Mirror Lake continues to have dissolved oxygen issues

Mirror Lake
Mirror Lake in early May. Photo by Mike Lynch

Mirror Lake didn’t experience its natural spring turnover for the second consecutive year due to its high concentration of road salt, according to the Ausable River Association.

Spring turnover occurs when top and bottom water levels mix after ice out. The mixing  causes a distribution of nutrients and oxygen throughout the water column. This turnover generally occurs in both the spring and fall when water temperatures become more uniform throughout the lake. The lake then settles into layers during the summer months.

“We’re not re-oxygening at the beginning of the spring when the lake would take a big deep breath and absorb a lot of oxygen before it becomes stratified in the summer,” said Brendan Wiltse, Science and Stewardship Director with ASRA.

The loss of dissolved oxygen in the lake is potentially harmful for lake trout, in particular, because they spend the warmer months on the cold lake bottom.

“It’s definitely stressful for the fish as well as many other aquatic organisms that need that deep, well oxygenated water,” Wiltse said.

Wiltse said that salty water is denser than normal lake water, so when it enters the lake it settles toward the bottom. Wiltse said that the last time the lake  mixed in the spring was 2016, after a mild winter.

Wiltse said the lake has mixed in the fall in recent years. If the fall mixing didn’t occur, that would be extremely problematic for species living in the lake.

“At that point, the dissolved oxygen in the lake bottom would drop low enough that the lake might not be able to support those cold water fish anymore,” Wiltse said. “And there would even be concerns with … oxygen dropping enough in the water column to see a significant decline for the aquatic life in the lake.”

Wiltse said his organization doesn’t have enough data to determine if the lake is close to not mixing in the fall.

“My gut is saying it’s not going to happen soon,” he said.

Wiltse was one of several presenters who spoke about the negative impact of road salt can have on the environment at the annual conference of the Adirondack Research Consortium Wednesday in Lake Placid.

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