Ocean Dead Zones May Be Worse Than Thought
September 30, 2008
Spanish researchers found that many species die off at oxygen levels well above what is now considered uninhabitable. The new study suggests that the extent of dead zones in coastal areas that support fishing industries is greater than previously known.
Since the mid-20th century, more than 400 dead zones have formed along continental coastlines, where fertilizer pollution causes algal blooms whose decomposition feeds oxygen-gobbling bacteria.
These so-called hypoxic regions now cover an area roughly equivalent in size to Oregon. Compared to Earth's total ocean area, that's relatively small, but they're grouped in places critical to commercial fishing. They're also spreading, in both size and frequency: Since the 1960s, the number of hypoxic areas has doubled every 10 years.
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