LAKE PLACID — After another year of testing the health of Mirror Lake, the AuSable River Association reports oxygen levels for lake and rainbow trout remain a concern as more data is compiled.

“Right now there is no oxygen in the very bottom of the lake,” said the association’s science and stewardship director, Brendan Wiltse, “and it’s pretty early in the season for that to happen.”

Wiltse said as of the start of this summer the association has the most complete picture yet as to how the lake at the center of this village has changed since the Lake Placid Shore Owner’s Association first commissioned studies in 1971.

Though he and the Mirror Lake Watershed Association remain encouraged that no signs point to an issue with the amount of phosphorous or algae growing in the lake, the lack of oxygen at the very bottom of the lake, especially early in the spring, is a problem, Wiltse said.

This past season’s sampling was the third in a row for Wiltse and his team, and though they said it remains unclear just how much the oxygenation problem is natural and/or caused by human use and development, the association is leaning toward human development —  particularly road salt runoff.

“It’s not definitive at this point,” Wiltse said. “We hope to find a definitive answer on that after this year’s sampling season. (There will be) extra work this summer to understand that process.”

Wiltse continued to say that Mirror Lake is an “oddball” body of water within the Adirondacks for a number of reasons. Among the 70 bodies of water, the AuSable River Association studies within the AuSable River Watershed, he said there is no body of water to compare to Mirror Lake as it is the most developed water body in the Adirondacks with 34 percent of the land area in its watershed developed.

Like any other body of water in the region that freezes, with water at its most dense at four degrees celsius, Mirror Lake’s water column turns over every spring and fall, thus resulting in oxygenation of its water column. Wiltse added that with this natural ecological schedule, low oxygen levels in the lake are expected at the end of summer. But in 2015 and this year, the association’s findings showed the concerning trend of very little to no oxygen in the lake much earlier in the year.

From its surface to lake bottom, Mirror Lake is 60 feet at its deepest point. Wiltse said the oxygenation issue results in 8 meters of oxygen for fish such as lake and rainbow trout to try to survive in, and below there is “virtually no oxygen.

“If you’re a cold water fish like lake trout or rainbow trout, you need cold water and oxygen,” he said. “So they get squeezed toward the end of the summer into a very narrow band of water.”

Wiltse added that regionally there is a concern with regards to how climate change may eventually squeeze the fish species out all together.

“Mirror Lake, if we start out with low oxygen to begin with (each spring),” that just makes the squeeze happen earlier in the year and more likely we will have problems for those fish species in the future.”

Wiltse added that the association is seeing a phenomenon in Mirror Lake they’ve never before seen in an Adirondack body of water: salt build-up at the bottom of the lake.

He said the association took samples of the bottom of the lake this past spring on days when it was raining and found increased saltwater runoff compiling at the bottom of the lake.

Wiltse elaborated that the association observed much more of this high concentration of chloride at the bottom of the lake through the entire summer of 2015 and again this year, though 2016’s numbers were much different. Village Trustee Peter Holderied, who owns the lakefront Golden Arrow Resort and Hotel, said he believed this was due to 2016’s warm winter, which required less salt application around the lake and an early ice-out.

The association also has taken core samples of the soil below the lake for several projects independent of its studies financed from village funding, and Wiltse added that moving forward, if funding is provided, the association could look at the core samples to see if the kind of oxygenation pattern observed is natural. He added that the cost to study core samples is a bit beyond what the association has asked from the village and town of North Elba thus far.

The association’s science and stewardship director also fleshed out more specific numbers with regards to the lake’s chloride concentration: he said in 1974, it was 4 milligrams-per-liter.

“Even then, that was a bit high for what we’d expect for an Adirondack lake,” he said.

“Now it’s 50 milligrams-per-liter and at times 125 on the bottom of the lake,” he continued, “many hundred of times higher than what’s natural for an Adirondack lake.”

Wiltse elaborated that the Environmental Protection Agency’s standard threshold as to what may result in a “dead lake” is 250 milligrams-per-liter.

“But we don’t want to let the lake get to that point,” he added. “Additional scientific literature suggests we should have a lower threshold.”

Wiltse added that at 250 milligrams-per-liter of chloride over time half of lake species can die.

“At 100 milligrams-per-liter we’re starting to be pretty concerned,” he said.

“The surface is halfway there,” he continued, “and the bottom is above it during certain times of the year. This spring the bottom of the lake was at 125 milligrams-per-liter.”

Wiltse provided further context that Lake George is at 15 milligrams-per-liter.

Wiltse commended the village for its efforts to divert stormwater runoff from the lake with its current eastside project underway, saying it will be beneficial. But he added that it’s time to “really be thinking hard” about the amount of salt applied to perimeter sidewalks, as he said high chloride concentrations exist around the entire perimeter of the lake.

“Anything that we can do to reduce that amount of salt would be a step in the right direction,” he said.

Lake Placid Mayor Craig Randall said with its Main Street reconstruction plans, improvements would carry stormwater to the east of Marcy Road to the current stormwater project being constructed on the eastside of the lake and away from the lake.

Wiltse also mentioned how the association for the first time has detected that there’s been an increased calcium concentration in the lake since 1971’s studies. He said he was unsure though he believed it was almost certainly due to development around the lake. Holderied said he believed it could be caused by concrete breaking up and entering the lake due to salt application.

Wiltse elaborated that increased calcium concentration is something to take seriously because unlike other Adirondack bodies of water, more calcium would facilitate the invasion of zebra mussels, a species not natural to the area.

He also said the association is conducting intensive monitoring of the Chubb River and AuSable River, which shows there may be groundwater contamination due to road salt.

“It’s high enough to take into account (at some point) the consumption of sodium in diets,” he said.

“It’s something we need to think about when we move stormwater to something like a retention pond or underground,” he continued.

“We are not there yet,” Wiltse added. “Nothing to be concerned about right now, but collectively as we address the road salt issue, we need to be thinking about these long term impacts.”

Wiltse added that village water drinkers would be safe from this kind of contamination as the village’s water comes from Lake Placid lake, which he described as “a great deal better” in quality than Mirror Lake.

To read the association’s full Mirror Lake report, visit www.ausableriver.org/watershed/lakes/mirror-lake.