Seven stations were established in the Quanzhou Bay (24.73 degrees-24.96 degrees N, 118.50 degrees-118.70 degrees E) in China on three cruises to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and the numbers of PAH-degrading bacteria in surface sediments. Assessing the biodegradation potential of indigenous microorganisms by measuring the respiratory intensity with the addition of PAHs in sediment samples was also one of the aims of this study. The results show that the total PAH concentrations of the sediments were 99.23-345.53 ng/g dry weight (d.w.), and the PAHs composition pattern in the sediments was dominated by phenanthrene, fluoranthene and pyrene. The numbers of phenanthrene. fluoranthene and pyrene-degrading bacteria during three cruises were 1.42 x 10(3)-8.93 x 10(4) CFU/g d.w., 8.29 x 10(3)-9.43 x 10(4) CFU/g d.w. and 7.05 x 10(3)-9.43 x(4) CFU/g d.w., respectively. The addition of three model PAH compounds (phenanthrene, fluoranthene and pyrene) showed a great influence on the increasing of the microbial activity in the sediments. And there was a significant correlation among the change of respiratory activity, PAH concentration and the number of PAH-degrading bacteria. The change in respiratory activity under PAHs selective pressure could, to a certain extent, indicate the potential degradative activity of the PAH-degrading microbial community.The National High Technology Research and Development Program ("863" Program) of China [2008AA09Z408]; National Natural Science Foundation of China [40576054]; Program for Changjiang Scholars and Innovative Research Team in University [40821063]; Science and Technology Foundation of Fujian Province, China [2008Y0061
