Tropical ocean dead zones could increase 50 percent by 2050
Jeremy Hance, mongabay.com
November 18, 2008
Hundreds of meters below the surface tropical oceans contain low amounts of oxygen, resulting in what scientists call ‘dead zones’ due to the inability of most marine life to survive in the area. Many such zones are created by humans dumping chemical nutrients into the water, such as the massive dead zone in the Gulf of Mexico, but these deep-water dead zones in the tropics are natural, though augmented by climate change.
"Carbon dioxide fertilizes biological production," Andreas Oschlies told Nature.com. "It's really like junk food for plants. When the carbon-fattened excess biomass sinks it gets decomposed by bacteria which first consume the oxygen, and then the nutrients."
As the dead zones rise vertically in tropic seas, many species will be threatened. According to Oschlies, most fish currently avoid the dead zones by swimming closer to the surface, but with a 50 percent increase in oxygen-depleted waters, fish stocks are likely to become imperiled.
Lothar Stramma, Gregory C. Johnson, Janet Sprintall, Volker Mohrholz. Expanding Oxygen-Minimum Zones in the Tropical Oceans. Science May 2, 2008.