Test Plot: Placing shell baskets in the Basin. © Theresa Chesnut/TNC

Stories in Maine

Science on the Half Shell

Working with oysters to counter the effects of climate change.

On a hot summer day, two scientists slipped below the ocean’s surface in a protected cove on Maine’s Midcoast. Surrounded by support boats and a team of sweltering colleagues, these divers weren’t exploring a reef, they were building one. This is part of a project to test oyster and blue mussel reef restoration techniques in the waters just off the Basin Preserve in Phippsburg.

Launched by The Nature Conservancy in Maine in partnership with local and state organizations, the project involves setting on the seabed special one-foot by one-foot tiles resembling sand castles that are designed to mimic the natural environment where young oysters attach to and grow. As part of the test, some of the tiles have been seeded with very young oysters called spat, along with small discarded mussels from a nearby aquaculture operation. Additionally, other methods, including setting oyster spat on recycled oyster shells, are being tested in the same grid area.

The Importance of Shellfish to the Environment

Oyster reefs and shellfish beds provide critical habitat for fish, crabs, shrimp and other marine life. They also improve water quality as shellfish filter-feed on phytoplankton and tiny pieces of detritus, removing excess nutrients and suspended particles. The cleaner, clearer water then allows species such as eelgrass to thrive, further improving the health and productivity of the area. Reefs also help stabilize sediments and provide natural shoreline protection as storms become more frequent and powerful. And shellfish are tasty!

Quote: Jeremy Bell

We've been really surprised by how quickly these shellfish have grown.

For two years, River and Coastal Restoration Director Jeremy Bell and Coastal Conservation Coordinator Amanda Moeser have been monitoring the different species and methods to compare their effectiveness at establishing shellfish beds and reefs. Early results have been encouraging.

"We've been really surprised by how quickly these shellfish have grown," says Bell. "But we've also learned it's about location, location, location." 

Project team places tiles and shell bags at a location with a harder bottom.
New Site Project team places tiles and shell bags at a location with a harder bottom. © Kelsie Daigle/TNC

Picking the Right Site

Initial siting of the project, chosen with permission from local, state and federal regulators, proved unfavorable to growing a reef. The muddy bottom and slow currents caused the experimental tiles to sink into the sediment—a poor environment for oysters and mussels.

A second site, with a harder bottom and stronger currents that sweep the sediment away, was identified, new permits were secured, and the tiles moved. While the conditions here are better for shellfish, it is not without perils. At both sites, a gooey colonizing invasive species, the pancake batter tunicate, has been spreading over the shellfish like its namesake, threatening to overwhelm its host.

Shellfish attached to a tile specially-designed to encourage attachment and growth.
Good to Grow Shellfish attached to a tile specially-designed to encourage attachment and growth. © Theresa Chesnut/TNC

To combat this problem, the team periodically pulls the tiles out of the water and allows them to dry. Oysters can stay out of water for a very long time with no ill effects. Tunicates cannot! Once the invasive colony dies, the surface is cleaned and placed back at the site.

"It's unlikely this project would work without regular maintenance," says Moeser. "Warming waters in the Gulf of Maine might allow oysters to grow quicker and spawn naturally, but it also creates an environment in which invasive species like green crabs thrive.” 

Shellfish Growers Working Together

In 2018, a group of seven shellfish growers, led by Bill Mook of Mook Sea Farm in Walpole, Maine, formed a partnership with The Nature Conservancy to create the Shellfish Growers Climate Coalition (SGCC). The coalition's members are dedicated to bringing about climate policy action by sharing their stories of how climate change is already harming their operations, their businesses and their communities. In less than a year, the SGCC grew to over 100 members with operations from Maine to Alaska, welcoming businesses from all food sectors wanting to engage with consumers and policy makers to help chart the country’s course towards a low carbon future.

"Growers have real, front-line experience with climate impacts, and their stories are compelling," says Sally McGee, director of TNC's Northeast Marine Program and TNC's coalition lead. "Because our growing coalition has considerable reach and a powerful story to tell, we expect it will have significant impact."

"The SGCC is committed to shining a light on how climate change is already affecting food production in the United States," McGee explains, "and using the stories of shellfish growers and other businesses endangered by climate change is a way to start a broader conversation about the urgent need for climate action."

Continuing the Learning

Back at the Basin, Bell and Moeser lift more tiles as they monitor the site to determine growth rates, ideal habitat conditions, costs and scalability of building oyster and blue mussel beds and reefs in Maine. When the study is complete, the reef will be handed over to the town of Phippsburg and maintained in partnership with the Maine Oyster Company, a local shellfish distributor and member of the SGCC.

"We've learned a lot about growing oysters and mussels out here," reflects Bell, "and are excited about working with businesses and communities to develop solutions in the face of the changes we're seeing all around us."

The Nature Conservancy is thankful for support and guidance along the way from the Town of Phippsburg, Maine Sea Grant, Casco Bay Estuary Partnership, the University of New England Marine Science Program, and the Department of Environmental Protection Marine Program.