Concentration of branched glycerol dialkyl glycerol tetraethers in surficial sediments of Lake Chala

The fractional abundance of branched glycerol dialkyl glycerol tetraethers (brGDGTs) including 5-methyl and 6-methyl isomers was analyzed in surficial lake sediments from Lake Chala, a small (4.2 km2), deep (~90 m), and permanently stratified tropical crater lake at ~880 m above sea level in East Africa (3°19'S, 37°42'E). The lake sediments were collected in January-February 2010 by gravity coring at three different water depths along a transect from close to the creek inlet (at 64.7 m water depth) towards the depocenter of the lake (at 61.6 m water depth).