Studies on Mediterranean Sea floor microalgae, Egypt

Abstract

The diatom and other microalgal flora of 274 sediment samples taken from 70 different localities along the Mediterranean Sea floor within the Egyptian territories were studied. This study explored the diversification of the microalgal community structure and revealed a clear variation in the paleogeographic and paleoclimatic conditions during the late Holocene. A total of 79 species and varieties from three different divisions (Bacillariophyta, Chlorophyta and Ochrophyta) were identified from the selected studied samples. The predominant taxa recorded were heavily silicified and robust such as Coscinodiscus radiatus, Thalassiosira oestrupii, Paralia sulcata and Actinocyclus octonarius, and mat-forming, e.g. Rhizosolenia pungens and R. settigera. Those diatom taxa were used according to their habitat preferences 7 and ecological conditions to predict the water quality and water level fluctuations. Diatom taxa belonging to fresh water habitat, counted in all sampling sites and at all depths, represent 26.6% of the total number of taxa identified; while the marine species are more represented, being 73.5% of the number counted for all samples studied. The number of fresh water individuals counted in all sites and at all depths was representing 23.3% of the total count, while the brackish and marine individuals represented 76.3%. This showed the quantitative and qualitative dominance of the brackish and marine taxa at all the sites examined.