EVALUATION OF BIOREMEDIATION AGENTS IN BEACH MICROCOSMS

A spill of weathered Arabian Light crude oil (3.7 kg m(-2)) on an inte rtidal sand zone was simulated in the laboratory. Respirometry, chemic al and microbiological methods were employed to assess the effectivene ss of two bioremediation agents: a slow-release inorganic fertilizer ( Max Bac(R)) and an oleophilic organic fertilizer (Inipol EAP22). Inipo l EAP22 stimulated additional CO2 evolution, increased both the total chemoheterotrophic population and the number of hydrocarbon-degrading microorganisms significantly, and increased the rate of mineralization of radiolabelled hexadecane. While the differences were not dramatic after 41 days of exposure, the residual oil extracted from the Inipol- treated sand was significantly more biodegraded (based on the applicat ion of the conserved biomarkers: phytane and 17 alpha, 21 beta hopane) than that observed within the other sand columns. There was no eviden ce that Max Bac stimulated natural oil biodegradation rates relative t o those observed in the control. These observations contrast with find ings made previously in the field. The results suggest that difference s in product formulations and their interaction with physical factors within sandy beach environments regulate nutrient release and persiste nce. These effects are significant factors in controlling the efficacy of bioremediation agents. Crown copyright (C) 1996 Published by Elsev ier Science Ltd.