The United States Coast Guard (USCG) recently introduced stringent regulations for the treatment of ballast water. Ultra-violet (UV) light is a useful technology in a ballast water treatment system (BWTS), for inactivating phytoplankton which could be invasive and harmful to humans and the environment. UV damages DNA and prevents replication, but the vital stain methods mandated in the USCG protocol do not detect UV damage. Alternative culture-based measures of reproductive capacity are yet to be approved, time consuming, and have limitations (not all species may grow).