Integrating Hydrodynamic and Water Quality Modeling of Cyanobacterial Blooms in a Shallow Urban Lake

Cyanobacterial harmful algal blooms (cHABs) pose increasing ecological and public health risks in shallow lakes subject to nutrient enrichment and climate change. This research describes and evaluates a three-dimensional hydrodynamic ecological modeling framework for Fairy Lake, Ontario, using MIKE 3 FM coupled with ECO Lab to simulate lake circulation, thermal structure, nutrient dynamics, and cyanobacteria (PC3) concentrations, with model calibration using 2022 data observations and validation using 2023 data. Hydrodynamic performance showed moderate agreement for lake levels (NSE 0.47–0.52) and strong predictive capability for water temperature (NSE up to 0.96 across depths). Nutrient simulations reproduced seasonal nitrate and phosphate trends, with sediment parameter adjustments to stabilize internal loading dynamics. Cyanobacteria simulations captured seasonal bloom timing and spatial variability between inflow and central basin zones during the calibration and validation periods. The results demonstrate that integrated 3D hydrodynamic ecological modeling reproduces seasonal bloom dynamics in shallow polymictic lakes employing calibrated models and subsequent data, to predict sediment nutrient processes and periodic reassessments. As a result, this framework provides a quantitative basis for evaluating bloom behavior and the ability to predict management scenarios able to test changing climatic and nutrient conditions.