Harwick Head, a sea-bird reserve, in Orkney, looking along the cliffs to the North Sea

The meridian line cuts through the Arctic, North and Mediterranean Seas in the northern hemisphere, and the South Atlantic Ocean and Southern Ocean, in the southern hemisphere.

Mediterranean

Cuckoo Wrasse and Whiting. The Mediterranean Sea contains approximately 6% of the world's marine species.

Photo: Charles Hood/WWF UK

The Mediterranean Sea is an enclosed sea, covering 2,500,000 km2 with an average depth of 1,500m. The Sea is connected to the world’s oceans at its western end by the Straits of Gibraltar. The coastline extends 46,000km and runs through 22 countries.

The Mediterranean Sea represents only 1% of the world’s marine cover yet it contains approximately 6% of its marine species. Some of the world’s most endangered species, such as the monk seal, can be found in the Mediterranean. Fish stocks are down to 20% of natural levels in some areas, and the region is now a net importer of fish.

The Mediterranean Action Plan was established by the bordering countries in 1975, which in turn led to the development of a number of specific conventions notably the Barcelona Convention in 1976. Further action, however, is still necessary to provide protection for wildlife and to reverse destructive trends.

The Atlantic Basin

Platboombai, on the coast of South Africa.

The Atlantic Basin stretches between the continents of Europe, Africa and the Americas. Few of the mineral deposits of the Atlantic are commercially viable, an exception being oil and gas reserves in the North Sea. In addition, massive exploitation of oil and gas reserves take place in both the marine and terrestrial region of West Africa – 150 million tonnes compared with 44 million tonnes in the North Sea. Further, some of the finest diamonds in the world are extracted from the coast of South West Africa.

The North Atlantic is the world’s most heavily fished ocean area, and many fish stocks suffer from over-fishing. In the North-East Atlantic, for example, 40 out of 60 commercial fish species are being fished unsustainably due to fisheries mismanagment. In the southern hemisphere, rich fisheries, comprising shrimp, lobster, sardine, anchovy and tuna occur along the West African coast as a result of the upwelling of cold, nutrient-rich water in the region.

The Southern Ocean

A group of Adelie Penguins rest on the ice of Antactica

The Southern Ocean encircles the Antarctic continent. This polar sea is incredibly productive during the short Antarctic summer. The drifting plankton (tiny plant and animals) support squid, fish, seals, whales and birds such as albatross and penguin. Lack of ownership or international agreement concerning the exploitation of resources in this area was one reason for the dramatic declines in wildlife resources over the course of the twentieth century. International treaties now aim to regulate the use of living and mineral resources.