Rapid Rise in Ocean Dead Zones

Oxygen-starved regions of the world’s oceans are spreading at a rapid rate, with the number of so-called “dead zones” increasing from almost none in 1970 to more than 140 in 2004, according to a new study. The study, published in the Proceedings of the National Academy of Sciences, says that the number of dead zones is growing at a rate of 5 percent a year, increasingly threatening populations of fish and crustaceans that cannot survive the low-oxygen conditions. The study’s authors report that the dead zones, originally found in places such as the U.S.’s Chesapeake Bay and the North Sea, have now spread worldwide to waters off Chile, Ghana, China, Japan, Australia, New Zealand, and Portugal. Global warming will likely create more dead zones since oxygen dissolves less readily in warmer water, the study says.