Relationships between Accumulation and Dying of Cyanobacteria and Black Spot

Though water environmental of Taihu Lake was improved through many years integrated management,most of the area was eutrophicated.Under proper condition,black spot might be induced because large area algal bloom was still possible.Based on in situ enclose,impacts of large amount of blue-green algae accumulation on water environment was analyzed as well as its relationship with black spot forming.The results showed that,anoxia or hypoxia would be induced and the mean concentration of DO was 0.2 mg /L during the later period of the experiment.TN,NH 4+-N,and TP concentrations increased rapidly in short time when large mounts of blue-green algae dead,with the peak concentration of 16,48 and 46 times higher than the background values.Algal salvage was an effective measure to avoid water environment degrading.The caused black matters could also be induced because of algal death.Abundant polluted sediment was key factor in forming black spot,while wind-wave disturbance was necessary in order to induce typical black spot.