Microbial community response to biostimulation and bioaugmentation in crude oil-polluted sediments of the Persian Gulf.

ABSTRACT

The Persian Gulf is a transit point for a lot of crude oil at the international level. The purpose of this research is to compare two methods of biostimulation and bioaugmentation for degradation of sediments contaminated with crude oil in the Persian Gulf. In this research, six types of microcosms were designed (Sediments from Khark Island). Some indicators such as the quantity of marine bacteria, enzyme activity (Catalase, Polyphenol oxidase, Dehydrogenase), biodiversity indices and the percentage of crude oil degradation were analyzed during different days (0, 20, 40, 60, 80, 100 and 120). The results of this research showed that the highest quantity of heterotrophic and crude oil-degrading bacteria was found in the sixth microcosm (SB). This microcosm represents a combination of two methods: bioaugmentation and biostimulation (3.9 × 106 CFU g-1). Following crude oil pollution, the activity of catalase and polyphenol oxidase increased and the dehydrogenase enzyme decreased. The bioaugmentation microcosm exhibited the highest activity of enzymes among all the microcosms studied. Predominant bacteria in each microcosm belonged to Cellulosimicrobium, Shewanella, Alcanivorax and Cobetia. The highest degradation of crude oil is related to the Stimulation-Bioaugmentation microcosm (SB). The statistical results of this research proved that there is a significant relationship between the type of method chosen for biodegradation with the sampling time and the quantity of marine bacteria. The results of this research confirm that crude oil pollution in the Persian Gulf sediments can be reduced by choosing the proper bioremediation method.