Distributions and Sources of Glycerol Dialkyl Glycerol Tetraethers in Sediment Cores From the Mariana Subduction Zone

Glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitously found in marine sediments. However, their presence, distributions, and sources in the subduction zone are not fully understood. We investigated isoprenoidal GDGTs (isoGDGTs) and branched GDGTs (brGDGTs) in two sediment cores from the sou...

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Published in:Journal of geophysical research. Biogeosciences 2019-04, Vol.124 (4), p.857-869
Main Authors: Ta, Kaiwen, Peng, Xiaotong, Xu, Hengchao, Du, Mengran, Chen, Shun, Li, Jiwei, Zhang, Chuanlun
Format: Article
Language:English
Subjects:
Archaea
Bacteria
BIT
brGDGTs
Carbon cycle
Cores
distribution
Glycerol
in situ
Lipids
Marine sediments
Microbial activity
Microorganisms
Oceanic trenches
Plate tectonics
Profiles
Sediment
Sediment samplers
Sediment samples
Sediments
Subduction
Subduction (geology)
subduction zone
Subduction zones
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Summary:Glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitously found in marine sediments. However, their presence, distributions, and sources in the subduction zone are not fully understood. We investigated isoprenoidal GDGTs (isoGDGTs) and branched GDGTs (brGDGTs) in two sediment cores from the southern and northern subduction plates of Mariana Trench, respectively. IsoGDGTs and brGDGTs exhibited covariation in most sediment samples, and total GDGT concentrations reached a maximum at the subsurface sediment depth ~10 cm. Concentrations of isoGDGTs and brGDGTs were clearly elevated at depths of ~10 and ~45 cm. These indicated that microbial activities potentially influenced the production of the specific membrane lipids of archaea and bacteria. We found that the branched and isoprenoid tetraether index and Rb/i values increased with depth profiles of the Mariana subduction zone, suggesting that deeper sediments likely hosted more brGDGT‐producing bacteria than crenarchaeol‐producing archaea. The extremely high abundance of cyclopentyl rings in brGDGTs was determined in subsurface sediments. We further proposed that most of the brGDGTs in sediments were produced in situ in the Mariana subduction zone. This study highlights that the extremophilic microbial communities of the Mariana subduction zone may represent a significant component of the global carbon cycle. Key Points Concentrations of isoGDGTs and brGDGTs in two sediment cores were clearly elevated at depths of ~10 and ~45 cm Deeper sediments host more of brGDGT‐producing bacteria than the isoGDGT‐producing archaea Most of the brGDGTs in sediments are likely to be produced in situ in the Mariana subduction zone
ISSN:2169-8953
2169-8961
DOI:10.1029/2018JG004748