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Is Florida Algae Linked To Mississippi River Pollution?

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By MIKE SALINERO | The Tampa Tribune

Published: November 7, 2007

Federal scientists think they have linked massive pollution outflows from the Mississippi River to intense red tide algae blooms that in recent years have devastated tourism and water-related businesses along Florida's Gulf Coast.

A new research model by scientists with the National Oceanic and Atmospheric Administration suggests early summer winds blow pollution east from the mouth of the Mississippi to waters offshore of Florida. The nutrients then feed thinly dispersed red tide algae cells, called Karenia brevis, until they multiply in sufficient quantities to form blooms.

Winds then carry the blooms near shore, where they can kill fish by the tens of thousands and cause respiratory distress for many beachgoers.

If true, the theory would answer a riddle that has puzzled researchers for years: Where do the red tide cells get the necessary food for growth in the relatively low-nutrient waters in the Gulf?

Some recent studies have suggested increasing pollution flowing out of Florida rivers into bays has fueled unusually intense and long-lasting blooms. But state scientists have cast doubt on those studies, insisting there is not enough evidence from historical records to establish a connection between the increasing nutrients flowing off the land and red tide.

Though Karenia brevis is technically a plant, it has the ability, unique among algae, to swim up and down in the water column at distances of 50 to 100 miles offshore.

NOAA scientist Rick Stumpf said the algae swim to deeper depths seeking the nitrogen that originated in the Mississippi River. As offshore winds push surface water out from the coast, the deeper waters are forced toward shore in an upwelling effect. As the cells accumulate into larger and larger biomasses, they rise to the surface and wait for winds to shift and blow them onshore.

"If they didn't have that swimming ability, they wouldn't come to shore," Stumpf said. "The swimming is a critical part of this."

NOAA is working in partnership with the Mote Marine Laboratory in Sarasota to test the hypothesis using underwater vehicles called "BreveBusters." The vehicles carry instruments, but no humans.

Reporter Mike Salinero can be reached at (813) 259-8303 or msalinero@tampatrib.com.

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