Environmental drivers for the distribution of Najas marina L. subsp. armata in Lake Burullus, Egypt

Najas marina L. subsp < em>. armata (Lindb.f.) Horn, family Najadaceae, which called Horreish in Egypt, is a submerged aquatic plant, inhabits fresh or brackish water. The plant collected from Nasser Lake (Egypt), dried, and kept to be used later as a vital source of fodder for sheep and goats in dry periods as it is offered in local markets as food in Hawaii.  This work is the first study on N. marina in the Nile Delta of Egypt as the global studies were rare and outdated. The ultimate goal of this work is to specify the environmental agents (water and sediment) controlling the N. marina distribution in Lake Burullus, identify the plant communities associated with N. marina, and assess the plants-environmental agents' relationship. Results obtained by Canonical Correspondence Analysis (CCA) indicated that the major efficacious environmental agents (water and sediment) that affect the distribution of N. marina in Lake Burullus, were salinity factors as, EC, TDS, Cl^-, HCO₃^- and some elements as Na⁺ and Mg⁺⁺ as well as nutrients (TN and TP). The analysis of Two Way Indicator Species Analysis (TWINSPAN) revealed six clusters (A-F); the indicator species were as follow, cluster A, Arthrocnemum macrostachyum; cluster B, Juncus acutus; cluster C, Suaeda vera; cluster D, Potamogeton pectinatus; cluster E, N. marina; cluster F, Phragmites australis. In addition, CCA analysis showed that there is a positive relationship between N. marina distribution and nutrients agents, but a negative relationship between the target plant and salinity agents. The studied locations in the north section were higher in salinity than that of the southern locations. It worth mentioning that the plant was disappeared from El Kom El Akhdar where the EC value was 13.7 mS/cm and TDS was 7.6 mg/l. Also, the plant was not found in the northeastern section, where the fishermen reported that the opening of Al-Bughaz increases the water salinity, and N. marina not found. Generally, the reciprocal relationship of plants-environment is embedded in all living systems, which are the fundamental basis for the various types of sustainable improvement, especially the essential basis for water sustainable development. Community features of the aquatic plants are essential indicators for water quality.