Thousands of tons of petroleum dumped on the seabed
When the Exxon Valdez sank off Alaska in 1989, the 25,000 tons of petroleum that leaked (a relatively small percentage of its cargo) destroyed a marine area about the size of the Aegean. Yet far greater quantities of petroleum are carried across the Aegean every year. Over 60,000 merchant ships, including 6,000 fuel tankers carrying over 100 million tons of petroleum, pass through the sea every year. Then there are the some 30,000 pleasure boats, motor yachts, small cruisers and other craft that sail its waters. According to some estimates, about 100,000 tons of petroleum end up in Greek waters every year (635,000 throughout the Mediterranean), and most of it not by accident. To be precise, just 55,000 tons leaked into the Mediterranean over the past 15 years because of accidents, according to the UN Environment Program. Most of the pollution from ships comes from the practice of releasing bilge water while en route. «This is ‘routine pollution,’» said Theodoris Tsibidis of the NGO Archipelagos. «Bilge water is a mixture of petroleum, grease and chemicals, a mixture that drops to the bottom of the sea without being noticed, a system known as ‘bypass,’ as it gets around the system for separating waste water from other substances.» A 25,000-ton, 10-year-old ship produces more than a ton of waste daily. Clearly very few ships follow the time-consuming separation procedure, and choose simply to release the waste into the sea. The «gas-free» process, that is, washing out the holds with chemicals and hot water, only makes the problem worse. «Huge quantities of waste water produced in this way are usually released into the sea in the early evening, so that most of the slick will have sunk by morning when the ship is 200 miles away.» An examination of satellite images over the past four years made by scientists at the Hellenic Center for Marine Research showed 579 oil slicks in the Aegean (about 12 a month) that are concentrated along the sea lanes. These are not the result of accidents, as over the past 15 years there have been less than 15 accidents in the Aegean and Ionian seas. As an example of the effects on the marine ecosystem of these accidents, invertebrate organisms such as sea urchins (a barometer of marine pollution), which were plentiful before the accident, have completely disappeared.
