In Mobile Bay, the oysters’ tale of woe

Commercial fishermen tong for oysters in Lower Mobile Bay, Ala. At the end of the 2024 season, approximately 25,000 sacks of oysters will have been harvested from the bay, totaling 2.1 million pounds. (Courtesy Billy Pope)

This article originally appeared on Inside Climate News, a nonprofit, non-partisan news organization that covers climate, energy and the environment. Sign up for their newsletter here.

Andy Depaola looks out across Mobile Bay, where water laps against the once-hidden pilings of his neighbors’ piers. For centuries, the bay’s thriving oyster reefs created prime habitats for hundreds of fish, shrimp and crabs. The water-filtering creatures cleaned the waste, contributed to wave control and helped maintain the shoreline’s sprawling seagrasses while supporting carbon sequestration.

But now the crumbling seawalls have been battered, large stretches of the bay are greenish, brown dead zones and the beaches where Depaola’s children once picked up crabs and gigged flounders have eroded. With so much murky water in the bay, predatory fish like bull sharks, stingrays and sea catfish flourish in the warmer, rising water, he says, with a frustrated, weatherworn voice.

“No one is here,” he laments. “It’s like silent spring, but it’s silent summer, with no more people.”

They’ve disappeared from the waterfront and an eerie quiet has descended on what he calls a “sea of derelict pilings” where the piers have been washed away by storms and hurricanes so many times that people are too tired or too broke to rebuild the docks that insurance won’t insure.

Not so obvious to the naked eye are the millions of missing oysters that once populated the brackish waters, where five of Alabama’s freshwater rivers, the Mobile, Spanish, Tenasaw, Apalachee and Blakely, flow into the bay to create a mix of freshwater and seawater on the Mobile-Tensaw Delta that oysters used to love.

Depaola, a retired federal government microbiologist, thinks Mobile Bay, and the oysters that have been his life’s work, can be brought back, and he’s developed technology designed to grow oysters at a much faster rate than many of the piecemeal efforts now underway can manage. But he’s under no illusions.

Now 71, Depaola grew up on the North Carolina coast fishing off piers with his dad, Depe, an Italian immigrant who fought in the Marines during World War II and later became a fire chief. His father was known as the “mentor of the pier” on Topsail Island, where he spent decades fishing on one particular pier, even securing young Angelo—Depaola’s birth name—with a leash to a light post on the dock to keep him safe while he reeled in sailfish and king mackerel.

The younger Depaola continued a life by the water, studied for a Ph.D. from the University of Florida and spent most of his 37-year career in Alabama working as a research seafood microbiologist at the Food and Drug Administration’s lab out in Mobile Bay on Dauphin Island.

After he retired in 2015, he established the Depe Oyster Farm and Angelo DePaola Consulting. The following year, he filed a patent for something he calls the “Shellevator” and broke his neck in a body surfing accident.

Depaola’s 10-year business plan now envisions an oyster farm with 100 Shellevators. But since he started growing oysters on his own dock for personal consumption in 2013, he’s learned, as something of an optimistic curmudgeon, that there’s nothing certain about growing oysters.

“I’ve learned keeping oysters alive is a lot harder than I imagined,” he says. “That nature is finding new ways to kill them each year.”

He’s also come to understand, as a scientist, that he was born to solve problems, there’s more than one way to do something and he doesn’t give up.

Underwater archivists

Oysters have a profound historical significance. They have been around for 15 million years, breathe like fish, eat algae and each one can filter up to 50 gallons of particulate matter daily from the water column, a reference scientists use to refer to the volume of water extending from the ocean’s surface to the sea floor. A juvenile, or spat, becomes an adult in about two years and can live for 20.

As generations grow and fuse on top of one another, they become the archivists of coastal waters. Much like tree rings, the rings on oyster shells document past climate conditions. Oysters paint a portrait of their landscape, a living memory of the seasons. Oysters tell the story of a time and place.

The story they tell of Mobile Bay over the past century is one of overharvesting, dredging and mining on the bay’s floor, decimating the oyster population. “We removed all of the oysters before we understood how important they are to the environment,” says Ben Raines, the environmental writer, author and documentary filmmaker. “Most people don’t understand how many oysters there used to be. They don’t understand that they are a keystone to holding the estuarine environment together.”

During the early 20th century, the state allowed dredging—dragging a large metal box behind a boat at any depth to scrape live oysters off the reef—and destroyed the reefs. From 1946 to 1982, the state also allowed the indiscriminate scraping of the seabed floor of old oysters and clam shells dozens of feet thick, dating back thousands of years, for aggregate material for road construction. The road from Mobile to New Orleans was paved with oyster shells.

