As the tideSlowly recedes A rugged swell full of oysters breaks the surface of Apalachicola bay. Greg Dietl, Paleontologist and Paleontologist, carefully navigates the uneven, slippery surfaces of exposed reefs. Dietl jokes that he’s “now in the oyster business,” but the curator of Cornell’s Paleontological Research Institution (PRI) in Ithaca, New York, has not yet come to harvest the living assemblages of eastern oystersCrassostrea virginica) poking above the water. He’s here to sample the dead shells entombed below.
Dietl has worked with Dietl over the past few decades. Florida’s Department of Environmental Protection (DEP) to collect tens of thousands of oyster fossils from reefs like this one. This work goes beyond paleontology. These fossils are essential for understanding the decline in oyster reefs in the Florida Panhandle and restoring this important habitat.
The Florida Panhandle has been an oyster paradise for many years. Apalachicola Bay—which is one of the last places in the country where oystermen are still required to use wooden tongs to harvest wild oysters, rather than dredging—has been its epicenter. These salty waters once produced 90 percent of Florida’s oysters, which were slurped up by connoisseurs throughout the Southeast. Over the past century, however, overharvesting and suffocating sediment have caused many of the panhandle’s oyster reefs to vanish. The rise in industrial waste along the coast has contributed to the coast’s decline. In 1971, the poor water quality led to an outbreak of disease that wiped out more than 90 percent of the region’s harvestable oysters. Apalachicola Bay closed its once-vibrant oyster farm in 2020. It did so for five consecutive years.
The ripple effect of the loss oysters had on the entire coast environment. Oysters are vital ecosystem engineers and top-notch water filters—a single adult oyster can filter up to 50 gallons of water in just 24 hours. Oyster reefs protect coastal areas from waves and storms. Due to their economic and ecological importance, the need to restore the area’s oyster reefs was obvious. The problem was that restoration efforts in the area hit a snag in 2018. It was because of poor environmental monitoring prior to the reefs’ collapse, no one knew what a successful restoration looked like. “The question I get asked all the time is, ‘what was this area like before?’” says Jonathan Brucker, manager of the Florida Panhandle’s aquatic preserves. “All I can say is, ‘I don’t know.’”
Paleontologists were therefore an unlikely ally for conservationists. “It’s the only way possible to answer these questions,” Dietl says.
“By digging down into the reef, we can essentially go back in time,” Dietl explains. “We’re filling in the data they never collected.” To accomplish this, Dietl and his team used sediment cores to dig through the top layer of living shells and access the compacted underworld of the area’s once-thriving oyster community. The shells age faster the deeper you dig. “The shell that was at that location in the past gets entombed in the reef framework,” says paleontologist Stephen Durham, who obtained his Ph.D. under Dietl at Cornell and now works for the DEP. “It was these historical buried shells that we were after.”
However, harvesting oysters was difficult. The oyster reefs are surrounded at low tide by viscous, sometimes thigh high mud. The shells are razor-sharp, and often covered with bacteria. This made heavy gloves and a solid balance necessary when maneuvering around the exposed coral reefs.
The gray, fossilized oyster shells, rough and often stippled with barnacles, don’t look like much, but collectively they preserve decades-worth of crucial data. The researchers were particularly interested in how oyster size had shifted over the course of the fishery’s collapse. According to Durham, the size of an oyster’s shell can tell you how fast the animal grew, how long it lived, and how it responded to changes in water quality during its lifetime, among other information.
Measuring the shell sizes of past generations and creating a timeline based on that data also helped the scientists combat the phenomenon of shifting baselines—what Dietl calls “generational amnesia.” Because environmental decline occurs over time, it can alter perception of natural conditions. Although the oysters that poke above the waves today may appear normal, researchers may discover that they are half the size and more robust than their ancestors.
After they are measured, the shells are deposited in PRI’s collection. Some 40,000 shells harvested from Florida’s oyster reefs have already made their way up to Ithaca, neatly arranged in drawers or swaddled in plastic and stored in buckets. Each shell contains important data that helps to determine the future of Florida’s oysters. All of the information is added to a database that will help environmental managers determine which reefs have declined the most—and which have the potential to be saved.
Dietl’s Historical Oyster Body Size Project is just one of several projects in the burgeoning field of conservation paleobiology, where fossil data informs modern conservation efforts. Karl Flessa, a geologist at the University of Arizona who has worked with Dietl on other projects, likens the effort to “putting the dead to work.”
Flessa uses the clam fossils in his own research to chart the decline and recovery of the Colorado River Delta. When the river was dammed in the 1930s, the amount of water reaching the delta’s wetlands slowed to a trickle. Flessa could study entire islands of desiccated oyster shells as a result. His work has helped to restore pockets of riparian habitat along the riverbed.
Environmental managers in Florida are already reaping the benefits from Dietl’s work. As they re-establish reefs by laying down limestone or fossilized oyster shells to provide sturdy surfaces for oyster attachment, Brucker’s team also collects living oyster samples. These oysters are measured and weighed back at the lab before being entered into a database. This is similar to their Ithaca fossilized kin. While the work is still in its infancy, it is promising. “We have seen more adult oysters than the last time we were out there, more than a year ago,” Brucker says.
This is especially encouraging considering the poor state of oysters around the world. Over the past two centuries, some estimate that 85 percent oyster reef habitat in the world has been lost. The Florida Panhandle’s eastern oysters are an example of this larger trend. Once found from Texas to MaineThey are now extinct along large swathes on the New England coast. Says Durham: “It’s an all-hands-on-deck moment in the oyster world.”