Protecting Candlewood Lake from invasive species

The drawdown at Candlewood Lake is almost done.

But the answer to the question on everyone’s mind — did it stop the lake’s nascent zebra mussel population in its tracks? — is still up on the air.

Divers, docks and mussel motels may answer it by fall. Now, it’s wait- and- see.

“It’s too early to tell,’’ said Neil Stalter, the Candlewood Lake Authority’s director of ecology and environmental education.

Here’s what is known. Last year, people found 39 zebra mussels — small, striped, seemingly innocuous — along the lake’s shoreline.

Stalter said he’s confident that the winter’s deep drawdown — which lowered the lake’s level by 11 feet — exposed any other shoreline zebra mussels to air, killing off the non- native, profoundly invasive mollusks.

What no one knows is whether other mussels anchored themselves on rocks in deeper water, readying to infest the lake, with its thousands of offspring producing thousands more.

If that’s the case, look south to Lake Lillinonah.

In 2010, divers found exactly one zebra mussel in the lake. The ones the divers didn’t find did the damage.

“Within three years, they were everywhere,’’ said Greg Bollard, a member of Save the Lake, the nonprofit organization supporting environmental efforts at Lillinonah.

Shannon Young, chairman of the Lake Lillinonah Authority, said that now, the weight of zebra mussel encrustations make some docks too heavy to haul out of Lillinonah’s water to repair.

Bollard said some lake residents have now built lifts to raise their boats’ hulls out of the water, lest mussels begin to glom onto them after a few days sitting dockside.

Young said to avoid contaminating any other lake with the mussel- contaminated bilge, he sticks to boating on Lillinonah.

“I never use any other water body, period,’’ he said.

When zebra mussels multiply in sufficient numbers, they feed voraciously on plankton and algae. Filtering out all that organic matter leaves the water very clear.

That’s not a good thing. Bollard said the clear water lets sunlight penetrate deeper into a lake. That means invasive aquatic weeds like Eurasian watermilfoil get extra sunlight and grow tall and thick — something that’s happening now at Lillinonah.

Watermilfoil is the other invasive species the drawdown at Candlewood Lake could knock back. The retreating water leaves the weeds exposed to winter’s frigid air, killing them.

But February’s heavy snows may have stymied that effort this year. The snow provides the watermilfoil with a nice insulating blanket, letting it survive until spring.

The snow also ended any attempt by volunteers to walk the lake’s 60 miles of shoreline, looking for zebra mussels on shoreline rocks and crevices.

“Clearly, the snow put the kibosh on that,’’ said Steve Kluge of New Milford, and a member of the Candlewood Lake Authority.

Now, Candlewood on the rise.

First Light Power Resources maintains the lake’s level via the Rocky River power plant in New Milford — it lets the lake’s waters flow down through the plant’s turbines in the fall to lower the lake, then pumps water from the river back up into the lake in the spring.

First Light spokesperson Len Greene said this year, the company dropped the lakes level from its working level of 429.5 feet above sea level to 418.5 feet. But it now has to return the lake to the working level by mid- April for the start of the fishing season.

“In the next month and a half, we’ll be pumping up quite a lot,’’ Greene said.

Full or drained, there is still hope Candlewood will be spared a zebra musselinfested future.

Because people found Candlewood’s 39 zebra mussels scattered in different spots along its shoreline, there’s the thought that the mussels aren’t concentrated in a clustered colony.

“There’s no pattern to it,’’ Kluge said.