Excessive nitrogen is ruining the ecology of our coastal ponds. It comes largely from individual on-site residential septic systems throughout the watersheds of each pond, which allow nitrogen-laden wastewater to flow through groundwater into our coastal waters. The expense of correcting this situation will be enormous and we need to find the most cost-effective techniques.
This section of the website gives an overview of Martha's Vineyard coastal ponds and how we can deal with deteriorating water quality due to nitrogen pollution. (This website will be expanded later in 2013 into a comprehensive summary and compilation of data, studies, and recommendations about how to deal with this growing challenge.) Here are some useful documents and links.
Coastal Ponds Overview and Status Report:a two-page report card on the ponds including: a map of all watersheds as well as a matrix with basic data about each pond and watershed including information about water quality and the status of planning and implementation efforts; it will be updated periodically.
Island Plan: section 10 Water Resources of the 2009 regional comprehensive plan for Martha's Vineyard provides a useful summary of the situation and recommendations.
Martha's Vineyard Water Alliance: an informal grouping of public and non-profit organizations that meets monthly at the MVC to share information about and to coordinate and advocate for efforts to improve water quality.
Cape Cod Wastewater Management Initiative: the Cape Cod Commission’s effort to prepare a Regional Wastewater Management Plan, funded with a major grant from the Commonwealth, will offer many useful lessons for the Vineyard.
Massachusetts Estuaries Project: is a collaboration between the Massachusetts Executive Office of Environmental Affairs and the University of Massachusetts's School of Marine Science and Technology to provide water quality, nutrient loading, and hydrodynamic information for 89 estuaries in Southeastern Massachusetts.
Martha's Vineyard Coastal Ponds
Martha’s Vineyard is ringed by 27 saltwater and brackish ponds that are vital to the Island’s health, environment, beauty, and prosperity.
Commercial Fishing: The ponds are productive sources of shellfish and fin fish, important to our commercial fishing industry.
Water Recreation: The ponds offer a wide range of recreational opportunities, including boating and sport fishing, so important to the Vineyard's visitor-based economy.
Shoreline: The ponds have more than 290 miles of shoreline, important environmental resources, favorite spots for beach activities, and prime locations for real estate and viewsheds for many to enjoy.
The16 great ponds (10 acres or more) and 11 other coastal ponds cover nearly 9,000 acres or 16 percent of the Vineyard.
Our coastal ponds are in trouble!
The water quality of most of our saltwater ponds has declined noticeably in the last generation as a result of growth on the Vineyard and beyond. About 64% of the Vineyard’s land area is made up of watersheds that drain into nitrogen-sensitive coastal ponds, either through runoff or groundwater flow. Excessive nitrogen over-fertilizes aquatic plants, resulting in odorous, unattractive ponds devoid of eelgrass, fish, and shellfish, adversely affecting the valuable tourist industry and coastal property values. There are three main sources of excessive nitrogen in our coastal ponds.
Atmospheric Sources: Rain deposits nitrogen from polluted air, largely from upwind coal-fired power plants and other industrial sources off-Island. (On average, this represents 29% of nitrogen pollution though the proportions vary considerably between watersheds.)
Wastewater: By far the greatest source of "manageable" (i.e. non-atmospheric) source of nitrogen pollution in our ponds comes from the urine in wastewater. About 90% of Vineyard homes have their own on-site Title 5 septic systems that deal well with pathogens but have little impact on nitrogen. (62% of nitrogen pollution).
Fertilizer: Much of the nitrogen-based fertilizer used on lawns, gardens, and farms ends up in the water table where it drains into ponds (9% of nitrogen pollution).
What can we do?
The Martha's Vineyard Commission has worked for many years with towns, pond associations, and the Massachusetts Department of Environmental Affairs (DEP) to gather and analyze data and identify the best ways to deal with this challenge. The Massachusetts Estuaries Project (MEP) is analyzing most Vineyard coastal ponds in order to establish safe levels of nitrogen loading and identify the most cost-effective ways to meet these levels. DEP then establishes the Total Maximum Daily Load or TMDL for each pond. Some ponds are already over these limits, others are projected to exceed their limits with future development, and others can accommodate all projected growth without exceeding their limits.
