Expansion of Myriophyllum spicatum (Eurasian water milfoil) into Lake Nasser, Egypt: Invasive capacity and habitat stability

The invasion of Myriophyllum spicatum into Lake Nasser, and its impact on submerged macrophyte communities are quantitatively documented. Samples of macrophytes, water and hydrosoil were collected from 17 sites, in October and November 2002. The average dry weight standing crop of each species per grapnel haul was determined at each depth zone (sampling site). Twenty-one environmental variables were measured (12 water and 9 hydrosoil variables). Canonical correspondence analysis (CCA) was used to determine species–environment relationships. Comparing these relationships of the present study with those detected in 1988–1990 indicated significant changes in water and hydrosoil characteristics. These changes are also implicated in the submerged macrophyte communities. M. spicatum has replaced the originally dominant submerged macrophyte Najas marina subsp. armata. The study indicated that the invasion of M. spicatum depends not only on its attributes, but also on the physico-chemical characteristics of Lake Nasser.