The week of April 15, 2005

If you think the red tide that plagued Boca Grande is worse than in the past, you're right. That's what a scientist told the Lee County Board of County Commissioners Tuesday.

Fifteen times worse.

"Since the 1950s, there has been a fifteen-fold increase in red tide biomass, on average, within five kilometers of shore," said Larry E. Brand, a professor of marine biology with the University of Miami, "and the red tide blooms now extend further off shore."

The blooms also last longer. Whereas red tide used to peak from October through January, blooms now start in August and often don't die out until May, Brand said.

Brand correlated the blooms with discharges from the Peace and Caloosahatchee Rivers and fingered the accumulation of nitrogen from agricultural waste water and phosphorus from phosphate mining as the prime culprits.

"For a fifteen-fold increase in biomass, there has to be a fifteen-fold increase in nutrients," he said.

"I think the science is strong that nutrients don't cause red tide, but they may make it stronger and last longer," Kim Honey, president of the Boca Grande chapter of Solutions To Avoid Red Tide, responded the day after Brand spoke.

"At certain times of year people cannot be on the beach because of red tide," Albion said. "We either solve it or we ignore it."

"It's getting worse," said Commissioner Bob Janes, who represents Boca Grande. "We depend on tourism. No one likes to come to Southwest Florida if the beach is covered with dead fish or red algae."

Commissioner Ray Judah, who asked for the public report, said the county is still studying the idea of suing the U.S. Fish and Wildlife Service for allowing the discharge into the Caloosahatchee River that is affecting national estuaries and the endangered Florida manatee.

The county is also asking the U.S. Army Corps of Engineers to redesign the South Florida Water Management District's planned C43 Reservoir near Labelle to control phosphate and nitrate pollution, Judah said.

"If there's just a one-prong attack, we'll all be disappointed," Honey said. "Red tide has been around for centuries. Stopping nutrients won't stop it."

Red tide is caused by Karenia brevis, a microscopic algae that sometimes undergoes explosive growth. It produces a powerful neurotoxin when it is stressed or dies. The poison suffocates fish, kills marine mammals that swallow it and irritates the lungs of humans who breathe it.

The latest outbreak to affect Boca Grande hit Southwest Florida from Tampa to Naples and lasted from mid-January to late March. Scientists with the Florida Fish and Wildlife Research Institute in St. Petersburg say it was a major factor, if not the primary cause, in the deaths of at least 44 manatees.

That's because the recent red tide occurred when the manatees were migrating from their winter territories in sheltered estuaries to coastal waters, Brand said.

Brand based his study on data collected by the state from the 1950s to the 1990s. While sampling in the intervening decades was haphazard, Brand said the data from those two decades withstood comparison.

In the 1950s, 70 percent of water samples taken off Mote Marine Laboratory in Sarasota showed no red tide. When they did, the average concentration was 10,000 cells per liter.

By the 1990s, only 40 percent of the samples showed no red tide, and the average concentration was up to 2 million cells per liter.

"Really large blooms are much more prevalent in the 1990s than they were in the 1950s," Brand said.

Data from satellites, collected by the National Oceanic and Atmospheric Administration, proved to be unreliable. The satellites can only detect extremely high concentrations of red tide and in one recent case indicated a "plume" that didn't exist, sending scientists on what Brand called "a wild goose chase."

Even excluding the satellite data, the red tide increase exists, Brand said. It's not a statistical artifact.

He showed documents from 1890 and 1962 describing the correlation between rainfall, river discharges and red tide. Because there is already an excess of phosphorus in the water, nitrogen was the limiting factor in the blooms, he said.

While Brand couldn't point to a "smoking gun," he attributed the rise in nutrients to modern agricultural practices, phosphate mining and population increase. He named organic peat in the Everglades Agricultural Area as a major contributor to nitrogen in the Caloosahatchee River.

"When exposed to air by agriculture, it releases nitrogen," Brand said. Cattle feed lots and human waste also contribute to the river's nitrogen load.

Lapointe, from the Harbor Branch Oceanographic Institute on Big Pine Key, made similar remarks about the red drift algae called Gracelaria, which clogged Lee County beaches last year. "It can double its biomass in two to three days," he said.

"It's Mother Nature dealing with pollution the best way she can. It may tie up nutrients and make them unavailable for red tide."

Complete Article