Ozone, ultraviolet light, ultrasound and hydrogen perozide as ballast water treatments: Experiments with mesozooplankton in low-salinen brackish water

Non-native aquatic species dispersed via ships’ ballast water create a threat for local marine ecosystems throughout the world. Increasing maritime traffic and faster ships have increased the risk for species introductions during the last decades and effort has been made to develop reliable methods for ballast water management. While various technologies such as ultraviolet irradiation and ultrasonication have shown promising results, the efficacy of any treatment depends on various chemical, physical and biological properties of water such as turbidity, salinity and the size and type of the organisms. Although many of the major harbours are located in estuaries with a wide range of salinity, technologies developed so far have not been tested in brackish environments. In this study, we assessed the efficacy of four potential ballast water treatment technologies – ozonation, ultraviolet irradiaton (UV), ultrasonication (US) and hydrogen peroxide (H₂O₂) – on indigenous brackish water zooplankton (copepods, cladocerans and rotifers as the main groups). All technologies showed promising results and high kill percents (>99 %) were achieved in these low-saline conditions. Different taxa responded differently to the various technologies but basically the most effective treatments were the combinations of US+UV and UV+ H₂O₂. Many issues, however, need to be addressed in order to define the feasibility of the technologies in full-scale applications.