Novel Deep-Sea Sampling and Experimentation system for hydrocarbon bioremediation monitoring under in situ conditions

During the Deepwater Horizon accident in the Gulf of Mexico in 2010, excessive subsea dispersant application and high pressures led to the confinement of hydrocarbons, creating an oil plume at depths of 1000–1200 m. The rapid and vigorous response of the indigenous microbial populations removed a major fraction of hydrocarbons in the plume. So far, the collection of deep-sea microbial communities involved depressurization of the sample during retrieval and in most cases, subsequent incubation experiments were carried out at atmospheric pressure. A novel sampling apparatus, was designed for the collection of indigenous microbial populations from the deep Eastern Mediterranean Sea, maintaining in situ pressure throughout the entire process of retrieval and experimentation to determine microbial oil degradation. The High Pressure (HP) Sampler collected seawater between 600 to 1000 m depth. A known volume of the collected sample was then transferred via a piston pump, without pressure disruption, into a HPReactor, at 10 MPa pressure and was incubated with crude oil at plume concentration for 77 days at in situ temperature (14οC). For the first part, Iranian light crude oil bioremediation was monitored for 35 days, and then the effect of dispersant addition (1:25 v/v COREXIT 9500) was observed until day 77. The results showed a high capacity of the indigenous microbial community for alkane degradation regardless of dispersant application; however, the removal of aromatic compounds was highly dependent on oil dispersion.