DISTRIBUTION AND ORIGIN OF DIATOMS IN THE BOTTOM SEDIMENTS OF THE SUEZ CANAL LAKES AND ADJACENT AREAS, EGYPT

Abstract

The diatom assemblages in the bottom sediments of Timsah Lake and adjacent sites, including the Great Bitter Lake, the northern part of the Gulf of Suez and the Mediterranean Sea at the entrance of the northern canal, have been recovered and studied in detail. A total of 394 species and varieties belonging to 96 genera were identified. Of these, 263 diatom taxa were detected in Timsah Lake sediments, 151 species and varieties from the sediments of the Great Bitter Lake, 119 from sediments of the northern part of the Gulf of Suez, and 167 from the coastal sediments of the Mediterranean Sea. The distribution pattern of the diatom assemblages in these studied sites are related to a variety of changes in the palaeoecological conditions, including current direction, sea-level fluctuations, salinity and climatic changes. The Timsah Lake is considered to be a mixing zone characterized by the occurrence of both autochthonous and allochthonous diatoms, as its basin floor includes taxa transported from both the Mediterranean and Great Bitter Lake through the Suez canal. The composition of the diatom assemblages indicates that non-planktonic taxa dominate over the planktonic forms. The assemblages are composed mainly of temperate littoral and shallow cosmopolitan marine species, accompanied by a considerable number of non-marine taxa, which are normally allochthonous and probably originated from the adjacent areas.