Dead zone on La.-Texas coast seen as size of Connecticut

Computer estimate of April through October 2016 low oxygen levels in Gulf

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By Mark Schleifstein, NOLA.com | The Times-Picayune 
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on December 06, 2016 at 4:38 PM, updated December 07, 2016 at 3:44 PM

A federal-state task force charged with reducing the nutrients that form the annual low-oxygen dead zone in the Gulf of Mexico along Louisiana’s coast on Tuesday (Dec. 6) outlined a variety of bright spots in their efforts to help Midwest farmers reduce fertilizer use or block it from entering rivers and streams. But task force members also heard that modeling indicates the size of 2016 summer low-oxygen area was still nowhere near the 1,930 square miles that the task force has repeatedly set as its long-term goal.

Two different models estimated the size of the 2016 dead zone at either 5,367 square miles — 13,900 square kilometers, seen in the upper map — or 8,146 square miles, or 21,100 square kilometers, seen in the lower map. The July cruise that normally collects samples to estimate the 2016 dead zone was cancelled when the ship that scientists were to use broke down and no replacement could be found.

This year, the size of the dead zone was estimated by a series of monitoring efforts made in August. A routine July cruise was cancelled when a National Oceanic and Atmospheric Administration ship had engine trouble and no substitute could be arranged.

‘Dead zone’ map cruise canceled; first time in 27 years

Scientific expedition was to determine whether June forecast of 6,824-square-mile low-oxygen zone is accurate

Scientists collaborating with the agency used the August information to feed two new computer models that are now being used to estimate the size of the low-oxygen area off the coast in three dimensions and over time. Those models estimated the 2016 dead zone at either 5,367 square miles or 8,146 square miles.

The analysis was conducted by Rob Magnien, director of the agency’s Center for Sponsored Coastal Ocean Research; Katja Fennel, an oceanography professor at Dalhousie University in Halifax, Nova Scotia; Dubravko Justic, an oceanography and coastal scientists professor at Louisiana State University; and Nancy Rabalais, an oceanography and wetlands studies professor at LSU.

Dead zone on La.-Texas coast seen as size of Connecticut

Low-oxygen area disrupts fisheries, kills bottom-living organisms

In his presentation to the the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, also known as the Hypoxia Task Force, Magnien said the computer models also are able to show that almost all of the area off Louisiana’s coast has been exposed to hypoxia — below 2 micrograms per liter of oxygen — for one or more days in both 2015 and 2016. The low oxygen conditions kill small organisms that live in bottom sediments, which often are used as food for fish and other, larger organisms. And the fish, shrimp and crabs that are mobile enough to escape the low oxygen must often travel dozens of miles to find survivable oxygen levels.

In 2014, the task force set a goal of reducing nitrogen and phosphorus pollution enough to lower the size of the low-oxygen zone to 1,930 square miles by 2035. An interim target of a 20 percent reduction was set for 2025.

However, that same goal was set by the task force in 2001, three years after it was formed, when it said it expected the goal to be met by 2015.

Hypoxia is formed in the Gulf after spring and early summer rainfall in the Midwest washes nutrients — nitrogen and phosphorus fertilizer — into rivers and streams that lead to the Mississippi and Atchafalaya rivers. The farming nutrients are joined by nutrients from agricultural feedlot operations and from industries, urban sewage treatment plants and rural septic tanks as they move downriver to the Gulf.

When the nutrient-rich freshwater exits the rivers, it forms a layer above saltier Gulf waters. The nutrients feed blooms of algae, which die and sink into the saltier water at the bottom and decompose, using up that lower water layer’s oxygen. The low-oxygen conditions continue until frontal weather systems or hurricanes mix the surface freshwater and the lower saltier water, often not until September.

The task force includes representatives of the U.S. Environmental Protection Agency, the Army Corps of Engineers and the departments of Commerce, Interior and Agriculture, and representatives of 12 states in the main part of the Mississippi’s watershed: Arkansas, Illinois, Indiana, Iowa, Kentucky, Louisiana, Minnesota, Mississippi, Missouri, Ohio, Wisconsin, and Tennessee. The National Tribal Water Council represents tribal interests.

The task force’s hypoxia reduction plans include mostly voluntary efforts aimed at enticing farmers to adopt better fertilizer use practices or to install vegetation buffer zones around their farmland to capture nutrients before they wash into waterways. At Tuesday’s meeting in New Orleans, the task force heard about various states’ successes in developing such plans and getting agricultural interests to participate.

Included were a presentation on Tulane University’s nitrogen reduction challenge. On Monday, the university announced it had chosen five finalists for a $1 million prize, which will be awarded in December 2017, after the finalists’ proposals are tested on farmland in northeast Louisiana.

5 finalists named for $1 million Tulane nitrogen reduction prize

Finalists propose ways to reduce farmland nutrients that create low-oxygen dead zones off Louisiana’s coast and elsewhere around the world

An EPA representative announced the beginning of a similar challenge aimed at finding new, cheaper nutrient monitoring devices.

But during comments from the public at the end of the meeting, May Nguyen,  community outreach director for the Tulane Environmental Law Clinic, and speaking on behalf of the Mississippi River Collaborative, warned that there’s still been no significant reduction in the size of the hypoxia zone in the Gulf resulting from the voluntary efforts. The collaborative has urged EPA to require states to mandate reductions in so-called “non-point” fertilizer pollution from farmlands, or to implement the regulations themselves.

In a November report entitled “Decades of Delay,” the collaborative demanded that the EPA require eight states that have not yet done so develop numeric criteria for phosphorus releases, and to require 10 states to develop similar nitrogen numeric criteria.

And during a scheduled presentation to the task force, Chalin Delaune, vice president of Tommy’s Seafood Inc. in New Orleans, warned that hypoxia is costing Louisiana fishers millions of dollars, either because they must travel greater distances to places that aren’t in low-oxygen areas, or because the low oxygen conditions are among the things responsible for recent reductions in catches for crabs and other seafood species.

Magnien said his team’s models also are producing troubling findings about the effects of global warming, if nothing is done to reduce nutrients entering the Gulf.  The computer models show the low oxygen area is likely to expand significantly by 2100 because of expected warmer water temperatures and increased rainfall on the U.S. interior, which would increase the nutrients in the water.

Equally disturbing, he said, is the potential that the increased nutrients could result in dramatic increases in the acidification of offshore waters by 2100. That would damage or kill shellfish and other fish species. The decomposition of the algae blooms creates carbon dioxide in the lower waters, which results in acidification.