An examination of factors controlling biogenic silica preservation in modern sediments from east-central Lake Tanganyika, East Africa

The biogenic silica (BSi) content of sediments has been used to infer past primary productivity in marine and lacustrine systems (Johnson et al., 2002; Verschuren et al., 2002). Biogenic silica is derived from the fossil remains of diatoms, sponge spicules, and plant phytoliths; however, diatoms make up the overwhelming source of BSi in most aquatic systems. Diatoms are important primary producers in Lake Tanganyika, comprising on average 1215% of phytoplankton chlorophyll A in the upper 20 m in the southern basin and Kigoma area (Climlake, 2005). Although BSi abundance in historical sedimentary records can be a powerful primary productivity indicator when applied carefully, it is essential to have a thorough understanding of the physical and chemical processes involved in the production, transport, and preservation of BSi in sediments before interpreting past sedimentary records.