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Abstract The dynamics of algae biomass distribution in Lake Hongze was simulated using a two-dimensional hydrodynamic-phytoplankton model. Lake Hongze was divided into three zones, i.e., northern zone, eastern zone and western zone. Chlorophyll a (Chl a) was used to represent algal biomass in Lake Hongze. The initial and boundary data for the hydrodynamic-phytoplankton model included hydrological, meteorological and water quality data. The spatial distribution of Chl a, nitrogen and phosphorus concentrations in January was used as the initial data. The boundary data included daily water flow, temperature and precipitation. Ten most sensitive parameters (e.g., maximum growth rate of phytoplankton) were identified based on sensitivity analysis, and was optimized based on the value ranges from previous study. The calibration results showed good agreement between measured and simulated Chl a (r2=0.281, RMSE = 2.52 μg/L). Based on the calibrated model, the dynamics of Chl a distribution in Lake Hongze during 2012 were simulated. The simulation results generally showed two Chl a peaks in April and August. However, simulation Chl a at central and outlet areas had one peak or no obvious peak. Simulation Chl a at Yanwei station showed many peaks in the year. Simulation Chl a in three spatial zones was significantly different. In western zone, Chl a was low and showed low spatial heterogeneity. Spatial heterogeneity of Chl a in northern zone was low due to the low water flow. Chl a in the nearshore area was relatively higher, and was significantly affected by wind conditions. In eastern zone, spatial heterogeneity of Chl a was high due to the inflow rivers with large discharge, such as River Huai. The model well predicted the overall trend of Chl a in Lake Hongze during 2012. However, the model fits at some stations were relatively low due to the existing model uncertain. The modeling practice in this study improved our understanding of algae dynamics in Lake Hongze, and thus benefited us in controlling algal blooms.
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Received: 02 March 2015
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