Comparative analysis of rotifer community in two Rayahs of River Nile, Egypt

Abstract

The rotifer communities were determined in El-rayah El-Nasery and El-rayah El-Tawfeky (Egypt) as small branches of River Nile by tracking seasonally variations in diversity and population density. It was found that the annual density of rotifers in El-Rayah El-Nasery (5442000 Ind. /m³) was higher than that in El-Rayah El-Tawfeky (3680000 Ind./m³).The highest density of rotifer occurring in spring season but the lowest density occurring in winter season in the two rayahs. A total of 40 rotifer species were identified in the present study. The highest number of species and richness was observed in summer and the lowest number and richness was recorded in winter season. Of these species, Prolides sp, Keratella cochlearis ,k. tropica, Brachionus calyciflorus, B. caudatus, Polyarthra vulgaris, Philodina roseola and Tricocerca pusilla were abundant. 148Gamal M. El-Shabrawy et al. MATERIALS AND METHODS Sites study:Rayahs are the main channels of fresh water from Damietta and Rosetta branches, which are vital for irrigation, navigation, fishing and other domestic uses in Egypt. Two rayahs were investigated in this study;1-El-Rayah El-Towfiky which starts from the Damietta branch at el-Kanater station and extends into the middle and the east of Delta heading north parallel to the Damietta branch until Mansoura city at station (T5) and then heading East ward within Dakahlia governorate even Manzalah city. This rayah extends with average length of 180-200 Km from El-Kanater and with average width 40-50 m and its average depth 2-3 m. this rayah characterized by existence of many water plants and electricity stations on its beaches which include large water stations such as: Banha station and small water stations which heavily scattered on both sides of Rayah. This Rayah branched at the Mansoura city into sub-main branches: the first one: extending north to Damietta city, it is characterized by a lack of water and lack of breadth (little width); almost water disappears in Faraskour city. So the water samples are not collected from this branch. The second: run east to Dekerness, El-Gamalia and El-Manzalah. This branch ends into Manzalah Lake previously but now it doesn't reach it. Also this branch is characterized with abundantly water as compared with the first branch. Seven samples were collected from this branch. 2-El-Rayah El-Nassery starts from the Rosetta branch at El-Kanater and runs in the West ofDelta where it is heading northwest in the direction of Nubaria canal, and meet it at Kanater Pauline (Kom Hamada), then heading to the northwest even Mediterranean Sea breaking Mariot Lake. The length of This Rayah could be up to 200 Km from El-Kanater and with average width 40-50 m and its average depth 2-3 m. This rayah characterized by existence of many water plants and electricity stations on its beaches especially on El Nubaria canal. Eight samples were taken from this rayah. Fig (1): Map of El-Rayah El-Tawfeky and El-Rayah El-Nasery demonstratingthe collected Stations. 149Comparative analysis of rotifer community in t...