Pronounced occurrence of long-chain alkenones and dinosterol in a 25,000-year lipid molecular fossil record from Lake Titicaca, South America

Calibration of alkenone unsaturation index with growth temperature for a lacustrine species, Chrysotila lamellosa (Haptophyceae)

“…Parke, 1974Parke, , 1975Green and Course, 1983) and that the same alkenone distribution pattern was found in this study and in the sediments from many lakes, we think that C. lamellosa is not only the alkenone precursor organism in Lake Xiarinur but, furthermore, is one of the most common precursors of alkenones in lacustrine systems. However, C 38 methyl alkenones have been found in other lakes such as Lake Balikun (Chu et al, 2005), Lake Titicaca (Theissen et al, 2005), and some lakes in Germany (Zink et al, 2001) and Greenland (D'Andrea and Huang, 2005). This shows that there are other precursor organisms, as yet unknown, occurring in lacustrine systems.…”

“…doi:10. /j.orggeochem.2007 have led to numerous studies of alkenone distributions and their relationship with temperature in limnic environments (Li et al, 1996;Thiel et al, 1997;Innes et al, 1998;Sheng et al, 1998;Wang and Zheng, 1998;Zink et al, 2001;Sun et al, 2004;Chu et al, 2005;D'Andrea and Huang, 2005;Theissen et al, 2005;Liu et al, 2006). Studies of the marine environment indicate that the U K 0 37 temperature relationships for the species C. lamellosa, I. galbana, E. huxleyi and G. oceanica differ significantly from each other (Marlowe et al, 1984;Brassell, 1993;Volkman et al, 1995;Sawada et al, 1996;Conte et al, 1998;Epstein et al, 1998Epstein et al, , 2001Yamamoto et al, 2000;Versteegh et al, 2001;Prahl et al, 2006a,b).…”

Late Quaternary climate variability and terrestrial carbon cycling in tropical South America

“…Alkenones, unsaturated methyl and ethyl C 37-40 n-ketones derived from coccolithophores and other phytoplankton, are ubiquitous in marine settings and also commonly found in lacustrine settings worldwide, including Lake Titicaca (Cranwell, 1985;Theissen et al, 2005). While the exact species producing lacustrine alkenones have not yet been identified, these molecules are almost certainly derived from aquatic algal organisms (Cranwell, 1985).…”

Origin and palaeoenvironmental significance of C25 and C27 n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa

“…The occurrence of long-chain n-alkenes (n-C23 to n-C31) in various types of lacustrine sediments has frequently been reported (e.g. Jaffé et al, 1996;Zhang et al, 2004Zhang et al, , 2011Theissen et al, 2005;de Mesmay et al, 2007), but even though these potential biomarkers sometimes dominate the apolar fraction of organic sediment extracts, their origin and fate remains ambiguous and are sometimes not even addressed. One major reason for this apparently modest interest is that sedimentary n-alkenes can have multiple natural sources.…”

“…In some studies they are argued to derive from allochthonous sources such as higher plants, including marginal reeds, ferns and peat (Giger et al, 1980;Cardoso et al, 1983;Cranwell et al, 1987;Duan and Ma, 2001). In other studies the compounds are attributed to an autochthonous (aquatic) source, such as algae in general (Jaffé et al, 1996;Zhang et al, 2004;Xu and Jaffé, 2009), cyanobacteria (Gelpi et al, 1970), or specific algal species such as the green alga Botryococcus 3 braunii race A (Theissen et al, 2005). Some studies interpret the n-alkenes as resulting from a mixture of both microalgae and higher plant input (e.g.…”