Abstract
Benthic archaea comprise a significant part of the total prokaryotic biomass in marine sediments. Recent genomic surveys suggest they are largely involved in anaerobic processing of organic matter, but the distribution and abundance of these archaeal groups are still largely unknown. Archaeal membrane lipids composed of isoprenoid diethers or tetraethers (glycerol dibiphytanyl glycerol tetraether, GDGT) are often used as archaeal biomarkers. Here, we compare the archaeal diversity and intact polar lipid (IPL) composition in both surface (0-0.5ĝ€cm) and subsurface (10-12ĝ€cm) sediments recovered within, just below, and well below the oxygen minimum zone (OMZ) of the Arabian Sea. Archaeal 16S rRNA gene amplicon sequencing revealed a predominance of Thaumarchaeota (Marine Group I, MG-I) in oxygenated sediments. Quantification of archaeal 16S rRNA and ammonia monoxygenase (amoA) of Thaumarchaeota genes and their transcripts indicated the presence of an active in situ benthic population, which coincided with a high relative abundance of hexose phosphohexose crenarchaeol, a specific biomarker for living Thaumarchaeota. On the other hand, anoxic surface sediments within the OMZ and all subsurface sediments were dominated by archaea belonging to the Miscellaneous Crenarchaeota Group (MCG), the Thermoplasmatales and archaea of the DPANN (superphylum grouping Micrarchaeota, Diapherotrites, Aenigmarchaeota, Nanohaloarchaeota, Parvarchaeota, Nanoarchaeota, Pacearchaeota and Woesearchaeota). Members of the MCG were diverse, with a dominance of subgroup MCG-12 in anoxic surface sediments. This coincided with a high relative abundance of IPL GDGT-0 with an unknown polar head group. Subsurface anoxic sediments were characterized by higher relative abundance of GDGT-0, -2 and -3 with dihexose IPL types, GDGT-0 with a cyclopentanetetraol molecule and hexose, as well as the presence of specific MCG subgroups, suggesting that these groups could be the biological sources of these archaeal lipids..
| Original language | English |
|---|---|
| Pages (from-to) | 4047-4064 |
| Number of pages | 18 |
| Journal | Biogeosciences |
| Volume | 15 |
| Issue number | 13 |
| DOIs | |
| Publication status | Published - 4 Jul 2018 |
Funding
Acknowledgements. Elda Panoto is thanked for assistance with molecular analyses. We would like to thank the captain and crew of the RV Pelagia as well as the cruise leader, technicians and scientists participating in cruise 64PE301. This PASOM cruise was funded by the Earth and Life Science and Research Council (ALW) with financial aid from the Netherlands Organization for Scientific Research (NWO) (grant 817.01.015) to Gert-Jan Reichart (PI). NIOZ is acknowledged for the studentship of Marc A. Besseling. This research was further supported by the NESSC and SIAM Gravitation Grants (024.002.001 and 024.002.002) from the Dutch Ministry of Education, Culture and Science (OCW) and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 694569 – MICROLIPIDS) to Jaap S. Sinninghe Damsté. We thank Julius S. Lipp, an anonymous reviewer and the associate editor Markus Kienast for providing constructive comments on this paper.
