Slime time: Septic tanks suspected as origin of Stuart algae bloom
Image via Susan Gardner.

slime stuart seagrass algae
'Just knowing how septic tanks work, it’s designed to fail.'

For the generations who grew up seeing green slime dumped on people to great comedic effect, it’s a kind of melancholy nostalgia to now see slime coating the water and killing vital marine plant life. Call it, “You Can’t Do That On Waterways,” but it’s happening on the Sailfish Flats near Stuart, threatening seagrass meadows Floridians took so much time and money to save.  

“In the past, the long past, a lot of times folks were somewhat reasonably pointing fingers that some of the problem was Lake Okeechobee discharges,” said Brandon Shuler, Executive Director of the American Water Security Project. “Other folks were pointing fingers that it is sewage issues and septic tank issues. It’s definitely got cyanobacteria and algae bloom issues going on over there, but … Lake O has not had a discharge and there have been very few basin runoffs from rain events, because we’re in extreme drought, for the last three and a half years.

“So, that takes one of the biggest voices that was blaming everything on Lake Okeechobee discharges being the issue and really kind of points back to, there are other issues here that need to be explained more deeply.”

With Lake Okeechobee excused from the lineup of usual suspects, that leaves two likely culprits — either septic tanks or legacy pollution.

It comes at the same time Jacqui Thurlow-Lippisch, a Board member for the South Florida Water Management District, posted aerial photos celebrating the return of seagrass to the area.

“Today’s photos highlight the area’s returning seagrass meadows after their disappearance primarily because of years of damaging cyanobacteria laden Lake Okeechobee discharges, especially in 2013, 2016, & 2018,” she wrote in late August.

As a result, the appearance of this toxic algae bloom — coating the water and wrapping around angler’s fishing lines — lends a sense of urgency to the need for action so as not to lose the rewards of all the work that went into restoring the seagrass so far.

One issue is an elevated level of nitrogen and phosphorus in the local basin waters compared to water that comes in from Lake Okeechobee.

“It’s really easy on the St. Lucie River to fall into the trap of thinking that all of our problems come from Lake Okeechobee, and if we could just stop the discharges, then we would have a healthy, pristine estuary,” said Nyla Pipes of the One Florida Foundation.

Whenever there is a time of less rain or drought, she said, and the water looks as it did in the photos posted by Thurlow-Lippisch, people feel ready to call it mission accomplished when it’s not necessarily the case.

“You have tons of septic tanks — Florida is, I think, No. 3 in the nation for the number of septic tanks that still service homes,” Shuler said. “Just knowing how septic tanks work, it’s designed to fail.”

Liquid wastewater exits the septic tank and goes into what’s called a drainfield, into which the wastewater filters through the soil before discharging into the groundwater.

“We know that we have to work on septic-to-sewer conversion,” Pipes said.

“The argument people say is, ‘When we don’t have releases, we don’t have any algae.’ I would say that this situation with that filamentous algae that’s covering the seagrass right now, shows that to be untrue. We just have a different kind.”

Another of the next steps, Shuler said, is to work with municipalities to do third-level wastewater treatment, taking nitrogen and phosphorus out of the sewage and returning nutrient-lowered water to the wider world without it having such a detrimental impact on local waterways. 

“The other part of that step that goes hand-in-hand is taking an inventory of septic tanks and really getting serious about upgrading our wastewater facilities to third-level treatment that takes most of the nutrient waste out,” he said, “and centralizing septic tanks and getting them connected back up to a centralized sewage treatment plant that actually is treated to levels that are outlined in (federal and state law).”  

Wes Wolfe

Wes Wolfe is a reporter who's worked for newspapers across the South, winning press association awards for his work in Georgia and the Carolinas. He lives in Jacksonville and previously covered state politics, environmental issues and courts for the News-Leader in Fernandina Beach. You can reach Wes at [email protected] and @WesWolfeFP. Facebook:


  • PeterH

    September 8, 2022 at 4:38 pm

    A maintained septic system can last twenty to forty years under ideal conditions. Salted soil can corrode steel and plastic tanks at an alarming rate. Tanks need periodic maintenance….and this usually occurs following a government inspection……but not in Florida where there are no inspectors.

    Florida has no location data as to where the two and a half million septics are buried. The cesspool and septic tanks are basically unregulated. There is a DPS oversight but there are absolutely no site plans indicating faulty systems or when they were last cleaned.

    Now, try to imagine what kind of ecological disaster will occur with rising sea levels and torrential rain as recently experienced in other States. Think about clean drinking water that the Everglades provides to your household faucet.

    Ask your Senator Rick Scott why he repealed septic system oversight bills in 2011 when he was Governor?

    Florida has suffered enough with 20 years of failed Republican stewardship.



    • Lou

      September 9, 2022 at 8:40 am

      Rick Scott was the worst governor ever.

  • Tjb

    September 8, 2022 at 5:24 pm

    Septic tank runoff has been a problem for years in Florida. Our long incumbent Republican legislators in Tallahassee has done very little to fix this issue because it would add to the cost of property ownership. As Floridians do we want to live in a pool of green slime or not spend a few extra dollars to protect and enjoy the waters that have made Florida a special place to live.

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    September 8, 2022 at 6:12 pm

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  • Lou

    September 9, 2022 at 8:10 am

    I don’t much care for Nyla Pipes. I believe she’s a bought and paid for shill for industrial farming but on septic tanks she’s correct.

    • Robert Himschoot

      September 15, 2022 at 6:39 pm

      Count the number of so called central sewer plants that discharge directly to the waterways under discussion. Then go and find out what treatment process is being employed. You will find that the great majority of the treatment plants do NOT treat for Nitrogen and Phosphorus reduction. They release highly disinfectant treated wastewater into the waterbodies to the tune of hundreds of thousands of gallons per day.. Hence your green slime. Septic Systems do not release any wastewater directly to water ways.

  • 78780

    September 16, 2022 at 2:41 pm

    I would imagine that growth has much to do with it. I worked for a city down south in the utilities dept. when the boom started there. Most of the time during peak periods the wastewater was just primarily treated while at certain times raw sewage had to be discharged. That could be what is happening here and you will never find anyone that will admit to it.

  • Kevin Mooney

    September 20, 2022 at 11:01 am

    This article is misleading an not 100% factual. Septic tanks are not the problem – a little knowledge of how the municipalities handle the sludge after it goes to the treatment plant would help this article be more accurate as to what the problem actually is.
    “Since the early 2000s, the recycling of biosolids on agricultural land has become a major environmental issue in Florida. Concerned about the effects of excess nutrients in the watersheds of South Florida, the Legislature banned the application of Class B biosolids in that part of the state. Instead, utilities began transporting biosolids north, to Indian River County and other lands near the headwaters of the St. Johns River. Since 2018, experts have suspected that nutrients leaching from biosolids in this part of the state are contributing to phosphorous pollution and algae blooms in Blue Cypress Lake, near the southern reaches of the river.” Source: 2020 River Report, prepared by the University of North Florida.

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