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

Abstract

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 R b/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.

Predominance of hexamethylated 6-methyl branched glycerol dialkyl glycerol tetraethers in the Mariana Trench: source and environmental implication

“…To our knowledge, there are only two studies reporting GDGTs in the Mariana Trench. Guan et al (2019) investigated iGDGT distribution in the surface sediments (4900-7068 m depth) from the southern Mariana Trench, while Ta et al (2019) analyzed iGDGTs and brGDGTs in two sediment cores (ca. 5400 m depth) in the subduction plate of the Mariana Trench.…”

“…However, one weakness of these proxies is the source uncertainty. Although brGDGTs were assumed to be specific for soil and peat bacteria (Hopmans et al, 2004;Weijers et al, 2007a, b), different compositions of brGDGTs among rivers (Zhang et al, 2012;Zell et al, 2013Zell et al, , 2014a, lakes (Sinninghe Damsté et al, 2009;Tierney and Russell, 2009;Loomis et al, 2011;Buckles et al, 2014), marine waters (Liu et al, 2014;Xie et al, 2014;Zell et al, 2014b), and sediments (Peterse et al, 2009;Zhu et al, 2011;Xiao et al, 2016) suggest multiple sources. Besides temperature and pH, oxygen (Qin et al, 2015) and moisture (Dang et al, 2016a) can also influence the composition of GDGTs.…”

The Sources of Organic Carbon in the Deepest Ocean: Implication From Bacterial Membrane Lipids in the Mariana Trench Zone

“…Unusually High Proportions of BrGDGTs in Oceanic Trench Sediments and Altered -Rocks BrGDGTs have been reported in the trench sedimentary environments, such as the Mariana Trench (Ta et al, 2019;Xu et al, 2020), the Kermadec Trench (Xu et al, 2020), and Atacama Trench (Xu et al, 2020). One notable observation was that relative high abundance of BrGDGTs was examined at two sites with water depths shallower than 6,000 m in the Mariana trench (Ta et al, 2019). In consistent to result of Ta et al (2019), our data further shows that approximately 58% of the sediment samples had BIT values over 0.15.…”

Intact Ether Lipids in Trench Sediments Related to Archaeal Community and Environmental Conditions in the Deepest Ocean

“…As a result, the source of GDGTs and the benthic archaeal community could not be reconstructed since important source information was lost during the IPL degradation into CLs. Furthermore, the studies of Guan et al (2019) and Ta et al (2019) are based on a single trench, which cannot mirror the entire hadal zone that is composed of over 30 trenches with different terrestrial influence, primary productivity, and maximum depth (Jamieson, 2015;Xiao et al, 2020;Xu et al, 2018).…”