Abstract:

Limnological region in middle and lower reaches of the Yangtze River is China’s most intensive and eutrophic freshwater lakes.As one of the main factors of primary productivity,the nitrogen and phosphorus increase will significantly affect the primary productivity in lakes.The vertically generalized production model(VGPM)and Talling model comprehensively consider the affecting factors of water temperature,photosynthetically active radiation at the water surface,chlorophylla concentration,euphotic depth to phytoplankton primary production.Using VGPM and Talling model,we studied phytoplanktkon primary production of lakes located in the middle and lower reaches of the Yangtze River.As the results show,the mean primary productivity was 0139~0381 gC/(m2·d)during 1987~1991,0128~0504 gC/(m2·d) during 2001 to 2005.The mean fixed carbon amount via the phytoplankton photosynthesis was 3 32125 tC/d during 1987 to 1991,and 3 76502 tC/d during 2001 to 2005 by VGPM,increasd 1336%.But it increased from 2 39964 tC/d to 3 27242 tC/d by Talling model,increased 3637%.