August 23, 2012
Good News From The Bad Drought: Gulf ‘Dead Zone’ Smallest In Years
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NOAA Gulf of Mexico Hypoxia Watch
The worst drought to hit the United States in at least 50 years does have one benefit: it has created the smallest “dead zone” in the Gulf of Mexico in years, says a Texas A&M University researcher who has just returned from gulf waters.
Oceanography professor Steve DiMarco, one of the world’s leading authorities on the dead zone, says he and other Texas A&M researchers and graduate students analyzed the Gulf Aug. 15-21 and covered more than 1,200 miles of cruise track, from Texas to Louisiana. The team found no hypoxia off the Texas coast while only finding hypoxia near the Mississippi River delta on the Louisiana coast.
“We had to really hunt to find any hypoxia at all and Texas had none,” he explains.
“The most severe hypoxia levels were found near Terrabonne Bay and Barataria Bay off the coast of southeast Louisiana.
“In all, we found about 1,580 square miles of hypoxia compared to about 3,400 square miles in August 2011. What has happened is that the drought has caused very little fresh-water runoff and nutrient load into the Gulf, and that means a smaller region for marine life to be impacted.”
DiMarco has made 27 research trips to investigate the dead zone since 2003.
DiMarco says the size of the dead zone off coastal Louisiana has been routinely monitored for about 25 years. Previous research has also shown that nitrogen levels in the Gulf related to human activities have tripled over the past 50 years. During the past five years, the dead zone has averaged about 5,700 square miles and has reached as high as 9,400 square miles.
Hypoxia is when oxygen levels in seawater drop to dangerously low levels, defined as concentrations less than 2 milligrams per liter, and persistent hypoxia can potentially result in fish kills and harm marine life, thereby creating a “dead zone” of life in that particular area.
The Mississippi is the largest river in the United States, draining 40 percent of the land area of the country. It also accounts for almost 90 percent of the freshwater runoff into the Gulf of Mexico.
“These findings confirm what we found in a trip to the Gulf back in June, and also what other researchers in Louisiana have discovered, so there is general agreement that the dead zone this year is a very, very small one.
“But the situation could certainly change by next spring,” DiMarco adds.
“The changes we see year to year are extreme. For example, last year, record flooding of the Mississippi River and westerly winds in the Gulf led to a much larger hypoxic area, particularly earlier in the summer. We’ll just have to wait and see what kind of rainfall is in store for the Midwest over the next 8-10 months.”
Participating at sea with DiMarco were Piers Chapman and Matthew Howard of the Department of Oceanography, Chris Shank of the University of Texas Marine Science Institute, TAMU graduate students: Ruth Mullins Perry, Emma Cochran, Laura Harred, Allyson Burgess Lucchese (Texas A&M-Galveston), and Marine Technicians Andrew Dancer and Eddie Webb and Alex and Tyler Mifflin of the Canadian TV show the Water Brothers.
On-shore participants included Lisa Campbell, Wilf Gardner and Mary Jo Richardson (oceanography), Antonietta Quigg (Texas A&M-Galveston) and Ethan Grossman (geology and geophysics).
The project was funded by NOAA’sCenter for Sponsored Coastal Ocean Research.
For more about hypoxia, go to:
Texas A&M University, Department of Oceanography, project website
About Research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $700 million. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.
What is Hypoxia?
(via the provided link)
Hypoxia is a condition in the oceans where dissolved oxygen gas concentrations in the ocean are low. Since the gases are dissolved, the seawater appears transparent or clear. So how can we measure the amount of dissolved oxygen in the water?
With CHEMISTRY of course!
A Winkler test determines the amount of dissolved oxygen in a sample by adding two chemical compounds- manganese sulfate (MnSO4) and potassium iodide (KI). A white precipitate (solid material) immediately develops and darkens to brown if high concentrations of dissolved oxygen are present. If the sample has little to no dissolved oxygen, the precipitate remains white and looks similar to snow. To measure the precipitate amount, we add a strong acid, such as hydrochloric acid (HCl), to the sample. The precipitate dissolves, changes color, and chemically reacts to form iodine (I). The scientists perform another chemistry technique, titration, to measure the amount of iodine formed. Titration is a common laboratory method that adds known concentrations of a chemical reagent to chemically react with an element in the sample, such as iodine. The volume of reagent used is directly related or equal to volume of element in the sample. Scientists can also use automated titration machines to perform the analysis at sea and provide instant measurements!
How does the oxygen gas even get into the ocean? Think for a second about land plants. What do plants contribute to the atmosphere?
OXYGEN through photosynthesis!
Photosynthesis also occurs in the ocean by microscopic plants called phytoplankton. The oxygen produced by the phytoplankton is dissolved in the ocean water. Waves at the surface can also trap oxygen from the atmosphere and move it into the water column. Naturally, there is more oxygen at the surface where there are high concentrations of wave activity and phytoplankton. When there is less than 1.4 ml/l of dissolved oxygen in the water, the waters are considered hypoxic and can be dangerous to respiring organisms, such as crabs, shrimp, and fish. Persistent areas of hypoxia are referred to as dead-zones in the world’s oceans.
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Based on a work at http://tamutimes.tamu.edu/2012/08/23/good-news-from-the-bad-drought-gulf-dead-zone-smallest-in-years/.
Texas A & M University News (2012).
Good News From The Bad Drought: Gulf ‘Dead Zone’ Smallest In Years
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