Several unexpected marine sterols in a freshwater sediment

Some unexpected stanols, 22,23-methylene-23,24-dimethyl-5α(H)-cholestan-3β-ol (gorgostanol and the related stenol), 24,26-dimethyl-5α(H)-cholestan-3β-ol (aplystanol) and most probably 24-isopropyl-5α(H)-cholest-22-en-3β-ol, have been found in the sediment of a eutrophic pond. These compounds possess side chains which have until now been considered to belong exclusively to sterols of marine origin. The presence of these stanols in a freshwater sediment suggests that considering their side chain structures as specific marine input markers can lead to erroneous conclusions. The vertical distribution of these compounds along a 6 m core shows that they arise from organisms which still exist except for aplystanol which was found only in the sections below 5 m