Effects of river sediment addition to the beach microbial communities

During the processes of claiming land from the sea, river sediments are used to fill and transform the sea area along the margin of islands and lands into new lands. These activities would probably affect microbial ecosystems of the beach sediment. However, little is known about these effects. In this study, a simulation test was conducted to evaluate these effects. Pyrosequencing technique was employed to assess the effects of river sediment addition to the beach bacterial communities. The used river sediments were collected from different rivers. The results indicated that river sediment addition greatly impacted microbial ecosystems of the beach and caused a clear shift in the beach bacterial community composition. These processes remarkably increased toxic metals and decreased the bacterial diversity in the beach sediment, mainly including the phyla of <i>Bacteroidetes, Cyanobacteria, Proteobacteria</i>, and <i>Spirochaetes</i>. River sediment addition caused an increase in potentially pathogenic bacterial genera of the beach sediment. Bacterial phylotype richness in the beach without river sediment addition was higher than that in the beach with river sediment input. There were significant differences in bacterial communities between beach sediments with and without river sediment addition, and the most dominant classes were <i>Gammaproteobacteria</i> and <i>Flavobacteria</i>.