BRUNSWICK

Local clammer David Wilson has been harvesting shellfish since he was in grade school. But recently, in the same flats where he’s made his livelihood for years, the clams are starting to disappear.

The culprit isn’t the notorious shellfish-eating green crab, but the milky ribbon worm: a long, pink, flat invertebrate that burrows in the mud flats off Maine’s coast.

The worm can split in two and regenerate when in danger, and it’s decimating local clam populations. The worm uses its proboscis — an extension of the mouth — to access the clam through the gaps in the clam’s shell before stunning the body of the clam, paralyzing it and digesting it in one fell swoop.

Wilson has been harvesting clams commercially since 1993 and is worried about the influx of the ribbon worm. He is especially worried by the worm’s ability to wipe out entire clam populations. Once the worms eat enough clams, he said, the clams turn rancid, raising the nitrogen levels in the soil and causing neighboring clams to die off.

The biggest problem with the worms is that no one knows for certain how to get rid of them. Though they are native to the area, it is unclear why they are just now posing such a problem. According to Wilson, there was once a time where it was not uncommon to see ribbon worms above ground, outside the cove on the shore. Because of rising water temperatures caused by climate change, they have moved into warmer waters that are now habitable to them.

Near the middle of the mud flat, glazed and perforated with clam holes, just one dig can upturn around 15 worms. They’re everywhere; during three conservation days about 300 pounds of worms were harvested.

Wilson has been pushing the Brunswick Town Council to hire a small team to manually extract the worms at various coves in the area, starting with those at Birch Island and Middle Bay. In his opinion, many people — even those in the shellfish industry — aren’t aware of the threat that ribbon worms pose because, as he explained, it’s a race: As soon as the worms eat enough clams in one area, the entire cove can go under. He cited examples at Scrag Island, White’s Island and Middle Bay.

“We could go out there last summer and get anywhere from 200 to 250, sometimes 300 pounds a tide,” he said. “There’s nothing out there now. You couldn’t go out there and get just a bucket to eat.”

According to Monique Coombs, the director of Marine Programs at the Maine Coast Fishermen’s Association, the ribbon worm crisis points to larger issues of climate change and ocean acidification. She’s been working on town committees and with a team at the University of New England to look into the issue further.

“The biggest problem is that we don’t know how to stop them,” she said. “They are covered in a noxious slime to protect them, which also makes them disgusting to predators. They don’t have a lot of predators — the ribbon worm’s number one prey is soft-shell clams.”

According to University of New England Professor of Marine Sciences Markus Frederich, soft-shell clams are preyed upon in their juvenile stage of life by the invasive green crab. Once they reach adulthood, however, milky ribbon worms become the primary predator.

Frederich’s research on ribbon worms and green crabs began five years ago at the behest of the Shellfish Conservation Commission. Alongside assistant research scientist Adam St. Gelais and graduate student Curtis Fahey, he hopes to figure out the problem scientifically.

Frederich is combining scientific evidence and anecdotal knowledge from local clammers to determine current worm population and distribution size, the sand grain size of the species’ preferred habitat and the stress responses of soft-shell clams to green crabs and ribbon worms.

“We need to be careful in figuring out if it’s new or just suddenly people care about it,” Frederich said. “If the green crabs decimated soft-shell clams, now any additional impact on those populations becomes way more obvious.

“In the whole context, the problem is real. Those clammers are making a living out of digging clams and the clams are disappearing,” he added.

Wilson has begun to invest in aquaculture techniques to grow hard-shell clams, called quahogs, in containment gear to prevent predation. Though it’s soft-shell clams that ribbon worms primarily attack, they sometimes prey on quahogs as well. He will also employ a water monitor to track climate coefficients like water temperature.

But according to Frederich, this might not be a long-term solution.

“What other people have shown so far is that the only thing that works is mechanically keeping the critters out, which would mean putting netting down there — which is a major impact on the ecosystem and therefore not really doable.”

For now, viable solutions are unclear — as are the causes. As the soft-shell clam capital of the world, Maine stands to see how this beloved industry will withstand the changing tides of the working waterfront. Only time, and scientific data, will tell.

“The Gulf of Maine is one of the fast-warming bodies of water on the planet,” said Frederich. “Of course this could affect everything. It’s all speculation at this point, which is why we’re so eager to be doing this study — to get some solid data about this.”

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