Waterline is an ongoing series that explores how nature-based solutions preserve and protect our water resources. It is funded by a grant from the Walton Family Foundation.
It’s a sight that stops Florida boaters and beachgoers in their tracks: a thick green sludge coating the water, smelling of rotten eggs and dead fish.
Ashley Smyth, a coastal biogeochemist at the University of Florida, likens the color and consistency to guacamole. “I used to say pea soup, but then I moved to Florida, and no one down here eats pea soup,” she says.
Either way, it’s a mixture no one wants to swim in. The toxic green brew is made up of algae that has gorged itself on nutrients from Florida’s highly populated coastal areas. Nitrogen and phosphorus are used as fertilizers in both agricultural and residential areas, where they boost plant growth — but when they wash off land into coastal waterways, they feed the harmful algal blooms that have increasingly plagued the state.
According to the Florida Department of Environmental Protection, 86 percent of Florida’s watersheds contain areas that are imperiled by nitrogen pollution. Thick mats of overfed algae float on the water’s surface, blocking sunlight and depleting oxygen levels in the water, which in turn chokes out other aquatic life. Perhaps the most dreaded and notorious type of harmful algal bloom is red tide, which taints the water a bloody hue and is accompanied by the gruesome sight (and smell) of rows of dead fish washed up on beaches around the state. In 2018 a red tide event impacted nearly 1,000 miles of Florida’s coastline from Pensacola to Port Canaveral, killing an unprecedented number of animals, triggering respiratory complaints in humans, and ultimately costing the state $2.7 billion in lost tourism and recreation dollars.
Unless Florida comes up with a fix, it will face more harmful algal blooms in its future. A trio of recent studies from the National Oceanic & Atmospheric Administration has upgraded red tide from an occasional problem to a chronic one, fueled by warming waters and increased development along the coast.
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This is where shellfish come in. Before they’re served cold with saltine crackers and lemon, or steamed in garlic-wine sauce, unassuming bivalves like clams and oysters are hard at work in coastal estuaries, scrubbing excess nitrogen, bacteria and algae from the water. Their ability to improve water quality has been well documented. A single adult oyster, for example, can filter more than 50 gallons of water per day. And while they’re cleaning the water, clams and oysters are also providing habitat for fish, crabs and other marine species.
“Shellfish are underappreciated,” says Smyth. “They’re tasty treats for us, but they also do a lot for the environment.”
With red tide and other harmful algal blooms threatening to become a fixture of Florida’s coastal landscapes, the state may enlist shellfish in the battle for cleaner water.
“What better [way] than to get more clams and oysters out in the water all over the state of Florida?” says Tim Solano, a shellfish farmer based in Cedar Key, a tiny Gulf Coast town that is the state’s top clam producer.
This could be achieved two ways: restoring Florida’s wild oyster reefs — most of which have been lost due to overharvesting, habitat loss and other factors — and farming more shellfish. Both are critical pieces of the solution, says Smyth.
A few years ago, Smyth was part of a team of researchers at the University of Florida and Florida Sea Grant that looked into the feasibility of incentivizing shellfish farming through what’s known as “nutrient credit trading.” The practice has yielded some success in regions like New England and the Chesapeake Bay. In Maryland, for example, oyster farmers who quantify the amount of nitrogen their oysters are removing from the water can qualify for state-issued credits, which they can then sell to polluters — municipalities and businesses that discharge harmful nutrients into waterways. By purchasing credits from oyster farmers or other eco-friendly industries, polluters are theoretically able to offset some of the environmental harm they’re causing.
Maryland’s water quality trading program, which launched in 2018, mostly generates credits from water reclamation or stormwater management best practices. Credits generated by local shellfish farmers are still a new — and limited — practice, says Gregorio Sandi, chief of the watershed restoration planning division within Maryland’s environmental department. But that practice has created a framework that states like Florida are now seeking to copy.
The income from selling nutrient credits could keep shellfish farmers afloat in difficult times, says Solano. During red tide events, for example, farmers are not allowed to harvest shellfish out of concerns that the meat might be tainted by toxins. The revenue from nutrient credits “would help us with feeling a little more comfortable with … not being able to sell a product,” Solano says, “because we know we still are getting a paycheck, and we can keep working through those months.”
Meanwhile, he adds, farmed clams and oysters are working to dispel red tide and other harmful algal blooms — and prevent them in the future.
Nutrient credit trading is built on the same idea as the carbon market: that companies or industries whose activities have measurably beneficial impacts on the environment can be compensated for those activities by companies or governments whose activities are polluting the environment.
It’s a controversial concept. Detractors say this “pay to pollute” model lets industries off the hook for shedding pollutants and heat-trapping gases into the air or waterways. In the case of shellfish nutrient credit trading, fertilizer manufacturers or wastewater treatment plants that would otherwise exceed their legal limits for discharging harmful nutrients can purchase credits that allow them to continue with business as usual.
Ultimately, Smyth allows, “the shellfish are a bandaid” over a wicked problem.
“The only way to really protect our water quality is to … not to have nutrients enter our waters,” she says. “So until we can figure out ways to prevent that, to keep those nutrients on land, I think we have to look at other options.”
Smyth and her colleagues interviewed representatives from wastewater treatment plants and oyster farmers in Florida about their willingness to participate in a nutrient credit trading program. The main stumbling block, they found, was that wastewater treatment plants wanted to buy more credits than shellfish farmers could provide. It was easier for them to turn to more established “mitigation banks” in the state, where they could purchase credits in bulk from organizations conducting large-scale wetlands restoration projects.
Florida’s shellfish aquaculture industry is still very young and very small. If it continues to grow, supply could start to match demand. Until then, Smyth says, it may be difficult to get a nutrient credit trading program off the ground in Florida.
Solano, however, is optimistic about the prospect. He points to a tool that Smyth’s team developed, a nitrogen calculator that estimates the amount of nitrogen a given shellfish farm removes from the water and the monetary value that could represent. The calculator could help the Florida Department of Agriculture & Consumer Services, the state agency that would administer the nutrient credit trading program, determine how many credits a shellfish farmer should earn and their dollar’s worth.
“If [and] when that program opens up,” he says, “it’s easy for us to get in the door, because we already have a nitrogen calculator created.” Solano, who serves on Florida’s Aquaculture Review Council, has recently spent more time “walking the Hill,” as he puts it — going to the state capital to speak with lawmakers about shellfish aquaculture interests. While the nutrient credit trading program has so far taken a backseat to issues like hurricanes and heat waves, which have recently wiped out entire shellfish crops, Solano stresses that revenue from such a program would help farmers survive such disasters.
“That’s definitely on the radar of what’s next — how can we get our farmers paid for the [water cleaning] services they’re doing,” he says.
Smyth, for now, has moved onto other research projects. “But I don’t feel fulfilled yet on this,” she says. “We’re getting the science down … but we still need the policy to talk to the science, and we still need the industry buy-in. There’s still so many pieces that have to fall into place to really make this feasible, but I hope that there’s opportunity there.”