Wednesday, August 2, 2017

2017 Gulf dead zone is largest ever, size of New Jersey, researchers say

WEDNESDAY, AUGUST 2, 2017 2017 Gulf dead zone is largest ever, size of New Jersey, researchers say Updated on August 2, 2017 at 12:51 PM Posted on August 2, 2017 at 12:50 PM Researchers measured the largest low-oxygen dead zone since 1984 during their 2017 cruise that ended Sunday (July 30), with this year's area totaling 8,776 square miles, larger than the state of New Jersey. Red on the map indicates hypoxia, where the oxygen level is less than 2 parts per million. (LSU/LUMCON) The low-oxygen dead zone along the Louisiana and Texas Gulf coast measured 8,776 square miles, the largest area since cruises began in 1985, and as large as the state of New Jersey, a team of researchers announced Wednesday (Aug. 2). The dead zone area likely was even larger, but limited monitoring time aboard their research ship during the six-day cruise that ended Sunday limited the team's ability to measure its stretch west along the Texas coast, said a news release. Scientists say this year's hypoxia zone is 4 1/2 times the size of the of the goal of about 1,900 square miles set by the federal-state Mississippi River Nutrient/Hypoxia Task Force. The task force has recommended that the dead zone size reach that goal by 2035, but in 2008, it had set the same reduction goal for 2015. Gulf's 'dead zone' is seen as 3rd largest in 32 years Gulf's 'dead zone' is seen as 3rd largest in 32 years Low-oxygen hypoxia might smother 10,000 square miles along Louisiana, Texas coasts Hypoxia, the scientific term for water containing less than 2 parts per million of oxygen, is known to kill organisms living in bottom sediments along the northern Gulf Coast, and recent research has shown that it also increases the price for some commercial fish catches, including shrimp, because the shrimp and fish stay out of the low-oxygen water, requiring fishers to travel farther to catch them. The monitoring cruise led by Louisiana State University marine scientist Nancy Rabalais found a solid band of water along the Gulf bottom with levels of less than 2 parts per million stretching from just west of the mouth of the Mississippi River in Louisiana well into the Texas coast area near Houston. LSU and Louisiana University Marine Consortium researchers actually estimated this year's cruise would show an even larger area of hypoxia -- 10,089 square miles -- based on the amount of nitrogen compounds carried by the Mississippi River in May. Nitrogen and phosphorus pollution enters the Mississippi throughout its watershed, which includes runoff from the Midwest cropland and factory livestock and chicken farms, and pollutants from sewer systems and septic tanks in other locations. About 30 percent of the Mississippi's water travels down the Atchafalaya River to the Gulf. The lighter freshwater containing the nutrients creates a layered effect when it reaches the Gulf and the nutrients trigger blooms of algae in the spring and summer. When the algae dies and sinks to the bottom, it decomposes, using up oxygen in the deeper heavy saltwater and creating dead zone conditions. Those conditions don't change until wind or weather, especially tropical storms or hurricanes, mix the freshwater at the surface into the saltier water.

No comments: