Unprecedented rates of environmental change have prompted ecologists to identify thresholds (or tipping points) where resilience of complex environmental systems may change abruptly and irreversibly. The objective of our research project is to investigate the effects of landscape characteristics on the resilience properties (i.e., resistance and recovery) of mountain lakes in two UNESCO World Heritage Site National Parks.
Climate change is altering the catchments of mountain lakes by melting glaciers and increasing vegetation coverage. These changes will affect lakes by modifying the type and amount of material input from the surrounding catchment, particularly glacial flour and chromophoric dissolved organic matter (CDOM). Glacial flour and CDOM both influence water transparency, a key regulator of lake ecosystem structure and function.
Using a space for time substitution to represent a chronosequence of glacial retreat and vegetation advance, we are testing the overarching hypothesis that resilience of water transparency changes systematically as lake catchments shift from glaciated to rocky to vegetated. Specifically, we predict that the resistance of water transparency will increase with glacial loss and decrease with vegetation advance. Additionally, we predict that recovery rates of water transparency will increase as the regulator of transparency shifts from turbidity in glacial catchment lakes to CDOM in vegetated catchment lakes.
To test these hypotheses, we have deployed high frequency monitoring buoys in five lakes in Banff and Yoho National Parks, Canada that vary across a gradient of glacial and vegetation coverage. Concurrent hydrological data will be used to better understand dynamics of turbidity and CDOM inputs and their relationships to meteorological data recorded at nearby stations.