Free,esterified and residual bound sterols in Black Sea Unit I sediments |
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| Authors: | JW de Leeuw WIrene C Rijpstra PA Schenck JK Volkman |
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| Institution: | Delft University of Technology, Department of Chemistry and Chemical Engineering, Organic Geochemistry Unit, de Vries van Heystplantsoen 2, 2628 RZ Delft, The Netherlands;Organic Geochemistry Unit, School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom |
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| Abstract: | Detailed compositional data for the sterols isolated from a surface, Unit I, sediment from the Black Sea are reported. A procedure based on digitonin precipitation has been used to separate the more abundant free sterols from those occurring in esterified forms. Saponification of the solvent extracted sediment residue liberated only a small quantity of residual bound sterols in contrast to studies of other sediments. 4-Methylsterols are much more abundant than 4-desmethylsterols in both the free and esterified sterol fractions which we attribute to a major dinoflagellate input, as in deeper Unit II sediment. The desmethylsterol fraction appears to derive from a variety of sources including dinoflagellates, coccolithophores, diatoms, terrigenous detritus and perhaps invertebrates. 5α(H)-Stanols are particularly abundant in the free sterol fraction. An analysis of the stanol/stenol ratios suggests that the 4-desmethyl-5α(H)-stanols are the result of specific microbial reductions of Δ5-sterols and/or the reflection of a contribution of stanol containing source organisms. |
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