The “dead zone” in the Gulf of Mexico shrank over the last year, researchers announced this week, suggesting at least some turnaround from 2017’s record-sized region where sea life struggles.
The zone is defined by water with severe oxygen depletion caused by the runoff of chemicals used on land. This year’s zone was 2,720 square miles, a huge reduction from 2017’s record 8,497 square miles and lower than the recent yearly average before that, according to the National Oceanic and Atmospheric Administration.
The “dead zone” forms each summer in a largely horizontal pattern not far off the Louisiana coast, running west to roughly the Texas border. To give some idea of the area affected, researchers compared this year’s zone to the size of Delaware, whereas last year’s was roughly the size of New Jersey.
While the reduced size was welcome news, environmentalists cautioned the Dead Zone still exceeds the goal set by the Gulf Hypoxia Task Force of 1,900 square miles. Researchers have been measuring the Dead Zone since 1985.
“There is nothing average about a human-caused area in the Gulf the size of Delaware where dissolved oxygen gets so low, sea life must swim away or suffocate,” said Matt Rosa, senior policy director for the Gulf Restoration Network.
The runoff into the Gulf is accumulated as the Mississippi River courses from its Minnesota headwaters to the Southern Pass, and with roughly a third of its water diverted by the U.S. Army Corps of Engineers through the Atchafalaya Basin, Mr. Rosa said. All told, the drainage involved more than 40 percent of the water from the 48 contiguous states, scientists say.
The ship used to take Gulf measurements has a deep draft and cannot patrol along Louisiana’s watery coast and its myriad bayous. Consequently, the full “Dead Zone” is probably slightly larger than the map released each year, and Mr. Rosa said in some years researchers on land have seen shrimp leaping out of the water on to the shore because they could not breathe in the water.
Shrimp are the fish most affected by the “dead zone,” according to the Gulf Restoration Network.
It said that the growth of the Gulf shrimp can be stunted, resulting in fewer and higher priced large brown shrimp and a drop in the price of smaller shrimp. What’s more, fishing costs rise because fishermen are forced to travel greater distances to get to spots in the Gulf unaffected by the “dead zone.”