Abstract:

In Guanting reservoir, biological nitrogen fixation rate (NFR) was measured with acetylene reduction method, the diversity of nitrogen fixation bacteria (NFB) was revealed with nifH gene PCR-DGGE fingerprint. The results showed that biological nitrogen fixation exists in Guanting reservoir, the rates of nitrogen fixation ranged from 0.172 to 9.35 nmol/(m³·d). There was a positive correlation between NFR and NH⁺₄-N (P=0.998, r=0.000), TN (P=0.986, r=0.000), TP (P=0.968, r=0.002) concentrations, respectively. DGGE fingerprint indicated the (NFB) abundance differed between six sites and positive correlations were found between NFB abundance and TN (P=0.737, r=0.094), TP (P=0.787, r=0.063). Shannon-Weaver index varied in a range of 0.80-2.45. During the process of eutrophication in reservior, nitrogen fixation bacteria diversity increased with the nutrient status and thereby NFR enhanced. In addition, biological nitrogen fixation could aggravate eutrophication in Guanting reservoir.

Key words: Guanting reservoir, biological nitrogen fixation, eutrophication, PCR-DGGE