These researchers are scaring baby oysters with crab pee. For science.

Science can be weird, but you judge the method by the results. Even if the method involves using crab pee to scare baby oysters.

A cutting-edge research effort in coastal Alabama, now entering its second year, is testing a method of toughening juvenile oysters and improving their odds of survival in new tide-zone reefs. Researchers at the Dauphin Island Sea Lab and their many partner organizations have a long way to go before they have the data for firm conclusions. But early indications hold out some tantalizing hopes.

The potential payoff is huge because oysters are delicate creatures with an outsize power to change fragile ecosystems for the better. The oysters themselves purify the waters they inhabit and serve as a food source. The reefs they build serve as habitat for other species, and protection for coastlines.

Give oysters a chance, and the oysters will give lots of other good things a chance.

"They’re incredibly important to the ecosystem. They filter a tremendous amount of water," says Christa Russell, a researcher involved in the effort. "They’re what's called an ecosystem engineer: They change their ecosystem so much by building these shells. They create habitat from nothing."

In June 2022, the first test reef was stocked. At the end of May 2023, the foundation for a second was laid. Here's a look at the work, and the many hands required to carry it out.

The giant plastic tubs in an open-air shed at the Sea Lab hold bags of oyster shells, and the shells are dotted with the tiny oysters known as spat. Life has been good for the spat for the last month, but things are about to change. For the students and scientists on hand, this will be a day of hard physical labor, as they move tons of shells by hand from tank to truck, from truck to boat, from boat to water. For the oysters, it's the day they’re kicked out of the nursery and dropped into the wild.

Christa Russell, a doctoral student conducting research at Dauphin Island Sea Lab, lifts bundles of "spat on shell" oysters being used to establish a test reef in June 2022.Lawrence Specker | [email protected]

Though the tubs are a safe haven, half of the spat have had reason to think they weren't safe: Their tubs contained caged blue crabs. The crabs couldn't actually get at them, but the spat could sense their presence.

Sea Lab scientist Lee Smee says researchers had been feeding the crabs -- what else? -- oysters. "Not only are they getting the scent of crab, they’re getting the scent of the crabs eating their friends," he says.

As diabolical as it sounds, it's actually good for the oysters. It also builds on established science and emerging aquaculture practice.

Becoming an adult oyster is a low-percentage life path. Eggs are fertilized in the water, drifting along as plankton for a couple of weeks. When the larvae are ready to become spat, they must find a suitable solid object to anchor to. The vast majority never do.

One approach to helping oysters along is what's called spat-on-shell: In a protected setting, such as the array of 750-gallon tanks at the Sea Lab, spat are given a chance to anchor on shells before the shells are dropped into a natural setting. But the survival rate remains low, thanks in part to predators.

It's been established that certain environmental triggers, such as the urine of blue crabs, will cause spat to harden up -- literally.

"The response is a stronger shell," says Ben Belgrad, a postdoctoral researcher working on this project at the Sea Lab. "They’ll add on more calcium carbonate and protein into their shell. It's harder for oyster drills to bore in, it takes them longer, and it's a lot harder for blue crabs and other crabs to crush that."

Dauphin Island Sea Lab scientist Lee Smee stands next to a tank of "spat on shell" oysters, in which oyster larvae have been given a chance to settle on empty shells. The cage he holds contains blue crabs, a primary oyster predator. The presence of a predator can cause the larval oysters to develop stronger shells.Lawrence Specker | [email protected]

Belgrad and Smee like the phrase "scared strong." One facet of their project, in partnership with other institutions, is to identify exactly what it is in crab pee that triggers the shell-strengthening reaction. They’re narrowing it down. Smee says his hope is that scientists will be able to synthesize "scary juice" that can be added to spat-on-shell operations, improving survival rates.

There's another important side to this specific project, though. "This is bringing it up to the reef restoration scale," Belgrad says. Spat-on-shell is not a new concept. But in the process of escalating it from thousands of spat at a time to hundreds of thousands spat at a time to millions of spat at a time, this is a big step. This run started with a couple million spat from the Auburn University Shellfish Laboratory.

Saturday's work begins with an early morning gathering at the Sea Lab, where Russell, a Ph.D. student at the University of South Alabama, rallies a team of more than a dozen volunteers. Smee says the project is part of Russell's dissertation; most of the rest are among the 200 or so undergraduates from all over the state who’ll spend time at the Sea Lab this summer.

"A lot of them are taking classes on restoration and conservation," says Smee. "So this is a practical application of what they’re learning in the classroom."

The first of six tanks is drained and Russell climbs in. She begins hoisting out biodegradable mesh bags of shells covered in spat and handing them to the nearest helper, so that they can be passed down a line to the bed of a waiting pickup.

"These can take a little bit of a beating, but don't throw them," advises Russell.

