Seminavis aegyptiaca sp. nov., a new amphoroid diatom species from estuary epilithon of the River-Nile Damietta Branch, Egypt

Abstract

During a recent floristic-taxonomic study on the algal flora, including diatoms, from the estuary of the Damietta Branch of the Nile in Egypt, an interesting epilithic diatom species belonging to the genus Seminavis (Naviculaceae) was collected and investigated using both light and scanning electron microscopy. This new diatom species shares morphologically some taxonomic diagnostic features with other related taxa such as S. insignis, S. robusta, and S. ventricosa. However, it still differs by having ventral central striae that are shorter and more or less straight in the middle of the smaller frustules to be clearly radiate in the larger ones and then become geniculate and only radiate near the poles, the central raphe endings are externally more distantly spaced than in the similar species, the elongate central nodule is internally less prominent, and the areola density is much denser. Therefore, we here describe it as Seminavis aegyptiaca sp. nov. Hydrochemical analyses revealed that S. aegyptiaca commonly inhabits typical marine, with a weak tendency towards brackish water, habitats. It was found to be tolerant to meso-eutrophic, nutrient-enriched conditions, based on the data available on seasonal concentrations of N and P compounds. These findings not only contribute to the inventory of Egyptian diatoms, but also increase our understanding of the autecology and distribution of this relatively poorly-known diatom genus.

Taxonomic and Ecological Observations on Some Algal and Cyanobacterial Morphospecies New for or Rarely Recorded in Either Egypt or Africa

“…As regards diatoms, curved forms of Aulacoseira ambigua f. japonica were observed in the River Nile basin for the first time in Egypt, and this observation also represented the second record for the whole African continent (Janse van Vuuren et al, 2018). As part of the ongoing PhyBiO project on the diversity and distribution of the Egyptian algal flora, the new epilithic amphoroid diatom species Seminavis aegyptiaca has also been discovered from the Damietta Branch estuary of the River Nile (Saber et al, 2020).…”

“…As regards other algal groups, some species new to science, e.g. Euastrum elfarafraense (Desmidiales, Streptophyta) (Saber et al, 2018b), and Seminavis aegyptiaca (Naviculales, Bacillariophyta) (Saber et al, 2020) have also been recently discovered from different Egyptian biotopes, providing some evidence for the possible occurrence of algal endemism in Egypt, pointing to this country as a shrine of relevant algal and cyanobacterial diversity. With respect to diatoms, our findings confirm the limited knowledge of the diversity of diatom species in the Egyptian habitats.…”

“…It is dammed about 20km inland of the river mouth by an engineered dam known as Faraskur Dam Barrage, forming the estuary. Along its main basin, the Damietta Branch serves as a pivotal water artery for a wide range of domestic, industrial, and agricultural, activities (Saber et al, 2020). The cyanoprokaryote Lemmermanniella uliginosa (Synechococcales, Cyanobacteria) was sampled on October 14 th 2016 from metaphytic materials in an inland, mineral, ambient spring known as "Ain Al-Molouk" (29° 11′ 2.7″ N, 25° 33′ 9.5″ E) in the Siwa Oasis (Western Desert, Egypt) at an elevation of -7.0±9.1m b.s.l.…”