Planktonic algal bloom significantly alters sediment bacterial community structure

Purpose

We determined the relationship of a planktonic algal bloom with spatial and temporal changes in sediment bacterial communities in a eutrophic urban river in the Taihu Basin, China.

Materials and methods

Surface sediments from different locations on the river, including with and without an algal bloom, were collected monthly for 1 year. Sediment bacterial communities were assessed by sequencing 16S rRNA gene amplicons using an Illumina MiSeq.

Results and discussion

There were distinct spatial and temporal changes in sediment bacterial community structure. Significant decrease in the Shannon diversity corresponded with the peak chlorophyll a (Chl a) concentration. Proteobacteria, Chloroflexi, and Bacteroidetes were the dominant phyla throughout the year; however, their relative abundances changed seasonally. At the time of peak Chl a concentrations, Proteobacteria and Bacteroidetes comprised a greater proportion of the bacterial community. Bacterial community structure also varied spatially at the operational taxonomic unit (OTU) level according to canonical correspondence analysis (CCA), especially in locations with an algal bloom compared with those without an algal bloom. There were positive correlations between multiple bacterial genera and Chl a content, suggesting the potential for facilitative relationships between phytoplankton and bacteria. Based on the CCA, water temperature, NH₄ ⁺-N, TN, NO₃ ^?-N, and TP in the sediment and Chl a contents in the water column were significantly correlated with sediment bacterial community structure (P < 0.05).

Conclusions

Planktonic algal blooms may influence sediment bacterial community structure at all taxonomic levels in urban rivers. This work emphasizes the need for more comprehensive studies regarding the impact of planktonic algal blooms on sediment bacterial communities.