Biofilms are known to contribute to disease through inherent protective mechanisms and propagation strategies. These multi-cellular systems also play essential roles in numerous environmental processes. The current study investigated the responses of a mixed community biofilm to carbon-starvation, and measured the effects of UV-C on pure-culture biofilms at different stages of maturity by monitoring metabolic and cell yield responses. Carbon dioxide production and biofilm-derived planktonic cell yield were used at the measurement parameters. The mixed community rapidly responded to induced carbon-starvation under continuous flow conditions by remaining metabolically inactive throughout the 96 and 120 h starvation periods, only to promptly return to a metabolically active state upon the reintroduction of carbon. The effects of UV-C on pure-culture biofilms was negligible, with no log activation being achieved, and metabolic activity remaining static.