Adam Lindquist tugged on a white rope tied to a Canton boat dock Saturday, pulling up a muck-covered cage full of young oysters from the murky water.
He gently rattled the metal crate and began scrubbing the top of the cage with a brush — side to side — so that wet flecks of sediment that had been submerged under the harbor waters didn't land on his jeans.
Lindquist, director of the Waterfront Partnership's Healthy Harbor Initiative, demonstrated how to remove sediment from the cages Saturday for a group of about two dozen volunteers, who helped clean the cages before returning them about three feet below.
The baby oysters — known as spat— are kept at eight locations around the Inner Harbor until the spring, when they are relocated to an oyster sanctuary near Fort Carroll, a man-made island near the Key Bridge.
The project is part of bay-wide restoration efforts aimed at increasing the oyster population. The oysters play an important function in cleaning the Inner Harbor, which is polluted with fecal matter from the city's aging sewage infrastructure that allows raw sewage to seep into waterways. Stormwater runoff and garbage are also problems.
"They help bring life back to the Inner Harbor," Lindquist explained to the group gathered at the Lighthouse Point Marina. "The water is still really polluted."
Recent reports show that the Inner Harbor's water quality has improved, but an overall low score shows that more change is needed, Lindquist said.
The oysters can help filter nutrients and other pollutants from the water. An oyster can filter up to 50 gallons of water a day. About 200 years ago, the oyster population could filter all of the water in the bay every three days.
The Great Baltimore Oyster Partnership, created by the Waterfront Partnership and the Chesapeake Bay Foundation, placed 200,000 new oysters in eight locations in the city. The spat were "planted" in September.
About every two weeks in the warmer months, volunteers are needed to help scrub off sediment. The buildup stifles the oysters, depriving them of oxygen and food and ultimately killing them. Despite that, the oysters are kept in a cage to protect them from predators, like crabs and fish. The oysters grown in sanctuaries throughout the bay have a 75 percent to 80 percent survival rate, compared to ones in the wild, which have a 1 percent survival rate.
In 2010, Maryland increased the number of sanctuaries that are off limits to oyster harvesting, where oyster populations have thrived. But populations have declined in areas open to harvest.
Lindquist said the volunteers play a crucial role in the survival of the oysters. The regular volunteer days help educate residents about the importance of improving the harbor's water quality.
"We definitely couldn't have this oyster garden without volunteers," Lindquist said.
Ralph Comegna, 56, from Harford County, volunteered Saturday because he values improving the bay's water quality.
"I'm an environmentalist at heart," he said. Near his home, he crabs and fishes. "It's important for me to keep the water clean and healthy," he said.
Another volunteer, Alyssa Masilek, 28, who lives in Ridgely's Delight, said she too felt compelled to help improve water quality because her father likes to crab and fish. She said it requires little effort to give back.
"It's like two hours of your time," she said.
Camera Thomas, program manager for the Healthy Harbor Initiative, walked a second group through collecting water samples and counting the young oysters. Groups measured and recorded the oysters' growth. They also tested the water, including temperature and salinity.
"We're doing it to engage people and give insight into what oysters need," she said.
The groups also looked for any possible intruders in the cages. A volunteer had pulled a male and a female blue crab from a cage that was recently cleaned. The crabs were then gently returned to the water.
Lindquist is optimistic that the harbor can improve, though he often faces cynics who think there is nothing living in the polluted water.
"This harbor is full of life," he said.