The Swampscott Conservancy and Dr. Phil Colarusso presented the importance of eelgrass.

Eelgrass is a seagrass species that thrives in shallow, calm waters up to about 30 feet deep in the North Atlantic. It is one of two seagrass species found in the region. These plants grow in large underwater meadows, fully submerged and anchored into the sediment.

“It’s an incredibly important habitat, nursery for fish, shellfish, crab,” Colarusso said. “We caught five or six different species of fish in all of 10 minutes.”

Colarusso used a weighted net designed to drag along the seafloor, capturing small marine animals as it’s pulled back to shore.

“When you drag the net through, the amount of biomass is incredible,” Colarusso said. 

The group observed 15 species during Saturday’s pull, as listed on iNaturalist. Species observed on Saturday ranged from long-clawed hermit crabs to Atlantic lion’s mane jellyfish and winter flounder At the time of writing, people in Swampscott have documented nearly 2,000 species, contributing to close to 13,000 observation points to the town’s iNaturalist project.

Eelgrass is important to the health of underwater coastal ecosystems. Their roots and horizontal stems stabilize soft sediment, making it less prone to erosion, according to the National Park Service. By buffering wave energy, eelgrass helps prevent coastal erosion and flooding.

Eelgrass is also able to sequester carbon. This process helps combat climate change by storing carbon dioxide and preventing it from accumulating in the atmosphere, where it contributes to global warming. 

“These are much more efficient collectors of carbon than tropical rain forests,” Colarusso said. “They hold onto it for decades and centuries. As long as the meadow stays intact, carbon will stay in this sediment below the meadow.”

In the 1930s, eelgrass almost became extinct across the East Coast, according to research in the National Library of Medicine. An infectious form of pathogenic Labyrinthula affected eelgrass from Maine to North Caroline on the Atlantic coast and from the Puget Sound on the Pacific coast. 

As a result, the bay scallop fishery crumbled, and it took decades for it to recover. 

“It’s a pretty substantial meadow of eelgrass (in Swampscott),” Colarusso said. “Eelgrass in general, regionally and globally, is in decline. So areas where we find it healthy and sizable like in Swampscott, it’s really important to conserve those.”

Eelgrass, however, is not immune from pollution and climate change effects today either. 

“If you’re living in the watershed here, one of the really most harmful elements to eelgrass is nitrogen,” Colarusso said. “Overuse of fertilizers is a problem. If you’re a local resident, you can reduce the amount of it that you use or get away from using it altogether.”

On the human-side, dredging could negatively impact eelgrass by directly removing it or reducing light penetration since there would be more sedimentation in the water. Swampscott currently does not allow dredging.

“We tend to discourage that,” Colarusso said. “It’s in their (the fishermen’s) interest to protect the habitat as well.”

To help protect eelgrass, a bill has been introduced in the Massachusetts legislature to designate the official marine flora of the Commonwealth. State Sen. Brendan Crighton, who represents Swampscott along with other neighboring towns, co-sponsored the bill. 

The bill was most recently referred to the Joint Committee on State Administration and Regulatory Oversight.

For Swampscott’s eelgrass meadow, Colarusso will return to Fisherman’s Beach on Monday, June 30 for an additional talk with the Boston Harbor Ecosystem Network. The group will discuss the use of eelgrass as a nursery habitat, eelgrass reproduction and research around eelgrass restoration.