Ubiquitous production of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in global marine environments: a new source indicator for brGDGTs

• Published in: Biogeosciences
• Main Authors: Xiao, Wenjie, Wang, Yinghui, Zhou, Shangzhe, Hu, Limin, Yang, Huan, Xu, Yunping
• Other Authors: Xu, YP (reprint author), Shanghai Ocean Univ, Coll Marine Sci, Shanghai Engn Res Ctr Hadal Sci & Technol, Shanghai 201306, Peoples R China.; Xu, YP (reprint author), Peking Univ, Coll Urban & Environm Sci, MOE Key Lab Earth Surface Proc, Beijing 100871, Peoples R China., Shanghai Ocean Univ, Coll Marine Sci, Shanghai Engn Res Ctr Hadal Sci & Technol, Shanghai 201306, Peoples R China., Peking Univ, Coll Urban & Environm Sci, MOE Key Lab Earth Surface Proc, Beijing 100871, Peoples R China., State Ocean Adm, Inst Oceanog 1, Key Lab Marine Sedimentol & Environm Geol, Qingdao 266061, Peoples R China., China Univ Geosci, State Key Lab Biogeol & Environm Geol, Wuhan 430074, Peoples R China., Xu, YP (reprint author), Peking Univ, Coll Urban & Environm Sci, MOE Key Lab Earth Surface Proc, Beijing 100871, Peoples R China.
• Format: Journal/Newspaper
• Language: English
• Published: BIOGEOSCIENCES 2016
• Subjects: TERRESTRIAL ORGANIC-MATTER; CBT PALEOTEMPERATURE PROXY; SEA-SURFACE TEMPERATURE; GDGT-BASED PROXIES; SOUTH CHINA SEA; MEMBRANE-LIPIDS; BIT INDEX; GEOCHEMICAL PROXIES; CONTINENTAL-MARGIN; LAKE-SEDIMENTS; Arctic
• Online Access: https://hdl.handle.net/20.500.11897/458678; https://doi.org/10.5194/bg-13-5883-2016

Presumed source specificity of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from bacteria thriving in soil/peat and isoprenoid GDGTs (iGDGTs) from aquatic organisms led to the development of several biomarker proxies for biogeochemical cycle and paleoenvironmental reconstructions. However, recent studies reveal that brGDGTs are also produced in aquatic environments besides soils and peat. Here we examined three cores from the Bohai Sea, and found distinct difference in brGDGT compositions varying with the distance from the Yellow River mouth. We thus propose an abundance ratio of hexamethylated to pentamethylated brGDGT (IIIa / IIa) to evaluate brGDGT sources. The compilation of globally distributed 1354 marine sediments and 589 soils shows that the IIIa / IIa ratio is generally < 0.59 in soils and 0.59-0.92 and > 0.92 in marine sediments with and without significant terrestrial inputs, respectively. Such disparity confirms the existence of two sources for brGDGTs, a terrestrial origin with lower IIIa / IIa and a marine origin with higher IIIa / IIa, which is likely attributed to a generally higher pH and the production of brGDGTs in cold deep water in marine waters. The application of the IIIa / IIa ratio to the East Siberian Arctic Shelf proves it to be a sensitive source indicator for brGDGTs, which is helpful for accurate estimation of organic carbon source and paleoclimates in marine settings. National Science Foundation of China [41476062] SCI(E) ARTICLE [e-mail] 20 5883-5894 13