Paleolimnology of Lake Kivu: Past Climate and Recent Environmental Changes
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This chapter reviews the sedimentation history of Lake Kivu back to 14,000 years before present (BP). Similar to other African lakes, the water level of Lake Kivu was lower during the dry period before 12,000 years BP. Maximum lake levels due to a more humid climate were recorded between 10,000 and 8,000 years BP. The Lake Kivu basin was probably closed between 8,000 and 6,800 years BP. The sediment record of Lake Kivu revealed dramatic changes around 5,000 years BP. The more recent past sedimentation (∼200 years) is investigated with a short core from the main basin. The sediment core revealed an abrupt change ∼50 years ago, when carbonates started to precipitate. Since the 1960s, the sedimentation fluxes of nutrient and soil minerals have increased considerably, while diatom frustules have decreased. These modifications are probably underlain by three non-mutually exclusive processes, namely: (1) the reduced top-down control over phytoplankton following the introduction of the non-native Tanganyika sardine, (2) bottom-up effects due to increased external nutrient inputs caused by the fast-growing population, and/or (3) increased rainfall leading to higher discharge of the subaquatic springs and thus enhanced upwelling of nutrient-rich deep water. These alterations might have induced a higher productivity in the lake, leading to increased sedimentation and to the onset of carbonate precipitation.
KeywordsTotal Phosphorus Sediment Core Lake Level Diatom Assemblage Carbonate Precipitation
This work was supported by the Swiss National Science Foundation and the Swiss Agency for Development and Cooperation under grant 207021-109710 (Nutrient cycling and methane production in Lake Kivu).
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