by Mike Holmes
Springtime brings yet another prediction that the Gulf Dead Zone will be larger and more deadly this summer than ever before. So what is the dead zone? Although it sounds like a Stephen King tale, it is probably more realistic. The dead zone is an area of oxygen-deprived water where fish and other marine creatures cannot live. This area—officially known as a hypoxic zone—is thought to be caused by excessive nutrients entering the Gulf, mostly from the Mississippi and Atchafalaya River drainages on the Louisiana coast.
The bulk of the material causing the problem seems to be nitrogen and phosphorus from agricultural fertilizer used in the U.S. Midwest. These nutrients are too much of a good thing, and simultaneously rob oxygen from the water and stimulate excessive algae growth. When the algae die and sink to the bottom, they further deplete the oxygen supply. When oxygen levels get too low, the water cannot support life, creating a hypoxic or “dead zone” along the bottom.
Shrimpers complain of low catch rates in dead zones, and sometimes no shrimp at all. Sport and commercial fishermen have trouble catching bottom-dwelling species such as red snapper. Compounding the problem is the dead zone’s enormity—the largest dead zone on record in 2002 covered more than 8,400 square miles! While the zone of oxygen-depleted water has been falling since that record level, it has still been estimated at 6,700 square miles and is expected by NOAA scientists to range between 1,200 and 6,200 square miles this summer. In 2009, commercial fisheries in the Gulf of Mexico were worth $629 million, so anything that hurts this resource can be very serious. Recreational fishermen also suffer, dealing additional damage to local economies.