Investigation of microbial community structure of a shallow lake after one season copper sulfate algaecide treatment

In present work we described, for the first time, the phylogenic structure of the microbial community in a shallow freshwater lake (Hawk Island Lake, located in the Lower Peninsula of the State of Michigan, U.S.A.) after one season (four times during May to August 2007) of CuSO4 treatment for algae growth control. The microbial community structure was characterized by terminal restriction fragment length polymorphism (TRFLP), clone library and 454 pyrosequencing. The similar structure of water chemistry measured across three sampling sites suggested that the lake was well mixed. The concentration of chlorophyll a (chl-a) and turbidity was low, 3.35 ± 1.62 μg/L and 2.5 ± 1.9 NTU, respectively, implying that photosynthesis was suppressed. TRFLP profiles showed that the lake was dominated by 16 terminal fragments (TFs), accounting for 85.5–92.6% abundance. Analysis of similarity (ANOSIM) showed that the difference in microbial community structure between upper and lower depths of the water column was not significant (P = 0.101). These results suggested that the microbial community structure within the lake was similar. Clone library and 454 pyrosequencing indicated that the lake was dominated by freshwater phyla, Proteobacteria, Bacteroides, and Actinobacteria. Moreover, the large number of unclassified bacteria (27.4% of total 2090 454 sequences) suggested a complex microbial community structure in the lake.