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Abstract
The diatom distribution pattern in the bottom sediments of Manzala Lake is very variable and is dependent on many factors. The relative abundance of diatom species has evolved over time, reflecting the change in environmental conditions from the pre-Aswan Dam before 1965 when Nile flood water continuously entered the lake, and the post-Aswan Dam, when the lack of Nile water is compensated by drainage and sewage waters entering the lake. The study was carried out on Recent subfossil material from six core sites taken from Manzala Lake.
A total of 212 diatom species and varieties belonging to 44 genera were identified and counted from 171 samples. The statistical data derived from the relative frequency of the diatom taxa provide fine resolution for paleoecologic interpretation of the recent sediments of the Lake. There are clear changes regarding alkalinity and salinity. The diatom composition of the sediment cores was analyzed by Twinspan program. This classifies the diatom taxa into six main assemblage zones. Each assemblage is mainly related to a certain environmental conditions and reflects recent environmental change. The paleoenvironmental reconstruction results for the lake are discussed in detail. It is concluded that the post High Dam drainage and seepage waters flowing into the lake have caused a change in the composition and distribution pattern of diatoms in the lake.