Ecological response of a shallow mesotrophic lake to multiple environmental stressors: a paleolimnological assessment of White Lake, Ontario

White Lake, located in Eastern Ontario, Canada is a large (surface area 56.08 km2), shallow (mean depth = 3.1 m), recreational lake that has a recent history of poor water quality due to water level changes, nutrient loading and invasive species. With monitoring data only extending to 2015, lake managers lack the long-term data needed to make informed decisions regarding lake management strategies. A paleolimnological study was conducted to assess historical water quality change in White Lake using diatoms as indicators of water quality. The recent introduction of zebra mussels (Dreissena polymorpha) has lowered nutrient levels and greatly reduced turbidity with Secchi depth reading jumping from 1.8 m to 7.5 m depth. However, the largest single change in the diatom assemblage of White Lake likely relates to water level changes through the damming of the lake in 1845 and subsequent changes to the water level management plan for the lake.