Mirror Lake 2020 Water Quality Update

Ausable River Association and Adirondack Watershed Institute

Leanna Thalman, Elizabeth Yerger, Lija Treibergs, & Brendan Wiltse

Although Mirror Lake’s chloride levels were lower in 2020 than in years prior, road salt continues to be a major concern. It inhibits natural turnover and reduces lake trout habitat (Wiltse et al. 2019). Higher chloride levels also create the optimal conditions for internal phosphorus loading with prolonged hypolimnion anoxia levels. This can lead to algal blooms in the lake, further depleting oxygen resources in the lake. Even when concentrations of phosphorus are low, the interruption of lake mixing due to road salt loading puts the lake at greater risk for harmful algal blooms.

In November of 2020, a harmful algae bloom was detected on Mirror Lake due to unseasonably warm air temperatures and calm waters. Although this algal bloom was not directly caused by high sodium and chloride concentrations, it is a reminder of the harm that can potentially be caused by high usage of road salt in the watershed. In 2021, water quality monitoring continues, and AsRA will continue working with the Village of Lake Placid, the Town of North Elba, our science partners, business owners, and residents in our efforts to reduce the use of road salt applications.