Some records of diatoms indicators of nutrient enriched freshwaters new for Egypt

During our investigation on the biodiversity and distribution of freshwater benthic diatoms in Egypt, applying start-of-the-art integrated diatom taxonomy standards, the small-sized naviculoid Sellaphora crassulexigua and S. saugerresii, Achnanthidium eutrophilum, and the centric diatom Cyclostephanos makarovae were discovered in the Damietta Branch of the Nile River, and identified as new records for the Egyptian freshwater diatom flora. Investigations coupled the description of diatom morphological diagnostic features, through light and scanning electron microscopy approaches, with the characterization of their ecological niche, indicating N and P enrichments and a general eutrophic state of the Damietta Branch of the Nile River waters. Considering their ecology and distribution, it is highly likely that these diatom species have been overlooked in the previous Egyptian studies due to the dependence of traditional taxonomic work upon light microscopy only. All these species, with the possible exception of Sellaphora crassulexigua, that might be linked to water-level fluctuations, are typical of fresh waters affected by nutrient enrichment and organic pollution, and are thus strategic indicator species in water-quality assessment systems.