Detection of algal bloom and factors influencing its formation in Taihu Lake from 2000 to 2011 by MODIS

Time-series MODIS data were used to extract and characterize algal blooms from the Taihu Lake study area. Water quality data including total nitrogen, total phosphorus, and dissolved oxygen; local meteorology data; and global climate trends were examined to reveal the factors influencing the formation of the algal blooms. Results for the 2000-2011 study period show that the annual algal bloom typically begins between March and May in Taihu Lake. All large-scale blooms originate from northern Taihu Lake (Meiliang Bay and Zhushan Bay). Some small-scale blooms originate from southwestern Taihu Lake, but the duration of these blooms is very brief because of episodes of turbulent mixing due to high wind speed. Nutrient supply is the main factor influencing algal mass propagation during bloom periods, and temperature changes may trigger algal recovery. The algal bloom area significantly decreased when wind speed is greater than 4 m/s, causing turbulence and changes in algal buoyancy. A strong East Asian summer monsoon transporting warm air to the lake is shown to extend the duration of algal blooms in Taihu Lake, as occurred in 2007.