General framework Lake Tanganyika is one of the oldest lakes in the world. Its present limnological cycle shows that it is very sensible to climate variability (Coulter, 1991; Plisnier et al., 1999). The winds and the air temperature fluctuations influence the mixing of the lake, allowing access of nutrient-rich deeper water toward the surface where biotic production takes place. When organisms die, they accumulate into layers at the bottom of the lake, where some of them may be identified and related to the lake conditions prevailing at the time of their deposit. Specific tasks The objective of the project was to check the possible influence of climate variability on Lake Tanganyika at two scales of time: the recent period (+/- last 50 years) and the last 1000 years. For the recent period, the project studied the teleconnections between ENSO and various data (oceanic, climatic, remote sensing data from NOAA/AVHRR, hydrological…) in the Lake Tanganyika area. For the last 1000 years, paleo-signals were studied in the sediments of the lake. The finely laminated sediments were studied particularly using diatom composition and thin sections analysis. Significant ENSO teleconnections were found with average air temperature, maximum and minimum air temperature, humidity, rainfall, winds, pressure and radiation. The project showed that the ENSO impact is highly differentiated in space in the investigated East African area. Many previous studies have postulated a single, region-wide impact of ENSO. It appears that the direction, magnitude and timing of this impact is controlled by the climate system at a regional scale and at a more local scale – e.g. as influenced by the presence of large lakes, local topography or proximity to the coast. During an expedition, 16 cores were retrieved in the southern basin of the lake, between 330 and 1200m water depth. Although 230 diatom taxa were observed in the two cores studied, only a few taxa were relatively abundant. In the upper finely laminated sediments “long” Nitzschia’s and Gomphonema clevei were relatively the most important diatoms, followed by Nitzschia lancettula, N. vanoyei, N. frustulum, N. fonticola and Gomphonitzschia spp. The diatom record revealed a cyclicity, with a provisionally estimated period of about 200 years, in the Kasaba core. This might be related to a 200 years cycle in the sun activity but this needs to be confirmed by data from longer or more time series. Among the diatoms, “long” Nitzschia spp. most clearly demonstrate this cyclicity. They are pennate, planktonic species which can replace Cyclostephanos spp. (centricate planktonic diatoms) in the plankton of East African lakes when Si/P ratios decrease (Haberyan and Hecky, 1987). The lack of well preserved undisturbed sediment prevented a close study of the ENSO signal in the sediment. The recent ENSO signal confirmed the hypothesis that ENSO may impact significantly the climate in the Lake Tanganyika area and the mixing conditions of the lake in the actual period. It was recommended that a monitoring in various fields (climate-hydrodynamics-phytoplankton…) could provide the required information to interpret the sediments signals and decrypt the coded information stored in the sediments.