Phytoplankton communities as indicators of environmental change in the Canadian Rockies

Remote mountain lakes in protected areas are sentinels of the ecological impacts of extreme and novel environmental changes occurring at broad regional scales. Ecosystem responses to such stressors are often first detected as shifts in community composition. We surveyed phytoplankton communities across 82 mountain lakes to test the hypothesis that taxonomic composition is indicative of more environmental changes than are aggregate properties, such as total biomass. Phosphorus was the only significant predictor of chlorophyll-inferred algal biomass, a correlative finding supported by evidence from our nutrient amendment bioassays. Interlake variances in taxonomically diagnostic algal pigments and 78 genera were indicative of changes in total phosphorus, glacial coverage, underwater light availability, and dissolved organic carbon. Lack of concordance was observed between ordinations of pigment-and genus-based data as environmental variables captured more variance in the pigment data. Our findings provide a baseline for future lake monitoring programs in the Canadian Rockies as they increasingly experience interactive effects involving climate change and landscape features, such as variation in turbid glacial meltwaters and aeolian phosphorus deposition from wildfires.

Automated summary

Remote mountain lakes in protected areas are valuable indicators for studying ecological impacts of extreme environmental changes. This study examined the relationships between phytoplankton communities and environmental factors in 82 lakes and found that taxonomic composition was more indicative of environmental changes than total biomass. Changes in total phosphorus, glacial coverage, underwater light availability, and dissolved organic carbon were reflected by variances in taxonomically diagnostic algal pigments and genera. The findings of this study provide a baseline for future lake monitoring programs in the Canadian Rockies as they face climate change and landscape variations.