1Unité de Recherches en Biologie des Organismes, University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium
2Section de Pétrographie-Minéralogie-Géochimie, Royal Museum For Central Africa, Leuvensesteenweg, 13, B-3080 Tervuren, Belgium
3Tanzania Fisheries Research Institute, P.O.Box 90, Kigoma, Tanzania
4Laboratory of Protistology and Aquatic Ecology, University of Gent (UG), Ledeganckstraat 35, B-9000 Gent, Belgium
5Institut d' Astronomie et de Géophysique G. Lemaître, Université Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve, Belgium
6Department of Research and Specialist Services, P.O. Box 55 Mpulungu, Zambia

Climate variability as recorded in Lake Tanganyika (CLIMLAKE)

Predictive climate models based on observations from the actual and instrumental period must be extended to historical periods such as the last 1500 years from proxies (sediments, ice cores, pollen, tree rings, corals). This is an important objective of several international programs (i.e., IGBP/PAGE, IDEAL). East African lakes are particularly interesting because they are highly sensitive to climate variability (Johnson and Odada, 1996).

The stability of tropical lakes fluctuates widely at high water temperature (Lewis, 1996). For this reason, lake hydrodynamics, which are heavily dependent of weather conditions, govern nutrient distribution in the water column, thereby affecting phytoplankton and food web productivity. During El Niño events, air T° is significantly greater in the Lake Tanganyika area (Plisnier et al., 2000). This could influence the water stability, nutrient distribution, and planktonic communities. Information over the instrumental period may be obtained from molluscs shells geochemistry while diatoms in the sediments are valuable indicators of paleoproductivity and climate changes over hundreds/thousands of years (Gasse et al., 1995).

In the anoxic waters of a lake as deep as Tanganyika, laminated sediments are well preserved. The CLIMLAKE project, financed by the OSTC (Belgian Federal Office for Scientific, Technical and Cultural Affairs), in partnerships with TAFIRI (Tanzanian Fisheries and Research Institute) and the Department of Fisheries (Zambia), is carrying out a study of the present ecological conditions (2002-2004) in Lake Tanganyika as influenced by climate. Two other time scales are investigated: the instrumental period (last 100 years) and the historical period (last 1500 years). The objective is to develop a model (ECO-HYDRO) to be used as a tool for interpretation of the proxy records observed in the lake as well as to better understand the current and changing limnology and fisheries of the lake.