High nutrient pollution levels have caused the Chesapeake Bay's underwater "dead zone" to expand unusually quickly this year: It covers a third of the bay and will likely become the bay's largest-ever area of oxygen-starved water. The dead zone, which sucks oxygen from deep waters and kills any marine life that can't escape it, stretched from the Baltimore Harbor to the bay's mid-channel region in June, a distance of about 83 miles. It has only grown since then, the Washington Post reports.
Nutrient pollution comes from chemicals, like fertilizer, and causes an increase of bay algae. In turn, the algae decomposes into a black, oxygen-sucking glop that kills oysters, shellfish, and any fish or crabs that can't get to surface waters. Dead zones occur annually, but this year saw an especially heavy flow of polluted water due to heavy rains and melted snow mixed with chemicals and sediment. The EPA has finalized an aggressive "pollution diet" to reduce the levels of chemicals and sediment allowed into the bay, but the plan will cost billions and is being challenged by lobbies and other groups.