Composition patterns of long-chain alkenones in lacustrine settings

Abstract

Long-chain alkenones have been used widely for reconstructions of paleoclimatological and paleoenvironmental changes, especially in marine environments. Over the last few years, the number of reported cases with alkenones found in lacustrine settings has increased dramatically, providing great potential to be used for terrestrial environmental studies. Here we review the reported occurrences of alkenones from lakes in China and around the world. We then evaluate whether alkenone composition patterns in lakes are distinct from those in marine settings, by comparing their three features: (1) the presence of tetra-unsaturated C37 alkenone (C37:4), (2) the ratio of C37 over C38 contents (C37/C38), and (3) the lack of di- and tri-unsaturated methyl CC38 alkenones (C37:3ME and C38:2ME). We also discuss that in some cases confounding compounds in lacustrine samples could interfere with alkenone peaks and thus could affect the identification of composition patterns. We conclude that alkenone composition patterns in lacustrine settings indeed differ from those in open oceans, which could be used to indicate depositional environments.