The Black Sea Bulgaria

Why Black? As you look out across the Black Sea, you may wonder why such an iridescent blue sea is called the black sea. Nobody really knows - it can be pretty stormy in winter, and it's thought that the name was given to it by sailors and pirates who were struck by its dark appearance when the sky turned leaden with storm clouds.

It has had other names in the past. The ancient Greeks knew it as the Scythian Sea, after the tribes who held its shores at the time. Shipwrecked sailors could generally expect no mercy from the Scythians, who plundered the wrecks and made wine goblets out of sailors' skulls. The Greeks also called it Pontos Axenos - the inhospitable sea - until they settled in Crimea, after which they changed their minds and called it Pontos Euxenos: the hospitable sea.

Marine life - Apart from Bottlenose and other species of dolphin, the sea has about 180 species of fish, including tuna, anchovy, herring, grey mullet, mackerel, and the famous white sturgeon, which you will find on the menu of most good restaurants.

There are also some seals in the Black Sea, but their numbers are declining rapidly. Bottlenose dolphins are in demand from amusement parks and dolphinaria because of their playful acrobatics and receptivity to training, and about 120 live Black Sea dolphins were traded internationally between 1990 and 2001. Black Sea dolphins are genetically distinct from those found in the Mediterranean and Atlantic and an attempt was made by Georgia in 2002 to use the Convention on Trade in Endangered Species to outlaw all further trade in the bottlenose to prevent it from being wiped out. The proposal for an outright ban was rejected but Georgia later succeeded in getting the Black Sea dolphins placed on a list that restricts trade through annual quotas - and in this case the quota is zero.

If you swim in the Black Sea at night, especially in August, you may notice that the waves have a strange luminous quality . This is phosphorescence of the sea, caused by plankton interacting in the water.

Noah's Flood - The Black Sea is very deep (1,271m at the centre) but it's less salty than most oceans. It began life as a fresh water lake about 22 thousand years ago. Then, about seven to nine thousand years ago, global warming melted glaciers and the polar ice-caps, sea levels rose and eventually the Mediterranean overflowed through the Bosporus, turning the lake into the Black Sea. Many archeologists think that this catastrophic event was in fact the Noah's Flood of the Bible.

The sea is unique in having two layers, an oxygenated upper layer, about 200m deep, teeming with life, and a `dead' lower layer, where until recently nothing was thought to be able to survive. The lower layer may have formed when the Mediterranean salt-water flooded in. Denser than the fresh lake water it displaced, it would have plunged straight to the bottom, leaving a diluted mix of fresh and salt water at the top. Over thousands of years great rivers like the Danube and the Dnipro poured organic material into the new sea. Due to a lack of vertical currents, the inrush of organic matter was too much for the bacteria that would normally have decomposed it aerobically, and the result was a loss of oxygen in favour of hydrogen sulphide. This means that the lower layer, 87% of the Black Sea's volume, is an almost sterile zone of water impregnated with hydrogen sulphide.
Another peculiarity of the Black Sea is the bi-directional current where it flows through the Bosporus straits on its way to the Mediterranean. The surface current flows westwards through the straits into the Sea of Marmaris, but there is a deep current which flows simultaneously in the opposite direction, back into the Black Sea.

Methane-eating life form - Recently, German scientists have discovered corals made by micro-organisms processing methane and sulphates in total darkness at the bottom of the Black Sea. These corals are now believed to be the world's oldest life form. Traditional views of early life on earth have centred on plants which began converting carbon dioxide into oxygen some three billion years ago. The newly discovered organisms live on methane and are thought to have originated four billion years ago. The German scientists believe they could prove useful in ridding the earth of excess methane, the second most important greenhouse gas after carbon dioxide.