Phosphorus concentrations continue to lead to harmful conditions in Crackrock Pond

Phosphorus concentrations at Crackrock Pond failed to meet U.S. Environmental Protection Agency (EPA) guidelines for the 5 th year in a row, according to a report from the Neponset River Watershed Association (NepRWA). In 2021, concentrations of Phosphorus remained 10 times higher than the EPA standard throughout the sampling year (May-October). While the Neponset Reservoir just upstream has struggled with Phosphorus pollution for decades, NepRWA first detected severely elevated concentrations of phosphorus at Crackrock Pond in 2017, which then skyrocketed in 2019, when levels
were 100 times higher than recommended. Though phosphorus concentrations have come down in the last two years, they are still well above the criteria for a healthy pond. As a result, the Pond is completely covered in aquatic plants and the water is almost entirely devoid of oxygen.

“Phosphorus is necessary for plant growth, but naturally is found in very low concentrations. Because of this, it is often the ‘limiting’ resource in the freshwater environment. We tend to see algal growth when
Phosphorus concentrations increase – because all the other required nutrients are likely already there,” explains Dr. Sean McCanty, NepRWA’s River Restoration Director. “Aside from the aesthetic factor, the
real problem is that when these extra plants and algae eventually die, they get eaten by bacteria. This process consumes oxygen – in extreme circumstances the dissolved oxygen levels get so low that fish and other animals die”, he adds. Data from NepRWA’s water monitoring program show that low oxygen conditions, referred to as “hypoxic” conditions, were observed from June through September of 2021 below Crackrock Pond.

“Another danger of elevated phosphorus is that certain types of algae, like cyanobacteria, produce toxins harmful to people and lead to beach closures. This has become an issue at other places in the watershed, like Lake Massapoag in Sharon” says Ian Cooke, NepRWA’s Executive Director. “In addition to the impact on Crackrock Pond, that elevated Phosphorus also flows downstream into the mainstem of the Neponset and can cause similar issues,” he added. Other parameters that the Association tests for, including pH and E. coli, were at acceptable levels
according to the Massachusetts Department of Environmental Protection (MassDEP) standards.

Neponset River Watershed Association | 2173 Washington Street, Canton, MA 02021 | 781-575-0354 |

The water quality monitoring program that collects this data is part of a larger watershed restoration effort. Throughout the Neponset River Watershed, efforts to improve water quality, restore river and
salt marsh habitat, and reconnect the streams to allow fish passage are all underway. “All of these issues are connected,” says McCanty. “Removing old dams helps prepare our communities for climate change,
improves fish passage and dissolved oxygen levels, and can limit the amount of algae overgrowth.

Replanting along the riverbank helps filter storm runoff and stabilize the banks, improving water quality for fishing, boating, and swimming.,” McCanty adds. The Neponset River Watershed Association is a local environmental non-profit that publishes an annual report on the health of the local streams and Neponset River in Foxborough and neighboring towns that drain into the Neponset River. The water quality data used in the report is collected as part of the Association’s volunteer-based “Community Water Monitoring Network” program, that collects water
samples monthly from May to October to test for constituents that impact safety for recreation and wildlife.

For the full water quality report visit NepRWA’s website:

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