The source and diagenesis of sediment organic matter in the upper Pearl River Estuary as indicated by amino sugars

The source and diagenesis of sediment organic matter (OM) based on amino sugar yields and compositions were investigated in sediment samples collected along a reach of the upper Pearl River Estuary in south China. Sediment samples were collected from the estuary. Three sediment size fractions—coarse particulate OM (CPOM), fine particulate OM (FPOM), and ultrafiltered dissolved OM (UDOM)—were analyzed for total hydrolysable amino sugars (THAS), total organic carbon (TOC), and total nitrogen (N). THAS contributed much more to sediment TOC and total N in UDOM than in CPOM and FPOM. Percentages of TOC as THAS increased with increasing sediment size. The low glucosamine/galactosamine ratios indicated a relatively large bacterial contribution to the sediment OM size fractions and the less reactive nature of sediment OM in the upper Pearl River Estuary. However, the depletion in muramic acid in the three sediment fractions, especially in UDOM, suggested that living bacteria or intact peptidoglycan units were not a major contributor to sediment OM. The increases of TOC as THAS and C-normalized yields of THAS with the different sediment size fractions demonstrated that they could be used as diagenetic indicators.