Island estuaries have a nitrogen issue

After a three-year study, MVC wants to continue water quality monitoring.

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Brian Howes, director of the Coastal Systems Program and a professor at UMass Dartmouth School for Marine Science and Technology, gives a report on water quality on the Island at Thursday's Martha's Vineyard Commission meeting. -Brian Dowd

After three years of study, the Martha’s Vineyard Commission, in tandem with Brian Howes, director of the Coastal Systems Program and a professor at UMass Dartmouth School for Marine Science and Technology, and several of his colleagues, has finished its Island-wide water quality monitoring study.

The study looked at the total maximum daily loads (TMDL) of 13 Island estuaries to determine their water quality. A TMDL identifies the maximum daily pollution a body of water can receive while still meeting water quality standards.

In a presentation to the commission Thursday night, Howes said the estuaries had a common theme.

“Most of the estuaries on Martha’s Vineyard are showing some level of impairment,” he said.

The Island’s estuaries are negatively affected by nutrient over-enrichment, primarily from nitrogen and phosphorus.

In a presentation on the Menemsha and Squibnocket Ponds in September, Howes said the Island has seen a steady population rise since the 1950s coupled with increased development, which has resulted in increased nitrogen loading.

Nitrogen and phosphorus are both nutrients vital to the growth of coastal ecosystems, according to the Massachusetts Environmental Police. These nutrients support the growth of aquatic plants, which provide food to fish, shellfish, and other organisms. But too much of these nutrients can have negative effects on ecosystems, resulting in a decline of aquatic plants and wildlife.

The Island’s estuaries have better water quality near the inlets where tidal flushing can occur and gets poorer near the headwaters (the furthest point from the inlet) where more nitrogen enters.

“Your systems, a lot of them, are sort of at the tipping point. They’re right at the level where they change a little bit, but if they go get worse they’re really going to become imparied,” Howes said. “Or if they get a little better then they’re going to be best.”

Edgartown Great Pond is in a somewhat different situation, Howes explained. Due to its wastewater treatment facility which reduces nitrogen loading.

The pond also has improved tidal flushing from the ocean. Both these factors have led to expanded eelgrass habitat which is a “very sensitive indicator of nutrient enrichment and associated water clarity,” according to the report.

On the other end, James Pond in West Tisbury has a very poor water quality.

“James Pond is not in good shape,” Howes said. “It has very high nitrogen levels.”

Looking ahead, the MVC will continue to monitor the estuaries to ensure ponds are not going above their TMDLs.

In other business, the MVC is using Transportation Improvement Program (TIP) funding to install six permanent traffic counters around the Island to better understand seasonal traffic patterns and flows.

This map shows where traffic data is collected on Island.

The MVC is now waiting for a final blessing from the Massachusetts Department of Transportation before installing the counters at key points around the Island.

“We’ve been bent on getting them in at the peak season so we can really start understanding the traffic patterns, the real high water marks not the anecdotal ones,” Dan Doyle, MVC special projects manager, said.

The counters will help the Island better understand its traffic trends, how far the shoulder seasons extend, what types of vehicles travel on the roads, and which direction the vehicles travel in. The counters will be placed on the side of the road connected to a utility pole. They are close to six feet tall and cost about $18,000 each. Doyle said the counters are likely to be installed and ready to go in June.

“Just the year round population figures alone…doesn’t really tell the true story of the wear and tear on our infrastructure out here,” Doyle said.