Microbial Respiration and Community Response to Crude Oil in Deep Eastern Mediterranean and the Great Australian Bight

The Deep Water Horizon (DWH) oil spill in 2010 was the largest deep ocean oil spill in world history. Very limited information about oil biodegradation is available in deep oceans other than GOM since DWH. In this study, we investigate the microbial communities’ response to crude oil contamination in the deep Eastern Mediterranean sea (E.Med) and Great Australian Bight (GAB). In addition, we will assess feasible methods for oil bioremediation in those locations.

First, we discovered the fast adaption of the E.Med deep water microbial community to oil contamination in terms of phylogeny and functional genes. Based on the 16S rRNA sequencing and GeoChip metagenomics results, oil contamination led to the increase of Proteobacteria and the enrichment of organic degradation genes. Oil biodegradation potential can differ between two depths that are only 200 m apart suggesting that depth profiles have major differences in response to crude oil.

After that, we found that both E.Med and GAB deep water microbial communities had strong carbon utilization and oil mineralization rates using in-lab microcosms of deep E.Med and GAB water. However, the deep GOM microbial community had a much higher cell growth and carbon utilization capacity compared to E.Med and GAB. Although there was an enrichment of oil degrading bacteria in E.Med and GAB, the oil degrading microbial communities were different after exposure to crude oil.

Last, we found that nutrient and dispersant amendments can increase the microbial carbon utilization in deep E.Med. Analyzing in-lab microcosms with 16S rRNA and GeoChip metagenomics, we observed that the application of dispersant and phosphate can effect dissolved organic matter and microbial community composition. Compared to uncontaminated water, the presence of crude oil can increase oil degrading bacteria and carbon degradation genes

Together, We observed rapid microbial response to crude oil contamination. The organic carbon from oil can be utilized in a short time at both basins. The amendment of dispersant and other limiting nutrients can work as prospective bioremediation methods for potential deep sea oil spills in E.Med and GAB.