Microporous suspended bioreactors immobilized with periphytons were submerged between sediments and overlying water to control phosphorus release and cyanobacterial (Microcystis aeruginosa) growth. The results showed that the periphyton mainly consisted of bacteria and diatoms. The application of periphyton bioreactor decreased the levels of exchange phosphorus (Exch-P) in sediments from 1.69 to 0.49 mg g-1 and total phosphorus (TP) from 0.75 to 0.30 mg L-1. The significant redn. of the total dissolved phosphorus (TDP) content was not only beneficial for the decrease of the cyanobacterial growth, but also stimulates the periphyton to produce natural cyanobacterial inhibitors such as gallic acid and ethyl-2-methylacetoacetate. These synergistic effects led to the growth inhabitation of M. aeruginosa when the initial concns. of M. aeruginosa were less than 119.3 .mu.g L-1. This study provides an environmentally-friendly and public acceptable method of controlling bacterial blooms when compared to traditional addn. of chems.