Were fertilizer bans a mistake? A new FAU study suggests so
For a decade, local lawmakers pointed to fertilizer as a key killer of the Indian River Lagoon. Others warned septic tanks and sewage spills were more at fault for the foul brown tides and other excess algae so fatal to seagrass, fish and manatees.
Brian Lapointe, a scientist at Florida Atlantic University, has been at the center of that debate. His latest study sows more seeds on familiar grounds long-fertile for arguments over what's worse for the lagoon.
The study, published recently in the journal Marine Pollution Bulletin, asserts that septic tanks and sewage play a much larger role than lawn fertilizer in delivering excess nutrients that fuel harmful algae in the lagoon.
That assertion once again questions the effectiveness of widespread summertime rainy season fertilizer "blackout" periods enacted throughout the lagoon watershed and elsewhere in Florida.
Lapointe and University of Florida researchers have argued for years that the bans have actually made the situation worse by distracting politicians and the public from the necessary but costly sewage fixes that have cured estuaries elsewhere.
"I just thought I better put something back out there," LaPointe said of his latest study. "Not that much emphasis is being placed on wastewater and septic tanks."
But some local scientists who've pushed for dredging rotted organic muck as a key lagoon restoration measure have questioned Lapointe's conclusions and defend Brevard's current lagoon cleanup priorities, which do address sewage and septic tanks.
While nitrogen and phosphorus are vital ingredients for life, in excess the nutrients can trigger too much algae that clouds out seagrass and can be toxic to fish and other marine life.
Governments along the lagoon face billions in stormwater, sewage and other fixes scientists say are needed over the next two decades to bring those two nutrients back to ecologically healthier levels in the lagoon. They must meet specific state-mandated benchmarks toward that goal every five years, with the clock starting for most a decade ago.
Resource managers estimate it will take another $5 billion and 20 years to save the lagoon's stressed ecosystem. Advocates say it's worth it: The lagoon brings $7.6 billion annually to the six counties that border the waterway, economic research shows. It's one of several reasons supporters say they want the tax back on the ballot before it expires in 2026.
But with so much at stake, Lapointe says hanging such hope on fertilizer ordinances never made much sense.
He estimates residential fertilizers contribute only 21% of the nitrogen to the lagoon, compared to 79% from septic systems, similar to the breakdown reported in other septic system-impacted urbanized estuaries.
What did he find?
LaPointe tests seaweed to determine the source of nitrogen in a waterway, since the nitrogen isotopes in fertilizer differ from those linked to animal or human waste.
His latest study included five lagoon segments from Jupiter Inlet to Ponce Inlet. He and his colleagues collected and tested lagoon water for dissolved nutrients and chlorophyll in 2011–2012 (pre summer fertilizer bans) and 2016–2017 (post summer fertilizer bans) during wet and dry seasons. They sampled nitrogen isotopes in submerged plants during the same periods.
The fertilizer-versus-sewage issue has drawn bitter debate for decades, with each side questioning the other side's science.
Lapointe points specifically to assertions in Brevard that residential fertilizers contribute 71% of the nitrogen to the lagoon. That assertion from conservationists and county government, coupled with UF's warnings to not fertilize before imminent rain, drove water managers, policy makers and environmental activists to push for the widespread summer rainy season fertilizing bans local governments adopted a decade ago.
But the lagoon got worse anyway, and Lapointe says he knows why.
"I think everyone is getting really frustrated that these ordinances passed," Lapointe said. "All this was passed without a lot of scientific support."
Your backyard: Learn about your local fertilizer ordinance
Budget brings fertilizer debate back to forefront
The turf battle regained steam in June, when Gov. Ron DeSantis signed the Florida budget, calling it "the strongest environmental budget we've ever had." But the budget bans local governments for a year from enacting new fertilizer ordinances or making existing ones stricter, until UF evaluates the effectiveness of local ordinances that ban fertilizer use in the summer rainy season.
The TruGreen lawn care company hired lobbyist and former House Speaker Steve Crisafulli to push the moratorium, according to nonprofit news site Florida Phoenix.
The Legislature approved $250,000 this year for the UF's Institute of Food and Agricultural Sciences (IFAS) to review current science on the topic and produce a report on the ordinances' effectiveness by the end of the year.
"I think there has been maybe an overemphasis on one piece rather than the whole," said Bryan Unruh, a professor and associate director at University of Florida's environmental horticulture department, West Florida Research and Education Center, who will participate in the state's scientific review.
UF has argued for years that depriving lawns of fertilizer during summer peak growth season weakens the grass, so it's less able to absorb fertilizer other times of the year, leaving excess fertilizer to run off into local waters.
Unruh likens it to an NFL football player's diet. A player may eat three or four times the calories of an average person during the season, simply because they're burning off the energy. But if they ate that during offseason, they would gain excessive weight and lose their competitive edge.
"Over the years, we had not felt that the blackout periods were consistent with sound science," Unruh said.
Do fertilizer ordinances work? It depends
A 2021 study by UF found fertilizer wet-season ban had no impact on nitrogen runoff in a lake in Satellite Beach and other lakes in areas with similar bans. Then another UF study last year somewhat echoed that conclusion. "Our results support their observations that wet-season ordinances have no detectable impact on nitrogen runoff," the authors wrote, referring to the 2021 study. But the latter study also concluded fertilizer ordinances "do have beneficial effects on lake water quality and potentially algal biomass, but not all ordinances have the same impacts."
