When diners slurp oysters from their shells in Anne Arundel restaurants, they contribute to a cycle that helps regenerate the oyster population in the Chesapeake Bay.
And when there are more oysters, water quality improves, said Stephanie Tobash Alexander, the hatchery manager at the University of Maryland's Horn Point Oyster Hatchery.
"They're vacuum cleaners," she said.
The Oyster Recovery Partnership works with state and federal agencies, scientists and others to restore oyster reefs by recycling used oyster shells from across the state.
The process begins with oyster larvae produced by the hatchery in Cambridge.
Scientists and volunteers facilitate oyster spawning.
"They're broadcast spawners," Alexander said. "They kind of throw it out there, eggs and sperm come in contact, and then they're drifted away through the water current."
At first, the only job for the microscopic babies is to swim and eat algae.
"Our goal is to make them as fat and happy as possible," she said.
At about 14 days old, the larvae, which look like coffee grounds, become mature and seek a place to attach.
When they're ready, 1 million to 5 million larvae are placed in a setting tank, with a carefully adjusted temperature and salinity. Within 48 hours, they should attach themselves to shells.
"If they like where they are, they secrete a glue and now we call them spat," Alexander said.
The spat on the shells are deployed by the Oyster Recovery Partnership's planting vessel, the Robert Lee. The shells are strategically placed on a firm planting ground on the bay floor to increase the chances of spat survival.
Beyond filtering water, oyster reefs also provide a habitat for other animals such as worms, fish and mud crabs, Alexander said. When oysters die, their shells became a safe haven for other animals to lay eggs.
"That's what we want to see," she said. "It's very dynamic."
The shells are collected through the Shell Recycling Alliance of the Oyster Recovery Partnership. Last year, over 26,000 bushels of oyster shells were collected from Maryland and surrounding states.
Three county restaurants were among the top shell contributors in 2015: Boatyard Bar & Grill in Annapolis, Mike's Crab House in Annapolis and Congressional Seafood Co. in Jessup.
Lemons and napkins from restaurants are sometimes found among the shells, said Paul Schurick, director of partnerships. But those are quickly sorted out.
The partnership says the donations will allow workers to plant over 100 million oysters.