Those destructive practices, meanwhile, have been compounded by the bay’s lower oxygen content from sewage outfall, agricultural runoff, urban and suburban development and air pollution, all of which fuel algae growth and create a harmful habitat for marine life.

“Flooding in Nebraska can kill oysters in the Gulf,” Lee Smee, an environmental fellow at The University of South Alabama, says. What’s known as the Bonnet Carre Spillway routes the Mississippi River around New Orleans to keep the city from flooding, he explains. When there’s extensive flooding upstream as far away as Nebraska, the spillway is opened and freshwater flows through the Mississippi River into the Gulf, reducing the salinity for several weeks.

Too long for oysters to tolerate, says Smee.

Without a bay full of water-filtering oysters acting as an architectural foundation, a mild breeze can stir the muddy floor, and a stronger wind can darken it for days. Decades of this oxygen-deprived dirty water have also meant the death of the seagrass beds on the eastern and western shores of the bay.

During the last 25 years, the oyster population has also been hit by historic hurricanes, overdevelopment, construction and maintenance of the Mobile Bay Ship Channel, not to mention pollution, including oysters ingesting microplastics in coastal waterways.

In 2004, Hurricane Ivan hit the bay, and in 2005, Hurricane Katrina left its destructive path. The catastrophic hurricane created a new pass called Katrina Cut, halving Dauphin Island. As a result of the increased salinity, the oyster population at Cedar Point Reef, the primary oyster harvest grounds in the bay, declined significantly.

In 2007, the predatory snail called an oyster drill, which thrives in high salinity, wreaked havoc on the oysters.

Then, in 2010, the cut was artificially closed, improving water conditions, but the Deepwater Horizon oil spill (134 million gallons of oil) occurred that year and an estimated 8.3 million oysters were lost, meaning an estimated additional 5.7 million per year were unable to settle and grow, according to the “Coastal Alabama Comprehensive Oyster Restoration Strategy.”

Finally, in 2011, the century-old year-round harvesting was restricted to replenish the population.

But by 2018 there weren’t enough young oysters to support an oyster season, according to Chris Blankenship, commissioner of the Alabama Department of Conservation and Natural Resources (ADCNR), which oversees managing harvest and oyster restoration.

Blankenship, well respected, was appointed commissioner after serving as director of the department’s Marine Resources Division from 1994 to 2017. He has a wealth of institutional knowledge and a long history both personally and professionally on the coast, having grown up on Dauphin Island as well.

Research, restoration and community engagement

Since the 1970s, the Alabama Department of Conservation and Natural Resources has been conducting oyster restoration mainly by relaying wild oysters to restoration sites built around hard surfaces for “cultch” planting, a process for providing hard material underwater for oyster larvae to settle onto. But the population still declined.

Oysters reproduce through “broadcast spawning,” releasing a cloud of billions of sperms and millions of eggs into the water column to create a critical mass to repopulate existing reefs and create new reefs. During the heyday of oyster reefs around the bay, spawning season meant trillions of larval oysters to repopulate the reefs and scatter in smaller clumps on hard surfaces underneath the water.

Today, the bay lacks enough oysters to create sufficient larvae to settle on other oyster shells, piers, or huge rocks and concrete matter deposited underwater. For this reason, the existing larvae often don’t survive due to warmer water with increased salinity, which is a friendly haven for oyster drills.

To recreate a cultch for oyster larvae to latch onto on the soft, sandy floor during spawning season, the Alabama Wildlife Federation has been implementing rock planting in the bay for the past decade. Most recently, in partnership with ADCNR’s Marine Resources Division and private companies, the federation continues to add more material by transporting tons of limestone on barges from north Alabama, and even Kentucky and Arkansas, to Cedar Point East. There, the limestone has been sprayed into the water using high-powered water cannons to provide 77 acres of prime oyster habitat so oysters don’t suffocate in the sediment.

The method of jumpstarting reefs by placing spat on shell in a hatchery and transporting the baby oysters to reefs is also risky because this creates a buffet for predators, Smee says. He is experimenting with growing oysters in tubs alongside blue crabs and oyster drills, which he said are like locusts and can destroy a restoration project in days. The predators can’t attack the oysters in the tubs, but when the oysters smell a predator, they grow a harder shell. Smee has discovered that the oysters’ survival is 50 percent higher under these conditions, so his team’s research involves creating a synthetic version of blue crab urine, which he calls “scary juice,” to add to the oysters’ tank to stimulate shell formation.

But without enough mature oysters in the water to spawn, cultch planting doesn’t work as well as it once did in Alabama and Mississippi, Smee says. The spat that settles on a monolayer of hard surfaces in May and June dies in August with the increasing water temperature, so the limestone also must be piled in mounds several feet high to keep the oysters from dying on the bottom in the hypoxic zone.

