Macrobenthic invertebrates in the main channel of Lake Nasser, Egypt

Samples were collected seasonally from ten sectors of the main channel of Lake Nasser during 2013. Macrobenthic community consisted of twenty-four species belonging to three phyla, Annelida (five species), Mollusca (nine species) and Arthropoda (ten species). Annelida ranked the first position and constituted 52% and 68% of total population density (P.D.) and biomass of macrobenthic invertebrates (M.B.I.) respectively. Annual average of M.B.I. was 529 organisms/m2 weighing 2.30 g/m2. The abundance of M.B.I. species was closely related with type of sediments and water level in the lake. Tushka was the richest sector in the area where 1132 organisms/m2 weighing 3.65 g/m2 were recorded, while El-Madiq was the poorest one where 127 organisms/m2 weighing 0.61 g/m2 were recorded. Southern sectors were more populated with bottom fauna than northern sectors. This mostly attributed to the increase of Limnodrilus spp. Benthic fauna attained its maximum during autumn, while summer season sustained the lowest density. Correlation Coefficient revealed strong negative relationships between temperature and the density of oligochaets and arthropods. The highest diversity index (H) and species richness (SR) were calculated in Abu-Simble while, the lowest (H) and SR were calculated in El-Madiq.