Gulf ‘Dead Zone’ The Size Of Massachusetts: 5 Things To Know

The Gulf of Mexico’s oxygen-deprived “dead zone” is expected to grow to approximately 7,829-swaure miles, an area about the size of Massachusetts, this year. These hypoxic zones are mainly caused by farm chemical and sewage runoff into the Mississippi River that eventually washes into the Gulf, killing marine life and crippling to the fishing industry.

Scientists from the National Centers for Coastal Ocean Science expect the dead zone to surpass the five-year average of 5,770 square miles, and will confirm the size of the 2019 Gulf dead zone in early August.

Unusually heavy spring rains in the Mississippi Basin region this spring are contributing to a larger-than-normal dead zone, the scientists said.

It won’t be the largest dead zone on record. That occurred in 2017, when the dead zone was 8,776 square miles.

Here are five things to know about the dead zone:

1. Dilution isn’t the solution.

You might think that as the fresh water from the Mississippi enters the ocean, it would simply be diluted in the larger water body. But freshwater is less dense than the saline seawater, so the nitrogen and phosphorus-laden runoff sits on top of the ocean surface and doesn’t mix, spurring an overgrowth of algae that consumes oxygen as the plants decompose.

The low-oxygen waters create the condition called hypoxia, and marine life suffocate and die. It’s warmer than the deeper ocean water, further contributing to the stratification. When the waters don’t mix, oxygen in the bottom waters is limited.

2. The Gulf shrimp and shellfish industry is in big trouble.

Most shrimp live in shallow waters close to the shore, but when they’re swimming in hypoxic waters with a limited oxygen supply, their growth is stunted. A 2017 study led by Duke University’s Nicholas School of the Environment determined the late-spring and summer Gulf dead zones “drive up the price of large shrimp relative to smaller size, causing economic ripples that can affect consumers, fishermen and seafood markets alike.”

“Because fishermen are catching more small shrimp and fewer large ones during these months, the price of small shrimp goes down and the price of large ones goes up, creating a short-term disturbance in the market that we can track,” said Duke’s Martin D. Smith, the George M. Woodwell Distinguished Professor of Environmental Economics.

The shrimp don’t necessarily die, but when oxygen is low, “any shrimp, crabs and fish that can swim away, will swim away,” Louisiana State University ocean ecologist Nancy Rabaliais told National Geographic. “The animals in the sediment [that can’t swim away] can be close to annihilated.”

As a result, shrimpers are going farther out to sea, an economic hardship for many.

Two shrimpers who traveled in late 2018 to Minnesota to meet with farmers near the headwaters of the Mississippi River said many shrimpers are abandoning the industry. There were about 100 shrimping families in Mobile, Alabama, three decades ago, but now there are only 10, Randy Skinner, who started shrimping as a 13-year-old 50 years ago, told Minnesota Public Radio.

3. Of the Midwestern 12 states contributing to the dead zone, Iowa is the leader.

The dead zone-causing runoff is traced to a dozen Midwestern states: Arkansas, Illinois, Indiana, Iowa, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Ohio, Tennessee and Wisconsin.

Iowa contributes to the dead zone more than any other state, partly because it has more federally subsidized cropland — 251,122 acres in 2017 — than any of the others. But that's only part of the picture.

Iowa, with a human population of 3.156 million, is also a top producer of livestock. If Iowa's hogs, cattle, poultry and other farm animals were counted along with people, the state’s population would be about 168 million, according to a University of Iowa analysis.

A study last year showed that despite the millions of dollars spent to reduce nitrate and phosphorus runoff into the state’s waterways by 45 percent, the pollution flowing from Iowa to the Gulf of Mexico has grown by nearly 50 percent over nearly two decades.

“Just based on water quality data, I think we can say we’ve not made much progress over the past 20 years in terms of nitrogen,” Chris Jones, a research engineer at the University of Iowa’s IIHR-Hydroscience & Engineering, told The Associated Press last year.

The plan is dependent on voluntary compliance by farmers and livestock producers, and that may not be enough, according to environmentalists.

“We’ve been pouring state and federal money into cutting nutrient pollution for decades, and this highlights the fact that the voluntary approach is not working,” Jennifer Terry, executive director of the Iowa Environmental Council, told The AP last year. “We’re not headed in the right direction. ... We need to follow the lead of other states and pass some environmental laws that will actually reduce loads and result in cleaner water.”

In a recent blog post, Jones wrote: “We have the equivalent of 168 million people here ... the scale of that's so enormous, we have no margin for error when it comes to water quality.”

4. Climate change isn’t helping.

Rabaliais, the Louisiana State University ocean ecologist, told National Geographic the growing dead zone isn’t a particular surprise, given torrential rains associated with climate change that inundated the Midwest this spring.

Farmers had already spread nitrogen and phosphorus-rich fertilizer in preparation for planting of corn and soybeans, but they washed into the Mississippi River before the farmers could get their crops in.

“The best way to solve the issue is to limit the nutrients at their source,” Rabalais told the magazine. “Once they're in the river, there's no good way to reduce them.”

Warming waters in the Gulf of Mexico could exacerbate the rates of hypoxia.

“That is a long-term concern,” David Scheurer, a scientist from the National Oceanic and Atmospheric Administration, told National Geographic. “If the climate does change in that region, there is a fair amount of evidence suggesting you would expect things to get worse.”

5. Dead zones are reversible.

Though it’s the best known, the Gulf of Mexico dead zone isn’t the only one. They occur around the world, some of them naturally, but primarily in areas with heavy agricultural and industrial runoff.

Dead zones are reversible if the causes are eliminated, as happened in the Black Sea after the fall of the Soviet Union in the 1990s, Scientific American reported. Nothing intentional was done to bring that about, but the cost of agricultural chemicals spiked in the unstable economy, and farmers simply didn't apply chemicals.

Scientists, policymakers and the United Nations took notice and pushed for industrial emissions reductions in areas where dead zones have occurred. Countries along the Rhine River, for example, have been able to reduce sewage and nitrogen levels reaching the North Sea by nearly 35 percent.