Effects of light intensity on the epiphytic bacterial community of sporelings of Saccharina japonica

Abstract

In the artificial hatchery of Saccharina japonica, sporelings suffer from various diseases caused by improper irradiance. On the other hand, the outbreaks of diseases of algae are also related to the changes of epiphytic bacteria. So far, little is known about the effects of light intensity on composition shifts of the epiphytic bacterial community of sporelings in S. japonica. In this study, we analyzed the effect of light intensity on the dynamic shift of diversity, the composition of bacterial communities on sporelings of S. japonica by using high-throughput sequencing based on 16S rRNA genes. The sporelings were exposed to different light intensities ranging from 0 to 200 μmol photons m−2 s−1 for a week. Our results showed that the composition of the epiphytic bacterial community shifted and the diversity increased when the light intensity was elevated. At the phylum level, the phylum Bacteroidetes showed increasing trends while phylum Proteobacteria decreased. At the genus level, Leucothrix and Colwellia were dominant in all treatment groups and the genus Leucothrix decreased in abundance while the genus Colwellia increased, as the light intensity was enhanced. The results of this study not only enrich the baseline knowledge of epiphytic bacteria associated with S. japonica but also help hatchery farms to take appropriate light management and to monitor the shift of epiphytic bacterial community which could mitigate disease outbreaks.