Crescent Lake has been getting cleaner for years. So why do volunteers in kayaks still pull more than a ton of floating green plants out of it on a single Saturday morning?
The water lettuce is a side effect of the repair. It comes from the same system that ended the lake's worst problem, which was the algae that used to bloom in winter. Once that makes sense, the plants along the shoreline, the eelgrass by the berm, and the construction planned for 2027 start to read as one long project.
A Lake Deeper Than It Looks
From the walking path, Crescent Lake looks like a calm 20-acre pond with the old water tower behind it. Below the surface it is more than 30 feet deep, and that depth caused the trouble.
In the hottest months the top layer of water heated up while the bottom stayed cool, so the two layers stopped mixing. The bottom layer ran out of oxygen and released large amounts of nutrients from the sediment. Then fall arrived. Cold fronts and their wind gusts stirred the lake back together, and all those nutrients rose to the surface at once.
Jim Bays is a retired ecologist and president of Stewards of our Urban Lakes, the nonprofit known as SoUL. He described the result in a Bay Soundings feature published September 28, 2026.
"What was coming off the bottom in the winter was almost as concentrated as wastewater effluent, and we'd get these horrible algae blooms."
This explained a puzzle in SoUL's early monitoring. Water quality improved over the summer after the first native plants went in, then the lake turned mucky in the cooler months. Years of sampling through Lakewatch, plus work with the City of St. Petersburg and a University of South Florida graduate student, traced the problem to that seasonal turnover.
Why the Green Moved to Summer
The city's answer was an aeration system that fully mixes the lake every eight days. With the water moving all the time, the bottom layer never sits long enough to build up that winter dose of nutrients. Bays says the winter blooms "are completely gone."
The sediment didn't go anywhere, though. Bays puts it at a century's worth, and constant mixing now moves it through the lake all year long. Its nutrients now show up each summer as a green bloom of water lettuce on the surface.
So the lake used to have a sudden, ugly problem every winter, and now it has a slower, visible one every summer. Mats of floating plants can be pulled out by hand, and the monthly cleanups do exactly that. The water itself has stopped getting the winter surge that once made it look like effluent.
| Season | Before aeration | With aeration today | After the planned 2027 project |
|---|---|---|---|
| Summer | Water layers stratify and the bottom loses oxygen | Water lettuce blooms as sediment cycles through | Water level can rise with seasonal rain |
| Winter | Cold fronts mix nutrients up and algae blooms follow | Winter blooms gone | Level designed to drop slightly in dry periods |
| Shoreline | Steep, mowed edges | Native plants along much of the edge | Wider shallow planted zones |
The Shoreline Is Doing Part of the Work
Before SoUL got involved, Crescent Lake looked like most Florida ponds. Its steep, man-made banks were mowed monthly to look tidy, and that left nowhere for wildlife and nothing to catch pollutants in stormwater. The group started in 2007 as Friends of Crescent Lake, funded by a Bay Mini-Grant from the Tampa Bay Estuary Program. Its first plantings went in at the north and south ends, where stormwater outfalls had built up natural deltas of sediment.
The plants along that edge include fire flag, bulrush, pickerelweed, canna lily, and spatterdock. Markers protect them from mowers and herbicide. Today they form a dense native shrub line along much of the lake that filters stormwater and gives birds places to nest.
The survivors are a small fraction of what was tried. SoUL planted more than 25 species and is down to a handful, because the lake's water levels behave oddly. The lake drains a 467-acre area called the Basin J watershed, more than twenty times its own surface. Bays says an inch of rain can raise the level by a foot. A plant that likes a certain depth gets drowned in a storm, so the ones that remain have proven they can take it.
The wildlife has followed. The eBird database lists 115 bird species at Crescent Lake Park, and Bays credits both better habitat and more birders keeping records. Frog numbers are rising, with tree frogs, pig frogs, and bullfrogs, and turtle numbers have grown along with them: soft-shelled and snapping turtles, cooters, and sliders.
The Next Stage Is Underwater
The next step is the lake bottom. The fish community is currently dominated by non-native species such as tilapia, and SoUL wants to restore submerged plants to support a healthier one. Volunteers wrapped eelgrass in soil and burlap, which Bays calls "little burritos," and dropped the bundles into the lake. "This year, with water levels dropping and clarity improving, we're seeing them all along the length of the berm," he said.
His comment about dropping water levels ties directly to the city's plan.
What the City Plans to Change at the Water's Edge
The City of St. Petersburg's Crescent Lake Water Quality Improvements Project is part of a state-supported restoration plan developed with the Florida Department of Environmental Protection. It has two parts.
The first expands the littoral zones, the shallow planted areas along the shore that soak up extra nutrients. The city says it will do this while keeping views of the lake and park enjoyable. The second rebuilds the outfall at the north end, where water leaves the lake toward Coffee Pot Bayou and then Tampa Bay. The current structure keeps the water level almost the same all year. A new compound weir will let it rise and fall more naturally with the seasons. The city says the change won't raise the lake and is designed to lower it slightly in dry periods. A flashboard riser will also let staff lower the level temporarily, for example before a big storm or for maintenance.
For anyone who walks the loop, this means the edge of the lake is meant to look different from season to season once the work is done. It also fits what SoUL learned the hard way about which plants can handle swings in depth. The Southwest Florida Water Management District has issued final permit approval. The city's timeline shows construction starting in April 2027 and finishing in October 2027. No newer schedule has been posted, so those dates are plans, not promises.
How to Get Your Hands on the Lake This Fall
SoUL and Keep Pinellas Beautiful hold a Crescent Lake cleanup on the last Saturday of every month. Between 20 and 100 people come depending on the weather. Some pick up litter in the park, some empty the Water Goat trash traps, and some paddle out in canoes or kayaks to pull water lettuce by hand.
The rest of the 2026 dates:
- Saturday, October 31
- Saturday, November 28
- Saturday, December 26
Volunteers meet at SoUL's storage unit in the TASCO Building parking lot, 1320 5th Street North. The listing gives 9 a.m. to noon but also says start times vary, so check the Eventbrite registration page before you go. Gloves, waders, safety vests, pickers, sunscreen, and bug spray are all provided. Wear closed-toe shoes, and anyone under 18 needs to come with an adult.
The Crescent Lake model has spread. Nine grants have let SoUL take its approach to other city lakes, including Mirror, Jungle, Round, Meadowlawn, Eagle Crest, Winston, and Lake Pasadena. "Other communities saw what we'd done at Crescent Lake, and came to us for help," Bays said.
SoUL's yearly fundraiser, the Legacy of Lakes benefit, is November 12 from 6:30 to 9 p.m. at The James Museum of Western & Wildlife Art, 150 Central Ave. The evening includes a silent auction, a program with Bays, a live paddle raise, and after-hours access to the galleries. Early-bird pricing runs through October 12: $75 per person, regularly $100, or $200 for a couple, regularly $250. The couple package includes four drink tickets and five raffle entries. Tickets are on SoUL's Zeffy page.
If you live near Crescent Lake Park and want to talk through how the 2027 shoreline work could affect your street, your view, or a sale you're planning, Melody Stang follows these projects closely and is happy to share what she knows. Let's connect — schedule a consultation.
