Arabian-Gulf coastal materials loaded with oil-utilizing bacteria, an overview

As a consequence of the 1990-1991 Iraqi occupation of Kuwait, during which crude oil was deliberately released from the Al-Ahmadi Terminal into the Gulf, coastal areas have become heavily polluted with oil sediments. This paper presents an overview of a decade of research on indigenous oil-utilizing microorganisms that we found associated with inanimate and animate materials along the Arabian Gulf coasts, and their roles in the self-cleaning of the oily areas. Animate materials viz. cyanobacterial mats, epilithic algal biomass and macroalgae collected from intertidal zones of oil-polluted and clean coasts were found heavily loaded with oil-utilizing bacteria. Each gram of those coastal materials was associated with up to hundred millions of oil-utilizing bacterial cells. Nearby coastal waters on the other hand, were much poorer in such bacteria, containing only hundreds to thousands of cells per ml. Inanimate materials, e.g. coastal sand were also found associated with oil-utilizing bacteria, but the numbers were lower than those associated with animate materials, yet much higher than those in coastal waters. Coastal gravel particles were found coated with blue-green biofilms also rich in oil-utilizers. Oil utilizing bacteria associated with coastal materials belonged predominantly to Acinetobacter, Rhodococcus and other nocardioforms, with several other less frequent genera, e.g. Bacillus, Pseudomonas, and others. These bacteria could utilize a wide scope of individual aliphatic and aromatic hydrocarbons as sole-sources of carbon and energy. It was concluded that coastal materials, especially animate ones, contribute to the self-cleaning of the oily Gulf coasts and the polluted Gulf waters during tidal movements.