Abstract: We measured the abundance and community structure of denitrifying bacteria in sediments in four typical habitats (oyster aquaculture area (OA), seagrass aquaculture area (SA), natural island reef (NR), artificial reef (AR)) and control habitat (CK, a natural sediment-laden harbor site) of Xiangshan Bay using high-throughput sequencing and qPCR techniques. We further analyzed the correlations between denitrifying bacterial communities and abiotic factors. The results showed that the abundances of nirKtype denitrifying bacteria didn’t differ among those five habitats and that the abundance of nirStype denitrifying bacteria was the lowest in the AR habitat. The abundance order ofnirStype denitrifying bacteria in sediments was AR<OA=SA=NR=CK. The abundance and Shannon diversity of nirStype denitrifying bacteria were consistently higher than nirKtype in all the five habitats. Results of NMDS ordination analysis showed that the AR supported distinct nirKtype denitrifying bacterial communities compared with the other four habitats. The nirStype denitrifying bacterial communities in the AR also significantly differed from those in the OA, NR, and CK, while the intermediate communities presented in the SA. Results of the RDA analysis showed that the nirKtype denitrifying bacterial communities were significantly correlated with sediment TOC content, but no association between thenirStype denitrifying bacterial communities and the abiotic factors. We concluded that there were abundant and diverse denitrifying bacteria in sediments in the five habitats of Xiangshan Bay and that denitrifying bacteria generally had lower abundance and diversity and different community structure in the artificial reef zone from the other habitats.

Key words: nirK, nirS, high-throughput sequencing, qPCR, nitrogen, biodiversity.