Dive Atlas of the World. Jack JacksonЧитать онлайн книгу.
have been determined by the convergence and recession of the continental plates of Eurasia and Africa squeezing and stretching the Earth’s crust. As they drifted apart, Eurasia turned clockwise and Sardinia, Corsica and Africa turned anticlockwise, opening a waterway to the ocean at the western end of the sea. There were many alternating phases of flooding and evaporation. Geological data suggests that there are currently at least six main areas of collision between Africa and Eurasia, resulting in volcanism, mountain building, and land submergence. Earthquakes occur frequently throughout the region, especially in Greece and western Turkey. Volcanic action formed many of the islands in the Mediterranean Sea and volcanoes, including Mount Etna, Stromboli, and Vesuvius, still erupt in the region.
SURFACE CIRCULATION AND TIDES
Mediterranean surface circulation basically consists of separate anticlockwise movements of the water in the western and eastern basins, but many small eddies and other local currents occur because of the complexity of the northern coastline and the many islands. Although only significant in the Gulf of Gabès and the northern Adriatic, tides add complications to the currents in narrow channels such as the Strait of Messina.
Historically, large seasonal variations were caused by the flooding of the Nile, which reduced the salinity of coastal waters of the southeastern Mediterranean and increased the stratification and productivity of these waters. This influence ended with the completion of the Aswan High Dam. The amount of Red Sea water passing through the Suez Canal into the Mediterranean is negligible.
The opening of the Suez Canal turned the Mediterranean into one of the world’s busiest shipping lanes and it became heavily polluted with oil, agricultural run-off, industrial pollutants and sewage, even spreading typhoid and infectious hepatitis. Eventually the United Nations Environment Program (UNEP) sponsored the Barcelona Convention for the Protection of the Mediterranean Sea Against Pollution, calling on all Mediterranean countries to clean things up. Recently there have been spills of toxic chemicals, leaks from offshore oil installations and a virulent alien alga discharged from an aquarium, but generally things are much improved.
Blackfaced Blenny (Tripterigion delaisi). Territorial males have black heads where the coloration does not extend to the pectoral fins, and yellow bodies.
Found in much of the Atlantic Ocean, including the Mediterranean, Salema or Saupe (Sarpa salpa) usually congregate on rocky or sandy seabeds with lots of vegetation.
Wide-eyed Flounders (Bothus podas) lie camouflaged on sandy bottoms where they feed on small fish and invertebrates. Both eyes are on the left side, with the lower eye forward.
L’Estartit, is the staging port for all sub aquatic activities to the Medas Islands. There are also several diving schools.
The Medas Islands became a marine preserve in 1983 and are renowned for the large number of friendly groupers, sea bream and colourful Gorgonian Sea Fans.
SPAIN AND FRANCE
by Lawson Wood
THE MEDITERRANEAN, WHERE THE FIRST sport diving took place, has received a bad press over the years. Population and industrial growth has resulted in vastly increased pollution levels. Much of the original coastline has been changed irrevocably by marinas, harbours and housing developments. Monaco has now lost some 75 per cent of its original coastline. The Mediterranean Sea is undoubtedly one of the world’s most threatened seas, due to the increased demand on its natural resources and pollution from homes, industry and intensive agriculture. Fortunately, the influx of fresh seawater from the Atlantic has managed to slow the deterioration.
While small areas such as the waters around Venice and the northern Adriatic, sections of the Greek coast and parts of Tunisia are under increased threat due to the pressures of tourism, this is usually on a seasonal, temporary basis and the marine life does regenerate itself. However, there is now a new threat: the introduction of alien species of algae to this enclosed sea as well as commercial fishing.
There are protected areas around the shores of the Mediterranean, but enforcement is difficult, particularly when it involves huge factory ships. Most countries now accept that a successful tourist industry relies on strict conservation policies. For this industry to succeed and prosper, tourists also have to be made aware of the impact they have on small areas. Membership of conservation agencies is an important step towards understanding and protection of marine habitats.
The South of France is still very popular with divers, despite the effects of the ‘killer algae’ Caulerpa taxifolia, which has overrun many coastal reefs. There are a number of marine parks along the southern French coast, starting with the nature reserve of Cerbère-Banyuls just north of the Spanish Border. Similar to the geology of Estartit, with many sea caves, the reserve is supported by the Arago Oceanographical Laboratory located at Banyuls-sur-mer to the north. The reserve is noted for its dead men’s fingers and precious Red Corals. Near Toulon, the island of Porquerolles is administered by the French National Trust and has many interesting wrecks nearby. The Côte D’Azur has excellent diving around the offshore islands near Cannes, Cape Juan and Cape Antibes with some superb walls and interesting topography.
Much of the southern Spanish coast is similar in topography and species diversity to Gibraltar. As you travel northeast towards the French coast there are a number of protected areas, with good diving and excellent marine life to be found at Al Muñequa and Fuengirola. The most famous of the protected areas is the Medas Islands off the coast near the resort of Estartit. These small rocky islands have been protected since the early 1980s and have huge concentrations of fish, including grouper, sea bass, bream, sardines and mullet.
MEDAS ISLANDS
Travelling south from the border of France into the Costa Brava region of Spain, the coastline rises perceptibly with huge limestone massifs eroded over aeons into a picturesque coastline dotted with islands, subterranean seamounts and carved with thousands of caves, many only accessible from underwater.
The largest group of islands is the Medas group, only a kilometre (⅔ mile) east of the deep-water marina of Estartit. The Medas Island group was declared a national marine park in 1983. The islands are known for the profusion of marine life due to the upwelling of a cold water stream from the central Mediterranean combining with organic material from the River Ter and the wide river deltas along the south coast of France. It was important to protect the islands from large-scale commercial fishing and drastic steps were taken in the early 1980s. After initial opposition, fishermen are now happy with their yields on the perimeter of the marine park and the upsurge in tourism boat traffic.
Red Dead Men’s Fingers soft corals (Alcyonium spp.) can be found covering large areas of the lower rocky cliffs, in shaded areas which are swept daily by the nutrient-rich waters of the northern Mediterranean.
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