Delayed Tisbury Great Pond report shows low nitrogen levels


A report on the health and well-being of Tisbury Great Pond released last month follows years of bureaucratic wrangling over costs. It is the long-awaited result of a study that began in 2005. The study has confirmed low but significant nitrogen levels in one of Martha’s Vineyard’s largest estuary systems.

Tisbury Great Pond — a 700-acre coastal salt pond that straddles the boundary between Chilmark to the west and West Tisbury to the east — is one of several Island ponds that were subjects of the state-wide study of coastal water bodies comprised in the Massachusetts Estuaries Project (MEP), a collaboration between the University of Massachusetts Dartmouth and the Massachusetts Department of Environmental Protection (DEP).

“The overall goal of the Massachusetts Estuaries Project is to provide the MassDEP and municipalities with technical guidance to support policies on nitrogen loading to embayments,” the study said.

Excessive nitrogen levels have become a common contributor to the decay of coastal ponds across the Island. “Tisbury Great Pond is in better shape than others,” Martha’s Vineyard Commission (MVC) water resources planner Sheri Caseau said this week. “But there’s definitely a need for the study. When the algae grows and then dies, it smothers everything underneath it, and this can cause a major die-off.”

According to the report, “… nutrient related water quality decline represents one of the most serious threats to the ecological health of the near shore coastal waters.”

Tisbury Great Pond supports a healthy population of wild oysters and local fauna, whose existence is compromised if septic wastewater and fertilizer runoff, the prime contributors of nitrogen buildup, continue to be overlooked, Ms. Caseau said.

“Unfortunately, almost all of the estuarine reaches within the Tisbury Great Pond system are near or beyond their ability to assimilate additional nutrients without impacting their ecological health,” the study concluded.

An increase in nitrogen stimulates algae growth, which leads to low levels of oxygen and poor water quality, the 150-page analysis found. The result is, “The loss of fisheries habitat, eelgrass beds, and a general disruption of benthic communities and the food chain, which they support.”

The study added that there is a critical need for “state-of-the-art approaches for evaluating and restoring nitrogen sensitive and impaired embayments.”

About time

While the state picked up half the cost of the report, Chilmark and West Tisbury taxpayers shelled out $80,000.

Although voters approved funding over the course of several annual town meetings, town officials criticized the time taken to produce the report. Disputes between DEP and UMass over rights to the study furthered officials’ skepticism.

“The MEP has not shown themselves to be well administered; it has been a slow, bureaucratic process that has been mired in foolish debate between UMass and the state, with no consideration of the towns,” Chilmark selectman Warren Doty said in 2011. “We authorized them [for funding] three years in a row, and it took them five years before they even came to get their money.”

In a telephone conversation last week, hydrologist Roland Samimy, technical coordinator for MEP, attributed the tardiness of the MEP’s report to what he said was the lack of a regional approach on behalf of the Island towns’ elected officials to see the project through.

“The towns on the Vineyard are not coordinated when it comes to water monitoring basics,” Mr. Samimy said. “It’s high time that we try and develop an Island-wide water monitoring program, because at the end of the day, all you end up with is a patchwork quilt of water monitoring, and it doesn’t become as useful.”

Despite the delays, Mr. Samimy said the study may still be used in an effective way. “The towns can now use it to manage the (nitrogen) loads to the estuary, before they get too high.”

Mixed views

At a selectmen’s meeting in March, Kent Healy of West Tisbury, a well-known civil engineer and longtime pond steward, expressed concern for what he considered to be a significant lack of evidence presented in the draft report.

“The MEP is in the nitrogen business,” Mr. Healy said. “And that’s what they measured. I’m not a not a nitrogen person, I’m a groundwater person, but there are major flaws presented in this study, problems that I consider to be serious errors.”

In a phone interview last week about the final report, Mr. Healy, who has been monitoring the groundwater in and about Tisbury Great Pond for more than 30 years, said, “Any proposal to reduce the level of nitrogen must be based on valid measurements and calculations. But they don’t measure the content of groundwater as it enters Tisbury Great Pond. Based on that alone, their [MEP’s] findings are inaccurate.”

Not everyone is critical of the MEP studies, which include the Squibnocket/Menemsha ponds system.

Wendy Weldon, co-chairman of the Squibnocket Pond Advisory Committee, has endorsed the MEP’s study since it’s inception.

“People worried about the state coming in, but it’s for that reason that I support it,” Ms. Weldon said. “It will help us make decisions down the road on how to manage our ponds that are loaded with nitrogen.”

How conclusive is the report?

“It’s a constant work in progress, to some extent it’s always a constant work in progress,” Mr. Samimy said.