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Abrupt onset of carbonate deposition in Lake Kivu during the 1960s: response to recent environmental changes

Pasche, Natacha ; Alunga, Georges ; Mills, Keely ; Muvundja, Fabrice ; Ryves, David ; Schurter, Michael ; Wehrli, Bernhard ; Schmid, Martin

In: Journal of Paleolimnology, 2010, vol. 44, no. 4, p. 931-946

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    Titre
    • Abrupt onset of carbonate deposition in Lake Kivu during the 1960s: response to recent environmental changes
    Auteur
    • Pasche, Natacha. Department of Surface Waters, Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Luzern, Switzerland
    • Alunga, Georges. Institut Supérieur Pédagogique, Bukavu, Democratic Republic of the Congo
    • Mills, Keely. Department of Geography, Loughborough University, LE11 3TU, Leicestershire, UK
    • Muvundja, Fabrice. Institut Supérieur Pédagogique, Bukavu, Democratic Republic of the Congo
    • Ryves, David. Department of Geography, Loughborough University, LE11 3TU, Leicestershire, UK
    • Schurter, Michael. Department of Surface Waters, Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Luzern, Switzerland
    • Wehrli, Bernhard. Department of Surface Waters, Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Luzern, Switzerland
    • Schmid, Martin. Department of Surface Waters, Research and Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 6047, Kastanienbaum, Luzern, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Journal of Paleolimnology, 2010, vol. 44, no. 4, p. 931-946. Springer Netherlands
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:311552
    Summary
    This study interprets the recent history of Lake Kivu, a tropical lake in the East African Rift Valley. The current gross sedimentation was characterized from a moored sediment trap array deployed over 2years. The past net sedimentation was investigated with three short cores from two different basins. Diatom assemblages from cores were interpreted as reflecting changes in mixing depth, surface salinity and nutrient availability. The contemporary sediment trap data indicate seasonal variability, governed by diatom blooms during the annual mixing in the dry season, similar to Lakes Malawi and Tanganyika. The ratio of settling fluxes to net sediment accumulation rates implies mineralization rates of 80-90% at the sediment-water interface. The sediment cores revealed an abrupt change ~40years ago, when carbonate precipitation started. Since the 1960s, deep-water methane concentrations, nutrient fluxes and soil mineral inputs have increased considerably and diatom assemblages have altered. These modifications probably resulted from a combination of three factors, commonly altering lake systems: the introduction of a non-native fish species, eutrophication, and hydrological changes inducing greater upwelling. Both the fish introduction and increased rainfall occurred at the time when the onset of carbonate precipitation was observed, whereas catchment population growth accompanied by intensified land use increased the flux of soil minerals already since the early twentieth century due to more intense erosion