The Monponsett Ponds, also known as the Monponsett Lake or Twin Lakes, is a large system of two basins, the east and west, located in Halifax, Massachusetts. These basins are divided by Route 58, but are connected by a small culvert at their southern ends. They are part of the Taunton River Watershed, which is formed by the convergence of the Matfield and Town rivers in Bridgewater. Stump Brook, in the northwest section of West Monponsett Pond, is the outflow for the basins. The Monponsett Ponds have an average depth of seven feet and a maximum depth of 13 feet. While the bottom is a mixture of sand and rubble, the emergent vegetation covers about 20% of the surface area of the ponds. More than ten species of fish call these ponds home! The fish observed in the East Monponsett Pond include bluegill, white and yellow perch, pumpkinseed, largemouth bass, chain pickerel and golden shiner. These are the same species observed in the West Monponsett Pond, in addition to the black crappie, brown bullhead, white sucker and American eel.
Though located right next to one another, there is a visible difference in the color of West Monponsett Lake and that of East Monponsett Lake. This past month, the Massachusetts Environmental Protection Agency posted a cyanobacteria advisory on West Monponsett Pond and declared it impaired. This means that the pond has visible scum, or a mat layer present, a blue-green cell count that exceeds 70,000 cells/milliliter of water or a microcytic toxic level that exceeds 14 parts per billion. The latest cyanobacteria update on the West Monponsett Pond was July 8th with samples reading nearly six times as high as they were the month prior and nine times as high as the human exposure guideline level! Factors contributing to this include the rivers innate flow from East to West, in addition to the dam blocking the river outflow to Stump Brook. The blocking of the river outflow is backing up the nutrients and ultimately allowing for the frightening growth of vast algal blooms in the West Monponsett Pond. Another factor contributing towards this algae issue is the high levels of nutrient pollution from developed areas surrounding the Monponsett Ponds. Nutrient pollution from developed residential areas can come from excess use of lawn fertilizers that runoff the lawns and into the watershed.
I wrote to the Monponsett Watershed Association (MWA) to see if they knew exactly why the west basin was experiencing such bad algae blooms, while the east appeared completely healthy. They reiterated the fact that the dam contributes to nutrient build up and stagnate water, which is the perfect habitat for algae to thrive, while also mentioning the involvement of active cranberry bogs. These cranberry bogs irrigate with and discharge into the West Pond causing a high concentration of nutrients. The Monponsett Watershed Association also contributed these high concentrations of nutrients to fertilizer runoff from the surrounding residential areas.
The MWA has already been taking steps towards the lakes improvement by means of aluminum treatment. When the aluminum is applied to water, it binds together with phosphorus and precipitates to the bottom. Though this a great effort, it does only reduce the amount of algae by 50%. The group is also reaching out to the government in order to get this issue resolved, which involves demanding Halifax selectmen to eliminate the use of phosphorus in fertilizer at the Winebrook Bog and upstream bogs that flow into the West Monponsett Pond. They also have a petition to the Massachusetts state government, specifically Governor Baker, listing four criteria from the association: (1) regular bacteria level tests of Monponsett Ponds (2) payment of lake treatments (3) dam gates left open for natural river flow and (4) requiring farmers to reduce/eliminate fertilizer discharge. This is an issue that cannot be pushed aside. It is important that the community do what it can to reduce these excess nutrients including the reduction or even elimination of lawn fertilizers onto their property. Get the muck out!
This blog post was researched and written by Tiana Tower, ORI Summer Intern, with some assistance from other interns.