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Abstract
The present work concerned with the study of biodiversity of order Naviculales in Egypt. Examination
of 154 diatom samples collected from different aquatic habitats in Egypt has been carried out. A total of 146
diatom taxa related to 18 genera and 4 families belonging to order Naviculales were identified in this study. Three
taxa of the total recorded ones have been considered as unknown species and 35 taxa have been considered as new records to Egypt. All the identified taxa were morphologically described and photographed using light microscope. The ecology and geographical distribution in Egypt so far as known were given for each taxon.
Synonyms of the recorded taxa were given when sufficient data are available. Identification keys are
constructed for the various taxonomic categories below the order level.
Family Naviculaceae (represented by 12 genera) was the dominant family and Navicula has the greatest diversity, including 34 taxa. The most widespread taxa that recorded in the present study were Navicula cryptocephala, Navicula cryptocephala var. veneta, Navicula cuspidata, Navicula cuspidata var. ambigua, Amphora coffaeiformis, Gomphonema parvulum, Navicula rhynchocephala, Navicula gastrum, Navicula pygmaea and Diploneis ovalis.
Alkaliphilous taxa were the dominant during the present work. The identified naviculoid diatoms in the present study could be classified according to their
salinity tolerance into three forms: oligohalobous, mesohalobous and euhalobous. The eco-diatomical analysis indicated that many naviculoid diatoms could be used as indicators of different degrees of pollution:
oligosaprobic, β-mesosaprobic, α- mesosaprobic and α- meso-/polysaprobic systems.
The results of the present study reflected and emphasized on the importance of naviculoid diatoms not
only due to their remarkable diversity and prevalence but also due to their great value as bioindicators of many
ecological parameters.