Modeling water quality in a subalpine lake

Subalpine lakes are valuable resources that are at increasing environmental risk. Aquatic ecosystem models are useful tools for understanding dynamics of lakes, however, there are few examples of these models being applied to subalpine lakes, which may differ from temperate lakes in dimensions such as physical setting and ecology. Here we apply the aquatic ecosystem model AQUATOX to the Loch, a well-studied lake in Rocky Mountain National Park in Colorado, USA, to assess the applicability of this model to a subalpine lake setting, and to identify modeling gaps. We found that AQUATOX could represent phytoplankton dynamics during the ice-off period. Attempting to calibrate the model during the ice-on period using the same structure and parameters as the ice-off period underestimated winter chlorophyll a concentrations. Additionally, the model was used to simulate a nutrient bioassay experiment – nitrate was well simulated; P was overestimated but consistent with the observed pattern. These results support the use of current models for subalpine lakes when data are sufficient. Areas identified for future model development include better models for boundary conditions, improved light data, modeling of mixotrophy, and better representation of ice formation and under-ice stratification.