FACTORS INFLUENCING CHLOROPHYLL A CONCENTRATION IN THE YANGTZE-CONNECTED LAKES.

To determine the environmental factors influencing phytoplankton chlorophyll a (Chl a), field investigations were conducted in three river-connected lakes (Dongting Lake, Poyang Lake and Shijiu Lake) of the Yangtze flood-plain in 2004. Results showed that the average Chl a concentration in these lakes ranged from 2.98 to 3.65 mg m^-3. The major factors influencing Chl a in lentic and lotic regions were total phosphorus (TP) and water velocity (U), respectively. Multiple relationships including total nitrogen (log₁₀TN) and water depth (log₁₀Z) were established. Further analyses found that the absolute Chl a and slope of log₁₀Chl a=f (log₁₀TP) in the river-connected lakes were obviously lower than those in the river-isolated lakes. This suggests the river-lake connectivity can significantly modify relationship between TP and chlorophyll a concentration. [ABSTRACT FROM AUTHOR]