Mudge Pond faces rising nutrient levels and invasive species

SHARON – A new scientific report highlights growing concerns at Mudge Pond, including declining water clarity, rising nutrient levels and the spread of invasive species, prompting local advocates to shift from monitoring the lake to taking action.

After several years of data collection, members of the Mudge Pond Association say the findings confirm that the lake is facing mounting pressures that will require intervention to protect both water quality and recreational use.

“Now that we’ve got a couple years of data, we’re going into the action phase,” said Andrew Cahill, chair of the Mudge Pond Association, a community organization dedicated to preserving ecosystem health and recreation opportunities on the lake.

The report, compiled by Connecticut consultancy Northeast Aquatic Research and based on data collected throughout the 2025 calendar year, found that invasive species and nutrient loading continue to threaten the lake. The study follows another from the previous year conducted by the same firm that reported similar findings.

Water quality trending downward

“Our lake is going in the wrong direction,” Cahill said. Average water clarity declined between the 2025 and 2024 data, from about 3.7 meters to 3.3. Clarity varies widely throughout the year, but 2025’s overall trend was downward compared to the prior year in a lake that is meant to be, by southern New England standards, quite clear.

The report identifies Mudge Pond as an “oligo-mesotrophic” lake, a term scientists use to describe water bodies that are just a step more vegetated and biodiverse than a crystalline alpine lake. Keeping Mudge Pond within that category should be the focal point of future lake management efforts, the report notes, as a more nutrient-dense environment could damage the lake’s ecosystem as well as put swimmers and recreators at risk from harmful algal blooms.

Cahill said he was especially concerned about the finding that toxic cyanobacteria, which are fed by nutrients such as nitrogen and phosphorus, were found in the lake at elevated levels. In August, the most productive time of the year for such harmful “blue-green algae” blooms, 35,160 cyanobacteria cells per milliliter of water sampled were found, above the “safe” management goal of between 10,000 and 20,000.

The World Health Organization considers densities above 20,000 to indicate a “moderate probability of adverse health effects,” according to the report.

High nutrient levels in the water column are likely due to two factors. Both studies found that a persistent layer of deoxygenated water at the lake bottom each summer, formed by a process called “stratification,” which separates warm, oxygen-rich water at the surface from colder, oxygen-poor water below, allows previously buried nutrients at the lake bottom to leach back into the lake.

The report also examined two inlets where runoff water flows into Mudge Pond, finding high levels of nitrogen entering the lake from one inlet during the spring. Cahill said that the Mudge Pond Association has contacted upstream landowners who had been very cooperative about exploring potential causes for this nutrient loading.

Northeast Aquatic Research has also recommended that lake managers explore installing an aerator to oxygenate the water, but Cahill said while the Association is open to exploring diverse strategies, this approach may be prohibitively expensive and potentially controversial.

Invasive plants abound, but no hydrilla

Cahill said that the Association will be focusing its most immediate efforts in 2026 on addressing the more immediately visible threat to Mudge Pond: invasive plants.

Four non-native invasive species were found in the lake – Eurasian milfoil, curly-leaf pondweed, water chestnut and fanwort. Eurasian milfoil and fanwort were the most abundant of the invasives, while water chestnut was the least established. Brittle naiad, another invasive plant that was found in the previous study, was not found by the researchers in 2025.

Despite the low prevalence, Cahill said the Association is prioritizing water chestnut as its first point of attack, as the lily-pad like plant becomes extremely difficult to eliminate when entrenched in the ecosystem. Also, in low numbers it can be hand-pulled, making for a relatively uncontroversial removal process.

Cahill said the Association is planning outreach events to train volunteers on how to identify and remove the plant, ultimately coordinating large-scale removal efforts in the summer and fall.

For the remainder of the invasives, though, the report recommends using herbicides, which historically has been a polarizing topic in Connecticut lake communities.

“As a town, we have to have that discussion,” Cahill said. “Do we want to do this?”

Cahill said the Association is planning to eventually organize a public forum for community input on the issue, eventually leading to a vote on how the town wishes to proceed.

Whatever the outcome, though, Cahill emphasized urgency is key in dealing with invasive plants. “The longer we wait, the more there will be.”

Hydrilla, a highly aggressive invasive waterweed that has invaded nearby water bodies and cost lake communities large sums in removal efforts, was not found in Mudge Pond in 2025. While that is encouraging news, Cahill said it’s too early to celebrate.

The lake’s public boat launch is controlled by the state, meaning the town has little regulatory power over it. With inconsistent oversight, Cahill said it may only be a matter of time before the plant gets into Mudge Pond.

“I think it’s going to fall to each of our lake communities to have a plan in place in case hydrilla arrives.”