A notable feature of the Black Sea is that oxygen is dissolved (and rich sea life is made possible) only in the upper water levels. Below a depth of about 230 to 330 feet (70 to 100 metres) at the sea’s centre and 330 to 500 feet (100 to 150 metres) near its edge, there is no oxygen. This means that its lower levels are, to all intents and purposes, almost biologically dead—not because of pollution but because of continued weak ventilation of the deep layers.
What’s notable about oxygen levels in the Black Sea?
Is the Black Sea freshwater or saltwater?
The Black Sea is a saltwater sea, but it is of lesser salinity than the oceans. The salinity of the Black Sea’s surface waters averages between 17 and 18 parts per thousand, which is approximately half that of the oceans. A marked increase in salinity, up to 21 parts per thousand, occurs in the Black Sea at depths of roughly 160 to 500 feet (50 to 150 metres).
