A reduction in spring mixing due to road salt runoff entering Mirror Lake (Lake Placid, NY)

Abstract

Wiltse B, Yerger EC, Laxson CL. 2019. A reduction in spring mixing due to road salt runoff entering Mirror Lake (Lake Placid, NY). Lake Reserv Manage. 36:109–121. Road salt has resulted in the salinization of surface waters across temperate North America. Increasingly, road salt is recognized as a significant regional pollutant in the Adirondack Park. Here we analyze biweekly limnological data from Mirror Lake (Lake Placid, NY) to understand the role of road salt runoff in an apparent lack of spring mixing in 2017. Water column profile data show notable spatial and temporal variability in chloride concentrations within the lake. Concentrations are highest at the lake bottom during the winter, with increases associated with the onset of road salt application to the watershed. High chloride concentrations in the hypolimnion persisted through the summer of 2017 due to a lack of complete spring mixing as the result of road salt induced density differences within the water column. Water density calculations and Schmidt stability point to an increase in water column stability due to the accumulation of salt at the lake bottom. The incomplete spring mixing resulted in greater spatial and temporal extent of anoxic conditions in the hypolimnion, reducing habitat availability for lake trout. Restoration of lake mixing would occur rapidly upon significant reduction of road salt application to the watershed and improvements in stormwater management.