We need to identify the lowest-cost ways to reduce nitrogen-loading so that the ponds meet their TMDL and start implementation, to avoid having DEP or the courts impose measures that may be much more costly and may conflict with other community objectives. The following are possible ways to deal with the manageable portion of excessive nitrogen.
Wastewater Treatment: Nitrogen can be reduced at the source with techniques such as composting or urine-separating toilets. Wastewater can be treated to reduce nitrogen, such as with sewering and centralized treatment that removes about 95% of the nitrogen or DEP-approved on-site innovative alternative septic systems that remove about 40-50% of the nitrogen, compared to standard Title 5 systems. Both methods are costly to install and maintain.
Tidal Flushing: Improving water circulation to the sea with widened inlets or more pond openings can help dilute the nitrogen in the pond.
Landscaping and Fertilizers: A number of landscaping techniques can be used to reduce nitrogen, including reducing the use of fertilizers and designing landscaping so the effluent from septic systems passes through vegetation where it is converted into gases taken up in the atmosphere.
Aquaculture: Growing oysters and other shellfish can reduce nitrogen in a pond, though this is not yet recognized by DEP.
Growth Management and Nitrogen Limits: Board of health and zoning regulations can be used to limit the nitrogen that will be generated in nitrogen-sensitive watersheds in the future, such as by limiting the number of bedrooms in a house, limiting how much nitrogen a new project can generate, and requiring that the nitrogen generated by a development project in a critical watershed is offset with nitrogen reduction elsewhere in the watershed. Land acquisition for open space also reduced the generation of nitrogen.
PONDS AND THEIR WATERSHEDS
Here is key information about the fifteen main coastal pond systems on Martha's Vineyard: the overall watershed, the pond itself, its water quality, the status of the MEP (Mass Estuaries Project), and the status of implementation of improvement measures.
Watershed: The 816-acre watershed is completely in Edgartown.
Pond: The pond has an area of 115 acres, a mean depth of 7.4 feet, and a tidal range of 2.0 feet.
Water Quality: The MVC categorized this pond as Quality Waters. Water quality is good and eelgrass is present, though blooms have been reported over the past several years.
MEP: Edgartown has approved the matching funds for the MEP and the study is currently underway.
Watershed: The 4850-acre watershed is almost completely in Edgartown, with a small area in West Tisbury.
Pond: The pond has an area of 544 to 840 acres, a mean depth of 3.0 to 4.3 feet, and a tidal range of 0.6 ft.
Water Quality: The MVC categorized this pond as Compromised. Water quality is impaired but varies with the success and duration of the inlet openings. Eelgrass is present but patchy.
MEP: The MEP Report was completed in December 2008. DEP determined a TMDL of 46 kg/day.
Implementation: In recent years, water quality has improved with regularly scheduled pond openings, dredging, and oyster population restoration. The Town of Edgartown extended sewers to serve an additional 300 homes. These measures meet the TMDL for the current level of development, but further efforts will be needed to deal with future growth.
Watershed: The 357-acre watershed is completely in West Tisbury.
Pond: The pond has an area of 38-55 acres, a mean depth of 3.5 feet, and a tidal range of 0.2-0.3 feet.
Water Quality: The MVC categorized this pond as Compromised. Eelgrass is not known to be in the pond. Known to be eutrophic with excessive filamentous and rooted weeds decaying in August. Low dissolved oxygen and high organic nitrogen. Pond is physically constrained and impacted.
MEP: There is no plan for an MEP study.
Watershed: The 3068-acre watershed is completely in Edgartown.
Pond: The pond has an area of 1695 acres and a mean depth of 9.8 feet.
Water Quality: The MVC categorized this pond as Compromised. Eelgrass is present but limited. The water has good transparency and dissolved oxygen, with strong current circulation. The pond is productive for oyster culture, quahogs, soft-shelled clams, and some bay scallops.
Watershed: The 3968-acre watershed is located mainly in Oak Bluffs, Tisbury, and West Tisbury with a small area in Edgartown.
Pond: The pond has an area of 544 acres, a mean depth of 9.3 feet, and a tidal range of 1.8 feet.
Water Quality: The MVC categorized this pond as Impaired. Water quality is seriously deteriorated, especially in the upper basin. There is still some patchy eelgrass.
