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Toxic red tide: Florida researchers investigate what's making it so bad for so long

Scientists are exploring whether agricultural pollution might be playing a role in Florida's red tide, which is killing sea life and making people sick.

In declaring a state of emergency in seven counties where the ocean is contaminated by a toxic red tide, Florida Gov. Rick Scott's office made two points this week: The state is supporting communities struggling with the scourge, and the siege of seafaring microorganisms is “naturally occurring.”

Indeed, scientists and historians note fish kills triggered by the infestations dating back as early as the 1500s. While scientists today acknowledge the natural roots of Florida’s red tides, they also are investigating the possibility that persistent blooms, like the one besetting the Gulf Coast this summer, might be getting a “booster shot” from man-made pollutants that spill into the ocean.

A scientist from Florida Gulf Coast University (FGCU) sampled coastal waters west of Fort Myers in recent days, searching for the type of nitrogen-rich pollution already blamed for fouling inland water, particularly in giant Lake Okeechobee.

It seems pretty damned obvious there is a connection. But that doesn’t mean there actually is one. That is why we are investigating. We have to dig deeper."

“Nitrogen is the limiting factor on the growth of anything in the sea,” said Bill Mitsch, director of Everglades Wetlands Research Park and a environmental science professor at FGCU. “We are looking for signature types of nitrogen, like those in the lake, to see if they scoot right through and into the Gulf, where the red tide is.”

Such a finding likely would reinvigorate calls for greater regulation of the prime source of the pollutants —agricultural runoff from sugar cane and other farms in South Florida. Farming fertilizers already are blamed for fueling another Florida plague — the blue-green algae that chokes inland lakes, rivers and canals in the south part of the state.

Both the coastal red tide and the inland blue-green algae have beset South Florida through the summer, killing vast numbers of fish and other wildlife, including dozens of dolphins, manatees, sea turtles, sharks and eels. Humans also have been sickened by brevetoxins, which are emitted by the tiny organisms — karenia brevis — that create the red tide. Breathing the fallout can constrict the lungs’ bronchioles and send asthmatics to emergency rooms with coughs and shortness of breath.

Scott last month declared an emergency because of the blue-green algae bloom that began in giant Lake Okeechobee, before spreading to multiple rivers and canals. The governor on Monday declared another state of emergency, in seven counties — Collier, Lee, Charlotte, Sarasota, Manatee, Hillsborough and Pinellas.

The declaration helped pave the way for assistance, including the deployment of biologists and other scientists from the Florida Fish and Wildlife Conservation Commission to rescue wildlife and to clear away the innumerable creatures that could not be saved.

Along with Scott’s action comes a $900,000 grant to Lee County, home to Fort Myers and the epicenter of the red tide, to help cope with the cleanup. That brings the total amount granted to the county, where some tourists have cut short their summer vacations, to $1.3 million.

Another $500,000 will go to Visit Florida, so the agency can support local tourism officials in mounting a campaign to try to bring visitors back to the red tide zone — which stretches more than 100 miles from Sarasota nearly to the tip of the state.

“We will continue to deploy all state resources and do everything possible to make sure that Gulf Coast residents are safe and area businesses can recover," Scott said in a statement.

Private companies, like Sea World, have also pitched in to the recovery effort. The theme park has treated 10 manatees at its critical care facility and is prepared to take more, as the flotilla of karenia brevis powers the red tide into a tenth month. Manatees that require longer ongoing care are relocated by the Manatee Rescue & Rehabilitation Partnership.

Image: Red Tide, Dead Fish
Dead fish near a boat ramp in Bradenton Beach in South Florida on Aug. 6.Chris O'Meara / AP file

Despite the long history of red tides in the Gulf of Mexico, scientists don’t know what causes them to persist. The microorganisms begin their lives in relatively deep water, 10 to 50 miles offshore. Winds and currents carry them to the coast.

At 10 months, the current bloom is a long one but not as long as the 17-month red tide that beset southern Florida from the end of 2004 until early 2006, or the red tide just a few years before that, which lingered along southwest florida for 21 months.

“We lack a consistent set of observations offshore in what we believe to be the formative region for these blooms,” said Robert Weisberg, professor of physical oceanography at University of South Florida. “That’s a critical missing piece of information. And that greatly inhibits our ability to predict what will happen next.”

Weisberg said the red tide initially tends to thrive in low-nutrient environments, where it does not have to compete with other organisms. But when the blooms take hold and move closer to shore, they can thrive on nitrogen and other elements that could be fueled by pollution. “There could be an indirect relationship between that and the red tide,” Weisberg said. “We don’t know that.”

The researcher Mitsch recalled his recent sampling trip along the coast, seeing the pollutants that brought the blue-green algae to the Caloosahatchee River spill into the Gulf just a couple miles from where the red tide “exploded,” near Fort Myers.

“It seems pretty damned obvious there is a connection,” Mitsch said, adding a cautionary note: “But that doesn’t mean there actually is one. That is why we are investigating. We have to dig deeper.”