Fatty acid composition of surface sediments in the subtropical Pearl River estuary and adjacent shelf, Southern China

Surface sediments (10 cm) of the subtropical Pearl River estuary and adjacent shelf, Southern China were collected. Fatty acids and compound- specific carbon isotopic analyses were determined to infer their sources and biogeochemical cycle of this lipid in the subtropical Pearl River estuary and adjacent northern South China Sea (SCS). The total concentrations of fatty acids ranged from w1.28 to w42.25 mg g 1 dry weight. The levels of polyunsaturated fatty acids (PUFA) were low (0.2e4.8% of total fatty acids), suggesting that fatty acids derived from algae were effectively recycled during the whole settling and depositing process. Bacterial fatty acids were significantly high and terrigenous fatty acids were low in the sediments. Principal component analysis (PCA) of the data also indicates that a clear separation of the biogeochemical sources can be seen. The d13C values of bacterial fatty acids, i.e., i/aiC15 ( 22.9&to 29.4&) suggest that bacteria within the sediments mainly utilize a labile pool of organic matter derived from algae for their growth in the subtropical Pearl River estuary system.