From the ABC 7 Weather team

Largest 'dead zone' in recorded history grows in the Gulf

June 15, 2011 - 02:22 PM
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Add this to our year of dismal records: The biggest known dead zone has sprouted in the Gulf of Mexico, thanks to fertilizers and the recent floods.

Add this to our year of dismal records: The biggest known dead zone is predicted to sprout in the Gulf of Mexico soon, thanks to fertilizers and this spring's extreme flooding.

Dead or "hypoxic" zones are areas in the water that have no oxygen; they effectively smother any sea life that passes through their borders. The zones are created when rain and floods wash fertilizers off of farmland and lawns, where they enter the seas and feed massive colonies of algae that suck all the oxygen from the water. The Chesapeake Bay is one big dead zone, but the Gulf is bigger: Every year it sprouts the second-largest area of hypoxia in the world. (The largest is in the Baltic Sea; see where others are worldwide in this map.)

And in 2011 the Gulf zone is predicted to be especially immense. Forecasters with Louisiana and Michigan universities say that the record flooding of the Mississippi this year is feeding the Gulf algae like never before. The busy green critters are expected to eat so much O2 that a killing field will spread to the size of New Hampshire, up to 9,421 square miles. Since dead zones were first noticed in the Gulf in 1985, the largest one yet measured was 2002's 8,400 square-mile zone. A bigger zone spells a world of hurt for the Gulf's imperiled fishing industry.

Here's NOAA's explanation for the zone's unusually bloated size:

During May 2011 stream-flow rates in the Mississippi and Atchafalaya Rivers were nearly twice that of normal conditions. This significantly increased the amount of nitrogen transported by the rivers into the Gulf. According to USGS estimates, 164,000 metric tons of nitrogen (in the form of nitrite plus nitrate) were transported by the Mississippi and Atchafalaya Rivers to the northern Gulf. The amount of nitrogen transported to the Gulf in May 2011 was 35 percent higher than average May nitrogen loads estimated in the last 32 years.

Read more about this developing problem at NOAA. Follow the jump for a neat animation showing how these suffocating behemoths form.

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