Concerns Arise Over Lagoon Pond Health

There’s life on Lagoon Pond. Noah Mayrand sees it every day: the herring flailing south toward the herring run, the osprey diving swiftly after them, and beneath the surface, the oyster farm he tends for a living.

But in recent years, the pond, which straddles the border between Oak Bluffs and Tisbury, has borne less and less resemblance to the pond he remembers from his youth. The eelgrass by the landing, where the pond empties into Vineyard Haven harbor, has disappeared. Bay scallops, which rely on eelgrass as a hiding place and nursery, have dwindled, too.

“I feel like Oak Bluffs hasn’t had a good [bay scallop] season up there by the drawbridge in many years,” Mr. Mayrand said.

The Lagoon’s changing ecosystem is concerning to its stewards, who see it as part of a complex web of interrelated phenomena both above and below the waterline that put the pond’s health in jeopardy. This year, the neighboring towns are working together to see if dredging the pond is part of the solution.

Last month, Oak Bluffs town meeting voters approved $100,000 to partially fund a dredging feasibility study, which will determine if digging up some of the pond’s growing sandy shoals will make the pond healthier. This week, the Oak Bluffs select board gave its support to a joint effort between the two towns to pursue a competitive Seaport Economic Grant for the same purpose.

“We will be working with stakeholder groups to help provide the historical and community context for the need for dredging and the benefits it will bring to the water quality, recreation and accessibility to the lagoon,” Oak Bluffs town administrator Wendy Brough wrote to the Gazette.

The last recorded dredging of Lagoon Pond was in 1972 — a “mini-dredging” off the tip of Hines Point on the Vineyard Haven side. The goal back then was the same as it is today: to improve water circulation and help out shellfish, which are keystone members of the pond ecosystem that help keep it clean.

Since then, no dredging has taken place. But it hasn’t been for a lack of trying. 

In 1990, a few Lagoon Pond Association members wrote a letter to the Gazette urging the other association members to prioritize dredging the pond. And in 1992, Tisbury town meeting voters managed to approve just shy of $140,000 to dredge the pond, to be spent only if the town secured a grant. There is no record, however, in Gazette reports that anything came of the project.

Donovan McElligatt, the Oak Bluffs shellfish constable, confirmed that discussions about dredging the Lagoon have spanned the last several decades. But changes in pond conditions over the last five years have created a new sense of urgency.

When the drawbridge was rebuilt in 2015, he explained, the flow of water between the pond and the ocean changed dramatically, thus changing the distribution of sediment and leading to areas of buildup. This likely means the pond is not flushing itself out as quickly and optimally as possible.

“When the drawbridge was finally rebuilt in its final form, it definitely changed the hydrodynamic flow of water coming into the Lagoon,” he said.

Using recent satellite imaging of the Lagoon from Google Earth, Mr. McElligatt pointed out several shallow, sandy areas jutting out from the pond’s perimeter, pale and tan against the rest of the pond’s deep blue. He zoomed in on the landing by the drawbridge.

“This used to be, from what I’ve been told, 12 to 15 feet deep. It was also very vibrant eelgrass beds, and it was a great bay scallop fishery,” he said. “All the eelgrass is gone.”

These changes, he said, are likely related to a trend invisible to the naked eye: an overabundance of nitrogen in the water.

In 2012, the Massachusetts Estuaries Project performed a comprehensive study of Lagoon Pond and developed recommendations for pond health management, including how much nitrogen the ecosystem can handle without becoming impaired. The Martha’s Vineyard Commission’s most recent available data on nitrogen load in the Lagoon, collected in 2023, shows that most areas of the pond saw nitrogen levels above that impairment threshold, with 76 per cent of reducible load coming from septic systems.

Getting the pond below impairment level would require an almost 35 per cent reduction in total maximum daily nitrogen load, according to the report.

The question remains: would digging sand buildup out of the pond help it flush faster, reducing its daily nitrogen load? That’s what the feasibility study is aiming to figure out.

“If we increase the flushing, that helps flush out the nitrogen, and that’s something that Oak Bluffs is very much looking at,” Mr. McElligatt said.

Because the Lagoon is shared by two towns, Mr. McElligatt has been working alongside Tisbury harbor master Michael Gately to help secure funding for the initial study. 

In addition to concerns about pond health, Mr. Gately is concerned that the growing sand flats are making it hard for boats to safely navigate through the drawbridge.

“I would say this is a very timely effort by Oak Bluffs and our town,” Mr. Gately told the Gazette. “We are in that discussion phase between our two towns, which I think is an awesome first step.”

