Hydro and biogeochemical investigations of lake sediments in the Kenyan Rift Valley The lakes in the Kenyan Rift Valley offer the unique opportunity to study a wide range of hydrochemical environmental conditions ranging from freshwater to highly saline and alkaline lakes. Because little is known about the hydro and biogeochemical conditions in the underlying lake sediments it was the aim of this study to extend the already existing data sets with data from porewater and biomarker analyses. Additionally reduced sulphur compounds and sulphate reduction rates in the sediment were determined. The new data was used to examine the anthropogenic and microbial influence on the lakes sediments as well as the influence of the water chemistry on the degradation and preservation of organic matter in the sediment column. The lakes discussed in this study are: Logipi Eight (a small crater lake in the region of Kangirinyang) Baringo Bogoria Naivasha Oloiden and Sonachi. The biomarker compositions were similar in all studied lake sediments; nevertheless there were some differences between the saline and freshwater lake…