Colonial Oyster Shells Recycled from Archaeological Dig

By Cheryl Costello

As many who care about the Bay know, oyster shell is invaluable as substrate for new oysters to grow on. And that’s why there are large-scale efforts on the Chesapeake Bay to recycle old, discarded shells from restaurants, oyster roasts, and—now—an archaeological dig site. Apparently colonial oysters are just as good as modern ones for planting oyster spat.

Enter a first-of-its-kind collaboration between the Oyster Recovery Partnership (ORP) and Historic St. Mary’s City, where the oyster shells are literally as old as dirt.

“It’s a little bit chalkier because it’s been underground and it’s a couple hundred years old, but you can tell it’s a native oyster for sure,” says Tommy Price. Price, ORP’s Shell Recycling Manager, shows us shells and fragments excavated from the site of a building dating back to the 1680s.

ORP was asked to come to Maryland’s first capital city to pick up thousands of shells to be recycled. And like so many things dug up in St. Mary’s City, they’re old.

“These are wild, natural Chesapeake Bay oysters. They’re thick-shelled. Some of them are pretty big, as you can imagine being a couple hundred years old,” says Price. But they’re not the oldest shells ORP has ever repurposed.

“We’ve worked with the State Highway Administration, they have an archaeological department for new roads and whatnot, and they’ve come across oyster middens from Native America sites, and also from colonial and pre-colonial.”

What sets this recycling effort apart is that it is the first pile of shells that was directly from a pre-Revolutionary War site. “Not just scattered throughout centuries,” Price explains. “This was one distinct period from one particular building.”

Ruth Mitchell, manager of archaeological services at Historic St. Mary’s City, calls the oyster shells “treasures” for archaeologists. “The building that we discovered dates to probably around 1680 and it underwent a lot of architectural changes and was probably abandoned by about 1720 or so. And in doing the abandoning of the building (which was a wooden structure), they had to fill in a brick-lined cellar and that’s where those oyster shells came from that we excavated.”

Other trash like broken bits of pottery and wine bottles were also found. The site was used as a planting field for various crops for a few hundred years before a 1950s classroom was built and then torn down decades later.

Historic St. Mary’s City gave ORP some 900,000 shell pieces but held onto about 5,000 to analyze. “We can look at salinity and the time that the oyster was harvested, growth rates, how old was this oyster shell … And so we squeeze as much data out of this shell as we can to try to understand past human activity,” says Mitchell.

But for ORP’s shell recycling purposes, the old fits right in with the new. “They’ll go to the hatchery to be seeded with larvae and create little oysters,” Price says.

They won’t be treated any differently than the rest of the recycled shell, despite their historical status. “These are the same species that we have coming from restaurants nearby, so they go to the shell pile. They don’t need to age, but they’ll age with the rest of our shell to make sure all the tissue breaks down, no diseases,” Price explains.

Just as useful as their modern-day counterparts? Not bad for being centuries old. “It’s really cool ‘cause it shows oysters were a staple of a diet down there and that oyster shells were kind of just a waste product. It was fill material,” he says.

Now they’ll be used to fill in the gaps to understand more about our beloved Bay oysters and to help the life cycle continue.