The present study included the effect of chronic exposure for two concentrations of NaC؛ salt on the biology of fresh water zooplankton species Brachionus calyciflorus (from ^otifera). The concentrations 0.5 , 0.75%o were used for chronic exposure to investigate its effects on the life tables, range of the rate of expectation for further life and reproduction. The rotifer B. calyciflorus was sensitive to salinity and may tried to protect the species by increasing the size (2.22 ind./clutch lor control group and 2.9ة for 0.5%o concentration) and number of clutches produced ؟.1؛ clutch/female for control group and 2.9 ' ' ' for 0.75 %0 concentration) beside stimulation the animal to produce the first clutch of eggs earlier■ ٨ small reduction in mean longevity of the animal was noticed (8.1 day for control grou^ and7.١ day for 0.75 %0 concentration) while there was no effect on its average length and daily increasing during its life span

تضمن البحث الحالي دراسة تأثير التعرض المزمن لتركيزين ملحيين من محلول الطعام في حياتية نوع من الهائمات الحيوانية للمياه العذبة

The effect spatial and temporal changes of benthic invertebrate's composition were studied in two selected sites, before and after north part of Main Drainage Channel meeting within drainage canals of Abu-Grabe, Al-Rhedwania and Al-Yosfiaa. Monthly samples were collected from September 2001 to August 2002. Water temperature ranged between 10 in January to 29.5 C in August. Salinity concentration and water turbidity recorded lowest mean values (3.4 gm/l and 8.8 NTU respectively) in the first site, whereas, highest values was (6.2 gm/l and 30.0 NTU respectively) in the second site. Dissolved Oxygen has been shown highest mean values reached 7.3 mg/l in the first site; while, the lowest was recorded in the second site reached 3.9 mg/l. The present study classified 33 species of benthic invertebrates, aquatic insect larvae, oligochaetes and molluscs formed 18, 11 and 6 species, respectively, as well as one genus only of crustacean. Three benthic invertebrate species were found to be dominate, namely Chironomous sp. (Chironomidae), Pristina aequiseta (Naididae) and Cypris sp. (Ostracoda). A total invertebrates density were recorded lowest values (4110.7 indi/m2) and highest ones (4906.6 indo/m2) in the first and second sites respectively. The highest values of total invertebrates density represented by oligochaetes and crustacean (3979.1 and 590.8 indi/m2 respectively) in the second site. A total biodiversity values in the Main Drain Channel reached 1.8 and 2.6 in the first and second sites respectively. The present study showed increasing in total density and biodiversity of benthic invertebrates in the second site of the north part of Main Drainage Channel after meeting within drainage canals of Abu- Grabe, Al-Rhedwania and Al-Yosfiaa.