Electron shuttling mediated by humic substances fuels anaerobic methane oxidation and carbon burial in wetland sediments

Profiles of ARGs and their relationships with antibiotics, metals and environmental parameters in vertical sediment layers of three lakes in China.

Heavy metals, pharmaceuticals, and other wastes released into the environment can significantly influence environmental antibiotic resistance. We investigated the occurrence of 22 antimicrobial resistance genes (ARGs) and 10 heavy metal concentrations, and the relationship between ARGs and heavy metals in surface sediment from seven sites of Lake Taihu. The results showed significant correlations (p

/pdf/distribution-and-relationship-between-antimicrobial-3ju3mtg8dr.pdf

Distribution and relationship between antimicrobial resistance genes and heavy metals in surface sediments of Taihu Lake, China.

. Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures
from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a
full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in
three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling
an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs)
are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and
nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset
( n =  182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors
from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the
biological underpinnings of their structural diversity. Warm-season temperature indices outperformed MAT in our regressions, with the mean temperature of months above
freezing yielding the highest-performing model (adjusted R2 =  0.91, RMSE  =  1.97  ∘C , n =  182). The natural
logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R2 =  0.83, RMSE  =  0.66,
 n =  143), notably outperforming pH in our dataset (adjusted R2 =  0.73, RMSE  =  0.57, n =  154) and providing a potential new
proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail
the advantages and disadvantages of each.

/pdf/revised-fractional-abundances-and-warm-season-temperatures-320g203swx.pdf

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Stratiform siderites from the Mesoproterozoic Xiamaling Formation in North China: Genesis and environmental implications

Biogeochemical processes controlling authigenic carbonate formation within the sediment column from the Okinawa Trough

The effect of methane seeps on the bacterial tetraether lipid distributions at the Okinawa Trough

Characteristics and implications of isoprenoid and hydroxy tetraether lipids in hadal sediments of Mariana and Yap Trenches

Hadal trenches have higher microbial carbon turnover rates as compared to adjacent abyssal plains. However, the source of organic carbon in the trench remains enigmatic. In this study, we show that a fraction of organic carbon is possibly derived in-situ and correlated with chemoautotrophic communities supported by the fluid discharge of water-rock interaction in the trench wall, based on analysis of glycerol dialkyl glycerol tetraether (GDGT) membrane lipids, including archaeal isoprenoid GDGTs (IsoGDGTs) and bacterial branched GDGTs (BrGDGTs), in sediments and rocks of the Mariana and Yap Trenches, northwest Pacific Ocean. These trench sediments contained relative higher BrGDGTs ratios, which was a rare observation in the open ocean. The BrGDGT-to-IsoGDGT ratios ranged in 0.02–0.88 (mean=0.10±0.11) in sediments and 0.09–0.38 (mean=0.17±0.13) in altered rocks. The calculated values of branched and isoprenoid tetraether (BIT) index ranged from 0.02–0.73 (mean=0.18±0.11) in sediments and from 0.16–0.9 in altered rocks (mean=0.37±0.27). Moreover, these GDGTs exhibited similar characteristics to those of altered basalt rocks, indicating inputs of organic carbon from the trench subsurface environment. Thus, in addition to organic-rich material settling, we propose chemoautotrophic activity in oceanic crust could be an additional source of organic carbon in the deepest part of the ocean, with an important role in deep-sea carbon cycles.

/pdf/the-sources-of-organic-carbon-in-the-deepest-ocean-2v2jq1c6w6.pdf

Zhiyan Chen

Papers

Biogeochemical processes controlling authigenic carbonate formation within the sediment column from the Okinawa Trough

The effect of methane seeps on the bacterial tetraether lipid distributions at the Okinawa Trough

Characteristics and implications of isoprenoid and hydroxy tetraether lipids in hadal sediments of Mariana and Yap Trenches

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