Thursday, August 03, 2017

Fertilizer runoff causes biggest oxygen-free 'dead zone' ever measured in Gulf of Mexico

The National Oceanic and Atmospheric Administration announced this week that the oxygen-deprived "dead zone" in the Gulf of Mexico is the biggest one ever measured, "adding fuel to a debate over whether state and federal governments are doing enough to cut pollution that comes from farms," Dan Charles for NPR.
This year's dead zone (National Oceanic and Atmospheric Administration graphic)
The New Jersey-sized dead zone is the result of heavy rains this year that washed fertilizer nutrients such as nitrogen and phosphorus from Midwest farms down the Mississippi River. "When it reaches the Gulf of Mexico, those nutrients unleash blooms of algae, which then die and decompose. That is what uses up the oxygen in a thick layer of water at the bottom of the Gulf, in a band that follows the coastline," Charles reports. Fish that live closer to the surface can get away, but bottom-dwelling organisms that form a vital part of the food chain die off.

Government agencies have promised to take action, and have encouraged Midwest farmers to limit fertilizer runoff by taking such measures as planting grassy strips along streams to use up the fertilizer. One Iowa farmer has been tinkering with crop rotation methods to reduce fertilizer use and waste. And scientists at the University of Illinois are tackling the problem with a filtration system made of woodchips. But former NOAA top scientist Don Scavia, who prompted the agency to start analyzing the dead zone in 1985, wrote in a blog post that voluntary measures will not be enough to improve the situation.

Scavia argues that the Gulf should receive the same kind of federal protection as the Chesapeake Bay. "In 2010, though, despite fierce objections from farmers, the federal government set mandatory limits on nutrient pollution entering the bay. State governments spent billions of dollars to meet those targets. Now pollution in the bay is down, and some wildlife in the Chesapeake is starting to recover," Charles reports.

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