Sterols of a contemporary lacustrine sediment

C₂₆, C₂₇, C₂₈ and C₂₉ sterols, including Δ⁵-, Δ²²- and Δ^5,22-sterols and both 5α- and 5β-stanols, have been identified in the contemporary lacustrine sediment of Rostherne mere (Cheshire, England). Amounts of total sterols decrease from ca. 400 ppm extracted sediment dry weight for the 0–7 cm sediment section to ca. 40 ppm for the corresponding 18–30 cm section. 5α-stanols are of far greater abundance than the 5α-stanol isomers. The carbon number distributions of unsaturated and saturated sterols and the increase in stanol: Δ⁵-sterol ratio with sediment depth provide indirect evidence for the operation of a sterol hydrogenation process. C₂₉ sterols preponderate at lower sediment depths, suggesting a predominantly higher plant input, whereas C²⁷ sterols are more abundant in the surface sediment.