Ultraviolet light alters experimental aquarium water microbial communities

The effect of ultraviolet (UV) light exposure, alone and in combination with CO2 exposure, on the water microbial community composition was tested in replicate experimental aquaria using source water from an established Amazon-themed exhibit housing mixed species of fishes. Total bacterial abundance, alpha-diversity metrics, and beta-diversity metrics were determined 3 weeks and 1 week before, and weekly during 8 weeks of continuous treatment. The UV treatment significantly lowered the overall bacterial abundance while CO2 treatment had no effect. However, the UV exposure effect was variable across phyla. Some phyla were decreased while others were increased, including some of potential clinical significance. At the genus level, there were no significant differences in the relative abundance of Mycobacteria between treatments and an increase in the relative abundance of Aeromonas spp. with UV light treatment. Further work is needed to determine if the observed effects are dose-dependent or if different exposure doses produce different results.