Indeed, the spat are a bizarre mix of toughness and fragility. It's hard to even see them if you don't know what you’re looking for. The shells are speckled with little transparent lumps a centimeter or less across. They looked kind of like fish scales stuck to the shells.

The "spat on shell" technique gives oyster larvae a chance to settle on old oyster shells before those shells are placed in the wild. The spat are visible as small, glistening discs that look somewhat similar to fish scales.Lawrence Specker | [email protected]

They’re barely there. And yet Smee, Belgrad and Russell are perfectly confident they’ll be just fine out of the water for the time it will take to drive them over to Lightning Point at Bayou La Batre, load them into Sea Lab skiffs, motor them out to the shoreline and unload them at their destination.

Belgrad points out another aspect of spat hardiness. It's well known that mature oysters filter large quantities of water. But even in the Sea Lab tanks, the spat show a remarkable ability to filter the constant stream of raw Gulf water being pumped in. Other tanks containing fish are so murky it's hard to see what they hold. The tanks full of spat are conspicuously clearer. They’re cleaning it as fast as it comes in. "It was quite incredible," Belgrad says of the effect.

In Bayou La Batre, the team is joined by Judy Haner, marine and freshwater programs director for The Nature Conservancy in Alabama. This oyster program was funded by the National Science Foundation and NOAA with additional support from NOAA's Sea Grant Program and the Alabama Department of Conservation and Natural Resources’ Alabama Coastal Management Program. But the site selected for the oysters shows how various conservation, restoration and research projects interlock along the coast.

The Nature Conservancy and other partners recently held a ribbon cutting for a massive restoration project at Lightning Point. It created 40 acres of new tidal marsh, protected by a segmented breakwater, where the bayou opens into Portersville Bay.

At the last stage of the journey, the Sea Lab boats converge on a tiny cove formed inside one of the gaps in the segmented breakwater. There, boatload by boatload, the team lowers the six to eight tons of shell into a compact site marked by rebar posts. Most of the bundles of shell have only the scant protection provided by the mesh bags. Some oysters are placed in the cages formerly used to hold the crabs; now these will keep crabs out. When researchers return later, they’ll be able to tell whether they’re losing spat to large predators or other factors.

The "scared strong" spat and their unscared brethren will face life side by side at this spot, with researchers checking to see if the scared ones do better.

Smee and Belgrad say that because survival rates for spat are naturally so small, the difference might not be impressive in absolute terms -- but it could be huge in statistical terms.

"There's very low survival at this stage," Belgrad says. "A small percentage increase really makes a difference when it reaches adulthood."

Once, Haner says, the shoreline at Lightning Point was protected by a lengthy reef. Projects like this one hold out the hope that one day, conservationists will be able to re-establish oysters on that kind of scale. In the meantime, she says, the work makes it feasible to incorporate oysters in new and ongoing projects.

"This adds into a larger restoration network that the state, Dauphin Island Sea Lab and TNC have been working on for years," she says. "This is science that means something. This is science that helps us do a better job of restoration."

In Mobile Bay and along the Mississippi Sound, the oyster harvest is a small fraction of what it was less than a century ago, when large and productive reefs provided fertile ground for generation after generation of spat to settle and grow. The crash is attributed to a variety of factors including the unfortunate decision to mine eons’ worth of shell for use as roadbuilding aggregate.

Since those days, the myriad ways that oysters benefit the environment have become better understood: The way they filter the water, the way their reefs stabilize the sea floor and help protect shorelines. It's hard to find a downside to oyster restoration, even if you don't like to eat them.

June 11, 2022: A team from Dauphin Island Sea Lab establishes a small oyster reef at Bayou La Batre's Lightning Point, stacking backs of "spat on shell" oysters in a tidal pool open to the Mississippi Sound.Lawrence Specker | [email protected]

Scientists can only do so much. Inland rainfall extremes could mean these oysters are exposed to salinity levels too low or too high for their health. A hurricane could wreck the site. Other circumstances could harm both the test oysters and the control group.

But if all goes well, data from the project will help scientists improve the odds for oyster survival.

"It's not always clear to non-scientists why it's important," says Smee. "I think the importance of this is very practical."

As you drive through Bayou La Batre, heading out Shell Belt Road toward Lightning Point, you’ll pass a lot holding a giant pile of oyster shells. The pile, mostly castoffs from local seafood processors, is a monument to the human appetite. It dwarfs the trackhoe parked atop it.

Smee is there early to welcome a group of scouts from Troop 292. One of them, Ethan Gates, is leading a project intended to help qualify him for Eagle Scout rank. He's motivated a crew of fellow scouts, as well as a few supporting adults, to spend the day helping build the second test reef at Lightning Point.

