High pressure sampling and experimentation for the study of deep-sea oil spills

The degradation of hydrocarbons by indigenous microbial communities from deep-sea environments is studied largely at atmospheric pressure entailing the risk of over- or under-estimating biodegradation rates. We present a system for high-pressure seawater sampling and experimentation, which is based on a 3-step procedure. A high-pressure sampling device (HP-Sampler), equipped with a unidirectional check valve, is set to retrieve seawater at a specific depth range and maintain pressure during retrieval. A known volume of sample from the HP-sampler is then passed into a high-pressure reactor (HP-Reactor) for experimentation via a high-pressure piston pump (HP-Pump) without disruption of the pressure continuum. We used this set-up to study the degradation of crude oil hydrocarbons at plume concentrations by deep-sea microbial communities from the Eastern Mediterranean Sea with and without dispersant application. Un-decompressed seawater from 600 – 1000 m depth was retrieved and successfully incubated for 77 days in the HP-Reactor at 10MPa and in situ temperature (14^οC). In the first part of the experiment, light Iranian crude oil was added at day 0 and was replenished regularly until day 35. The incubation was maintained for the second part of the experiment (42-77 days), which involved the addition of dispersant (1:25 v/v COREXIT 9500) with weekly replenishment. Subsampling took place to determine alkane and aromatic hydrocarbons concentration. Our results show high capacity of the indigenous microbial community for hydrocarbon degradation regardless of dispersant application.