Scientists and citizens have joined forces to protect the meadow, the second largest on North America’s Pacific Coast.

BAY VIEW, Skagit County — On a cloudy Friday morning, a group of volunteers huddled on the shore of the Padilla Bay National Estuarine Research Reserve, peering over Angelica Lucchetto’s shoulder at an array of shed crab exoskeletons, called molts.

“You can tell this is a green crab because it has five marginal teeth,” explained Lucchetto, an invasive species specialist at the Reserve, pointing out the spikes along the front of a spotted greenish molt.

At that same time, similar groups gathered across the Salish Sea as part of a “Molt Blitz” to see if they could find any molts belonging to the invasive European green crab.

Though invasive crabs are a concern to ecosystems across Puget Sound, Padilla Bay must protect something extra special: 8,000 acres of eelgrass.

A powerful meadow

Eelgrass might not seem like a top priority — it certainly doesn’t look like one. At low tide, when Padilla Bay turns into a muddy expanse, the soggy eelgrass is left strewn across the ground like forgotten party ribbons.

But Jude Apple, the research coordinator at Padilla Bay National Estuarine Research Reserve, insists that the eelgrass meadow, which is the second largest on North America’s Pacific Coast, is worth protecting.

“It’s habitat for all the commercial organisms that we’re interested in … juvenile Dungeness crabs, herring, salmon — all kinds of organisms use the eelgrass as a home or as a nursery,” Apple said.

Many of those organisms are also “culturally significant species and first foods,” according to Sophia Ammons, a GIS program manager for the Samish Indian Nation’s Department of Natural Resources.

“It’s really important that we have that habitat so we can continually protect the species that are important for Samish and other coastal tribes,” Ammons said.

Eelgrass also has other superpowers. It keeps the sediment on the bay’s floor in place, which reduces erosion of the shoreline and lowers flood risk. Studies show that landscapes like Padilla Bay also capture and store a lot of carbon dioxide from the atmosphere — more than a forest the same size could. That helps slow the rate of climate change and keeps the ocean’s water from turning too acidic, which harms organisms like shellfish.

One 2024 study even found that eelgrass could clean up pathogens that would otherwise end up in seafood. Though they aren’t sure how it works, the authors of that study found that mussels living near eelgrass contain up to 65% less harmful bacteria than mussels far from eelgrass, suggesting eelgrass could be used as a tool to ensure food safety and security.

Threats to eelgrass 

Padilla Bay’s eelgrass is going to get harder to protect, as rising ocean temperatures will make it harder for eelgrass to survive and facilitate the spread of fatal eelgrass wasting disease. If European green crabs become common, they’ll put even more pressure on the already threatened ecosystem. The crabs tend to uproot the eelgrass as they dig for sea worms or shellfish in the silt, and sometimes even gobble up the eelgrass itself.

“It’s not a threat yet, but there’s potential as the population increases,” Apple explained. “That’s why we’re doing a lot of trapping to prevent green crab populations from getting established.”

On Washington’s outer coast, established populations of European green crabs now dominate some coastlines. In 2024, more than 1 million European green crabs were caught between Willapa Bay and Gray’s Harbor alone.

Laura Kraft, a Washington State University researcher working in Willapa Bay, hopes that biologists around Puget Sound can keep invasive crabs out of precious sites like Padilla Bay. The urgency of that goal became even clearer in May, when a study Kraft worked on found that even young European green crabs could be a big threat.

Kraft’s team observed that juveniles are just as capable as adults of breaking open many species of clams and oysters to eat. Plus, they’re menaces around eelgrass.

“Not only were European green crabs feeding on eelgrass, but they were also just arbitrarily clipping it,” Kraft said, “and when the leaf is gone from the plant, it’s no longer able to grow.”

Kraft’s team conducted the study to try and figure out which species are the most important to protect now that it’s likely too late to get rid of European green crabs on the outer coast. But the reality of it being too late was hard for Kraft to come to terms with.

“I almost want to pause and grieve that for a moment,” Kraft shared. “It’s very frustrating to not have a better solution.”

Puget Sound is more protected than the outer coast — with shallower waters and only one way in and out — so it took some time before the European green crabs wound up here. The first one was spotted in the sound in 2016. But the numbers have only gone up since then: In 2023, only a few dozen green crabs were found in Puget Sound; in 2024, that number shot up to more than 200.

A Salish Sea-wide effort

Padilla Bay — let alone Puget Sound — is massive. That’s why Washington Sea Grant, the organization that coordinated the Molt Blitz, created a way for citizens to help with monitoring efforts.

The blitz was not the only opportunity to contribute to invasive crab monitoring efforts; any Puget Sound resident can help collect data for the Molt Search program, any time of year.

At the end of their search on Friday, volunteers circled back together to sort the crab shells they found by species, counting up how many of each kind they had. Their piles only contained the multicolored molts of familiar native crabs — no European green crab molts in sight.

“That’s what we like to see,” Lucchetto said.

Risa Schnebly is an environmental/science reporter, placed at CDN through the American Association for the Advancement of Science (AAAS) Mass Media Fellowship. Reach her at risaschnebly@cascadiadaily.com.