That means sacking up a whole bunch of oyster shells to serve as the foundation for a new batch of spat-on-shell coming from the Sea Lab in a few weeks.

"We’re about to do this about a thousand times, so pay attention," says Assistant Scoutmaster Will Gates, Ethan's dad, as Smee demonstrates how to fill and tie off a bag of shells.

Ethan Gates, second from left, passes a bag of oyster shells to a line of fellow scouts on May 31, 2023. As part of his work to earn Eagle Scout rank, Gates led a project to help establish an oyster test reef at Bayou La Batre's Lightning Point.Lawrence Specker | [email protected]

There's some equipment that's supposed to help, but it ends up coming down to hand labor. The boys shovel and bag the dry shells. Every time they’ve got a truckload, Smee drives it down to the boat launch at near Lightning Point, where girls from Troop 251 help load them into a skiff and then into the water.

Also in the water: Russell, who guides the placement of milk crates and oyster sacks, and Eliza Croom, an undergraduate at Talladega College. She's a biology major eyeing a future in medicine, but she's spending the summer at the Sea Lab as part of Research Experiences for Undergraduates, a program funded by the National Science Foundation. The REU program illustrates the myriad ways the Sea Lab works with schools across Alabama and beyond: The seven other REU students this summer represent UAH, USA, Auburn, Coastal Alabama Community College, Rogers State University in Oklahoma, Grinnell College in Iowa and Jacksonville University in Florida. The experience offers a taste of something quite unlike their usual classrooms.

"It's a little different than medical school," says Croom, up to her waist in water, moving carefully on the muddy bottom at the reef site. "But I’m kind of liking it."

The new reef is maybe 100 yards from the old one, in another sheltered nook of the Lightning Point shoreline. The new one already incorporates lessons learned from the first one, though that one won't get its official one-year survey for another couple of weeks.

Preliminary results look good, Smee says. The control group, the "unscared" lot, seems to show about 10% survival. The "scared" oysters seem to be doing quite a bit better, maybe a 25% to 30% survival rate. "I was expecting like a 1% to 5% difference," says Smee.

Smee cautions that those are estimates and he expects a rigorous analysis to show more modest returns. Even if the numbers are positive, this is only the first of many data points to come, as more reefs are built and more years go by. But that's all fine, he says: even a small change in the survival rate can be a big deal when you consider the millions of larvae that oysters cast into the water.

"We learned a couple of things in the last year," says Smee. One was that stacking two layers of sacked spat-on-shell didn't pan out. The bottom layer sank into the mud and mostly suffocated. The new reef will stack a single layer of oysters on top a layer of empty shells stacked atop milk crates. There's some other science going on there – the crates help with sediment studies – but mainly the goal is to let the milk crates and empty shell sink into the mud while the spat-on-shell stays above it. "It basically allows us to double the footprint of the reef," says Belgrad.

Another lesson: Putting these test reefs in the intertidal zone – where they’re exposed to the air at low tide – does a lot to protect them. Oysters don't mind being out of the water for a few hours. Oyster drills, the snails that are one of the oyster's main predators, hate it and tend to avoid oysters so exposed. The downside, Smee says, is that the oysters grow more slowly.

Another: The first reef drew other species into the neighborhood, making for a livelier ecosystem. Russell says the scientists have seen more fish and birds coming in. And more fish have meant more fishermen, too. "They create a nursery habitat for some of our favorite commercial and [recreational] fishing species," says Russell. "Things like specked trout and drum love these reefs."

Another: Smee and the other say they were surprised to see the first reef having a distinct effect on the shoreline behind it. It has caused silt to build up in the gap between the reef and the shore, and vegetation has already begun to sprout up closer to the reef. It's a remarkable illustration of the way reefs bolster living shorelines. Now that the researchers have seen it happen on the first reef, they know to take baseline measurements so they can quantify it at the second reef.

There's a lot of work left to do, a lot of data left to be gathered. But these early steps seem to show that the work is worth doing.

May 31, 2023: A crew including scouts from Troop 292 and 251 helps pass bundles of oyster shells to Dauphin Island Sea Lab researchers. In the background, from left, are Talladega College undergraduate Eliza Croom (red shirt), researcher Ben Belgrade and doctoral student Christa Russell (with milk crates).Lawrence Specker | [email protected]

"The idea is to try to get as many of these little pilot reefs out here as we can, so we can have more and more data," says Russell. "Living shorelines are challenging because no two sites are the same … so having lots of reefs helps us understand when things do and don't work."

Oysters are definitely things that work, at least when they’re given a fighting chance. They clarify murky water, stabilize muddy bottoms, form reefs that protect shorelines, provide habitant for small species that become a food source for larger ones.

It's all about giving them that fighting chance, and a toehold in places where they once thrived. And if that starts with scaring them a little, so be it.

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