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Abstract
The aim of the present study was to evaluate the relationship between physico-chemical parameters, seasonal variations in zooplankton and total bacteria, as well as indicator bacteria and pathogenic bacteria in the River Nile during 4 seasons. The study also aimed to evaluate different types of pollution and its effect on biological and microbiological organisms. Four stations were chosen as sources of pollution; the Cement factory station represented the chemical pollution, the Starch factory station represented the organic pollution, Kasr El Nile station represented the sewage pollution and the Power station represented the thermal pollution. During the experimental study the grazing effect of zooplankton on indicator bacteria was up to 99%.
The results obtained were as follows:
• Water Temperature (ºC)
The values of water temperatures ranged between a minimum 16 ºC during winter and a maximum 34.5 ºC during summer. Site III of the power station was responsible for high temperature values during the study by 5 ºC during spring, 2 ºC during autumn and 6 ºC during summer and winter.
• Dissolved Oxygen (DO)
DO recorded a maximum value of 10.5 mg/l during autumn and a minimum value 2.8 mg/l during summer, showing a gradual increase from Cement factory station up to the power station during all seasons.
• Ion Concentration (pH)
Values of pH were always towards the alkaline side (> 7) with a small range of variation. The maximum pH value was 8.8 recorded during autumn and the minimum pH value was 7.6 recorded during spring.
• Turbidity (NTU)
Water turbidity widely varied between the four stations. The maximum value recorded was 12.1 NTU at site (I) of the power station during spring, while the minimum value was 2.5 NTU recorded at site III of the Starch Factory in winter. The last 2 stations (Kasr El Nile and the Power station) showed high values of turbidity than the first 2 stations (the Cement and the Starch factories).
• Biological Oxygen Demand BOD (mg/l)
The BOD values ranged between maximum 7.0 mg/l at site (I) of the Starch factory during autumn and minimum 0.0 mg/l at the majority of sites during winter. Kasr El Nile encountered the highest BOD values during the investigation period, followed by the Starch factory station.
• Chemical Oxygen Demand COD (mg/l)
The highest values of COD 39 mg/l recorded during winter season, and the lowest values 5 mg/l were observed during summer.
• Nitrogen as nitrate NO3 (mg/l)
The maximum value was 3.29 mg/l at site III of the Cement Factory during winter and the minimum value of 0.24 mg/l at site (I) of the Power Station during summer and in front of Cement Factory during autumn.
• Nitrogen as ammonia NH4 and nitrite NO2 (mg/l)
During the present study, nutrient nitrogen NH4 and NO2 were under the detection limit of the analyzing instrument except in few samples. The maximum values of ammonia recorded 0.127 mg/l at site (I) of the Cement Factory in spring and in front of the Starch Factory during autumn while the nitrite values recorded a maximum value of 0.72 mg/l at site (III) of Starch Factory during autumn.
• Phosphorus as Orthophosphate (mg/l)
Orthophosphate recorded a maximum value of 0.120 mg/l at site (II) of the Starch Factory during summer and a minimum value of 0.010 mg/l at site (II) of Power Station during spring, site (III) of the Cement Factory and site (I) of the Starch Factory in autumn.
• Heavy Metals (mg/l)
The analyzed heavy metals represented by Aluminum, Iron, Manganese, Lead, Strontium, Cupper and Zinc. The average values of the 7 metals were within the accepted values of Nile water.
Zooplankton
Zooplankton was represented by protozoa which formed (78.2%), Rotifera (21.6%), Cladocera (0.13%) and Copepoda (0.11%) of total zooplankton crop.
• Protozoa
Protozoa was represented by 31 species belonging to 28 genera. Spring was the flourishing season for Protozoa, recording average density of 1296.4 organism/l while summer season encountered the lowest protozoan density with average value of 440.2 organism/l. Kasr El-Nile station recorded the highest average density 1345.08 organism/l while the least abundance was observed at site (I) of the Cement factory station with average value of 480.48 organism/l. Vorticella (42.6%), Tintinnidium (17.4%), Bursellopsis (10.6 % ) and Strombidium (5.4 %) were the 4 genera dominated the protozoan community during the present investigation. The other protozoan species constituted 24 % of total protozoa crop.
• Rotifera
Rotifera recorded 51 species belonging to 27 genera. The average density ranged between a maximum of 575.6 organism/l during autumn and a minimum of 111.6 organism/l during summer. Site (I) of the power station recorded the highest average density 339.4 organism/l and site (I) of the Cement factory recorded the lowest average abundance 193.95 organism/l. Rotifera was dominated by 4 main genera. Keratella (55.5 %), Trichocerca (8.64 %), Brachionus (9.50 %) and Collotheca (7.23%). The other rotifera species formed only 6.88% of total rotifera.
