The Mediterranean and Black Sea Marine System: An overview of its phySico-geographic and oceanographic characteristics

The Mediterranean and Black seas compose a semi-enclosed intercontinental marine system (MBMS) connected to the Atlantic Ocean, hosting a coastal population that exceeds 150 million inhabitants that share a coastline of 54,000 km long and being involved in various economic activities. The MBMS has a total marine surface area of similar to 3000 x 10(6) km(2), representing about 4% of the global ocean, while its drainage basin covers an area of > 7000 x 10(6) km(2) providing annually > 1000 km(3) of freshwater and > 1300 Mt. of sediment. The MBMS has an overall negative water balance that is compensated by the inflows (Le., 1260 Km(3)y(-1)) of the Atlantic water through the Strait of Gibraltar. The MBMS is microtidal (astronomical tidal range < 0.2 m) and is characterized by mean significant wave heights of < 1.5 m (high waves > 7 m). In both Mediterranean and Black Sea basins, the general surface water circulation is cyclonic, characterized by a large number of permanent gyres and coastal eddies. The MBMS trophic status varies considerably, with the Mediterranean Sea being generally oligotrophic, the upper layer of Black Sea mesotrophic and the Marmara Sea eutrophic. On the other hand, it demonstrates a great biodiversity with > 10,000 marine species (442 of them are native), which represent 7% of all the worlds known marine species. Therefore, any natural change or human intervention that may take place in the MBMS complex environment could have variable direct or indirect effects on its status at a regional scale and/or at an interregional extent.