Gulf of Mexico dead zone shrinks

By Kate Spinner, Sarasota Herald Tribune,
Monday, July 27, 2009 at 2:45 p.m.

The vast oxygen-starved dead zone in the northern Gulf of Mexico shrunk by about half its typical size this year, but scientists are not celebrating.

The dead zone covered about 3,000 square miles of sea floor this year, compared with an average of about 6,000 square miles over the past several decades.

The dead zone forms because nutrient pollution from farmland, cities and sewage flows down the Mississippi River, fueling giant algae blooms in the northern Gulf. When the blooms die, they sink to the ocean floor and rob the water of oxygen. The lifeless region threatens a $2.8 billion recreational and commercial fishing industry.

Predictions made earlier this year called for the vast area void of sea life to expand farther than ever, based on nearly record high nutrient pollution. Changing flows in the Mississippi River, as well as unusual wind patterns and oceanic currents prevented the zone from growing, by stirring up the waters. The mixing of water introduces oxygen, which is needed for life to live in the world’s seas.

Supported by the National Oceanic and Atmospheric Administration, scientists at Louisiana Universities Marine Consortium have been tracking the dead zone for decades. The federal government has set a goal to reduce the dead zone size to 2,000 square mile by 2015.