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Scientists Say Area That Cannot Support Some Marine Life Is Near Record Size
The “dead zone” in the Gulf of Mexico, an area on the seabed with too little oxygen to support fish, shrimp, crabs and other forms of marine life, is nearly the largest on record this year, about 8,000 square miles, researchers said this week.
Only the churning effects of Hurricane Dolly last week, they said, prevented the dead zone from being the largest ever.
The problem of hypoxia, very low levels of dissolved oxygen, is a downstream effect of fertilizers used for agriculture in the Mississippi River watershed. Nitrogen is the major culprit, flowing into the Gulf and spurring the growth of algae. Animals called zooplankton eat the algae, excreting pellets that sink to the bottom like tiny stones. This organic matter decays in a process that depletes the water of oxygen.
Researchers expected the dead zone to set a record — even more than the 8,500 square miles observed in 2002 — after the Mississippi, swollen with floodwaters, carried an extraordinary amount of nitrates into the Gulf, about 37 percent more than last year and the most since these factors began being measured in 1970.