Abstract
AimsThe aim of this study was the baseline description of oil‐degrading sediment bacteria along a depth transect in the Faroe‐Shetland Channel (FSC) and the identification of biomarker taxa for the detection of oil contamination in FSC sediments.Methods and ResultsOil‐degrading sediment bacteria from 135, 500 and 1000 m were enriched in cultures with crude oil as the sole carbon source (at 12, 5 and 0°C respectively). The enriched communities were studied using culture‐dependent and culture‐independent (clone libraries) techniques. Isolated bacterial strains were tested for hydrocarbon degradation capability. Bacterial isolates included well‐known oil‐degrading taxa and several that are reported in that capacity for the first time (Sulfitobacter, Ahrensia, Belliella, Chryseobacterium). The orders Oceanospirillales and Alteromonadales dominated clone libraries in all stations but significant differences occurred at genus level particularly between the shallow and the deep, cold‐water stations. Alcanivorax constituted 64% of clones at FSC135 but was absent at deeper stations. Pseudoalteromonas and Oleispira dominated the bacterial community at 500 and 1000 m.ConclusionsThe genus Oleispira emerged as a major player in the early stages of crude oil degradation in deep‐sea sediments of the FSC particularly at subzero temperatures. This finding is offering a direction for future research into biomonitoring tools for the detection of low levels of crude oil contamination in the deep FSC, and possibly high latitude cold waters in general.Significance and Impact of the StudyOil and gas exploration in the FSC occurs at depths >1000 m but baseline environmental data necessary for the assessment of ecosystem recovery to prespill conditions in the event of an oil spill are lacking. This study will contribute to our ability to assess the impact of oil release in the FSC and guide the direction of bioremediation strategies tailored to the area.
Highlights
As much as 12% of oil is currently extracted from the deep sea, compared to 2% in 2001 (Larkin et al 2015)
All isolated strains obtained from enrichment cultures were subjected to sequence analysis of the 16S rRNA
Several isolates obtained from FSC135 were unique among stations; strains closely related to Ahrensia sp. (Rhodobacterales, Alphaproteobacteria), the genera Belliella, Aequorivita and Brumimicrobium (Bacteroidetes), and the family Kineosporiaceae (Actinobacteria) were not found at deeper stations
Summary
As much as 12% of oil is currently extracted from the deep sea (at depths >200 m), compared to 2% in 2001 (Larkin et al 2015). Recent empirical studies show that the probability of accidental oil release is positively correlated with drilling depth suggesting increased risks of deep-sea oil spills in the future (Muehlenbachs et al 2013). Up to 50% of the discharged oil and essentially all of the natural gas was sequestered in a deep-water hydrocarbon plume at 1000– 1300 m depth (Joye 2015; Passow and Hetland 2016) while 2–15% of spilt oil was deposited on the Gulf seafloor mainly via the sedimentation of oil-associated marine snow from surface waters (Passow et al 2012; Chanton et al 2014; Valentine et al 2014; Ziervogel et al 2016). Of particular concern is the persistence of certain hydrocarbons in deep-sea sediments for decades and the risk of prolonged ecotoxicological effects as these compounds gradually enter the food web (Yan et al 2016)
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