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The Mediterranean Sea is an intercontinental sea situated between Europe to the north, Africa to the south, and Asia to the east. It covers an area, including the Sea of Marmara but excluding the Black Sea, of about 970,000 square miles (2,512,000 square km). It has an east to west extent of some 3860 km and a maximum width of about 1600 km. Generally shallow, with an average depth of 1500 m, it reaches a maximum depth of 5150 m off the southern coast of Greece.
The Mediterranean Sea is an almost completely closed basin where the continuous inflow of surface water from the Atlantic Ocean is the sea's major source of replenishment and water renewal. It is estimated waters take over a century to be completely renewed through the Strait of Gibraltar wich is only 300 m (1000 ft) deep. The scarce inflow, coupled with high evaporation, makes the Mediterranean much saltier than the Atlantic Ocean.
To the southeast part, the Suez Channel, which is an artificial channel, connects the Mediterranean Sea with the Red Sea. Through it many xenobiotic species are now colonizing the Eastern Mediterranean basins.
The low concentration of phosphates and nitrates, necessary for marine pastures, limits the food availability and thus quantity of marine life in the Mediterranean which should be considered an oligotrophic sea. In this context, overexploitation of the sea's marine resources is a serious problem.
On the contrary, some areas, like the Corso-Ligurian Basin and the Gulf of Lion, are characterized by high levels of primary productivity related with up-welling of nutrients.
Itís greatest depth is in the Ionian Basin south of Greece at 16,800 feet (5,121 m) below sea level. Itís linked to the Atlantic Ocean by the Straight of Gibraltar. It was thought to be the remnant of the Tethys Sea, which formerly girdled the Eastern Hemisphere. It is now known to be a structurally younger basin. Itís continental shelves are relatively narrow.
Marine Mammals : In the Mediterranean Sea, 19 species of cetaceans can be encountered; 8 of them are considered common (Fin whale Balaenoptera physalus, Sperm whale Physeter macrocephalus, Striped dolphin Stenella coeruleoalba, Risso's dolphin Grampus griseus, long finned Pilot whale Globicephala melas, Bottlenose dolphin Tursiops truncatus, Common dolphin Delphinus delphis, Cuvier's beaked whale Ziphius cavirostris), while 4 are occasional (Minke whale Balaenoptera acutorostrata, Killer whale Orcinus orca, False killer whale Pseudorca crassidens, Rough toothed dolphin Steno bredanesis), and 6 accidental, alien to the Mediterranean, but occasionally sighted in the last 120 years (among them the Humpback whale Megaptera novaeangliae); moreover, we have to consider the presence of a small population of Harbour porpoise Phocoena phocoena in the Black Sea. A table shows the scientific names along with the common names in different languages.
The Mediterranean Monk Seal (Monachus monachus) is the only pinniped to be found within the Mediterranean Sea. It is now very rare and listed as an endangered species. The only known colonies are in the Alboran Basin and in the Aegean Sea. It is very unlikely that any animals will be encountered around Sicily or Malta.
Ecological concerns : In the Mediterranan Sea marine life is heavily threatened by habitat degradation mostly due to human activities, such as fisheries, ship traffic, water pollution, coastal anthropization.
The cetacean population are currently affected by heavy pollution which contaminates the marine food web, by overexploitation of marine resources due to unsustainable and not selective fishery, and also by direct and indirect take of cetaceans.
Also, we have to consider that the Mediterranean and the Black Sea form an integrated oceanographic system. The waters of the Black Sea, which are at a higher level than those of the Mediterranean, flow into the Mediterranean basin through the Bosphorus, the Sea of Marmara and the Dardanelles. The Black Sea collects waters coming from an enormous drainage basin wich includes a large part of central and east Europe and Turkey. Due to the pollution brought mainly by rivers, the Black Sea is dying; as its polluted waters continuosly flow into the Mediterranean, all marine life, ecological balance and biological resources are seriously threatened in the whole system.
To the west the Mediterranean Sea is connected to the Atlantic Ocean by the Strait of Gibraltar, which at its narrowest point is only 8 miles (13 km) wide and has a relatively shallow channel.
The effect of anthropogenic noise on the marine environment is a new serious concern for scientists. The effects of intense sounds on cetaceans can vary from physical damage including temporary or permanent hearing loss to a variety of potentially, still unknown, disruptive behavioral effects which may have an impact on the status of the stocks. The scarce availability of baseline scientific information about cause-effect relationships prevents the adoption of appropriate conservation policies.
Very little is known about the critical habitat requirements of marine mammals. The lack of adequate knowledge about the cetacean population in terms of distribution, size, trends, dynamics, reproductive cycles, migratory habits, sensitivity to human activities, ecological roles, communication abilities, dramatically limits the ability to develop strategies and policies for their conservation. This makes all cetacean species particularly vulnerable to increased disturbance and habitat degradation. Other than general principles of environmental protection, strong regulation measures are urgently needed in order to increase our awareness about critical habitat requirements and to reduce direct and indirect impacts caused by human activities.