Research on algicidal effect of bioactive metabolites of Brevibacillus laterosporus on Oscillatoria sp.in shrimp pond

Oscillatoria sp.is a common and harmful cyanophyte in shrimp culture pond.In this study,the sterile filtrate of Brevibacillus laterosporus and Oscillatoria sp.were used to study the algicidal effects in their different growth stages.The algae dry weight,chlorophyll-a and phycocyanin content were measured in order to explore the best algae-lysing period and the algicidal mechanism.The final aim was to provide the basic theory for improving water environment in shrimp pond.The results showed that algicidal effects of the sterile filtrate on Oscillatoria sp.were very significant(P0.01)when the algae-lysing bacteria was in the stable and decline phases.After 7 days,the algae dry weights were reduced by 51.77%,47.04% respectively,the contents of chlorophyll-a were decreased by 67.60%,59.13% respectively;the phycocyanin contents were increased by 33.51%,30.97%,respectively.Similarly,the algicidal effect of the sterile filtrate of algae-lysing bacteria was so conspicuous(P0.01)on the lag phase Oscillatoria sp..7 days later,the algae dry weight was reduced by 63.90%;the content of chlorophyll-a was decreased by 69.72%;the phycocyanin content was increased by 54.17%.The conclusion was that the sterile filtrate of Brevibacillus laterosporus in the stable phase had the best algicidal effect on the lag phase Oscillatoria sp..