Red Tide blame points to Mississippi

A new NOAA study links the state's costly algae blooms with the river's pollutants.

By CRAIG PITTMAN, Times Staff Writer
Published November 8, 2007

A new theory on the source of Florida's Red Tide blooms lays the blame on the Mississippi River and the same pollutants that have created a "dead zone" off Louisiana.

Red Tide, which produces toxins that can kill fish and make beachgoers cough, has plagued Florida's Gulf Coast for centuries.

No one knows what makes the tiny creature known as Karenia brevis suddenly erupt into massive algae blooms that drive away tourists and their dollars.

Theories have included everything from African dust to fertilizer-laden storm runoff in developed coastal areas. Scientists have sought for years to find some way to predict when a bloom might hit.

Now, researchers led by Richard P. Stumpf of the National Oceanic and Atmospheric Administration have concluded that nutrients flowing from the Mississippi River may stimulate blooms growing on the continental shelf off the west coast of Florida.

Wind patterns play a role as well, Stumpf said in a conference call with reporters Wednesday.

Normally, water flowing out of the Mississippi travels west toward Texas. But seasonal wind changes in late summer and fall move the cells of algae eastward, according to the study, published in the journal Continental Shelf Research.

"The cells accumulate faster than can be explained by just growing," Stumpf said.

Instead, the study said, the wind shift appears to sweep the accumulated offshore Red Tide algae and its nitrogen fuel together into a massive bloom that is then pushed toward Florida's gulf beaches.

If the NOAA study is right, then "offshore areas should be examined for both small increases in nutrients and modest concentrations of the algae at the start of the bloom season," Stumpf said.

Cindy Heil, a Red Tide scientist with the state's marine science laboratory in St. Petersburg, noted that the NOAA theory runs counter to the findings of a similar study published last year by a group of University of South Florida oceanographers.

That study found that while pollutants in the Mississippi fueled Red Tide blooms off Texas, the Mississippi River's pollution had no effect on Florida's Red Tide, Heil pointed out.

The lead author of that study, oceanographer John Walsh, could not be reached for comment Wednesday.

Heil, who works for the Florida Fish and Wildlife Research Laboratory, said that her studies have found that by the time the Mississippi's flow gets to Florida's offshore waters, "it's generally stripped of nutrients."

The so-called "dead zone" in the gulf, first discovered in 1972, is an area off the Louisiana coast where massive algae blooms have left the water devoid of oxygen and, thus, devoid of marine life.

In 2006, the zone measured 6,622 square miles. NOAA scientists predicted earlier this year that in 2007 it could grow to more than 8,000 square miles. Scientists have found that the algae blooms are stimulated by nutrients such as nitrogen and phosphorus flowing in the Mississippi and Atchafalaya rivers.

Red Tide has been mild to nonexistent along much of the Gulf Coast this year, but it's currently bedeviling Escambia, Santa Rosa and Okaloosa counties in the Panhandle.

A massive Red Tide bloom in 2005 lasted through early 2006 and stretched from Pinellas to Collier counties, leaving large areas of the sea bottom devoid of marine life.

Stumpf said the jury is still out on whether polluted runoff from coastal areas could be fueling more intense and longer-lasting blooms like that one.

"That's an area of lively debate in the scientific community," he said.

FAST FACTS:

On the Web

The National Oceanic and Atmospheric Administration has provided Red Tide forecasts since 2004. For forecasts, click on www.csc.noaa.gov/crs/habf.

The Florida Fish and Wildlife Research Institute provides regular Red Tide status reports and maps. To see those, click on: www.floridamarine.org/features/view_article.asp?id=9670.

[Last modified November 7, 2007, 23:22:42]