Microbial community analysis via 16S sequencing of subarctic sediments exposed to different pressures and temperatures.

The Hatton-Rockall Basin in the North East Atlantic is an area with potential for deep (2900 m) hydrocarbon exploration. Following the Deepwater Horizon oil spill, many investigations into the responses of sediment microbial communities to oil pollution have been undertaken. However, hydrostatic pressure is a parameter that is often omitted due to the technical difficulties associated with conducting experiments at high pressure (>10 MPa). In this work we have collected sediments from 2900 m deep in the Hatton-Rockall Basin and incubated them in factorial combinations of in situ and atmospheric pressure, 5 and 20 °C and contaminated or not with a hydrocarbon mixture to evaluate the effect on microbial community composition. Our results revealed that pressure, temperature and oil contamination influenced the composition of the bacterial community within the sediment. Hydrocarbon-degrading bacteria Pseudomonas, Colwellia and several Bacteroidetes dominated communities at in situ pressure. In contrast, other hydrocarbon degraders decreased in relative abundance at the same conditions. The work highlights the importance of considering high hydrostatic pressure in microbial oil pollution research.