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

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