Relationships between chlorophyll-a content and TN and TP concentrations in water bodies of Taihu Lake,China

Based on the monitoring data from May to September in 1993-2002,this paper studied the relationships between the chlorophyll(Chl-a) content in algae and lower the total nitrogen(TN) and total phosphorus(TP) concentrations in water bodies of Taihu Lake,with the favorable TN and TP concentrations for algae growth discussed.The results showed that the relationships between Chl-a content and TN and TP concentrations were quite different in the monitoring zones.The Chl-a content increased with increasing TN and TP concentrations when they were lower than 5.4 and 0.31 mg·L-1 in Meiliang Bay and lower than 4.5 and 0.27 mg·L-1 in the northwest part of the Lake,but decreased with increasing TN and TP concentrations when they were higher than 5.4 and 0.31 mg·L-1 in Meiliang Bay and higher than 4.5 and 0.27 mg·L-1 in the northwest part of the Lake,respectively.In Gonghu Bay and in the central part of the Lake,Chl-a content had positive correlations with TN and TP concentrations,and increased very fast when the TP concentration was higher than 0.1 mg·L-1.In Dongtaihu Bay and in the east part of the Lake,Chl-a content varied little with the changes of TN and TP concentrations;while in the southwest part of the Lake,Chl-a content increased with increasing TP concentration,but had no significant correlation with TN concentration.The favorable water body's TN and TP concentrations for algae growth in Taihu Lake were 5.4 and 0.1-0.31 mg·L-1,respectively.