The water lettuce that covered Crescent Lake this summer grew out of a lake that is getting healthier. In 2021 the City installed an aeration system that ended the algae blooms that used to hit the lake every winter. Jim Bays, who leads the volunteer lake group SoUL, says the summer water lettuce bloom showed up as about a century of sediment began moving through the lake all year.
That gives the green mats a fair amount of context. They are what a 20-acre urban lake looks like partway through a long repair. Volunteers do part of that repair by hand once a month. The City has scheduled a bigger piece of construction for 2027, and it will change how the edge of the lake looks from the walking path.
The lake used to go bad in the cold months
Crescent Lake is more than 30 feet deep, and that depth caused its old problem. Jim Bays is a retired ecologist and president of Stewards of our Urban Lakes, known as SoUL. He explained the sequence in a profile that ran in Bay Soundings and Creative Loafing Tampa Bay the week of September 24.
- In the hottest months, the top layer of water warms up while the bottom stays cool, so the two layers never mix.
- The bottom layer runs out of oxygen and starts releasing nutrients stored in the sediment.
- Cooler weather and cold-front winds stir the lake back together, and those nutrients spread through all the water.
- Algae bloomed every winter. Bays said what came off the bottom was "almost as concentrated as wastewater effluent."
SoUL worked this out over years of monitoring. It used samples analyzed through Lakewatch, work with the City of St. Petersburg, and research by a University of South Florida graduate student. The early data had been confusing. Early monitoring showed water quality improving over the summer after the shoreline plantings went in, then the lake turned into what the Creative Loafing piece called a "mucky mess" in the cooler months.
The City's fix was an aeration system that mixes the water completely every eight days. "The winter blooms are completely gone," Bays said, "but we're seeing a green water lettuce bloom in the summer as 100 years' worth of sediment is moving through the system all year long."
Why 2026 was a heavy year
The St. Pete Catalyst reported on August 13 that water lettuce had crowded out the lake's open water. The paper wrote that it was spoiling the view for many visitors and for residents of Historic Uptown. Bays has lived in Historic Uptown for about 20 years and has watched water lettuce come and go on the lake that whole time. He pointed to several causes of this year's bloom. A drought followed by heavy rain fed the growth, summer heat sped it up, and much of the City's equipment was in the shop for repairs. The main tool for large removals is a floating harvester that moves across the lake collecting plants, and that job is slow even when everything is running.
The yearly cycle is predictable. Water lettuce starts creeping back into the lake around May, grows very little through the cooler months, and accelerates as temperatures rise. A green summer on Crescent Lake is the normal pattern, and 2026 was simply a heavy year.
The plant is officially invasive in Florida, though Bays noted that lake and marsh sediment studies show it has been in the state's ecosystem for about 11,000 years. A thick mat blocks sunlight from reaching native plants underwater. The same shade also limits light for algae, which helps suppress harmful blooms. Insects gather around the leaves and feed birds, and crayfish and other small invertebrates live among the hanging roots. Bays's view is that the plant causes trouble when it dominates the lake. In smaller amounts it is one part of the habitat.
The hand-pulled part of the repair
SoUL started in 2007 as Friends of Crescent Lake, with a Bay Mini-Grant from the Tampa Bay Estuary Program to put wetland plants along the shallow shoreline. Nine more grants since then have expanded the work to nine other lakes around the city, including Mirror Lake, Jungle Lake and Lake Pasadena. "Other communities saw what we'd done at Crescent Lake, and came to us for help," Bays said.
Monthly cleanups at Crescent Lake draw anywhere from 20 to 100 people, depending on the weather. Some volunteers pick up trash across the park. Others clean out the Water Goats, and others take canoes or kayaks out to pull water lettuce by hand. Creative Loafing reported that volunteers removed more than a ton of plants at each of the last few cleanups. Bays told the Catalyst he wants to recruit enough volunteers next year to clean up several times a month during heavy growth, instead of once.
The plantings along the shore took years of trial and error. Round after round of planting on the shoreline and the narrow shelf below it used natives like fire flag, bulrush, pickerelweed, canna lily and spatterdock. Of the more than 25 species SoUL planted, only a handful survived. Native shrubs now form a thick band along much of the shoreline. The markers you see beside them on the walk are there to keep mowers and herbicide away from the plants.
