Temporal and Spatial Variations of the Bacterial Diversity in a Deep Alkaline Lake

This study aimed to investigate the effects of thermal stratification and complete mixing conditions on the bacterial diversity of a deep alkaline lake. For this purpose, the water and sediment samples were collected during the winter turnover and stratification periods, and bacterial communities were assessed by metabarcoding. The results showed that temperature shaped the bacterial community patterns in the lake. While the bacterial communities of the water samples showed high similarity during the mixing period, communities had distinctive patterns in the epilimnion and hypolimnion during stratification. The diversity and evenness of the bacterial communities increased with depth, whereas the bacterial communities of sediments were more even and diverse than in water. Proteobacteria members dominated the sediment communities representing 41% to 62% of the total reads in the samples. Particularly, Gammaproteobacteria was the major class found in the sediment; higher abundances were recorded in the mixing period representing 33–51%. Additionally, Actinobacteria species were more abundant in the water samples representing 22–52% of all reads during the stratification period. Due to the complete mixing conditions in the lake, a homogenized bacterial community structure was observed in the lake with minor spatial changes, and a clear divergence was observed between epilimnion and hypolimnion. On the other hand, the sediment bacterial community showed a more stable profile.