Island officials hope a new report that explores ways to cut down the amount of nitrogen pollution in up-Island ponds could serve as a blueprint for local planners.

While there is no “magic bullet” for handling the degraded water quality in West Tisbury, Chilmark and Aquinnah, the new Martha’s Vineyard Commission report, titled “Potential Solutions,” offers several options to clean the watershed. Upgraded septic systems, pond openings and aquaculture are all floated as possibilities.

“We like to think of it as a menu of potential solutions,” said Dr. Rachel Sorrentino, an environmental consultant who worked with commission water resource planner Sheri Caseau on the report.

The report is the second phase of a larger up-Island watershed plan, a critical step in planning and funding local nitrogen mitigation efforts. The project started in January 2021, focusing on Chilmark Pond, James Pond, Squibnocket Pond, Menemsha Pond and Tisbury Great Pond.

Runoff from on-site septic systems has long been known to be the primary source of nitrogen pollution in many up-Island ponds, but the region’s rural nature represents a major hurdle. While down-Island towns can use centralized sewering to deal with nitrogen from wastewater, such systems are infeasible in the less-dense up-Island towns.

“Their conditions are pretty similar, they’re rural and they’re spread out, so their options are going to be much different than the ones from the down-Island towns,” Ms. Caseau said. 

The high volume of septic systems up-Island caused significant nitrogen pollution in some area watersheds, leading to toxic cyanobacteria blooms and environmental degradation. A bloom in Chilmark Pond triggered a “red grade” notice that warned people from going into the pond or eating any seafood from the waters. James Pond and Squibnocket Pond both had lower-level warnings.

One of the major takeaways from their most recent report, Ms. Sorrentino said, is the importance of upgrading to “innovative/alternative” (I/A) septic systems which remove more nitrogen.

Ms. Sorrentino proposed that up-Island towns might take a cue from Tisbury, which now requires an I/A system to be installed any time a septic system fails or a new home is built.

Certain dense pockets of habitation in West Tisbury and Chilmark could also be considered for “package plants,” smaller centralized wastewater processing facilities that can serve communities in lieu of a larger sewer, she said.

Other common mitigation methods, like the practice of digging beach channels to allow ponds to flush out pollution to the ocean, might be impacted by climate change.

A lack of rain in recent summers has lowered pond water levels, making it more difficult to establish an outward flow.

“If the ocean is higher, you’re not going to get that flush that clears out a channel for you,” she said.

Squibnocket Pond and James Pond, meanwhile, don’t have regular openings, and aren’t in heavily populated areas. Most of their nitrogen pollution, Ms. Caseau said, comes from the atmosphere, originating with coal burning plants.

Growing oysters and seaweed, which consume the nitrogen as they grow before being removed from the pond ecosystem, might provide a solution for those bodies, she said.

With the new report out, Ms. Sorrentino and Ms. Caseau are now beginning work on the next phase of a larger regional watershed plan. The next phase will provide quantified data for towns to make decisions about the proposed technologies.

Completing a regional watershed plan is essential for the up-Island towns, said Ms. Caseau, explaining that individual towns without sewers cannot undertake the same conventional planning process that the down-Island towns are working on. In addition to giving them direction, she said, the towns will be able to use this management plan to unlock new avenues of state funding.

“Right now, there’s a lot of money out there with the current administration,” she said.