More: Environmentalists worry DeSantis will usurp home rule over local fertilizer ordinances
Lapointe's research echoes that of studies in other urbanized areas in the northeast that have shown human waste as often the largest contributing source of nitrogen that drives excess algae.
But again, not everyone's convinced that's the case in the lagoon.
Scientists at Florida Institute of Technology, who have supported dredging organic muck as a primary solution to the lagoon's problems, say Lapointe's use of stable carbon and nitrogen isotopes in marine plants is oversimplified and doesn't necessarily mean sewage is the most important driving force of lagoon algal blooms. They see nutrients fluxing up from lagoon muck as the much bigger driver of blooms.
Lapointe counters that other peer-reviewed studies validate his isotope methods and that he also finds high levels of sucralose — an artificial sweetener used as a tracer for human waste — in the lagoon.
That's "a step in the right direction," John Trefry, a geochemist who spent four decades at Florida Institute of Technology studying the lagoon's nutrient overload, said via email. But for both nitrogen isotopes and sucralose, "there need to be calculations that can be replicated (proven) and that directly show the magnitude (tons) of specifically sewage nitrogen going into the lagoon, Trefry added. Nitrogen isotope values vary with sewage content and type of processing, he added.
While scientists agree sewage/septic pollution is a factor in the lagoon's excess nutrients and algae, Trefry says its relative importance isn't quantified and more data regarding lagoon sewage is needed.
"Yes, the lagoon contains sucralose and a large fraction of heavy nitrogen isotopes," Virginia Barker, executive director of Brevard County's Natural Resource Management Department, wrote in an email. "Those could both be explained by many sources including: septic, sewer leaks and overflows, remnants of secondarily treated sewage that was discharged into the lagoon at a rate of 50 million gallons a day until the mid-1990s, organic fertilizer (like Milorganite that is made from biosolids and marketed at big box stores), or from irrigating with reclaimed water.
Brevard sticking with summer fertilizer bans
As the debate goes on, local governments, including Brevard County, assure they have made sewage fixes and septic system conversions a priority but that it just takes time and lots of money.
They also defend summer fertilizer blackouts as a cheap, fast and easy way to reduce excess nitrogen. Lapointe's paper doesn't change that, they say.
"The (Lapointe) paper supports the county’s monitoring and modeling that also indicates that sewage/septic is an important contributor of nutrient pollution to the lagoon, though our analysis indicates stormwater and muck flux are bigger sources of nutrient loading to lagoon waters and fertilizer control is a worthwhile endeavor," Barker wrote.
County projects that reduce nitrogen and phosphorus from sewage and septic systems are receiving the largest share of funds in the county's Save Our Indian River Lagoon plan, she added, funded by the half-cent sales tax Brevard voters passed in 2016. The 10-year tax raises more than $50 million a year for lagoon cleanups.
"Furthermore, wastewater projects also receive substantial funding from grants and local utility programs," Barker added.
Officials estimate it would cost at least $1.19 billion to convert Brevard's 59,500 septic tanks to central sewage treatment, so the county targets the septic systems with the highest potential impacts to the lagoon.
"I don’t think you will find any county record proposing that fertilizer regulations alone would solve the lagoon’s problems," Barker added. "Nonetheless, discouraging excess and harmful use of lawn chemicals can still be a part of the solution, rather than continuing to add to the problem."
Story continues below:
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Brevard and other lagoon-region governments cited seagrass recovery after summer fertilizer bans in the Tampa Bay region to justify similar bans here.
But most of the seagrass recovery in Tampa Bay happened before local municipalities enacted fertilizer blackout periods in 2010 and 2011, said Mac Carroway, executive director of the Environmental Research and Education Foundation, Inc. He says he's an advocate for turfgrass, landscape, golf, professional lawn care and other "Green Industries," but also of property rights. And keeping homeowners from fertilizing won't solve the lagoon's problems, he said.
"Florida has an epidemic of raw sewage flowing into local waters with what seems like a response from local government that's not proportional to the problem." Carroway said. "It's the human-waste element. If you look at the signature of the nutrients, that's where the problem is. I think the evidence is now so overwhelming that something needs to be done with septic, sanitary sewer, wastewater discharges and all the human-based forms of nutrients."
Florida's aging infrastructure unleashed untold gallons of raw sewage during Hurricane Ian.
Carroway points to local governments stopping sewage dumping into Tampa Bay, strict stormwater management, and water reclamation and treatment projects as the key reasons the bay recovered.
"There's a lot more to this than the simplistic idea of a one-size-fits all fertilizer ordinance curing all the nutrient problems in coastal Florida," Carroway said. "Our view was that it never was going to work."
Despite the science, Carroway doubts any local governments will repeal their fertilizer blackout periods. But he and Lapointe take the critics of doing so in stride.
"In science, if everyone always agreed there would be no advancement in science," Lapointe said.
Jim Waymer is an environment reporter at FLORIDA TODAY. Contact Waymer at 321-261-5903 or jwaymer@floridatoday.com. Or find him on Twitter: @JWayEnviro or on Facebook: www.facebook.com/jim.waymer
This article originally appeared on Florida Today: Sewage, not fertilizer, blamed for toxic algae in Indian River Lagoon
