Largely hidden from sight, eelgrass, or Zostera marina, plays a vital role in coastal environments. It shields shorelines from erosion, removes nitrogen through respiration and provides habitat for dozens of juvenile species, from lobsters to bay scallops. 

In Maine, more than half of native eelgrass has receded, drawing scientists’ attention. Many factors have contributed to this, including stormwater pollution, warming waters and invasive green crabs munching on the grass beds. However, there are still many unknowns. 

Since 2021, the Collaborative for Bioregional Action Learning and Transformation’s (COBALT) Team Zostera has surveyed the remaining seagrass meadows, identified the species’ reproductive season and determined the best time for seed collection. Working with the Casco Bay Estuary Partnership, Friends of Casco Bay, Maine Department of Environmental Protection and the U.S. Environmental Protection Agency, the team has also started to explore solutions, including transplantation. 

On Oct. 17, 2024, divers initiated a pilot-scale project, scattering 40,000 eelgrass seeds near Cousins and Little John Islands, just off the coast of Yarmouth, and reserving some for Bowdoin College senior Lucy Dutton to test germination rates this winter.

Dutton’s viability analysis seeks to understand how aquatic plants respond to natural stressors, which is vital knowledge for guiding future restoration along the East Coast.

“Eelgrass has become a hot-ticket item,” said Janelle Goeke, a staff scientist with the Casco Bay Estuary Partnership who helped organize a seagrass summit on Jan. 14.  “We want to contextualize the work being done in the field between project partners and other scientists. It’s great to all work on this, but it’s best we do it together.” 

The meeting was the first of its kind; it allowed those in the field to share their findings and brainstorm actionable next steps. The main takeaway was a commitment to raising public awareness by engaging locals in stewardship practices. 

If the pilot-scale effort goes well, the goal is to advance toward large-scale restoration. 

“Eelgrass is important for the fishing industry and the underwater ecosystem,” Goeke said. “But Maine has a unique phenotype that, if lost completely, would be hard to replace.” 

Setting the stage

The summit began with a review of the decline in eelgrass, which the state DMR and DEP have traced back to 1993 through mapping. From 2001–2013, biomass sharply declined, followed by another decrease in 2022.

In a handful of decades, the total eelgrass biomass reduced from 8,200 acres at the turn of the century to 2,200 acres. 

The Casco Bay Eelgrass Consortium was formed in 2018 to address the species’ statewide decline and later expanded to the Maine Seagrass Consortium.

Last year, the group found that the eelgrass beds on Cousins Island and Little John Island, which were healthy in 2022, became desolate over two years.

“We suspect the 2023 winter storms contributed to this loss,” Goeke said. “But still, it was striking. … We want to understand why this is happening — is this decline a result of environmental conditions, potential disturbances or something else entirely? That’s why we’ve turned to the scientific community.” 

Representatives from Friends of Casco Bay, Manomet, Team Zostera and the DEP shared their insights on the optimal conditions for eelgrass growth and the challenges faced. Surprisingly, green crabs may not be the primary threat. 

Green crabs may not be the top culprit

Mike Doan, a staff scientist at FOCB, described six water-monitoring events conducted last year, from June to September, at three sites during different tidal stages. 

One of the locations was near the current Cousins Island restoration site. 

Phytoplankton abundance, light attenuation, temperature, water quality, salinity, nitrogen, nitrate and ammonium levels were measured, indicating promising conditions for marine ecosystems to support eelgrass growth.

“Now, we wait,” said Doan, acknowledging the pilot project underway. “Conditions are always changing, so it’s hard to say what will happen.” 

Jessie Batchelder, Manomet Fisheries project manager, spent the summer monitoring green crabs. Her team conducted a baited-trap survey in Casco Bay from June through October. 

Although fewer green crabs were trapped than usual, she noted those caught were surprisingly large. 

