Restoration of Lajoie Lake: Investigating climatically induced meromixis

Lajoie Lake is a small montane lake located 90 km northwest of Lillooet, British Columbia. In recent decades, long-time residents have observed water quality degradation and eutrophication despite no apparent increase in external nutrient inputs. This study investigates an alternative hypothesis for the cause of this degradation: Lajoie Lake's topographic shielding predisposed it to a climatically induced mixing regime shift. Based on lake thermal and chemical properties collected during the 2022 ice-off season, Lajoie Lake is now meromictic and does not undergo complete spring and autumn circulation. The lack of sufficient wind energy during autumn suggests that topographic shielding predisposed Lajoie Lake to this shift, but climate change likely facilitated the transition. The mixing regime change likely resulted in nutrient regeneration, which contributes to increased primary productivity and the water quality changes observed. Lake circulation using compressed air to induce complete mixing is recommended to recover dimictic lake processes.