Habitat and seasonal variations in bacterial community structure and diversity in sediments of a Shallow lake

Benthic bacteria are drivers of aquatic ecosystem material circulation and energy flow, and are sensitive to environmental changes. In this study, a total of 79 sediment samples were collected from four representative habitat types (duck farm, fish farm, lotus pond and residential area) and one reference site (conservation district) of Baiyangdian Lake, North China, in three seasons (winter, spring and summer). The physical and chemical properties and the levels of contaminants in sediment were determined. Bacterial communities were studied by 16S rRNA high-throughput sequencing techniques. The result showed that, Proteobacteria, Chloroflexi, Bacteroidetes, Firmicutes and Actinobacteria were the dominant species at the phylum level in Baiyangdian. Sulfuricurvum, Thiobacillus Dechloromonas, Sulfurovum, Nitrospira and Desulfatiglans were the dominant species at the genus level. The dominant genus was different among different habitats. Proteobacteria exhibited the highest relative abundance in all seasons, and the relative abundance of dominant bacteria was highest in winter. The main functional group from the sampling sites were contamination tolerance bacteria, such as sulfur-oxidizing, sulfate-reducing and nitrifying bacteria. Sulfur-oxidizing bacteria were found mainly in duck farms and residential areas, whereas sulfate-reducing bacteria and nitrifying bacteria occurred in lotus ponds. Habitat type was the most important factor influencing the bacterial community composition, evenness and diversity. Sediment pH and the amount of active phosphorus played the most important role in the composition of the bacterial community, and the heavy metals (Zn, Mn and Cr) and organic pollutants (polycyclic aromatic hydrocarbons, PAH) also had moderate influence. As Baiyangdian Lake is the central of Xiong'an New Area, the water quality management has become the hottest topic. Plenty of researches about environmental variables and aquatic species were taken, but lacking report of bacteria. This study provide basic information of bacterial community composition in this area, and help to understand the response of the bacterial community to habitat and seasonal change, which provide a scientific basis for the recovery and reconstruction of the degraded ecosystem.