Friday, April 13, 2012
Dead Zones Continue to Rise
The number of dead zones from the 1960's to 2008 has doubled and continues to grow. From 1997-2007 the Virginia Institute of Marine Science has recorded that dead zones have increased form four to four hundred. The newest dead zones are being found in the southern hemisphere- South America, Africa, parts of Asia says Robert J. Diaz of the Virginia institute of Marine Science. Diaz says some of the increase is due to just discovering low oxygen levels that have existed for years are just being found, also new ones have developed. Scientist mainly blame fertilizers and other farm run off. Diaz say that as fertilizers become more expensive farmers will begin seriously looking at ways to retain them on the land. In the late 80s and early 90s, the Black Sea was the largest dead zone in the world, however between 191-2001, the process was reversed due partly because of the Soviet Unions fall and high prices of fertilizers. Sewage discharge also contribute to the problem because they help the algae blooms to flourish. Climate change could be adding to the problem as well. The lack of oxygen can also force fish into warmer waters closer to the surface, perhaps making them more susceptible to disease. Many regions are expected to experience more sever periods of heavy rain, which could wash more nutrients from farmland into rivers. A portion of Big Glory Bay in New Zeland became hypoxic after salmon farming cages were set up, but began recovering when the cages were removed. A dead zone has been newly reported off the mouth of Yangtze River in China, this area has been hypoxic sense about the 1950's. Ove Hoegh-Guldber, a professor at the ARC Centre of Excellence for Coral Reef Studies(CoECRS) and the University of Queensland in Australia, says there is growing evidence that declining oxygen levels in the ocean have played a major role in at least four of the planets five mass extinctions. It is found that it can cause fish to have smaller ovaries, produce fewer eggs, so larvae are smaller and less likely to survive. According to a study form the Leibniz Institute of Marine Sciences in Germany, marine dead zones will increase by 50% by 2050.