The total hydrolysable amino acid (THAA), total organic carbon (TOC), total nitrogen (TN) and the isotopic compositions (13Corg and 15N) of organic matter (OM) were determined in surface sediments of coastal areas of China. The contents of THAA in the sediments are in the range between 440 and 2370 μg/g (dry weight). The TOC, TN, C/N ratios, 13Corg and 15N are in the range of 0.16%~1.08% (wt), 0.05% ~0.20% (wt), 3.3 ~7.7, -25.0‰~-21.2‰ and 3.9‰ ~5.7‰, respectively. The 13Corg values indicate that OM derived from two sources, terrestrial and marine. Ratios of acidic amino acids to neutral amino acids show that the sedimentary environment was slightly alkaline. The spatial distributions of THAA, TOC and TN are broadly similar, suggesting that the OM is closely related to the particle size of the sediments. Factors such as hydrodynamic condition, variation of biomass, degradation of OM and the influx of dissolved inorganic nitrogen from land are responsible for the contributions of amino acid to total nitrogen (TAAN). The potential regeneration of nitrogen from amino acids in the sediments taken from the Yellow Sea is stronger than that from the South China Sea due to the influence of the cold water mass in the Yellow Sea. The contents of TAAN in the sediments taken from Zhejiang to Fujian coastal-line are low, which might be caused by the dilution of large input of inorganic nitrogen. The ratios of Asp/β-Ala, Glu/γ-Aba,(Phe+Tyr)/(β-Ala+γ-Aba)and the principal component analysis (PCA) indicate that the degrees of degradation of sedimentary OM are different from each other in the studied area. With the increasing of OM degradability, contribution of amino acid to TOC (TAAC) reduced correspondingly. The distributions of individual amino acid indicate that the compositions of amino acids in the surface sediments are related to several factors. |