Eutrophication has been recognized as a pollution problem all over the world. Blooms of the cyanobacterium are ubiquitous phenomena in eutrophic lakes and reservoirs in many countries. Although a number of published reports concern cyanobacteria, the mechanisms governing the blooms are poorly understood. In particular, nutrient dynamics are crucial in bloom processes, but they have mostly been addressed inadequately. Phosphorus is primarily responsible for limiting the growth of phytoplankton in freshwater systems. It is difficult to describe bloomrelated processes without considering bioavailability of phosphorus in benthic environments that act as sources of phosphorus. In addition, microbial degradation of organic matter is mediated by enzymes operating outside the cells. Extracellular phosphatase plays a key role in phosphorus regeneration. Thus, a study on phosphorus status in benthic environments, including species and regeneration, is of ecological interest because of its implications for water blooms in the ecosystems. The phosphor-us forms and kinetic parameters of alkaline phosphatase activity (APA) in the overlying, interstitial water and sediment, size-fractionation of APA in overlying and interstitial water, as well as organic matter in the sediments, were studied in adjacent ponds located in the eastern suburb of Wuhan. Ponds with occurrence or bloom of Microcystis aeruginosa showed significantly higher concentrations of orthophosphate (O-P) in overlying water, or different P species in interstitial water, whereas the pond void of Microcystis aeruginosa showed the lowest concentrations of chlorophyll a in surface warer and different P species in overlying and interstitial water, indicating close relation between algae bloom and benthic phosphorus status. Sediment P was dominated by Fe bound P fraction in all ponds studied. In the pond with heavily bloom of Microcystis aeruginosa, the lowest Fe bound P and the highest organic matter contents were observed in the sediment, coupled with the higher affinity for the substrates (lower Km values) and reaction velocity (higher Vmax values) of APA in the bottom. These results suggested that organic matter may cause anoxic status, and induce higher APA with different kinetic characteristics in the overlying, interstitial water and sediment, thereby accelerating O-P release and initiating bloom.