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Abstract -1’2- SUHNARy The present investigation was initiated to follow up the changes that might take place in distribution and species composition of phytoplankton community in some aquatic ecosystems of the Nile at Qalubia governorate, in relation to hydrological regime and eutrophication problems. Accordingly, six ecologically different sampling stations were selected to represent the different habitats in this province. These stations were further grouped into four habitats covering the whole study ,area. Habitat I : (stations, I,ll) The sites of these stations were distributed length wise Damietta branch of the River Nile in the vicinity ot Benha city. Habitat II : (stations III~IV) These stations were located at Elryah stream. Eltawfiky Habitat III: (station V) This station was selected to represent Elfailfaila irrigation canal. Habitat IV : (station VI) These station represent the polluted drain (Qalubia main drain) . -193- Subsurface water samples were collected at regular monthly intervals from these sites for a period of one year extending from September 1990 up to August 1991. The physico-chemical characters of water as well as identification and counting of phytoplankton species in these samples were carried out. Moreover, the effect of effluents of oils and soap factory at Benha on phytoplankton crop and species composition using synthetic media and receiving water from laboratory. the Nile were assayed in the The following is a summary of the results obtained I 1- The general climate of the stUdy area is that of the moderate tropical zones. Mean monthly values of water temperature ranged between 16·C to 29·C at all studied habitats. Generally, no wide variations observed in temperature maxima and minima between all stations. 2- The pH values at all sites lie on the alkaline side being ranged between 7.5 to 9.2 in Damietta branch of the Nile and irrigation canals, while the relatively neutral pH values were recorded in polluted drain water being fluctuated between ’7.4 to 8.3. )- The average transparency values fluctuated between 48cm and 123 cm at River Nile and Elryah Eltawfiky stream, from 32 cm to 53 cm (Elfailfaila irrigation canal), > from 15 cm to 27 cm (polluted drain). Generally, -1’4- stations of the polluted drain and narrow irrigation canal showed always the lowest transparency levels, mainly due to the increased turbidity of the contaminated water. 4- Electrical conductivity fluctuated between 305 to 457 Micromhos in Damietta branch of the Nile and irrigation canals habitats, and between 1148 to 1621 Micromhos at the polluted drain. 5- Dissolved oxygen of surface water in polluted drain was comparatively low being ranged between (4.7 and 7.4 mgl-I) compared with those of River Nile and irrigation canals which ranged between (6.5 and 8.8 mgI-l). 6- The polluted drain habitat showed relatively higher contents of total hardness and <the major nutrient anions (P04’ N03, N°i, NH3, Si03, 5°4’ CI, C03 and Heo) as compared with those of the Nile (Damietta branch) and irrigation canals habitats. Similarly, concentrations of monovalent (Na+, K+) and divalent (ca2+, Mg2+) cations in the drain water exceeded always that of the Nile and irrigation canals. 7- The chlorophyll (a) content of water at all sites showed irrigular local seasonal variations. 8- standing crop of total phytoplankton at all stations showed distinct seasonal variations. Thus, the average maximum yield at Nile water (3334 org. ml-l) was recorded during summer, while the average mimimum (2820 org. ml-li was attained during autumn. In Elryah -195- Eltawfiky stream the total standing crop ranged between minimum average (3016 org. ml-1) r~ached during autumn and maximum average (3902 org. ml~l) exhibited during winter. Similarly, in the narrow irrigation canal the total·standing crop·attained maximum average (1002 org. ml-l) during winter, while the minimum one (560 org. ml-1) reached during autumn. In polluted·’drain the total standing crop ranged between minimum average (355 org. ml-1) reached during autumn and maximum average (1808 org. ml-I) during spring. 9- The main phytoplankton groups showed considerable seasonal variations at all sites, Bacillariophyta was the most influential group of phytoplankton counts, where it show higher percentage during winter at all studied habitats, Chlorophyta also represented higher percentage during winter allthrough the stUdy habitats, Cyanophyta contributed to higher percentage during spring in Damietta branch and irrigation canals, and during autumn in the polluted drain. 10- It is to be noted that the polluted drain waters and the narrow irrigation canal harboured generally low standing crop compared with other studied habitats, since a total of 52 phytoplankton species were recorded allthrough the study period at the polluted drain. Out of these, 24 species belong to Bacillariophyta, 14 to Chlorophyta,l1 to Cyanophyta and only three species to Euglenophyta.An average of 79 species were recorded -196- in the narrow irrigation canal habitat. out of these, 25 belong to Bacillariophyta, 38 to Chlorophyta, 10 to cyanophyta, two species to Dinophyceae an? 4 to Euglenophyta. The number of species identified in Elryah Eltawfiky stream was comparatively high (91 species). out of this number, 32 belong to Bacillariophyta, 41 to Chlorophyta, 13 to cyanophyta, two species to Dinophyceae and three species to Euglenophyta. The number of species recovered in Damietta branch of the River Nile was 83 species. out of these, 29 belong to Bacillariophyta, 40 to Chlorophyta, 10 to cyanophyta, and only two species to each of Dinophyceae and Euglenophyta. 11- Some species such as : Navicula placentula~ Nitzschia amphibia (Bacillariophyta), staurastrum paradqxum (Chlorophyta), oscillatoria chalybea, oscillatoria chlorina, spirulina major (cyanophyta), seemed to be as pollutant indicator species since they were of high occurrence in polluted waters. Another species such as: Cyclotella meneqhainiana, cyclotella ocellata, Melosira granulata, synedraYlnA (Bacillariophyta), Dictyospherium pUlchellum~ Pediastrum simplex~ scenedesmus guadricuada (Chlorophyta), AnabaeDopsis raciborskiiJ Gomphospherialacustris, Merismopedia tenussima~ Microcystis Aeruginosa (cyanophyta), could be considered as main component species of freshwater -197- habitats, since they were recovered in all sampled waters. 12- concerninq to the effect of industrial effluents of oils and soap factory at Benha on the phytoplankton communit~ growing under controlled conditions in synthetic media, it was manifested in the form of a rise in phytoplankton total count, chlorophyll (a), dry weight gain and pH of the cultures media with increasing effluent concentration along’ the experimental period. Melosira granulata (Bacillariophyta) and ~cenedesmus guadricauda (Chlorophyta), were the most dominant species and they induced vigorous growth as time lasted with increasing effluent concentrations. 13- supplementation of the industrial effluent to the water samples collected from Elryah Eltawfiky resulted in rise of standing crop, dry weight gain and pH value of cultures. Melosira granulata~ Nitzschia kUtizingiana~ Synedra ulna (Bacillariophyta), Scenedesmus guadricauda (Chlorophyta), Anabaena ~onstricta (cyanophyta), were the most dominant species recovered in treated water. The propagules of such species tended to flourish with elevation in effluent concentration and as time prolonged. |