Long-term (1956-1999) dynamics of phosphorus in a shallow, subtropical Chinese lake with the possible effects of cyanobacterial blooms.

This paper describes the long-term dynamics of phosphorus concentrations in both the lake water and the sediment in a subtropical Chinese lake, Lake Donghu. The total phosphorus (TP) concentration in the lake water experienced an upward trend from the 1950s, and peaked in 1983/1984, but declined obviously afterwards. From the 1950s to thel990s. TP content in the upper 10cm sediment of the lake increased steadily from 0.307 to 1.68mg P gDW(-1) at Station I and from 0.151 to 0.89 mg P g DW(-1) at Station II, respectively. The TP increase in the lake water before mid-1980s was mainly attributed to the massive input of sewage P. The outbreak of cyanobacterial blooms coincided with the peaks of TP and Orthophosphate (PO4-P) in the water in mid-1980s, and the maximum TP of the water reached as high as 1.349mg/l at Station I and 0.757mg/l at Station II (in 1984), respectively. The declines of TP and P04-P in the water after mid-1980s was coincident with the disappearance of cyanobacterial bloom.