Despite the ups and downs, Blankenship, the state’s top conservation official, believes oyster restoration is rebounding and moving in the right direction.

“We have invested heavily in oyster research, reef mapping, oyster larval transport models and research, and hardscape restoration activities,” he says.

In partnership with the University of South Alabama and Auburn Shellfish Lab, his department has mapped the reefs, conducted research and experimented with placing spat on shells in a hatchery and transporting them in the bay. In 2021, ADCNR published a revised plan taking climate change projections into account and recently received a $7 million grant from the National Fish and Wildlife Foundation for additional oyster restoration.

“There’s a certain amount of things that we can’t control, but we are doing our best to set the stage so that with the right environmental conditions, oyster resources in Alabama will flourish,” Blankenship says.

PJ Waters, a professor and director of Auburn University’s Marine Extension and Resource Center, who’s been working for the past 20 years to engage and educate the public about different issues facing the health of Alabama’s estuarine system, often sends his wife and daughter pictures of oyster florets—oysters stacked upon each other like a floret of flowers, a natural phenomenon he finds beautiful.

They humor his reverence for a seemingly odd pile of rough rock-like shells as he’s been working to take the complex science of how the estuarine system functions and put it in the hands of the local community, whom he calls “citizen scientists.” He hopes through their oyster gardening to solve the problem of the decades-long decline of oyster reefs in the Mobile Bay.

At the Auburn Shellfish Lab on Dauphin Island, Waters raises oysters for the oyster gardening program. Through thermal shock that warms the water, the oysters think it’s spring, and they are encouraged to spawn. Once the larvae settle on recycled shells, they are coddled and cared for in the hatchery.

They’re transported to a site for volunteers in May or June, where homeowners raise them in baskets hanging off their piers. Volunteers handle the baskets, making sure they are hung properly, cleaned weekly of the biofilm that accumulates and shaken so the oysters don’t grow into the mesh. Each site produces 1,000 to 2,000 oysters per season until it ends in November. The program includes around 150 piers, which each house four to sixteen baskets.

Waters summed up the process with pride. “We’ve taken an oyster off the bottom, we put that oyster through the restaurant, somebody eats it, we recycle the shell, reset it with new oysters, and we put it back on a reef. That’s its full cycle,” he says.

As far as the daunting task of replenishing the bay, he believes connecting individuals and the generations of families who’ve been in the program for decades is not only putting oysters back in the bay but also restoring our humanity and the connection to nature which is often lost in the modern world.

“I’d rather have 10 new sites with 10 new people than one new site that produces 10 times the oysters, right? Just because of the educational aspect of it,” Waters says.

Mobile Baykeeper

On Madison Kimbrough’s first day as an Americorp volunteer working for the nonprofit Mobile Baykeeper’s oyster gardening program, her waders filled with forty-degree water. On other days, she worked in blistering heat and heavy humidity as she checked one of the 160 cages hung on 20 volunteer docks.

Despite the resident alligator near one dock, twice weekly, she and other volunteers pressure-washed the algae off the cages and checked for destructive drill snails or a greedy blue crab stuck inside the cage. Sometimes, a blue crab was crafty enough to unlock the cage and let 100 oysters loose.

Last year, the Mobile Baykeeper, under the guidance of Auburn University’s Marine Extension and Research Center, placed 40,000 oysters back into the bay. This year, they’re on track to place 61,000, says Cade Kistler, the organization’s official baykeeper.

He’s responsible for strategies to revive and protect the bay’s health, and he wants to emulate the Chesapeake Bay project in Maryland, which has spent $87 million since 2012, restored over 1,000 acres of reefs and put a billion spat on shells last year.

As in the Chesapeake Bay, Kistler says, restoration is important, but water quality—”which we can control, unlike weather”—is the key to success.

And so, in July, Mobile Baykeeper and the Center for Biological Diversity filed a formal notice of intent to sue the U.S. Army Corps of Engineers to stop the dumping of dredge “spoil” in the bay from a $366 million project to deepen and widen the shipping channel, unless the spoil is used beneficially. They claim the project, in its third year of four years, endangers the sturgeon, a protected species. Once completed, the channel will be around 50 feet deep and widened by around 100 feet.

“Oysters can’t run away when you have low oxygen,” Kistler says, explaining that mud from dredging the ship channel and river runoff from construction sites upstate are smothering the remaining oyster reefs, “and a whole bunch of restoration energy can get covered up pretty quick.”

Of the dredged ship channel mud, says Depaola, “where they’re going to spread this stuff, there’s nothing to kill anymore.”

