Distribution and impact factor of alkaline phosphatase activity in the intertidal surface sediments of the Yangtze Estuary

Spatial and temporal distributions of alkaline phosphatase activity (APA) in the intertidal sediments of the Yangtze Estuary were investigated, together with abundances of phosphate solubilizing bacteria and the phosphorus forms. It was shown that there were significantly seasonal and regional variations of alkaline phosphatase activity in the intertidal sediments. The alkaline phosphatase activities were relatively lower in winter (January), with values of 0.65~1.59 μg·g^-1·h^-1. In contrast, higher alkaline phosphatase activities were detected in summer (August and September), with values of 1.80~5.64 μg·g^-1·h^-1. Statistical analyses indicated that the alkaline phosphatase activities were related significantly to the numbers of phosphate solubilizing bacteria (r_OPB=0.91, r_IPB=0.89, p<0.01). This implied that the numbers of phosphate solubilizing bacteria were the primary factor controlling the changes of alkaline phosphatase activities. In addition, the alkaline phosphatase activities in the intertidal sediments were also affected by phosphorus forms, C:N molar ratios and salinity. However, there were no significant correlations of the alkaline phosphatase activities with the contents of sand, clay, silt, organic carbon (OC) and organic nitrogen (ON) in the sediments at the study area.