Most of the losses came down to the shape of the lake. Natural lakes usually slope gently, but Crescent Lake was dredged steep when the surrounding neighborhoods were built. On top of that, 467 acres of streets, roofs and businesses drain into a 20-acre lake. That drainage area is about 23 times the size of the lake, so its level can rise a foot after an inch of rain. Few plants can handle that much change at the waterline.
The progress shows up in the wildlife. The eBird database lists 115 bird species at Crescent Lake Park. Bays credits better habitat for part of that, and more birdwatchers logging what they see for the rest. Frogs and turtles are rebounding too, including tree frogs, pig frogs, bullfrogs, softshell and snapping turtles, cooters and sliders. This year SoUL is trying to bring back underwater grasses. Volunteers wrapped eelgrass in soil and burlap "like little burritos," Bays said, and dropped the bundles in the lake. With water levels down and clarity improving, he now sees eelgrass all along the berm.
What the City builds next, and what changes at the waterline
The City's Crescent Lake Water Quality Improvements Project is aimed at the problems SoUL has been working around by hand: shoreline plants that can't keep up with the water level, and a lake that collects runoff from a large urban area. It is part of a state restoration plan developed with the Florida Department of Environmental Protection and part of the City's Stormwater Master Plan.
| Element | What exists now | What the project changes |
|---|---|---|
| Littoral zones | A narrow planted shelf on steep banks | More shallow planted areas along the edge, designed to keep views of the lake and park open |
| Outfall structure | Keeps the lake at nearly the same level all year | A compound weir that lets the level rise and fall with the seasons, set to run slightly lower in dry periods and never higher |
| Storm control | No dedicated drawdown feature | A flashboard riser so City staff can temporarily lower the lake before a big storm or for maintenance |
According to the City's timeline, design and construction plans were due to be finalized in July 2026. Construction is set to start in April 2027 and finish in October 2027. The Southwest Florida Water Management District has given final approval to the permits. The City says it will share details on how the work affects park visitors as the start date gets closer.
Taken together, the steps make sense as a sequence. Aeration ended the winter blooms. Volunteers work out by trial which plants can survive on the steep banks. The 2027 construction adds more shallow planted zones and seasonal water levels that the City says support healthier plant growth.
Fall at Crescent Lake Park
The bloom slows as the weather cools, which makes the next three months good ones to be at the lake. Two of the groups doing the repair work hold events there, and Halloween weekend is especially busy.
| Date | Event | Time | Where |
|---|---|---|---|
| Friday, Oct. 30 | The Haunting of Huggins, with haunted houses, scare zones, a ghost tour, a movie and a costume contest | 7 to 11 p.m. | Huggins-Stengel Field |
| Saturday, Oct. 31 | St. Pete Audubon field trip | 8 to 10 a.m. | TASCO parking lot, 15th Ave. N and 5th St. N |
| Saturday, Oct. 31 | SoUL monthly cleanup with Keep Pinellas Beautiful | 9 a.m. to noon | Storage unit, TASCO Building lot, 1320 5th St. N |
| Thursday, Nov. 12 | SoUL's Legacy of Lakes benefit | 6:30 to 9 p.m. | The James Museum of Western and Wildlife Art |
| Saturday, Nov. 14 | St. Pete Audubon field trip with a Merlin and eBird lesson | 8 to 10 a.m. | TASCO parking lot |
| Saturday, Nov. 28 | SoUL monthly cleanup | 9 a.m. to noon | TASCO Building lot |
| Saturday, Dec. 12 | St. Pete Audubon field trip | 8 to 10 a.m. | TASCO parking lot |
| Saturday, Dec. 26 | SoUL monthly cleanup | 9 a.m. to noon | TASCO Building lot |
On October 31, the Audubon walk and the SoUL cleanup overlap by an hour and meet in the same TASCO lot. Someone who starts with the birders at 8 a.m. can walk over and join the cleanup without moving the car. You can find tickets for Legacy of Lakes and dates for future volunteer work on SoUL's website. The St. Pete Audubon field trip calendar lists the bird walks.
The Crescent Lake Neighborhood Association also has its own fall traditions, including the Halloween Walk and the Monster Mutt March. It posts dates on its social media channels instead of its website, so those pages are the place to check for this year's schedule.
Around Crescent Lake, long-term projects like the 2027 shoreline work are part of what shapes the blocks near the water, and we follow them closely. If you are thinking about what the lake project means for a home near the park, Plotkin Homes can walk you through the timeline and what we're seeing on the surrounding streets. Contact Us.
