Gulf of Mexico "Dead Zone" larger than ever

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http://green.yahoo.com/news/ap/20080723/ap_on_sc/dead_zone.html

Researcher says Gulf dead zone bigger than ever

By MICHAEL GRACZYK, Associated Press Writer Posted Wed Jul 23, 2008 2:39am PDT


HOUSTON - A "dead zone" in the Gulf of Mexico off the Texas-Louisiana coast this year is likely to be the biggest ever and last longer than ever before, with marine life affected for hundreds of miles, a scientist warned.
"It's definitely the worst we've seen in the last five years," said Steve DiMarco, a Texas A&M University professor of oceanography who for 16 years has studied the Gulf of Mexico dead zone, so named because the oxygen-depleted water can kill marine life.
The phenomenon is caused when salt water loses large amounts of oxygen, a condition known as hypoxia that is typically associated with an area off the Louisiana coast at the mouth of the Mississippi River. The fresh water and salt water don't mix well, keeping oxygen from filtering through to the sea bottom, which causes problems for fish, shrimp, crabs and clams.
This year's dead zone has been aggravated by flood runoff from heavy spring rains and additional runoff moving into the Gulf from record floods along the Mississippi.
DiMarco, joined by researchers from Texas A&M and the University of Georgia, just returned from an examination of 74 sites between Terrebonne and Cameron, La. He said the most severe hypoxia levels were recorded in the mid-range depths, between 20 and 30 feet, as well as near the bottom of the sea floor at about 60 feet.
Some of the worst hypoxic levels occurred in the western Gulf toward the state line.
"We saw quite a few areas that had little or no oxygen at all at that site," DiMarco said Tuesday. "This dead zone area is the strongest we've seen since 2004, and it's very likely the worst may be still to come.
"Since most of the water from the Midwest is still making its way down to the Gulf, we believe that wide area of hypoxia will persist through August and likely until September, when it normally ends."
Last year, DiMarco discovered a similar dead zone off the Texas coast where the rain-swollen Brazos River emptied into the Gulf.
The zone off Louisiana reached a record 7,900 square miles in 2002. A recent estimate from the National Oceanic and Atmospheric Administration and Louisiana State University shows the zone, which has been monitored for about 25 years, could exceed 8,800 square miles this year, an area roughly the size of New Jersey.
DiMarco said a tropical storm or hurricane likely would have no impact on this year's zone, believed to be caused by nutrient pollution from fertilizers that empty into rivers and eventually reach the Gulf.

Copyright © 2007 The Associated Press. All rights reserved. The information contained in the AP News report may not be published, broadcast, rewritten or redistributed without the prior written authority of The Associated Press.
 
I don't understand the mechanism that's causing this to happen, is it the fresh/salt meeting or the fertilizers?
 
i dont know either.... but whatever it is it sucks!
 
Arachnar;2005305; said:
I don't understand the mechanism that's causing this to happen, is it the fresh/salt meeting or the fertilizers?

A combination of both, but mostly just freshwater mixing with saltwater. The main reason alot of marine life is being killed is because the large amounts of rain/ flooding in the midwest around Iowa, Missouri, Nebraska, and Kansas...

When freshwater and saltwater mix in river deltas, freshwater naturally rises above seawater because seawater obviously has a higher specific gravity. The freshwater lays on top of the saltwater and does not mix. It creates a barrier of sorts. Because of this barrier, gas exchange going on at the surface of the Gulf of Mexico only translates into higher oxygen levels in the freshwater and little to no oxygen levels in the saltwater. The layer of freshwater on the surface of the Gulf slowly starves the underlying saltwater of oxygen because the layer of saltwater is not exchanging gases at the surface...
 
I was always under the impression that the excess nutrient runoff from the american breadbasket caused a phytoplankton bloom that explodes exponentially until their metabolism depletes oxygen to a level where they, and all other organisms, experience a population crash, the decaying of which favors production of sulphur dioxide molecules over respiratory activity. correct me if wrong.


that being said... I think we need a 'blue revolution' in order to counter the 'green revolution'. eat sustainable and low on the food chain!
 
srikamaraja;2005352; said:
I was always under the impression that the excess nutrient runoff from the american breadbasket caused a phytoplankton bloom that explodes exponentially until their metabolism depletes oxygen to a level where they, and all other organisms, experience a population crash, the decaying of which favors production of sulphur dioxide molecules over respiratory activity. correct me if wrong.


that being said... I think we need a 'blue revolution' in order to counter the 'green revolution'. eat sustainable and low on the food chain!

You sound very informed on the topic... I can not comment on your reasoning as I have no idea. I am only familiar with hypoxia because of my research on the potential of the Sea of Japan freezing over and halting trade because of hypoxia....

I read another article on the "Dead Zone" issue a while back. If I remember correctly I think it said that the waters mixing was the main culprit. If I use common sense, I can see waters mixing as the main cause for one reason. Namely, how much has fertilizer usage in the midwest increased between last year and this year, when the "Dead Zone" was its usual size? 5-15% at the most? How much has flooding increased between this year and last year? ALOT!:( In my mind, the dramatic increase in flooding correlates to the extremely large dead zone that we are seeing this year...
 
You are right, the flooding leads to the erosion of the nutrient rich topsoils, no matter how much the fertilizer use increases.
 
srikamaraja;2005419; said:
You are right, the flooding leads to the erosion of the nutrient rich topsoils, no matter how much the fertilizer use increases.

You were right as well my friend. I had no idea about fertilizers leading to a phytoplankton bloom. I just looked it up and you are completely on point :thumbsup:
 
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