This story is part 3 of a series of 4. Read why the restoration of the Indian River Lagoon matters, the economic benefits of this work, and how partners are restoring seagrass and wetlands.
After decades of environmental decline, Florida’s Indian River Lagoon is beginning to show signs of recovery. With funding from NOAA Fisheries’ Office of Habitat Conservation, the Indian River Lagoon Council is leading a system-wide effort to restore the habitats that once sustained the lagoon’s fish and wildlife.
Three scientists and a fisherman are tackling the challenges of restoring four critical habitat types: coquina rock reefs, shellfish beds, seagrass meadows, and wetlands. Through innovative approaches, new technology, and hands-on fieldwork, each project leader is helping move the lagoon toward recovery.
A Lifelong Fisherman Designs a Solution to Replace Lost Coquina Reef Habitat
Charlie Sembler is a fifth-generation fisherman on the Indian River Lagoon. He remembers seeing schools of fish so large they could be spotted from the highway, rolling along the coast like a wave.
“When I saw the fish from the road, I would drive back to the fish house and tell somebody, ‘Hey, there’s a good set of mullet up there,’ or ‘There’s redfish moving in that direction,’” said Sembler. “These occurrences were commonplace. You don’t see that today.”
Over the decades, Sembler observed fish populations decline and important fish habitats such as seagrass beds, wetlands, and coquina rock reefs disappear.
“The loss of it—the Indian River and what it used to be—is haunting,” he said.
Sembler likened that feeling to hiraeth, a Welsh word that describes a deep longing and grief for a place and time that no longer exists.
That sense of loss stayed with him as he moved from fishing to aquaculture, and later motivated him to take action against habitat loss.
As restoration efforts around the lagoon focused on rebuilding seagrass, wetlands, and oyster reefs, Sembler saw a gap. Those living habitats would take years to mature into fully functional fish habitat. Drawing on decades of experience building what he needed for his fishing and aquaculture businesses, he set out to design something fish could use immediately.
He looked to the lagoon’s once-common coquina rock and the honeycomb-like reefs built by sabellariid worms. These natural hard-bottom structures provided shelter from predators and nursery habitat for young fish. Much of this rock was mined for construction material during the last century.
The result was the Spartan Reef.
Spartan Reefs are compact, cross-shaped concrete structures reinforced with fiberglass rebar to prevent corrosion. Each unit weighs about 50 pounds and can be carried and installed by hand, often beneath docks near seagrass beds or shorelines.
“The simplicity of it is the genius of it,” Sembler said. “It starts working almost immediately.”
Within days of installing the first Spartan Reef, fish began inhabiting it. Barnacles, mussels, and other filter-feeding species quickly encrusted the structures, attracting shrimp, crabs, and other predators. Monitoring video from this deployment shows dense fish activity around the reefs.
“They’re a force multiplier,” Sembler said. “You get habitat from the bottom of the food chain all the way up.”
The reefs have also proven durable. Two days after installation at Joe’s Cove in Martin County, one reef was hit by a storm with 60-mile-per-hour winds. Sembler called the Florida Oceanographic Society, a project partner, to check on its condition.
“They called back and said, ‘Charlie, it’s incredible—it looks exactly like the day it was put in,’” he said.
In addition to withstanding storms, Spartan Reefs resist conditions that can damage living habitats.
“Freeze, heat, algae blooms—it doesn’t kill them,” Sembler said. “They’re bulletproof.”
NOAA funded the reef installation at Joe’s Cove and will support two additional deployments in Indian River County and Volusia counties. All are located near existing habitat and designed to complement seagrass, oyster, and wetland restoration.
While Spartan Reefs are not a cure-all, Sembler sees them as an important piece of the lagoon’s recovery.
“We’re not recreating the past,” he said. “But we can rebuild function.”
He hopes the reefs also help restore public confidence.
“People hear a lot of bad news about the lagoon,” Sembler said. “This is something they can see working. If this sparks new ideas and new approaches, that’s a win.”
How “Super Clams” Are Bringing Back a Missing Species
In the 1990s and early 2000s, the Indian River Lagoon sustained an abundance of clams.
“If you wanted clams, you could jump out of your boat anywhere in the lagoon and harvest them by the bucketful,” said University of Florida professor Todd Osborne, who is leading clam restoration efforts for the NOAA-funded project.
The lagoon’s hardshell clams supported a multi-million dollar fishery and helped keep the lagoon clear by filtering out algae. Beyond serving as food for people and marine animals, clams also make food for other species. When clams are full from filtering, they spit out “pseudo feces,” which are essentially little bundles of algae and food particles. Shrimp, crabs, and fish gobble up these highly nutritious snacks.
By the 2010s, however, overharvesting and a series of massive algal blooms caused what Osborne called “a kind of environmental apocalypse.” Clams became virtually extinct in the Indian River Lagoon.
In 2018, Osborne and his research team searched the lagoon for surviving clams. After 8 weeks, they found just 39, all adults of similar size and age.
“These 39 clams represented a genetic opportunity,” Osborne said. “We could capitalize on the unique traits that allowed these individuals to survive. We spawned the adults and got 40 million larvae.”
And so, the “super clam” was born—a name coined by a retired restaurateur friend of Osborne to help the project gain traction outside the lab. It worked.
Osborne and his team have since grown and outplanted 65 million juvenile seed clams and adults in the lagoon. Monitoring shows that about half of the outplanted adult clams survived after two years, while 10 to 13 percent of seed clams survived after 1 year.
The primary threat to clams is the influx of freshwater from stormwater and agricultural runoff and other sources. Clams require brackish water with a salinity of 18 to 35 parts per thousand. If influxes of freshwater drop the salinity for several days, clams can die.
Through data analysis and trial and error, Osborne’s team mapped areas where clams have a higher chance of survival. Under the NOAA award, Osborne helped select two sites for outplanting 21 million clams. So far, the team has released 7 million seed clams and 2 million adults near Stuart, Florida.
Despite the challenges, Osborne remains optimistic. Local governments are developing solutions to issues such as stormwater runoff and septic tank leakage. One county is paying homeowners to convert their septic systems to sewer systems.
“We’re making progress and doing something positive,” Osborne said. “This isn’t rocket science. If we have the will, we can use science and engineering to solve the lagoon’s problems.”
Read about seagrass and wetland restoration in the Indian River Lagoon.
