isopycnic surfaces. At the coastal shallow-water stations, samples were taken from the surface and near-bottom horizons. Precipitations were sampled by automatic precipitation collectors at the meteorological stations located on Pavlovsky Cape in Sevastopol and at the Black Sea hydrophysical subsatellite polygon (the Southern coast of Crimea).

Conclusions. The location of upper boundary of the suboxic zone varies from σ_t = 15.7 kg/m³ to σ_t = 15.9 kg/m³, that in the depth scale corresponds to the interval of ⁓ 40 m. The vertical distribution of hydrogen sulfide is more of isopycnic character, the boundary of isosulfide 3 µM appearing is located within σ_t = 16.10–16.15 kg/m³. On the vertical profile of nitrates, their maximum concentration not exceeding 4 µM, is observed within the range σ_t = 15.2–15.5 kg/m³. It is shown that the content of oxidized nitrogen forms has almost returned to the pre-eutrophication level. The concentration of ammonium ions in the aerobic and suboxic zones predominantly does not exceeds 0.5 µM, the ammonium concentration starts to increase at the depth of isopycne σ_t = 16.10–16.15 kg/m³, at which hydrogen sulfide appears. The maximum concentrations of ammonium ions (96 ± 5 µM) were noted at the depth 1800 m and below that corresponded to the earlier obtained data. The phosphates vertical distribution is characterized by their minimum (˂ 0.5 µM) content at σ_t = 15.8 kg/m³ and by their maximum one (not more than 8 µM) at σ_t = 16.2 kg /m³. The hydrogen sulfide content at the depths exceeding 1750 m in the Black Sea is currently 383 ± 2 µM. The pH value of surface waters was 8.29–8.38 decreasing to 7.67 below ∼ 50 m. Total alkalinity varied within the range 3268–3335 µM, below σ_t = 16 kg/m³ it increased sharply reaching its maximum value ∼ 4364 µM in the bottom layer. The results obtained confirm the immutability of the previously established features of the vertical distribution of hydrochemical components and the ranges of their concentration variations. The spatial distribution of nutrients clearly shows a decrease in their concentrations from the coastal areas to the deep-sea ones. One of the largest external sources of nutrients the Black Sea waters is atmospheric precipitations. On the synoptic spatial-temporal scales, they can become the main source of inorganic nitrogen, phosphate and silica entering the sea surface layer.