The Black Sea

The Black Sea’s water is a mix of fresh water from rivers and rainfall with the saline water of the Mediterranean (via the /Egean Sea) that is pulled into the Black Sea thanks to a strong undertow current. The Black Sea’s unique characteristic is that these two strata of waters don’t really blend, so the top layer remains lightly saline (about 17 percent as opposed to the Mediterranean’s 35 percent) while from a depth of about 50-100 metres (164-328 feet) the water’s salinity increases. The bottom layer, below 200 metres (656 feet) - and around 90 percent of the sea’s volume - is technically anoxic, or oxygen free, as there are no deep currents; it’s inhabited only by plankton. The sea is nutrient rich despite these unusual strata. Pollution levels are being reduced now that there are more controls on industry around the basin of the Sea.