| Oligotrophic marine sediments cover nearly 90% of the ocean's floor, yet in contrast to the continental margins, their biogeochemistry and microbiology has been little explored. Oligotrophic sediments exhibit dramatic nutrient limitation due to the slow rain rate of photosynthetic carbon, and consequently display a greatly expanded zone of higher-energy electron accepting activities relative to margin sediments. The working hypothesis that the most-energetic available electron acceptor structures subsurface microbial communities predicts that different microbial lineages occur in oligotrophic vs. organic-rich margin sediments. This study examines this hypothesis by considering the archaeal diversity, as revealed in clone libraries, for an ultraoligotrophic, fully oxic site, as well as the archaeal and bacterial diversity of an oligotrophic, oxic/suboxic site. Finally, I compare the archaeal diversity of available oligotrophic and representative continental margin sites, and find evidence for oligotrophic sediments as hosting a distinct, deeply divergent assemblage of Archaea, possibly adapted to exploit the higher-energy electron acceptors present therein. |
