Comparison of bacterial communities on the surface of concrete breakwater structures and ambient bacterioplankton

Breakwater structures made of concrete are used widely around the world, and the bacteria living on these surfaces can cause the concrete to deteriorate. In this study, we collected bacterial biofilms from concrete breakwater structures located along the coast of an island, a mainland coast, and a freshwater riverbank as well as planktonic water samples from each site, and we analysed their bacterial community structures using Illumina sequencing. At the phylum level, Proteobacteria and Actinobacteria dominated planktonic samples, whereas Cyanobacteria, Proteobacteria and Bacteroidetes dominated the biofilm samples. High Cyanobacteria abundance was found in all biofilm samples. Bacterial communities significantly varied between planktonic and biofilm samples and between biofilm samples from seawater and freshwater. Only a small number of bacterial operational taxonomic units were shared by planktonic and biofilm samples from each sampling site. The permanganate index in ambient water had a more significant impact on biofilm bacterial communities than on planktonic samples. Additionally, ammonia nitrogen and total nitrogen contents were positively correlated and salinity was negatively correlated with bacterial beta diversity in biofilm samples.