Algal bloom disturbed the planktonic microbial foodweb and function in Lake Taihu: comparison of areas with and without algal bloom.

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Citation abstract

Algal bloom is one of the major current problems, while the impacts of algal bloom on the planktonic microbial community remain unclear. This study investigated the nutrients in water quality and surface sediment, and planktonic microbial community in twelve sampling sites from the western, eastern, northern, and center areas of Lake Taihu during the algal bloom period. We found that the mean total nitrogen, ammonium nitrogen, Chlorophyll(a) and chemical oxygen demand concentrations in overlying water varied significantly (p < 0.05) among four areas. The alpha diversity index of both bacterial and micro-eukaryotic communities was the highest in eastern Lake, and species turnover was important in compositional dissimilarity of the planktonic microbial community. Five algal bloom (ABM) and five non-algal bloom sites (UABM) were according to nutrients, Chlorophyll(a), and principal coordinate analysis results. The null model revealed that stochastic processes other than deterministic processes played a greater role, while decreased dispersal limitation and increased heterogeneous selection were observed in the microbial community within ABM compared to UABM. Network analyses revealed that algal blooms destabilized planktonic microbial food web by disrupting interactions among phytoplankton, protozoa, metazoans, and bacteria. Partial least squares path modeling analysis showed that sediment nutrients have significant impacts on water quality, and the algicidal microbial community was driven by the algal group. Redundancy analysis results showed that algicidal flora was positively related to Chlorophyll(a) and water quality but not to Cyanobacteria. Interestingly, bacterial organic carbon biosynthesis, ammonification process, and dissimilatory sulfate reduction decreased, while organic carbon decomposition and assimilatory sulfate reduction functions increased in ABM compared to UABM. These results highlight the algal bloom disturbed the nutrients cycle and planktonic microbial community and suggest that algicidal flora in the bloom area may primarily target eukaryotic algae rather than Cyanobacteria.