Effects of Trophic State on the Composition and Distribution of Bacteria in the Surface Sediments of Lake Taihu

ABSTRACT 1. The trophic state of water significantly affects the structure of bacterial communities in sediments. The direct and indirect impacts of trophic state, along with trophic‐induced changes in the properties of organic matter, on the composition and distribution of bacteria in sediments, remain largely unknown. 2. We collected surface sediments from 21 sites across five areas of Lake Taihu, the third largest freshwater lake in China. These sites represented a range of trophic states from mesotrophic to moderately eutrophic. We investigated how trophic state influences bacterial composition and distribution in the surface sediments of Lake Taihu. 3. Proteobacteria , Firmicutes and Bacteroidetes were the most abundant phyla identified in the DNA sequences of surface sediments from the sampling sites in Lake Taihu, regardless of the water trophic state. The relative abundance of Proteobacteria and Firmicutes in the surface sediments increased with trophic level index (TLI) of the water column. In contrast, the relative abundance of Bacteroidetes , Acidobacteria and Fibrinobacteria decreased with increasing TLI. The α‐biodiversity of the sediment bacterial community in Lake Taihu did not vary significantly among different water trophic states. However, surface sediments from sites with varied trophic states exhibited different groups of bacteria that were either specifically present or in higher relative abundance. 4. Several factors influenced the sediment bacterial communities in Lake Taihu, including sediment total nitrogen, sediment total phosphorus, sediment organic carbon, δ 13 C and trophic state. However, the primary influencing factors varied between sites and trophic states. For mesotrophic states, sediment organic carbon was the most important factor, while for moderately eutrophic states, trophic state was the most significant factor. 5. Our findings provide evidence for both the direct and indirect influences of water trophic state on the composition and distribution of bacteria in sediments.