Lipid Compounds and Distribution in the Carcareous Sediments from the Nakagusuku Bay of Okinawa Prefecture

The 12 carcareous sediment samples from the Nakagusuku Bay of the south eastern part of the Okinawa Island of Okinawa Prefecture were analyzed for the mud contents, CaCO_3, δ^C and lipid compounds. The surveyed area are divided into 3 areas, that is, bay head, mid bay and strait. The L/H (L≦C , H≧C ) of n-alkanes is lower in the bay head sediments. The L/H of n-alkanes is higher in the mid bay sediments and strait sediments. A total of 16 4-desmethyl-sterols were identified. The mean value of the 4-desmethyl-sterols in the 11 sediments is 2.08μg/g without one sediment sample that the content of St.11 sediment is 15.09μg/g. The 4-desmethyl-sterols are rich in the bay head sediment samples. The predominant 4-desmethyl-sterols are cholesterol, brassicasterol, stigmasterol and β-sitosterol. In a triangular diagram of C_, C_, C_-sterols, the sediments of the strait are plotted on "open marine". The sediments of the mid bay and bay head are plotted on "estuarine or bay". Fatty acids consist of saturated fatty acids, and mono- and poly-unsaturated fatty acids. Saturated fatty acids were the most abundant compounds class such as C_, C_, C_ and C_. The monounsaturated fatty acids such as C_, C_, and poly-unsaturated fatty acids such as C_, C_ were the abundant compounds. The presence of unsaturated fatty acids implies that the organic matter have not undergone extensive degradation or alteration