School Zone 80x80
Get into the News 8 School Zone

Making our schools better

Terry’s Take: The dead zone

Posted on: 10:55 pm, June 27, 2013, by

Terry Swails Weather Blog

A possibly record-breaking, New Jersey-size dead zone may put a chokehold on the Gulf of Mexico this summer, according to a forecast released this week. Unusually robust spring rains and resultant floods across the Midwest are flushing agricultural runoff—namely, nitrogen and phosphorus—into the Gulf and spurring giant algal blooms, which lead to dead zones, or areas devoid of oxygen that occur in the summer.

aa

AREA DEFINED AS THE DEAD ZONE

A dead zone, which is commonly found in the oceans and Great Lakes, is an area usually in the bottom waters where there’s not enough oxygen to sustain life. It’s generally caused by algae stimulated by lots of agricultural nutrients in surface waters. When nutrients enter the water, they create an algal bloom. When the algae sink, bacteria start decomposing them, which uses up the available oxygen.

a2

RUNOFF FROM AGRICULTURAL NUTRIENTS REACH THE GULF

The forecast, developed by the University of Michigan and Louisiana State University with support from the National Oceanic and Atmospheric Administration (NOAA), estimates a Gulf dead zone of between 7,286 and 8,561 square miles. The largest ever reported in the Gulf, 8,481 square miles, occurred in 2002.

During summer the waters of the Gulf become stratified which inhibits oxygen from the atmosphere getting down to the deep water. As the bacteria use up oxygen, it’s not being replenished, so oxygen concentrations decrease until you get to two milligrams of oxygen per liter of water, which is very bad for fish. Below that, fish and organisms that can leave will and those that can’t will die.

a

HOW THE DEAD ZONE FORMS

The types of organisms that would die are animals that live on the bottom. Worms, clams, the kind of things that fish like to eat. Some fish would have serious trouble. Thus dead zones are important because most often the areas that become uninhabitable by fish, are the ones they prefer as habitat. To draw on an analogy that’s ironic, it would be like taking thousands of square miles of land in the Midwest out of production. The trickle down effect would allow food prices to sky rocket!

a1

DEAD ZONE FORECAST COMPARISONS