“It was as though they were Jonah crabs,” said Batchelder, mentioning that Dan Devereaux, Brunswick’s coastal resource manager, echoed her surprise. “Over a 10-year period, there’s been a major increase in size, which I find interesting. The crabs we saw moved through the beds without burrowing or interacting with shoots. We believe they are likely part of the puzzle, understanding eelgrass decline, but not the entire picture.” 

She hypothesized that, given that higher populations of green crabs are typically found in intertidal zones, their presence may be driving eelgrass beds to grow a bit deeper. 

“Continued monitoring of green crab behavior will be vital for gauging the success of restoration efforts,” Batchelder said. “It is also important to track changes; if their size continues to grow, we should explore what that means.” 

Goeke pointed out that sea otters are eating green crabs on the West Coast, thus reviving seagrass. On that note, Glenn Page, global lead of COBALT, cited Swedish researcher Eduardo Infantes’ theory on green crab consumption of eelgrass seeds.

“It seems worthwhile to look into this,” Page said. “The more footage we get of green crabs engaging with eelgrass, the better.” 

In 2013, the DEP hired Seth Barker to map the decline of eelgrass. During the summit, DEP biologist Angela Brewer shared the data he collected, noting significant loss in Middle and Macquoit Bay and the shallower areas of the Harris, Royal and Cousins rivers.

“There isn’t a straightforward answer to this issue,” Brewer said. “But we have found that eelgrass thrives in shallow embayments — areas with fringing beds that are well-flushed or in slightly rockier areas seem to perform well.” 

Pilot restoration check-in

So, how’s the current restoration project going? Page updated the group. 

Once the weather warms, Team Zostera will implement growth-monitoring plans at both sites to determine when germination occurs and to what degree the seeds take hold on the seafloor. 

The last time the quadrants were checked, Jan. 12, there was little activity. The meadow near Cousins Island was still small and turf-like. 

As for Dutton’s work, her data analysis is still ongoing. However, preliminary evidence corroborates numerous studies that find that lower salinity and higher temperatures produce algae growth conditions, stimulating seed germination. 

Dutton agreed with Batchelder that green crabs may not be the biggest culprit. At Schiller Coastal Center, she has seen horse mussels and polychaete worms that seem to eat eelgrass seeds. 

“We’ve seen considerable reproductive variation,” Dutton said. “Analyzing seeds from different collection sites across Casco Bay has been beneficial for identifying potential donor sites in the future and streamlining our collection process.” 

Eyeing large-scale restoration

The action plan discussed at the seagrass summit will serve as a guidance document to embracing an uncertain future.

Attendees agreed that to increase awareness of eelgrass as a vital habitat in Maine, scientists needed to work with coastal municipalities to educate residents, whether by hosting more public workshops or engaging with artists and storytellers to amplify the importance of community involvement in ecosystem stewardship. 

Moving in this direction, the Osher Map Library will host a “For the Love of Eelgrass” event from 3-6 p.m. Friday, Feb. 14, where area sculptures, poets and musicians will share their depictions of the importance of seagrass conservation. 

There was also a consensus to recruit citizen scientists to help out actively, whether by monitoring algal blooms or reducing fertilizer use on lawns. 

Page mentioned that besides the University of Maine at Orono and the Maine Maritime Academy, no local dive programs support underwater research, so Team Zostera is stepping up to create one for Casco Bay. 

As a unit, state scientists plan to collaborate with harbormasters, creating outreach materials on the efficacy of conservation moorings in locations such as Harpswell and advancing the political will for critical eelgrass meadows to achieve “protected area” status. 

The hope is to facilitate time-series data collection by engaging undergraduate, graduate and postdoctoral students in hands-on restoration work and standardizing sampling methodologies (SOP).

This summer, the consortium will complete its third and final year of the phenology study, documenting the life cycle of eelgrass in Casco Bay. Around the same time, Team Zostera will check in on the status of its transplantation project. 

“Working together as a scientific community — and a broader community — is essential to seeking solutions,” Goeke said. “Every person has their areas of expertise and their blind spots; no one knows everything. When we ask questions and drive work forward [as one], we can rely on the collective knowledge and design projects that are more impactful than those any one person or organization can take on.”

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