Outside the Marblehead Harbormaster’s office sits a big white box that has been attracting curious looks all summer.
Inside are six orange buckets containing about 25,000 tiny oysters — some no bigger than a grain of rice — quietly doing their part in an ambitious effort to restore oyster populations and improve the coastal ecosystem.
The box is an oyster upweller, installed in June as a joint project involving Sustainable Marblehead, Salem Sound Coastwatch and the Massachusetts Oyster Project.
The baby oysters, known as seed, arrived July 1 at just 2 millimeters across. Some have since grown to about 10 millimeters.
Harbor water is continuously pumped into the bottom of the upweller and through the buckets holding the oysters. The flowing water delivers a steady supply of phytoplankton, algae and other naturally occurring food, helping the young shellfish grow before they are moved into open water.
The oysters are expected to leave their Marblehead nursery at the end of September. Many will be moved to an oyster reef in Ipswich that the Massachusetts Oyster Project has been working to restore for about five years.
And no, these oysters aren’t destined for anyone’s dinner plate.
The project is about restoration, not harvesting.
Oysters once fared poorly in Salem Sound, which stretches from Marblehead north to Manchester. Water quality has improved significantly over the past several decades, but much of the area remains prohibited for shellfish harvesting. The upweller offers scientists and environmental groups a way to learn how young oysters grow in local water while keeping them protected and closely monitored.
For environmental advocates, the little shellfish pack an ecological punch.
“This is important because to have a healthy ecosystem and healthy coast, we have to have healthy habitat for all the different species,” said Gitte Venicx, Salem Sound Coastwatch executive director. “Oysters are one of those, and getting to raise them in an oyster upweller is one step towards an eventual restoration that we can do, and it’s also showing that the water has gotten cleaner over the last 30 years, and that we can do this. We wouldn’t have been able to keep them alive like this then.”
Oysters filter water as they feed and build reefs that provide habitat for other marine life.
“Oysters have just tons and tons of reasons that they’re so mighty,” said Liv Woods, executive director of the Massachusetts Oyster Project. “The most important thing that people don’t usually know is that they’re reef builders, and so they create habitat. And that habitat is a place for fish and animals to be, up to 200 different species at a time.”
Those reefs can also play a role in reducing coastal erosion and flooding, she said.
A summer of oyster tending
Salem Sound Coastwatch volunteers have checked the upweller daily, cleaning it, making sure the pump is operating and taking water-quality measurements. The Marblehead installation is one of nine upwellers in the Massachusetts Oyster Project network, designed to give young oysters a protected head start.
Once large enough, many of Marblehead’s oysters will move to the restoration reef in Ipswich, where organizers say wild oysters have begun settling alongside those planted there — an encouraging sign that the reef is beginning to sustain itself.
Sustainable Marblehead is also exploring what may be possible closer to home.
Steve Wolf of Sustainable Marblehead said organizers have identified five locations around Marblehead Harbor where oysters could potentially be placed in controlled cages, monitored by shellfish wardens and the harbormaster.
That could help answer a basic question: Can oysters survive, grow and eventually thrive in today’s Marblehead Harbor?
The effort follows earlier local experiments at Lead Mills, where adult oysters have been placed in cages and monitored. Young oysters have also been attached to slate plates and placed in the water under controlled conditions, another step toward determining whether larger-scale restoration could eventually work in Marblehead.
Cleaner water, but challenges remain
The project also highlights the complicated state of local water quality.
Organizers stressed that describing Salem Sound simply as “contaminated” doesn’t tell the whole story. Some of the data underlying shellfish classifications is old, they said, while more recent monitoring suggests conditions have improved. Changing an area’s shellfish status, however, requires extensive state testing.
For a shellfish classification to change, Woods said, the state must conduct regular testing over 12 to 18 months to demonstrate that conditions meet the required standard.
There are still real water-quality concerns. Salem Sound Coastwatch monitors bacteria at outfalls near beaches throughout the Sound and reports its findings to municipalities, helping communities identify pollution sources that can include stormwater runoff, aging pipes and leaking septic systems.
Lead Mills presents another challenge. The site was once home to a lead factory, leaving contamination in the sediment. The former coal-fired power plant across Salem Harbor also left a legacy in local sediment. Organizers say oysters placed in areas like Lead Mills need to be monitored for metals such as lead and chromium as well as bacteria.
No one involved in the project is predicting when Marblehead’s waters might be opened more broadly to shellfishing.
“I think we’re trying,” Wolf said. “We’re making progress, so I can say we’re moving in that direction.”
