This year Texas A&M University researchers, led by oceanographer Steve DiMarco, left Galveston on June 25 and immediately found areas of low-oxygen, or hypoxic water, off the Texas coast.
The team found two other distinct dead zones: one near the Barataria and Terrebonne region off the Louisiana coast, the second one south of Marsh Island (also Louisiana). They found no hypoxia in the 10 stations visited east of the Mississippi delta.
Dead zones are areas of this hypoxic water in which fish, shrimp and crabs are stressed and can sometimes die due to oxygen starvation. They are caused by excess streamflows that carry excess nutrients, particularly nitrogen and phosphorus, into the Gulf. These nutrients create large algae blooms which, upon decomposition, suck oxygen out of the water.Dr. Steve DiMarco stands on a Gulf of Mexico beach
DiMarco’s was the first comprehensive cruise of the northern Gulf of Mexico to be conducted in June. A Louisiana-based group led by Nancy Rabelais has cruised the Gulf nearly every July since the mid-1980s. Dead zones are believed to peak in late July.
DiMarco’s cruise found a dead zone that measured 3,260 square miles. Earlier this year Rabelais and colleagues predicted this year’s dead zone will be the largest ever, reaching a maximum extent of about 9,400 square miles.
So does the area DiMarco found mean the dead zone will nearly triple during the next month? Or might the prediction be off? “We have no way of knowing,” he said.
This is one of the big reasons why DiMarco’s team went out in June. NOAA wants to develop a circulational model to track and predict how dead zones change in size over time. DiMarco received a $3.7 million grant in 2009 to cruise every June and August through 2014.
Finding a dead zone off the Texas coast this summer was mildly surprising, as the state’s drought has precluded have river flows from the state reaching the Gulf of Mexico.
“It was a bit surprising to us,” DiMarco said. “My guess is that it is because of the large amount of fresh water coming from the Mississippi River.”
The Mississippi River, of course, has had some record-breaking flooding this summer. In any case, we’ll soon know for sure.
During the cruise DiMarco’s team collected samples of the hypoxic water. As it turns out an analysis of isotope values in the water will allow scientists to determine what latitude the rain water came from. So from the chemical analysis they’ll be able to tell if its Texas water or Mississippi River water.
DiMarco’s team will be back out in August to assess the size of the dead zone again. I told him it’s a shame the dead zone doesn’t peak in March or April.
See DiMarco's findings on the research blog http://hypoxia.tamu.edu and the original story on Eric Berger's Houston Chronicle blog SciGuy.
Contact: Steve DiMarco at 979.862.4168 or