Dead zones, a major threat for aquatic life?
What is a dead zone?
Dead zones, zones deprived of oxygen, are multiplying in the oceans, both in the depths and on the shore. As a result of the misuse of chemicals and global warming, these 245,000 km2 areas continue to grow alarmingly. Thus in the bay of Bengal, on a surface of 60 000 km2, the marine fauna, no longer finding the oxygen necessary for its survival, disappears, fleeing the region not to die. But sedentary species, such as crustaceans, can not do it, and simply die! The oceans have known this phenomenon of deoxygenation forever. But since the 1980s, the phenomenon has become critical. In 50 years, affected areas have quadrupled. In 2003, there were 150 dead zones in the world, in 2008, they increased to 400 … More than 245 000 km2 are affected, and mainly in the South Pacific, the Baltic Sea, the Gulf of Mexico and the coasts of Namibia.
What are the causes of dead zones?
Industrial pollution in the runoff is the cause of the accumulation of organic matter, which causes the proliferation of algae. When they decompose, the microbes they produce consume all the oxygen! This phenomenon is aggravated by global warming because the renewal of water is too slow. When the temperature is high, the water does not have the same density and there is less exchange between oxygenated water depths and surface water, and these are then no longer supplied with oxygen. For scientists it is urgent to regulate the excessive use of pesticides and other chemicals in agriculture. It is also necessary to create marine protected areas, as well as to ban fishing in areas where wildlife takes refuge during the decline of oxygen. If we want to stem this plague, and preserve the marine world, it’s at this price …