To ensure the success of oyster restoration efforts, Kistler says, “we’ve got to stop dumping four and a half million cubic yards every year of mud in the bay from the ship channel. And we’ve got to work hard on making sure the construction sites do what they’re supposed to” by controlling erosion.

‘The magic bullet’

For Depaola, it all feels like he’s at ground zero. Living in the middle of the bay for the past 44 years, he says, “the harm is metastasizing.” While he believes oyster restoration efforts raise awareness and generate more funding, he thinks “we’re on the highway to hell” as climate change warms the bay’s waters.

And though he supports oyster gardening, he thinks it’s “window dressing.”

“We need oysters on a scale that no one is delivering right now. We’re in the stone age as far as oyster restoration,” he says. “Even though we may have a million oysters it’s still a minuscule fraction of when the bay was healthy.”

That’s where his patented invention, the Shellevator, enters the picture. With this machine, he envisions growing hundreds of thousands of oysters much more quickly than current “gardening” regimes to restore the spawning biomass while providing a template for addressing food insecurity and reducing carbon.

In 2013, Depaola started growing oysters on his pier, and a couple of years later, when he retired, he became a commercial grower. Tired of the extensive lifting of the cages after his body surfing neck injury, he developed the labor-saving, portable and submersible platform for growing oysters in racks of cages, which can be raised from the water using a compressed air system by the push of a button.

Depaola hopes to create a company to sell Shellevators for commercial oyster farming purposes. Conventional oyster farming methods grow about 100,000 oysters in an acre in a year, maybe 200,000, Depaola says.

With the Shellevator, he believes he can grow over 1 million because the cages are stacked vertically and use the whole water column without extensive human labor.

Depaola also plans to create an oyster restoration and coastal engineering company to help save the planet with “The Reefer,” still in the planning stages. It is a nature-based technology deployed in tandem with the Shellevator that uses rolled crab trap wire to improve oyster growth and survival.

Oysters grow exponentially; a gram of oyster larvae (seed) can increase a million-fold within a year to a metric ton. The Reefer is a lightweight internal scaffolding matrix that suspends oyster seed in 3D using the crab trap wire throughout the entire water column to grow reefs in a few years—a process that would take centuries in nature or with previous technology.

Depoala points out that in Alabama, you can go to fossil deposits and find a 35-million-year-old oyster shell still holding all the carbon that oyster ever sequestered.

He understands the enormity of solving climate change. “In the next twenty-five years, we’re expected to spend $16 trillion on climate change trying to get carbon out of gas through air sequestration and growing kelp and other technologies, hoping to achieve one gigaton between now and 2050,” he says of the U.N.-led efforts. “But by that time, we’ll emit 37 gigatons, so the whole point is none of it is working.”

But to Depaola, that doesn’t mean he or anyone else should stop experimenting and working on oyster growing solutions. Every ton of sequestered carbon helps.

Depaola says he has discovered through his experiments that “each time you do something, it’s going to get better,” and his perseverance generates an epiphany, often by accident. Even in the face of dire climate change, he says he considers himself “overly optimistic.”

Recently, Depaola and Raines, the author and documentary filmmaker, were among the top 100 finalists for Elon’s Musk’s $50 million XPRIZE for Carbon Removal. Participants in this four-year contest had to demonstrate that their device could remove 1,000 metric tons of carbon annually.

Depaola and Raines are also seeking funding through state and federal grants and venture capitalists. Even though Depaola says most people think he’s selling snake oil, he believes the current solutions are too expensive, too slow and too small in scale. He also believes bad things happen faster than good and there’s an urgency behind his innovations.

Depaola remembers on shrimp season’s opening day during the late 1980s, he could almost step between the crowded boats bobbing in the bay outside his house all the way to the Fowl River. He says in his small boat with a shrimp trawler, he could net 25 pounds of shrimp with every drag.

“I haven’t seen a boat out there on opening day probably this whole century,” he says.

He believes his Shellevators could be deployed throughout the bay, and the Gulf, as a solution for the collapsing ecosystem. To be sure, he understands that “getting the genie out of the bottle is a lot easier than getting the genie back in.” And as he’s transitioned from scientist to entrepreneur, he’s learned that “passion doesn’t get you very far in business.”

Still, each season, he’s also learned something new and important about growing oysters successfully, and he’s modified and adapted the Shellevator on his quest to revolutionize aquaculture.

His ultimate goal is to create an autonomous, energy-neutral platform to grow food on a scale to feed the world while sequestering carbon. Other systems for growing oysters, he believes, are too labor intensive and uncertain.

Now, as he looks out across at the once-hidden pilings, his neighbors long gone, DePaola can’t help thinking that this machine he’s built out of air pumps and pontoons just might be the thing—“the magic bullet,” he says—that brings the oyster back to Mobile Bay.