Abstract: Based on the statistical method of correlation analysis and stepwise multiple regression, authors collected the aquatic environmental and meteorological data in the east part of the Yangcheng Lake from 2010 to 2011 to analyze the connection between the cyanobacteria density and the previous environment factors. The results showed that(1) the cyanobacteria density was greatly affected by water temperature, dissolved oxygen, nutrition salts, air temperature, rainfall, wind direction, wind speed and other environmental factors in the Yangcheng Lake. (2) The air temperature was the main factor of confining the breakout of cyanobacteria. Sunshine condition was not a vital restricting factor to cyanobacteria growth. Low wind speed and little precipitation were apt to accelerate the floating up rate of cyanobacteria. The southward or northward movement of cyanobacteria in the surface water layer of the Yangcheng Lake was in essential agreement to the prevailing wind direction.(3) When the water quality was satisfied with eutrophication,the blue algae in the Yangcheng Lake was ready to bloom under the average meteorological condition of the preceding 5 days, such as the daily mean temperature less than 30℃,the daily sunshine duration changed from 4 to 10 hours, the daily average precipitation less than 2.5 millimeters, daily average wind speed drifted from 1 to 2.5m/s and the prevailing wind directions lasted over 2 days.(4) A multiple stepwise regression equation was built up to forecast the blue algal blooming and the results of fitting and trial forecasting showed that the simulation values could reflect the changing trends of cyanobacteria density well, but it still had its limit to the forecasting for peak events of algal bloom.

Key words: Cyanobacteria density, Aquatic environmental factors, Meteorological condition, Stepwise multiple regression