Emma Green-Beach, executive director of the Martha’s Vineyard Shellfish Group and a member of the Oak Bluffs select board, is concerned about elevated nutrient levels in the pond and its ecological impact.

“As you go down south in the Lagoon towards the herring run, the water quality continues to decline,” she said.

Like Mr. Mayrand, she’s seen both the bay scallop and eelgrass populations drop in recent years.

“We’ve definitely seen the scallop population decline over time, down to almost no commercial harvest on either side of the Lagoon,” she said.

For Ms. Green-Beach, taking a look at dredging is an important step in trying to break this cycle. Her office at the old state lobster hatchery overlooks the Lagoon, and from her window, she can see the sand flats by the drawbridge, so high that they are often exposed when the tide recedes.

“They could be restricting flow and restricting the movement of nutrient-rich water from moving out of the Lagoon,” she said.

In terms of pond health, “nutrient-rich” is something of a misnomer. While the phrase conjures images of a lavish feast for happy fish and mollusks, nutrients, including nitrogen, can feed harmful algal blooms that impede shellfish’s ability to thrive.

“When it’s the right kind of phytoplankton, the shellfish grow like popcorn,” Ms. Green-Beach explained. “But then when the environmental conditions change and a different phytoplankton becomes dominant, such as a less desirable dinoflagellate, then it can kill the baby shellfish in the hatchery.”

Sherry Countryman, president of the Lagoon Pond Association, said this is an issue the pond is already facing.

“Last year, we had a cyanobacteria bloom, the first one that I’m aware of ever on the Lagoon,” she said. “That’s really concerning.”

The Lagoon Pond Association has a monitor that stays in the pond to continuously track different metrics of pond health. The machine indicates essentially no dissolved oxygen in the pond deeper than 15 feet — a product of too much nitrogen feeding algal blooms that block sunlight from the pond’s depths, Ms. Countryman said.

“Looking at dredging is one of the components that we need to look at in terms of the health of the pond,” she said.

But there’s a lot that remains unknown about what the impact of dredging the Lagoon could be, or if it will help address its issues. For example, it’s possible that improving flow in the north will not meaningfully improve water quality in the south, where the water quality is worse.

The Lagoon also faces the inevitable pressure of development and a growing population, the effects of which are increasingly difficult to outrun. The Lagoon is surrounded by residential properties, many of which have septic tanks that produce nitrogen runoff — a major driver behind elevated nitrogen levels, per the MVC data.

To combat this, the Lagoon Pond Association is starting a urine diversion pilot program, which aims to decrease nitrogen runoff into the pond by installing urine-diverting toilets in the homes of its neighbors.

“If you take the urine out of your wastewater, you’ll take out 80 per cent of the nitrogen otherwise going into your wastewater,” Ms. Countryman said.

For Ms. Green-Beach, looking at ways of increasing pond health outside of dredging is crucial.

“We have to get creative with solutions, and we’re also going to have to get creative with funding,” Ms. Green-Beach said.

In October, Tisbury and Oak Bluffs will know whether or not the Seaport Economic Council approved their joint grant application for the feasibility study. Officials are hoping that, by working together, the two towns will produce a more compelling application.

But securing these initial funds for a study is just the beginning of a long, expensive process. There will be the costs of the dredging itself, which includes disposing 20,000 to 50,000 cubic yards of sand to an approved disposal site far off Vineyard shores. 

“Is there going to be that appetite if it costs $2 million to dredge the lagoon?” Mr. McElligatt asked. “Can the towns take on that burden? Can the taxpayer take on that burden?”

Time is of the essence to make sure its health doesn’t slip further, says Mr. Gately.

“The Lagoon, like many of our Island resources, has a lot of users,” he said. “While there might not be readily apparent concerns, there’s a lot going on below the water line.”

Mr. McElligatt said the same.

“The pond looks beautiful, but if it continues to die, you’re going to drive past a smelly pond covered in harmful algae blooms,” he said. “If you wait until it’s too late, it’s too late.”

But the thrust behind the towns’ efforts is that it is not yet too late.

Both the Martha’s Vineyard Shellfish Group and shellfishers like Mr. Mayrand have been working diligently to introduce more mollusks into the pond. And according to Ms. Green-Beach, some eelgrass patches have even popped up on both sides of the pond.

”We’re always looking for hopeful spots, shiny spots, something to hold onto, to build on,” Ms. Green-Beach said.

A moment of hope came for Mr. Mayrand just this past winter, when he saw a seal poke its head out of the Lagoon.

“I think that’s a good sign nature wants to come back,” he said.

This article appears in May 29, 2026.