Federal report: Salt causes release of more blue-green algae toxins into local waters

A federal report  suggests that the presence of salt causes blue-green algae cells to burst and release all toxins into the water.

The United States Geological Survey report shows that while blue-green algae blooms like the one experienced this summer typically start in Lake Okeechobee, the amount of toxins released by the algae may increase as it moves toward the salty coast. 

Saltwater causes the toxin-carrying membranes to rupture, releasing toxins that were stored inside, the recent report says. 

"This study indicates that as freshwater cyanobacteria are transported to brackish and marine waters, there will be a loss of membrane integrity which will lead to the release of cellular microcystin into the surrounding waterbody," the report says. 

The historic Everglades system starts just south of Orlando and stretches to the Florida Keys. 

"If it’s very salty outside of the cell, all of the water that’s in the cell will rush out into the saltwater, and that kills the cell," said Jim Beever, with the Southwest Florida Regional Planning Council. "And the contents of the cell will get out into the water column. This is a good study, and they’ve confirmed the specifics of the species that bloom in Lake Okeechobee and how they react when they get into the system."

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Developers worked with the state and the federal government to connect the Caloosahatchee and St. Lucie rivers to Okeechobee decades ago to drain lands south of Lake Okeechobee for farming and urban communities. 

The report describes Lake Okeechobee as a "shallow waterbody that has undergone ecological changes because of external nutrient loading from agriculture and, more recently, by internal loading of phosphorus from lakebed sediments. Ample phosphorus and other nutrients create the ideal conditions for cyanobacterial blooms and have been documented in the lake since 1970." 

Those conditions, the report says, provide a nursery of sorts for the blue-green algae to develop and thrive. 

The blooms develop in the upper portion of the historic Everglades system and work their way to coastal areas, where saltwater interacts with the cells carrying and releasing the toxins. 

Large blooms have occurred several times over the past two decades. 

A bloom this summer caused massive ecological and economical losses when local waters were murky, chocolate-brown and filled with deadly toxins and dead wildlife. 

Gov. Rick Scott declared a state of emergency for three counties in 2016 after El Niño rains in the dry season dumped more than a foot of rain on the landscape while a blue-green algae bloom was thriving in Okeechobee. 

He did the same thing this year after a combination of a blue-green algae bloom and red tide outbreak hit Southwest Florida simultaneously. 

The report says that toxic algae was flushed from Lake Okeechobee or the canal system downstream to the Fort Myers-Cape Coral area on the west coast and the St. Lucie area on the east coast. 

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Estuary conditions in the Caloosahatchee system reach up to the Franklin Lock and Dam in Alva. 

Calusa Waterkeeper John Cassani said the information in the report is useful but that its application may be difficult for water managers. 

Flows from Lake Okeechobee would need to be high at this time of year to keep the salinity levels down in the estuary. 

But that amount of water could be deadly for the estuary's plants and animals that form the base of the marine food chain and Southwest Florida's world-class coastal fisheries. 

"If you want to keep the salinity low to delay the movement of cyanobacteria into the saltwater environment, then you could be impacting the estuary because the salinity is too low," Cassani said. "It might be difficult to manage the river for cyanobacteria independent of impacts to the estuary."

The sample used for this report was taken in the northwest section of Lake Okeechobee in July 2017. 

Rick Bartleson, a water quality scientist at the Sanibel-Captiva Conservation Foundation, said the study may work in a lab environment but that it may not apply to conditions in the Caloosahatchee River estuary. 

Although saltwater causes the cells to burst and release toxins, the volume of toxins is offset because the algae is being killed. 

"Salinity decreases the growth rate, and that means the cells and the toxins are being dispersed or diluted," Bartleson said. "The dilution effect is going to be working against the increased toxin release of the cyanobacteria."

This interaction of algae and salt has been going on for thousands of years.

But the amount of nutrients flowing to the coast has increased over the past several decades, which causes various water quality issues. 

"The organism exists in nature, and when they bloomed in the past it was much more limited, and the system would rebalance itself," Beever said. "We’re way out of balance now. It’s a combination of the (nutrient) input and the way the water is being managed. Lake Okeechobee was not a closed system for most of its existence. Water could flow into it and out of it, but it’s basically managed as a reservoir."

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