• Cladocera
Cladocera constituted 0.13 % of the total zooplankton during the present investigation. The maximum average density was observed during winter with a value of 6.3 organism/l and the minimum average density was 0.08 organism/l during summer. Site (II) of the Cement factory recorded the highest average density 4 organism/l while site (II) of Kasr El Nile recorded 0.5 organism/l. Cladocera was represented by Bosmina, Daphnia, Alona, Dunhevedia, Chydorus, and Diphanosoma. These genera constituted 32.9 %, 26.8 %, 20.7 %, 9.8 %, 8.5 % and 1.2 %, of the total Cladocera respectively.
• Copepoda
Copepoda was recorded as a rare group during the present study, contributing 0.11 % of total zooplankton. Spring and autumn recorded high crops in contrast with summer and winter recorded lower crops. Site (I) of Kasr El Nile recorded the maximum average 6.75 organism/l while site (III) of the Starch factory recorded the minimum average 0.0 organism/l. The Copepoda included Nauplius larvae (90 %), Mesocyclops sp (5.7 %) and Thermocyclops crassus (4.3 %) of total Copepoda during the study.
• Total Bacterial Count (cfu/ml) at 22 °C
The maximum count was 39200 X 104 cfu/ml recorded during summer while the minimum bacterial count was 2 X 104 cfu /ml during winter. Site II of the Starch factory recorded the highest average count 11903.93 x 104 cfu/ml while site (III) of the power station recorded the lowest average count 124 x 104 cfu/ml.
• Total Bacterial Count (cfu/ml) at 37 °C
The highest seasonal average was 14880 X 104 cfu/ml during summer while the minimum seasonal average count was 8.58 X 104 cfu /ml during winter. Site (I) of the Cement factory recorded the maximum average count 9519 X 104 cfu/ml while site (III) of the power station recorded the minimum average value 647.85 X 104 cfu/ml.
• Bacterial indicators
o Total Coliform (cfu/100 ml)
The maximum average count 4589 cfu/100 ml was recorded during spring while the minimum average count 396 cfu/100 ml recorded during autumn. Site (II) of Kasr El Nile recorded the maximum average count 7770 cfu/100 ml, while site (I) of the power station recorded the minimum average count 552.5 cfu/100 ml.
o Faecal Coliform (cfu/100 ml)
The maximum average count 704.2 cfu/100 ml was recorded during spring while the minimum average count 396 cfu/100 ml recorded during autumn. Site (III) of the power station recorded the maximum average count 1157.5 cfu/100 ml, while site (III) of the Starch factory recorded the minimum average count 121.5 cfu/100 ml.
o Faecal Streptococci (cfu/100 ml)
The maximum average count 86.25 cfu/100 ml was recorded during spring while the minimum average count 9.92 cfu/100 ml recorded during autumn. Site (I) of Kasr El Nile recorded the maximum average count 99.5 cfu/100 ml, while site (I) of the Starch factory recorded the minimum average count 21.5 cfu/100 ml.
• Total count of gram negative bacteria
During summer the maximum average count recorded 694.3 x 105/100 ml, while the minimum average count 11 x 103/100 ml recorded during winter. Site (I) of the Cement factory recorded the highest average count 8615.4 x 103/100 ml while site II of the Cement factory recorded the lowest average count 4848.2 x 103/100 ml. Seven species of pathogenic bacteria were identified. E.coli (62.4%), Klebsiella pneumoniae (21.75%), Salmonella choleraesuis (8.67%), Pseudomonas aeruginosa (4.05%), Protens vulgaris (2.32%), total Shigella spp. (0.76%) and Serratia liquefaciens (0.05%).
• Grazing Experiment
The Protozoa and Rotifera were the two main grazers in the experiment. Protozoa formed 90.92 % of total zooplankton crop, while Rotifera constituted 9.08 % of total zooplankton. Protozoa was represented in the experiment by nine species Actinobolina, Vorticella, Epistylis, Strombidium, Tintinnidium, Burselopsis, Halteria, Paradexiotricha and Difflugia forming 57.82 %, 20.52 %, 7.05 %, 6.71 %, 4.06 %, 2.22 %, 0.66 %, 0.55 % and 0.41 % of total protozoa, respectively. Rotifera was represented by seven species Trichocerca, Polyarthra, Proals, Philodina, Cephalodilla, Cononchilus, and Collotheca forming 71.87 %, 16.77 %, 3.84 %, 3.43 %, 2 %, 1.07 % and 1.02 % respectively. The total coliform started with count 2400 cfu/100 ml and declined to 1400 cfu/100 ml after 24 hours. The faecal coliform recorded 46