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Although a large number of recent ecological studies have focused on freshwater bacterioplankton populations, knowledge of the primary factors influencing bacterial communities in urban rivers is limited. Bacterial community structure in three rivers located in Shanghai city was studied over a 1-year period using denaturing gradient gel electrophoresis (DGGE). Subsurface samples were collected every 2 months from two study sites in each river. Water was characterized when biological samples were collected by measuring temperature, pH, chloride ion, total dissolved solids (TDS), total N and total P. complex DGGE band patterns indicated high bacterial diversity in the rivers. Analysis of similarity (ANOSIM) showed that variation of the bacterial communities was higher between rivers than it was between samples from the same river. When evaluated using principal component analysis, samples collected during warmer months from any particular river tended to group together while cold-season samples generally clustered, suggesting significant seasonal impacts. Redundancy analysis was used to identify relationships between environmental factors and bacterial community composition in each individual river. Temperature, TDS, pH, TP and salt concentration were all identified as being related to bacterial community structure, with temperature being the most influential parameter in all three rivers. Our results indicated that bacterial community composition was different in the three different rivers. Even though the rivers were located in heavily disturbed urban ecosystems, temperature was the major driver of bacterial community composition, just as it is in natural systems.

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