Friends of Casco Bay and other conservation groups said they'll launch a two-year pilot project this summer to study an alarming decline of eelgrass in Casco Bay.
Eelgrass meadows are a vital fish habitat that reduce erosion, buffer the effects of ocean acidification, and capture carbon.
State mapping shows eelgrass habitat in Casco Bay has decreased by 54% in just four years.
Casco Baykeeper Ivy Frignoca said the pilot project will study two healthy eelgrass beds that could shed light on what is causing the decline.
"We'll be very carefully boating over it and testing samples to be analyzed for nitrogen there specifically. We haven't done that in a while, targeting nitrogen loads in a particular eelgrass bed," Frignoca said.
Frignoca said water temperature and turbidity and invasive green crab invasions will also be studied this summer.
By contrast, state mapping of eelgrass beds from Eliot to Cape Elizabeth has showed increases in the habitat in recent years.
But the habitat from Phippsburg to Port Clyde have not fared so well, according to Angela Brewer, who heads the mapping program for the Department of Environmental Protection.
In 2023, DEP staff documented a 60% decline in eelgrass from the prior survey in 2005, Brewer said. The decline resulted mostly from losses of formerly extensive eelgrass in Great Salt Bay, the Medomak River estuary, and around Westport Island.
An excerpt from the full report: “Seagrass was largely absent from the upper reaches of estuaries, which may be attributable to light limitation from precipitation-derived turbidity in the water column. European green crabs (Carcinus maenus) and epiphytic growth can also lead to seagrass decline, although relatively low abundance of both were observed throughout the survey. However, whether high levels of rainfall in the spring and summer of 2023, epiphytes, or green crabs may have been related to any recent seagrass losses or growth limitations cannot be clearly established since the Midcoast Region had not been mapped since 2005, and changes in seagrass distribution could have occurred at any time since the prior survey.”
Learn more inthis report to the legislature in March.
Brewer said the DEP will be mapping seagrass and salt marsh in the Penobscot Bay region this year, which is an area that has not been mapped since 2003.
Friends of Casco Bay held a webinar Thursday, April 25 to educate residents and engage volunteers to help with the pilot project.