Lake Okeechobee is not the lone culprit in the recurring algae blooms that plague Treasure Coast waterways, but an accomplice aided by thousands of nitrogen-spewing septic tanks, according to a recently published FAU study.
A peer-reviewed Florida Atlantic University paper that appeared in December’s issue of the journal Harmful Algae, says that algae in freshwater lake discharges grows exponentially when it reaches the St. Lucie Estuary because of heavy nitrogen levels in the waterway.
First, the fresh lake water weakens the ecosystem, which is accustomed to more brackish water, then the algae feeds on the reactive forms of nitrogen, such as ammonium and nitrate, that come from septic tanks, according to the report.
Brian LaPointe, lead author of the study and a research professor at FAU’s Harbor Branch Oceanographic Institute, said the study was able to trace the nitrogen’s source not to fertilizer – long blamed for the growth – but to human sources.
“This is compelling evidence that the problem we are seeing with the algae blooms, even though they can originate in the lake and be carried into the estuary, is exacerbated by elevated nitrogen that is locally sourced from septic tanks,” LaPointe said. “Not to say there aren’t fertilizers there, but our work shows the wastewater signal is a major contributor supporting the bloom.”
LaPointe presented the research at the National Harmful Algae Bloom conference in November.
“Everyone wants to blame this on the farms and there is a lot of denial about the wastewater problem,” LaPointe said. “People overlook the role of population growth on the Indian River Lagoon, and a lot of that growth has relied on septic tanks.”
A 2015 study by LaPointe found there are more than 300,000 septic tanks in a five-county area between the Jupiter Inlet and the Ponce Inlet in Volusia County. But LaPointe said Monday it could be closer to 600,000 because decades-old septic tanks may not be recorded in county records.
“The harmful blooms aren’t just in the St. Lucie Estuary, we are seeing problems up and down the Indian River Lagoon,” he said.
LaPointe’s research came under fire during the summer of 2016 when a widespread algae bloom grew in the St. Lucie Estuary after the Army Corps of Engineers began releasing Lake Okeechobee water to lessen pressure on the aging Herbert Hoover Dike.
“It isn’t all about septic tanks,” said Mark Perry, executive director of the Florida Oceanographic Society in Stuart. “I don’t want to discount that they could be a problem if they are located in a bad area, but lets not lose focus on the big problem and that is Lake Okeechobee discharges and agricultural runoff.”
FAU released information about the journal publication this morning, the same day a report is due to state lawmakers on building an up to $2 billion reservoir south of Lake Okeechobee to alleviate flows to the estuaries and end algae outbreaks.
LaPointe said he didn’t know the report was due Monday.
The reservoir is part of legislation pushed last year by Sen. Joe Negron, R-Stuart. Negron’s original proposal was for 60,000 acres of land south of the lake, including on property owned by U.S. Sugar, be used for the reservoir.
That was reduced to about 34,000 acres of state-owned land in western Palm Beach County.
LaPointe said the reservoir may reduce releases to the estuaries, but he’s concerned about the water that will be sent out of it into the Everglades.
He said water treatment areas that use plants to remove nutrients from the water work well on phosphorous, not nitrogen.
“When we move water south into Florida Bay that is carrying nitrogen, it’s not good,” he said.
Bill Louda, a Florida Atlantic University research professor who studies phosphor us and nitrogen amounts in Florida’s waterways, vouched for LaPointe’s findings.
“It’s too many people, and too much poop,” Louda said. “But it’s not just septic tanks. It’s lawn fertilizers, agriculture and everything.”