Environmental Dynamics of Lake Victoria: Evidence from a 10,000 14C yr Diatom Record from Napoleon Gulf and Sango Bay

Abstract

Bio-proxies provide relevant information on ecosystem health and environmental dynamics. In this study, diatom assemblages of two cores collected from the Ugandan side of Lake Victoria at Napoleon Gulf ("NAPG1" (GPS, 00º25'44.5" N, 033º14'10.4" E)) and Sango Bay ("SAGB2" (GPS, 00º51'48.0" S, 031º42'47.8" E)) provide evidence of long term changes in the Lake Basin from ca 10,500 years to present. Diatom information was supported by phytolith data from the same cores. The period from ca 10,500-8,100 calyrBP experienced moderate precipitation, strong turbulence with reduced forest cover in the lake's catchments. During the phase ca 8,100-6,600 calyrBP, the lake basin experienced increased precipitation but with reduced mixing of the water column. This period was also characterized by increased forest vegetation cover as reflected by phytolith assemblages. The period from ca 5,900-1,400 calyrBP was characterized by regular changes in precipitation, turbulence and vegetation taxa in the catchment areas. The phase from ca. 1,800 calyrBP to present was characterized by significant increase in Fragilaria and Nitzschia species as well as increase in Nitzschia: Aulacoseira ratio which may be attributed to human involvement in the ecological functioning of Lake Victoria ecosystem.