Mediterranean-Atlantic Region

(Mediterranean-Lusitanian region), a zoogeographic region of the world ocean, encompassing that part of the Atlantic Ocean bordering on southern Europe and northern Africa, the Mediterranean Sea, the Black Sea, and most of the Sea of Azov. The region is divided into four provinces: Lusitanian, Mauritanian, Mediterranean Sea, and Black Sea (including the Sea of Azov).

The rich and varied fauna of the Mediterranean-Atlantic region is genetically diverse and includes boreal, subtropical, and endemic species. Among the endemic species are many descendants of the tropical fauna of the ancient Tethys Sea. Southern boreal species predominate in the Lusitanian province, and subtropical species prevail in the Mauritanian.

In the Mediterranean Sea boreal species are found primarily in the north at depths greater than 50–60 m; subtropical species occur in shallow water (except in the north). Endemic species constitute roughly one-fourth of the sea’s fauna (except in the extreme western part). Isolated populations of certain West African tropical species, relicts of warmer ages, have survived in the southern and southeastern parts of the Mediterranean Sea. After the Suez Canal, connecting the Red Sea with the southeastern Mediterranean, was opened in 1869, tropical Indo-West-Pacific species appeared in the Mediterranean; this phenomenon, known as the De Lesseps migration, intensified significantly after the flow of the Nile River was brought under control.

The fauna of the Black Sea is greatly impoverished. The virtual absence of subtropical elements imparts to the fauna a certain resemblance to the Atlantic boreal fauna. Almost all species are also found in the Mediterranean; there are very few endemics. The depths are contaminated by hydrogen sulphide, and, as a result, only bacteria live there.

The biological productivity of the Mediterranean-Atlantic region is very high along North and West Africa and low in the Mediterranean Sea.