Several studies have assessed the effects of the released oil on microbes, either during or immediately after the Deepwater Horizon accident. However, little is known about the potential longer-term persistent effects on microbial communities and their functions. In this study, one water column station near the wellhead (3.78 km southwest of the wellhead), one water column reference station outside the affected area (37.77 km southeast of the wellhead), and deep-sea sediments near the wellhead (3.66 km southeast of the wellhead) were sampled 1 year after the capping of the well. In order to analyze microbial community composition, function, and activity, we used metagenomics, metatranscriptomics, and mineralization assays. Mineralization of hexadecane was significantly higher at the wellhead station at a depth of ∼1,200 m than at the reference station. Community composition based on taxonomical or functional data showed that the samples taken at a depth of ∼1,200 m were significantly more dissimilar between the stations than at other depths (surface, 100 m, 750 m, and >1,500 m). Both Bacteria and Archaea showed reduced activity at depths of ∼1,200 m when the wellhead station was compared to the reference station, and their activity was significantly higher in surficial sediments than in 10-cm sediments. Surficial sediments also harbored significantly different active genera than did 5- and 10-cm sediments. For the remaining microbial parameters assessed, no significant differences could be observed between the wellhead and reference stations and between surface and 5- to 10-cm-deep sediments.
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