How+long+does+a+dead+zone+last?+Karoliina,+Jordan,+Mandy,+Lilyann

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 * How long do the blooms last?**
 * Blooms can last days, weeks or months, depending on conditions. Scientists cannot predict when or where blooms will occur or how long they will last; the blooms run their course and dissipate naturally.

Scientists have found 200 "dead zones" in the world's oceans — places where pollution threatens fish, other marine life and the people who depend on them. The United Nations report Thursday showed a 34 percent jump in the number of such zones from just two years ago.

By 2030, the world's rivers will pump 14 percent more nitrogen into seas and oceans than that found in the mid-1990s, according to new U.N. research released at a meeting in Beijing.

The United Nations marine experts said the number and size of oxygen-deprived zones has grown each decade since the 1970s. Not all the dead zones persist year-round; some return seasonally, depending on winds that bring nutrient-rich water to the surface. http://www.sfgate.com/cgi-bin/article.cgi?file=/n/a/2006/10/19/national/w102903D83.DTL&type=printable