Science & Technology
; Life Sciences & Biomedicine
Environmental Sciences & Ecology
In order to illuminate the characteristics of excreting alkaline phosphatase (AP) by cyanobacteria and verify the feasibility of alkaline phosphatase activity (APA) as the indicator of soluble reactive phosphorus (SRP) deficiency, daily investigation in situ was conducted during a complete process of cyanobacterial bloom in the Xiaojiang River, a tributary of Three Gorges Reservoir. Changes of phytoplankton communities, SRP, chlorophyll a (Chl a), physic-chemical parameters and APA were screened. The complete process of cyanobacterial bloom could be divided into two stages. In the bloom stage, Microcystis sp. dominated the phytoplankton communities, water temperature (WT), dissolved oxygen (DO) and the total APA (APA(T)) kept a high level and Chl a displayed an ascending trend and reached the peak. APA(>3.0 mu m) occupied the main proportion of the total APA (APA(T)) and showed the significant positive relationship with SRP (p<0.05). In the bloom decaying stage, the predominant species was Anabaena sp., the values of WT, DO, Chl a, APA(T) and APA(>3.0 mu m) declined and lower than that in the bloom stage; APA(>3.0 mu m) still occupied the main proportion of APA(T) and showed the significant negative relationship with SRP (p<0.05). It was proved that AP was mainly excreted by phytoplankton and there were at least two different AP excreting mechanisms in cyanobacteria, APA was not reasonable treated as the indicator of SRP deficiency when Microcystis sp. dominated the phytoplankton communities.