Mississippi River carrying fertilizer to the Gulf of Mexico. Credit: NASA
Dead zones are areas in the ocean where there isn't enough oxygen to support life. They occur mostly near populated coastlines where more chemical nutrients (usually fertilizers) make their way into the water, causing increased algae blooms that, when they die off, suck up oxygen during decomposition. Dead zones have been steadily increasing, and today brings a little good news and a little bad. The good news is the Gulf of Mexico's dead zone is only about half the size of estimates for this year, though the bad news is that it's a whole lot worse than expected. According to PhysOrg, the dead zone in the gulf - created in large part form agricultural run-off from the Mississippi - is "just" 3,000 square miles, instead of the 7,500-8,000 sq mi that was expected this year. But the zone is unusually thick, reaching from the ocean floor nearly to the surface.
Nancy Rabalais, a researcher for the Louisiana Universities Marine Consortium who specializes in the problem said that in some areas where the oxygen was lowest, usual bottom dwellers like crabs, eels and shrimp were seen swimming at the surface.
She and other researchers are conferencing today with with Jane Lubchenco, head of the National Oceanic and Atmospheric Administration, to discuss implications and possible solutions for dead zones.
One proposed solution we saw recently is the idea of crop biodiversity. The logic is that since fertilizers and agricultural runoff are a big culprit, if we practice crop biodiversity - which cuts down on the need for fertilizers, pesticides and other chemicals - then we can shrink dead zones. The link is fairly clear, and also underscores the interconnectedness of land and ocean systems.
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More on Dead Zones
Climate Change Causing Ocean Dead Zones to Grow
Tropical Dead Zones Set to Expand by 50 Percent Under Climate Change
Ocean "Dead Zones" Increasing: 400 Oxygen-Deprived Areas Now Exist
A Primer on Global Warming-Caused Marine Dead Zones