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. 2012 Jan 9:2:274.
doi: 10.3389/fmicb.2011.00274. eCollection 2011.

Production of Branched Tetraether Lipids in the Lower Pearl River and Estuary: Effects of Extraction Methods and Impact on bGDGT Proxies

Chuanlun L Zhang  1 , Jinxiang Wang, Yuli Wei, Chun Zhu, Liuqin Huang, Hailiang Dong
Affiliations

Production of Branched Tetraether Lipids in the Lower Pearl River and Estuary: Effects of Extraction Methods and Impact on bGDGT Proxies

Chuanlun L Zhang et al. Front Microbiol. .

Abstract

Branched glycerol dibiphytanyl glycerol tetraethers (bGDGTs) are known as bacterial lipids that occur widely in terrestrial environments, particularly in anaerobic peat bogs and soil. We examined the abundance and distribution of bGDGTs in both core (C) and polar (P) lipid fractions from the water column and surface sediments in the lower Pearl River (PR) and its estuary using two extraction methods (sonication vs. Bligh and Dyer). A number of soil samples in the lower PR drainage basin were also collected and extracted for bGDGTs using the sonication method. The results showed aquatic production of bGDGTs as supported by substantial abundances of P-bGDGTs in the water column and sediment samples. The bGDGT-based proxies (BIT, CBT, and MBT) were not affected by the method of extraction when C-bGDGTs were analyzed; in such case, the pH(CBT) of the sediments reflected the soil pH of the lower PR drainage basin, and the temperature close to the annual mean air temperature (MAT) in the lower PR basin. On the other hand, the P-bGDGT-derived proxies were inconsistent between the two methods. The P-bGDGTs (particularly those extracted using the sonication method) may not be reliable indicators of annual MATs.

Keywords: Pearl River; bGDGTs; estuary; paleoclimate proxies.

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Figures

Figure 1
Figure 1
Map of the lower Pearl River and estuary. Insert “A” shows filter samples from water column (solid circles, PR1–PR10) in the lower PR. Insert “B” shows filter samples in the estuary (solid circles, PR11–PR14). Soil samples in the lower PR drainage basin and estuary are shown in white squares. The sediment samples were collected at the same locations at which filter samples were collected.
Figure 2
Figure 2
Core (C)- and polar(P)-lipids (L) of bGDGTs in the water column (A) and sediments (B) from the lower Pearl River to the estuary. Zero distance is arbitrarily set at PR-9 in Figure 1 and increasing distance is toward the estuary. The error bars in (A) represent SD of the average values between the surface water- and the bottom water samples in the estuary.
Figure 3
Figure 3
Comparison of concentrations of C- and P-bGDGTs extracted using the sonication (Soni) and Bligh and Dyer (BD) methods for water column (A,B) and sediment (C,D) samples from the lower Pearl River and estuary. CL, core lipids; PL, polar lipids.
Figure 4
Figure 4
Scatter diagrams of TOC in sediments vs. clay-normalized bGDGTs in ng/g × 102 (A), and pH vs. clay-normalized bGDGTs in ng/g × 102 (B) and TOC-normalized bGDGTs in ng/g × 102 (C) for both sonication (Soni) and Bligh and Dyer (BD) methods. CL, core lipids; PL, polar lipids.
Figure 5
Figure 5
Changes in BIT, MBT, and CBT in the water column from lower Pearl River to the estuary for C-bGDGTs (A–C) and P-bGDGTs (A′–C′) for the sonication and Bligh and Dyer (BD) methods. Zero distance is arbitrarily set at PR-9 in Figure 1 and increasing distance is toward the estuary. The error bars in each panel represent SD of the average values between the surface water- and the bottom water samples in the estuary.
Figure 6
Figure 6
Changes in BIT, MBT, and CBT in the sediments from lower Pearl River to the estuary for C-bGDGTs (A–C) and P-bGDGTs (A′–C′) for the sonication and Bligh and Dyer (BD) methods. Zero distance is arbitrarily set at PR-9 in Figure 1 and increasing distance is toward the estuary.
Figure 7
Figure 7
Comparison of CBT-derived pH to measured pH values of soil and sediments for the sonication (Soni) and Bligh and Dyer (BD) methods. CL, core lipids; PL, polar lipids.
Figure 8
Figure 8
Comparisons of MBT–CBT-derived temperatures from the sonication (Soni) and Bligh and Dyer (BD) methods to measured annual mean air temperature and monthly mean air temperatures of the lower Pearl River drainage basin, and water column temperature in the lower Pearl River and estuary. CL, core lipids; PL, polar lipids.
Figure A1
Figure A1
Structures for branched GDGTs and crenarchaeol.
See this image and copyright information in PMC

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