FIG 1.

Relative abundances of 16S rRNA gene tags for bacteria (genus level) (A) and archaea (family level) (B) in the ambient, oily, and asphalt sediment. For each sample and depth, only the 10 most abundant clades are depicted. In the ambient sediment, the sequences of mostly aerobic and partly planktonic microorganisms were found. The oily site contained many archaeal sequences related to ANME-1, “Ca. Methanoliparia,” and “Ca. Argoarchaeum” (GoM-Arc1) as well as Deltaproteobacteria described as oil degraders (Desulfobacula, Syntrophaceae) and syntrophic partner bacteria of ANME (SEEP-SRB1). In the asphalt sediment, sequences of “Ca. Methanoliparia” were found only in the proximity of the asphalt pieces.