Seashells From Centuries Ago Show That Seagrass Meadows on Florida’s Nature Coast Are Thriving
- camilarosiaz
- 3 days ago
- 3 min read
During a day at the beach, it’s common to see people walking up and down the shore collecting seashells. Most people dig up shells in the sand and see beautiful color patterns or unusual shapes. As a paleontologist and marine ecologist, we look at shells a bit differently. We tend to focus on how old these shells are and what they tell us about the habitat they come from.
Seagrass meadows are an essential part of Florida’s coastal ecosystem. Jenny Adler
You may be surprised to learn that the translucent spiral shell you plucked from the sand belonged to a snail that lived long before Columbus sailed to the New World. And that unassuming clamshell you might nonchalantly toss away belonged to a mollusk that filtered seawater when pharaohs ruled Egypt. Using methods such as radiocarbon dating, scientists can assess the age of shells scattered around Earth’s surface.
Increasingly, paleontologists and conservation biologists are turning to these remains as potential treasure troves of information about what various habitats were like before humans entered the picture. This approach, known as conservation paleobiology, can result in more effective conservation, restoration and management strategies.
Over the past decade, we have applied conservation paleobiology to Florida’s Nature Coast, home to an extensive and intricate patchwork of seagrass meadows and sand. Prior to these studies, scientists’ understanding of those meadows was largely uninformed by historical data.
A curious young manatee approached our team of scientific divers at work in Wakulla Springs in May 2020. This charismatic marine mammal inhabits seagrass meadows along Florida coasts, but in the winter and spring it shelters in warm waters of Florida springs and rivers. Michal Kowalewski
Seagrass meadows are among the most important structural habitats on the planet. Myriad species, including sea turtles and manatees, forage, shelter or reproduce in those habitats, making seagrasses major hot spots of biodiversity. They also oxygenate ocean waters, draw down carbon dioxide, stabilize bottom sediments and dampen wave energy, helping to protect shorelines and coastal communities from tropical storms and hurricanes. By providing all these services, seagrasses fuel a tremendous economic engine that generates global revenue in excess of US$6 trillion annually.
Globally, however, seagrass meadows are in decline due to environmental changes and an onslaught of local human impacts. One challenge in studying them is that seagrasses don’t have a hard skeleton, so they are rarely found in the fossil record. Instead, researchers found that the shells of mollusks that prefer to dwell in seagrass are a reliable proxy for the grass itself.
In an initial study examining a 40-mile stretch of nearshore habitat just north of the Suwannee River, scientists found that seagrass meadows often span only a few acres, forming a regional patchwork of vegetated and open-sand habitats. Using radiocarbon dating, they showed that about half of the shells found belonged to mollusks that lived prior to the Industrial Revolution, with many dating back to previous millennia.
Remarkably, the species of dead mollusks found in seagrass patches were very similar to those living there today. The same was true for open-sand habitats. This suggests that this mosaic of seagrass patches and open-sand bottoms has been remarkably stable for hundreds of years.
These mollusk shells were collected by divers from Florida seagrass meadows in Tampa Bay in October 2025. Such shells typically provide a record of diverse organisms that inhabited the area over hundreds of years. Invertebrate Paleontology Division, Florida Museum of Natural History
In a broader study covering a 93-mile stretch of the Nature Coast, researchers again found strong similarities between mollusks living today and those from centuries and millennia ago. The same changes in dominant species between northern and southern regions appeared in both modern and ancient shells, indicating that not much has changed since preindustrial times.
Knowing that these seagrass meadows have maintained their ecological character and integrity for centuries is a powerful argument for their continued protection. Studying stable and resilient systems like Florida’s Nature Coast can help scientists understand which conservation efforts are working and how best to restore and maintain similar habitats elsewhere.