Scientists report largest ever dead zone in Gulf of Mexico

Scientists measured the largest dead zone ever recorded for the Gulf of Mexico, a whopping 8,776 square miles, massive enough to cover all of New Jersey. And only dramatic shifts in farming practices are likely to prevent even bigger problems in the future.

Dead zones, which disrupt fishing industries and threaten aquatic species, are caused by industrial and agricultural runoff. Every spring, the Mississippi River funnels a rush of nutrients into the gulf that fuels an explosion of growth of microscopic algae called phytoplankton. The bloom of life for the algae is short-lived, and their corpses sink to the depths below, where their decomposition gives rise to a burst in bacterial growth. The microbes rapidly consume not only the plankton but also all of the oxygen dissolved in the deep.

At the same time, the incoming river water forms a layer on the surface of the gulf, preventing new oxygen from dissolving and mixing with the depleted waters below. Fish that do not flee suffocate, as do stationary species and plant life.

The size of the Gulf of Mexico dead zone fluctuates annually, but increased precipitation this year amplified runoff. The result is an oxygendepleted area almost 50 percent larger than what has been seen on average for the past five years.

Dead zones occur throughout the world and can be reversed. After the collapse of the Soviet Union, nutrient runoff was reduced threefold to fourfold, eliminating a 15,000square-mile dead zone off the northwest continental shelf of the Black Sea.

A dead zone in the Chesapeake Bay also has shrunk in recent years.