Assessment of Sedimentary Botryococcenes in Vietnamese Maar Lakes as Paleoclimate Proxies

Summary In contemporary settings, suites of C30-C37 hydrocarbons with botryococcene-related structures, including monocyclic and bicyclic components, have been identified in East African maar lakes and in the Everglades. The sedimentary concentrations of these compounds can be substantive, dwarfing other aliphatic hydrocarbon constituents. Distributions of botryococcenes in sediment samples spanning the past 32 kyr from Lake Masoko, Tanzania, reveal temporal variations attributed to variations in dominant strains of B. braunii rather than a response to changing environmental and climate conditions. Recognition of similar suites of botryococcenes in Vietnamese maar lakes with records that extend back past the Last Glacial Maximum now affords the opportunity to further assess the possibility that botryococcene distributions may record climatic information in these settings. The relative abundances of C34:2 botyrococcene (A) and C34:3 monocyclic botyrococcene (M) in a sediment core from Lake Ia M’He in the Central Highlands of Vietnam, expressed as % M/(A+M), reveals a progressive decrease in the proportions of the monocyclic component relative to the acyclic botyrococcene from the last glaciation to the recent past. These data suggest that assessment of links between the distribution of these specific botyrococcene components in Lake Ia M’He sediments and changes in climate is merited.