Researchers affirmed last week that water quality in Candlewood Lake and Squantz Pond is improving, but recommended ways to help stave off emerging threats to the health of both bodies of water.

Larry Marsicano, of Aquatic Ecosystem Research, also the former executive director of the Candlewood Lake Authority, presented a report to the authority’s board last week along with his colleague, Mark June-Wells.

The pair discussed how the results of water testing in 2017 fit with trends shown in an earlier study of test results going back decades, revealing that water quality has moderately improved in both Candlewood and Squantz since the monitoring program began in the mid-1980s.

Levels of nutrients such as phosphorus and chlorophyll have been declining and the water’s transparency has increased, according to that earlier study, which was published by Marsicano and several professors.

“That’s a testament to the work (the CLA), the community in general and the land use agencies have done in trying to reduce nutrients getting into Candlewood Lake,” Marsicano said.

But many of the researchers’ recommendations focused on what Marsicano called the ‘flip side’ of the data. Even though typical causes of blue-green algae blooms, such as high nutrient levels, are decreasing, blooms have become more frequent and intense in the last five to 10 years.

The algae blooms can release a toxin that irritates skin or is harmful if ingested.

The number of blooms was about average in 2017, Marsicano said, and none were serious enough to force a beach closure. But in past years, blooms have forced Candlewood and Squantz’s local beaches to close for long stretches during the summer.

Marsicano and June-Wells said the increase of blooms is likely because of other ways the lake is changing — such as an increasing pH levels, increasing salt content and changes in the way the water separates itself into layers by temperature.

Such conditions, especially in warmer months, can give blue-green algae an advantage over other types of algae, the researchers said.

“As much as I hate to use the term ‘a perfect storm,’ you have all the conditions that favor blue-green algal dominance when the temperature is right,” June-Wells said.

One of the eight recommendations from the report was for the authority to foucs on blue-green algae in further research. Another recommendation was to commission a watershed study, which could help determine how to control the use of road salt near the lake.

Marsicano and June-Wells said increasing levels of sodium, calcium, magnesium and chloride levels are a trend in lakes across the state, likely because road salt is making its way into the water.

“Unless it’s some lake in a town park completely surrounded by woods, this is what you see,” Marsicano said.

Candlewood Lake towns generally try to moderate their use of salt on town roads, Marsicano said, but private communities that border much of the lake often handle their own snow removal, and their use of salt is more difficult to regulate.

“(A watershed study is) certainly a way of trying to address the road salts and trying to crack the nut of the private roads,” he said.

Other recommendations included consolidating and updating the lake’s management plan and exploring why water quality seemed to be best after deep “drawdowns” of water in the winter months. FirstLight Power Resources, which owns the lake, has been lowering lake levels up to 10 feet each winter as a way to kill invasive Eurasian watermilfoil.

The earlier study revealed that water quality was best following a deeper drawdown, about 10 feet below typical lake levels, rather than a more shallow four- or five-foot drawdown. Marsicano hypothesized that this was because milfoil could release nutrients from the soil into the water, and that the more milfoil plants are killed in deep drawdowns, the fewer such nutrients find their way into the lake.

But he told the authority last week that more research is needed to prove if this is the case, or if other factors, such as a lower pH when there are fewer plants photosynthesizing, are contributing to better water quality. Photosynthesis drives up the pH level, he said.

“These are all hypotheses that are worth trying to understand more,” Marsicano said.

The researchers also touched briefly on changes surrounding another invasive species: zebra mussels. Higher calcium levels have created an increased “colonization potential” for the mussels in both bodies of water, more so in Candlewood than Squantz, they said.

Marsicano suggested this could be a focus area when updating the lake’s management plan.

Another recommendation suggested was for the authority to perform further studies of the lake’s sediment and phosphorus levels.

These studies would allow the authority to consider long-term options for preventing algae blooms such as aeration or treatment with aluminum sulfate.

“Both of those (studies) together mean if you ever wanted to pull the trigger on some large-scale initiative, you’d be ready to go,” June-Wells said. “Those are the things you’d need to know.”

Chairwoman Phyllis Schaer thanked the researchers and said the delegates would review the presentation. She said some of the recommendations, like a watershed study and consolidating the lake management plans, are already goals for the authority this year.

aquinn@newstimes.com