Ready Biodegradability Test in Seawater: A New Methodological Approach

To estimate the persistence of xenobiotic in the environment, a new ultimate mineralization approach for assessing ready biodegradability in seawater has been developed, based on the OECD 301 B guideline for freshwater. A few changes in the currently accepted procedure have been made to adapt the test to seawater. The assays, realized with seawater as test medium and inoculum, give high variability results of biodegradability. To lower this variability a synthetic marine medium joined to a highly concentrated inoculum from a marine aquarium filter have been used. The results reveal (i) a decrease of variability, together with an increase in degradation rate of the tested chemicals due to a better control of inoculum and test medium, and (ii) no difference in easy biodegradable compound (sodium benzoate) biodegradation rate when two marine aquarium inocula are tested. This study demonstrates that the ready biodegradability test developed on synthetic marine medium and inoculum from marine aquarium filter minimizes the effect of the sample location on the biodegradation results of compounds and allows classifying chemicals as a function of their biodegradability.