Island authorities must radically cut nitrogen pollution in the Edgartown Great Pond, state officials told a public hearing Wednesday at Edgartown town hall about the final report from the Massachusetts Estuaries Project.

The Massachusetts Department of Environmental Protection held the hearing to discuss the pond’s nitrogen problems and the requirement for a Comprehensive Wastewater Management Plan to limit nitrogen seeping into it.

The report calls for more homes to be connected to the town sewer and more frequent opening of the pond to the sea, especially in summer, so excess nutrients might be flushed out.

Nitrogen effectively acts as a fertilizer which encourages algae; other life in the pond is starved of light and oxygen. The high load in the pond has led to a dramatic loss of eelgrass beds and had a serious impact on fish and shellfish habitat, the estuaries project report found.

Total nitrogen load into the pond now is 25.61 kilograms per day, and the report puts the target at 21.06 kilograms.

Nitrogen loading overall should be cut by 18 per cent, the report said, and nitrogen pollution from septic systems reduced by 30 per cent.

But the report makes no mandate for how these goals are to be achieved, said Christine Duerring, the department’s environmental analyst for the division of watershed management who led the discussion on Wednesday.

“This is not a mandate. The [federal] Environmental Protection Agency, through the Clean Water Act, can require towns to make some of these changes in the report, but that is a last resort. The [DEP] would rather work with towns to come up with a workable solution. So far we haven’t had to force towns to make changes,” she said.

Edgartown officials already have implemented many of the report’s recommendations.

Shellfish constable Paul Bagnall said the town already punches open breaches in the pond’s southern edge four times a year, the maximum amount allowed by law. He said the duration of those openings varied from a few days to several weeks, depending on weather conditions and water levels in the pond.

“We’re basically maxed out for openings in the pond . . . we’re way ahead of you,” he said.

Mr. Bagnall also suggested a simpler solution to reducing nitrogen levels in the pond: shellfish. Several studies have shown that a healthy population of shellfish in a coastal pond will eventually lower the nitrogen levels and increase the overall health of the pond. “The best part of that solution is you get to eat the shellfish afterwards,” he said.

Wastewater superintendent Joe Alosso said the town has connected some 100 homes in the pond’s watershed into the town sewer system since work on the report began almost five years ago. And the town is planning to connect 200 more homes in the coming years.

Mr. Alosso asked whether the town would still be required to draft a comprehensive wastewater management plan, which he said would be costly and time consuming, if officials took steps on their own to connect more homes to the town sewer and lower nitrogen levels.

Ms. Duerring said the town nevertheless would need the plan.

The Edgartown board of health is close to completing new regulations that would require all homes within the pond watershed to connect to the town sewer by a certain date, if the sewer line is close by and the homeowners are able to connect, Mr. Alosso said after the meeting.

This regulation will effect between 300 and 350 homeowners, approximately half of whom have already connected to town sewer, he estimated.

Brian Howes, the marine scientist and technical director of the estuaries project, said at the close of the meeting that the town was making progress to meet the goal of reducing nitrogen in the pond. “You guys are the real experts on coastal ponds out here on the Vineyard. You’re on the front line, more so than most other communities in the state. You’ve been dealing with this for years,” he said.