Gulf red tide blooms waning


Published: Tuesday, January 9, 2007 at 6:01 a.m.
Last Modified: Monday, January 8, 2007 at 12:00 a.m.

SARASOTA — Following six months of iffy beach days caused by red tide blooms that stretched and shifted from Collier to Pinellas counties, the Southwest Florida Gulf Coast is starting to clear.

For the past month, red tide cell counts from the shores of Bradenton to Boca Grande have been dropping. The last count showed no red tide north of Venice and very little to the south.

While red tide has not been strong enough to ruin beach days for at least a month, scientists won't say the bloom is over.

"Things have definitely gotten a lot better, but we still have some lingering populations of red tide," said Jay Abbott, a red tide scientist with the research arm of the Florida Fish and Wildlife Conservation Commission. "As long as it's around at concentrations like we're seeing, we can't really say that it's gone."

Historically, red tide disappears, or at least drops, in the cool winter months. But a bloom persisting past December can occur, especially when the average temperature is above normal, as it has been the past month.

A 2005 bloom, one of the worst in recent decades, cropped up in winter and spread deadly toxins from north of St. Petersburg to south of Naples at its peak in late September.

The 2006 bloom was not as severe, but still caused respiratory problems and killed marine animals.

Red tide algae naturally occur in marine waters in background concentrations. When the algae encounter conditions that allow them to feed and grow, they form a bloom.

Generally, the algae prefer saltwater, warm temperatures and calm waters.

Scientists debate the role nutrient pollution plays in the algae's growth to bloom status, but all algae need nutrients, such as nitrogen and phosphorus, to survive.

The algae's life cycle is short and when they die, they emit brevetoxin, a poison that kills dolphins, sea turtles, manatees and fish.

In 2005, 92 manatees died from exposure to red tide. Statistics show 53 died in 2006 as of Dec. 20.

Allen Foley, a state sea turtle scientist, said he suspects red tide caused double the average sea turtle strandings on Southwest Florida beaches in 2005 and 2006.

On average, scientists recover about 250 sea turtles from the shore. During 2005 and 2006, that number reached near 500.

Most sea turtles die and sink to the sea floor. Those that scientists document represent about 10 percent of actual deaths. So, the death toll from red tide could be anywhere from 250 to 2,500 sea turtles, Foley said.

Red tide also affects people, though not as severely.

When the wind blows toward shore during red tide blooms, the poison drifts up to 1 miles inland.

Even healthy lifeguards feel the typical cough and sometimes end up with a stuffy nose. The poison can cause breathing problems for people with asthma.

Last year, 4,865 people called the Department of Health's aquatic toxins hot line to complain about exposure to algae poisons.

About 95 percent of the calls came from coastal counties north of Naples and south of Tampa, said Fernando Senra, a spokesman for the Department of Health.

"The number of calls we get is absolutely related to the size and location of the red tide bloom," Senra said via e-mail. Calls dropped off in November as the bloom waned.

Abbott said that while the bloom has shrunk to the point where it is not causing much harm now, it's impossible to predict whether and when it will sprout again.

On Friday, a small bloom was detected off Sanibel and a few dead fish had washed ashore, along with mats of red seaweed.

Abbott said the fish kill may be linked to the bloom.

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