Sample preparation and analysis for C content of wood and sediment samples followed methodologies outlined by Tue et al. (2011). Briefly, the wood and sediment samples were completely dried at 60 °C in a drying oven, and subsequently pulverized using an agate mortar and pestle. For sediment organic C analysis, the pulverized sediments were first treated with acid HCl 1N for 24 h to remove carbonates. After acid treatment, the samples were thoroughly rinsed by Milli-Q filtered distilled-deionized water and re-dried at 60 °C in a drying oven for 24 h. The C content of the sediment and wood samples was analyzed by a combustionmethod using an element analyzer connected to an isotope ratio mass spectrometer (ANCA-GSL; Sercon, UK).