MEP: The MEP Report was completed September 2012. DEP determined the TMDL to be (74kg/day) for the entire system
Implementation: Oak Bluffs set up a committee to prepare recommendations about how to meet the TMDL. Oak Bluffs and Tisbury are working jointly to determine strategies to reduce nitrogen. Oak Bluffs is having MEP do an attenuation study of the freshwater pond at the south end of the pond. Shellfish aquaculture is implemented. Oak Bluffs is also doing studies to sewer areas in the watershed.
Watershed: The 1832-acre watershed is in Aquinnah and Chilmark.
Pond: The pond has an area of 665 acres, a mean depth of 4.7 feet, and a tidal range of 2.9-3.0 feet.
Water Quality: The MVC categorized this pond as Quality Waters. Eelgrass is present and in good condition in the pond. Water quality is good. There is a limited bay scallop fishery, large commercial oyster aquaculture, and a significant herring run.
MEP: Currently under study.
Oak Bluffs Harbor
Watershed: The 367-acre watershed is completely in Oak Bluffs.
Pond: The pond has an area of 30 acres, mean depth of 6.5 feet, and a tidal range of 1.7-2.0 ft.
Water Quality: The MVC categorized this pond as impaired. Eelgrass history is not known. Nitrogen load is high.
MEP: Currently under study. Expected release in fall 2013.
Watershed: The 2685-acre watershed is mostly in Edgartown, with a small area in West Tisbury.
Pond: The pond has an area of 208 acres, a mean depth of 6.6 feet, and a tidal range of 0.5 ft.
Water Quality: The MVC categorized this pond as Compromised. Eelgrass is limited and has not been mapped in the pond. Total organic nitrogen is high, there is strong stratification, and a significant algae bloom has been documented. A few oysters present.
MEP: Currently under study.
Watershed: The 921-acre watershed is completely in Edgartown.
Pond: The pond has an area of 210 acres, a mean depth of 2.5 feet, and a tidal range of 1.9 feet.
Water Quality: The MVC categorized this pond as Compromised. Historically eelgrass is not known to be in the pond. Total organic nitrogen load is high.
Watershed: The 4464-acre watershed is located mainly in Edgartown and Oak Bluffs, with a small area in West Tisbury.
Pond: The pond has an area of 726 acres, a mean depth of 3.0 feet, and a tidal range of 0.6 ft.
Water Quality: The MVC categorized this pond as Impaired. Eelgrass is in decline. Nitrogen is high in some inner areas with periodic extensive wrack algae.
MEP: The MEP Report was completed in January 2011. DEP determined that the TMDL is 50kg/day) The TMDL recommended a 45% reduction of nitrogen in Majors Cove and a 64% reduction in Trapps Pond.
Implementation: Oak Bluffs and Edgartown Boards of Selectmen set up a joint committee to prepare recommendations. The joint committee submitted its report in October 2012 and recommendations are being reviewed. An oyster aquaculture project is to begin May 2013.
Watershed: The 1,229-acre watershed is in Aquinnah and Chilmark.
Pond: The pond has an area of 603 acres, a mean depth of 4.7 feet, and a zero tidal range.
Water Quality: The MVC categorized this pond as Compromised. Historically eelgrass is not known to be in the pond. Nitrogen load is high, transparency is periodically very low. The pond contains oysters and has a substantial herring run.
Watershed: The 2,605-acre watershed is in Tisbury, West Tisbury and a small area of Oak Bluffs.
Pond: The pond has an area of 269 acres, a mean depth of 4.3 feet, and a tidal range of 2.0 feet.
Water Quality: The MVC categorized this pond as Impaired. Eelgrass is present but declining. Total organic nitrogen load is high and there is reduced transparency at the south end. There is no real bay scallop harvest.
MEP: Currently under study. Report expected summer 2013.
Watershed: The 11,005-acre watershed is in Chilmark and West Tisbury.
Pond: The pond has an area of 662-800 acres, a mean depth of 5.4-8.2 feet, and a tidal range of 0.6ft.
Water Quality: The MVC categorized this pond as Compromised. Little, widely varied eelgrass. Occasional problems with wrack algae. Low dissolved oxygen in deep water. Water quality varies with duration of pond openings.
MEP: Draft MEP study released March 2013. Recommended nitrogen reduction of 19%.