A littoral survey in Lake Tanganyika: spatiotemporal variations in nutrient concentrations, phytoplankton biomass and bathymetry near the Kigoma Region

Nutrient cycling in Lake Tanganyika is influenced by the tilting of the thermocline (Coulter 1991). Prevailing southeast winds during the four month dry season (May through September) cause the thermocline to rise in the south bringing nutrient rich waters from depth to the surface at the southern end of the lake (Coulter 1991). However, related upwelling events also occur in the north, bringing silica, phosphorous and nitrogen rich waters into the epilimnion in the pelagic zone (O’Reilly et al. 2002). Other indications of upwelling include higher wind speeds and a rising thermocline (O’Reilly et al. 2002). Such upwellings may arise from residual internal waves caused by thermocline seiching during the wet season (Coulter 1991) or by weakening in the stability of the thermocline when the upper surface water temperature is cooled by evaporation, convective mixing and wind generated mixing (Naithani et al. 2003).