Source and implication of fatty acids in surface sediments from the Pearl River Mouth Basin, South China Sea

摘要

Present study consists the fatty acid composition of five samples of Site 4B surface sediment from the Pearl River Mouth Basin in the South China Sea. Total fatty acid (TFA) content of the ranged from 5.14 mu g/g to 8.99 mu g/g (mu g FA/g dry sediment), and the carbon number ranged from C-12 to C-32. The fatty acids detected in the five surface samples include the normal saturated fatty acids, branched-chain fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and isoprenoid acids. Short-chain fatty acids in the normal saturated fatty acids were mainly from the marine microorganisms, whereas the long-chain fatty acids were from terrigenous higher plants. The higher concentration of short-chain fatty acids relative to the long-chain fatty acids indicates that the input from marine microorganisms in the surface sediment is far greater than that from terrigenous higher plants. The branched-chain fatty acids i/a15:0, i/a17:0, and 1 Ome16:0 and the monounsaturated fatty acids 18:1(09 and 16:10)9 were mainly synthesized by sulfate-reducing bacteria, whereas 16:1 omega 7 was from the sulfur-oxidizing bacteria. Relative content of the different fatty acids indicate that the surface sediment is dominated by a reductive environment. In addition, eight isoprenoid acids including phytanic acid, 17 beta(H),21 beta(H)-32-bi-homohopanoic acid, and pristane acid were detected in the surface sediment, and they mainly originated from chlorophyll a and bacteria.