The Black Sea is a closed sea of the basin of the Atlantic Ocean. It is connected to the Sea of Marmara, to the Aegean and Mediterranean seas, and also to the Sea of Azov. The area of the Black Sea is 422 000 km². The largest depth is 2210 m. The main feature of the Black Sea is total absence of life at depths more than 150 — 200 m because of a hight level of hydrogen sulfide in water. Only anaerobic bacteria live at this depth.