Scientists this week said the oxygen-deprived "dead zone" off the coast of Louisiana and Texas is the third-largest in history.
The phenomenon, also known as Hypoxia, occurs when fresh water on the surface caps the oxygen in the heavier salt water below. Nitrogen, from sources including fertilizer, erosion and sewage, speeds up the process by feeding algae.
But when the algae die and plummet to the ocean floor their decay depletes oxygen rapidly. Eventually, the lower layer holds too little oxygen for fish and other aquatic life.
While the duration of the dead zone is influenced by weather and currents, experts are placing much of the blame for the dead zone on high levels of nitrates in the Mississippi River.
According to a report by researchers from Louisiana Universities Marine Consortium, the "dead zone" now measures 7,900 miles, or about the size of New Jersey. Environmental groups from states up and down the Mississippi River are using the report to push for increased funding of conservation programs in the upcoming farm bill.
Susan Heathcote, Water Program Director/Iowa Environmental Council: "I think that this hypoxic zone, being the third largest ever on record, is a wake-up call for us. And, we need to respond to this with the opportunities presented in this Farm bill."
The "dead zone" was predicted to be large this year because of increased demand for corn. Environmentalists blame the dead zone primarily on nitrogen-based fertilizers used by farmers in the Mississippi watershed.
In Iowa, the nation's top corn producing state, nitrates associated with agricultural runoff have been a problem for years, particularly on the Raccoon River. . So much of a problem, that the Des Moines Water Works, built the world's largest nitrate removal facility there in 1991. Still, the Water Works says the Raccoon River on average has the highest nitrate concentration of any of the 42 largest tributaries in the Mississippi River Basin."
While agriculture often is blamed for much of the problem, some groups are taking a proactive approach. Over the past seven years, the Iowa Soybean Association has spent more than $2 million to help farmers reduce nitrates.
Roger Wolf, Director of Environmental Programs/Iowa Soybean Association: "We're involved in four river basins in Iowa, eight sub watersheds, and our programs look at nitrogen in these watersheds. Well, the answers are different across each of these watersheds and it just further validates that there is no silver bullet and the solutions will have to be customized."