AME 88:109-122 (2022)  -  DOI: https://doi.org/10.3354/ame01987

ABSTRACT: Microbes are the main drivers of the biogeochemical cycles of carbon and other elements in marine sediments. The distribution of microorganisms, particularly at the centimeter scale, demonstrates the critical role of the local biogeochemical environment. The Atlantic Ocean has enormous hydrocarbon reserves, yet microbial diversity in hydrocarbon reservoir areas, a unique habitat for microorganisms, remains poorly studied. We investigated microbial diversity of sediments from the Gulf of Guinea and the Namibia Slope, 2 oil and gas reservoir areas of the eastern Atlantic Ocean. Microbial diversity was paired with geochemical analyses and provided valuable information in understanding and interpreting the bacterial and archaeal community structure. Environmental factors, especially dissolved inorganic carbon (DIC) and SO₄^2-, drove the microbial community structure in the eastern Atlantic Ocean. Methane oxidation may be coupled with the reduction of sulfate on the continental slope of the Gulf of Guinea, or with nitrate reduction on the Namibia Slope. The sediments there provide a suitable habitat for microbes. However, the composition of microbial communities varied among sites. The microbial diversity and richness in the Gulf of Guinea was high, which may correspond to the high concentration of metal ions. The metabolism of Gammaproteobacteria may respond to the concentration of SO₄^2- and DIC. Asgardarchaeota and Bathyarchaeota could play an important role in carbon reactions, and the abundance and metabolism of Lokiarchaeota may be related to the concentration of metal ions. These findings revealed the microbial diversity and represented a baseline of the microbial communities and constriction in this critical area.

KEY WORDS: Sediment · Porewater · Illumina sequencing · Microorganisms · Hydrocarbon reservoir