Effect of reclaimed water recharge on bacterial community composition and function in the sediment of the Chaobai River, China

Purpose Reclaimed water has been widely used in river landscape restoration. Bacterial communities living in river sediments are the main bearers of metabolic activity in most river ecosystems. When reclaimed water is used to restore river landscapes, its effect on bacterial communities in river sediments remains unclear. Materials and methods Sediment samples were taken from the 15-year reclaimed water recharge channel and the non-reclaimed water channel of the Chaobai River. The 16 s rRNA high-throughput sequencing technology was used to test the bacterial community composition. FAPROTAX database was performed to functional annotation prediction. Results and discussion Reclaimed water increases the abundance of bacteria in sediments by decreasing pH, increasing salinity, carbon, and nitrogen contents, but has no significant effect on Shannon and Simpson diversity. Sediments in reclaimed water recharge sites formed a habitat that was more suitable for the growth of denitrifiers than nitrifiers, resulting in these sites containing more Hydrogenophilaceae and Bacteroidetes_vadinHA17 and less Nitrosomonadaceae . Bacterial community variations at the family level were related to pH, total nitrogen, total phosphorus, Hg, Cr, and Zn. Functional predictions from FAPROTAX indicate that upstream reclaimed water recharge sites have enhanced functions related to nitrogen respiration, nitrate reduction, carbon cycling, and sulfur cycling while inhibiting nitrification. NO 3 -N, total nitrogen, total carbon, Hg, and Zn were strongly correlated with functional groups. Conclusions The discharge of reclaimed water caused changes in sediment bacterial community compositions and ecological functions by increasing nutrient and heavy metal levels. Graphical Abstract