WASHINGTON -- The number of oxygen-starved ``dead zones" in the world's seas and oceans has risen more than a third in the past two years because of fertilizer, sewage, animal waste, and fossil-fuel burning, United Nations specialists said yesterday.
Their number has jumped to about 200, according to new estimates released by UN marine specialists meeting in Beijing. In 2004, UN specialists put the estimate at 149 globally.
The damage is caused by explosive blooms of tiny plants known as phytoplankton, which die and sink to the bottom, then are eaten by bacteria, which use up the oxygen in the water. Those blooms are triggered by too many nutrients -- particularly phosphorous and nitrogen.
The UN report estimates there will be a 14 percent rise in the amount of nitrogen that rivers are pumping into seas and oceans globally over a period from when the levels were measured in the mid-1990s to 2030.
Oxygen starvation robs the seas and oceans of many fish, oysters, sea grass beds, and other marine life. The number of oxygen-starved zones has grown every decade since the 1970s.
Dead zones first were reported in the Chesapeake Bay in the United States, the Baltic Sea, the Kattegat bay in the North Sea, the Black Sea, the Adriatic Sea, and some Scandinavian fjords. Others have appeared off South America, China, Japan, southeast Australia, and New Zealand, according to UN research led by Robert Diaz, a marine scientist at the College of William & Mary.