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Effect of Nile River water quality on algal distribution at Cairo, Egypt
Environment International, Vol. 11, pp. 465-474, 1985 Printed in the USA. All rights reserved.
0160-4120/85 $3.00 + .00 Copyright © 1985 Pergamon Press Ltd.
EFFECT OF NILE RIVER WATER QUALITY ON ALGAL DISTRIBUTION AT CAIRO, EGYPT Salwa A. Shehata and Sabah A. Bader Water Pollution Control Laboratory, National Research Center, Dokki, Cairo, Egypt (Received 23 June 1984; Accepted 5 July 1985) Changes of phytoplankton density and their relation to physicochemical characteristics along the Nile River have been noted in the Cairo district between 1976 and 1982. Three major phytoplankton groups were found to dominate the river Nile: green algae, blue-green algae, and diatoms. Diatoms represent the most dominant group and comprised from 42°70 to 96070 of the phytoplankton community during the investigated period. Blue,green algae comprised from 0.707o to 4807o of total cell number. Green algae represent the low percentage group, which ranges from 0.2070 to 41070 of Nile water algae. High species diversity (H') was detected in green algae (1.22) followed by diatoms (0.84); the lowest diversity was in blue-green algae (0.45). The density of total phytoplankton count fluctuated between 10' and 10' organism/L. The concentration of chlorophyll-a ranged from 5 to 37 mg/m 3. Primary production rates in the Nile River ranged from 8.5 to 52 mg O2/m 3 h. Statistical analysis revealed significant positive correlations between chlorophyll-a content, and concentrations of phosphorus and nitrate. Phytoplankton diversity, primary production, ammonia, and nitrite content revealed that there is no indication of pollution in the Nile.
Introduction
Cairo district during different years. In addition; the investigation covers the physicochemical changes relative to algal densities during various seasons.
The Nile system consists principally of two major streams, the White Nile and Blue Nile rivers, whose combined waters flow for 3080 km as the main Nile from Khartoum to the Mediterranean sea. The creation of Lake Nasser has had a marked affect on the river downstream by regulating flows and by modifying the physical, chemical, and biological characteristics of water. Mississippi River impoundments considerably influence the types and amounts of suspended matter downstream, and thus impact composition of communities downstream (Fremling, 1960). Because of a change in physicochemicai characteristics of Nile water, changes might be expected in phytoplankton communities. The number a n d variety of phytoplankton are determined by the amounts and kinds of nutrients that are available (Palmer, 1962). Biologically, temperature and solar radiation occupy an important role in the control of planktonic life. Temperature changes not only effect of physiological processes of cells but also influence the kind of life that is present in water. Garret et al. (1978) found that temperature was the major factor influencing both algal growth and phosphorous removal. The present investigation deals with the study of the phytoplankton community recovered from the Nile River at three stations along a 60-kin distance within the
Material and Methods The investigation started in January 1976 and extended to March 1982, and it included three stations: Helwan, E1-Gezira and EI-Kanater. Composite water samples were collected along a 60-km reach within the Cairo district at the above three stations. Standard sampling bottles with Kipp thermometers were employed to collect composite water samples at three different depths [subsurface (0.5 m), 5 m, and 7 m], and from the two littorals (right and left). Enumeration of phytoplankton, quantification of chlorophyll-a concentration, phytoplankton productivity, and physiochemical characteristics were accomplished according to Standards Methods (APHA, 1975). Determinations of physicochemical characters involved the pH of water, its turbidity, electric conductivity, total alkalinity, total hardness, calcium hardness, magnesium hardness, chlorides, sulphates, free ammonia, nitrite, nitrate total organic nitrogen, phosphorus, silica, and its dissolved content. Counting of phytoplankton (organism/L) was determined by Sedgwick-Rafter cell. From the well-mixed sample, a 1-mL sample was drawn 465
466
S.A. Shehataand S. A. Bader
and placed into the Sedgwick-Rafter cell. Counts were made from 50 fields using a calibrated micrometer adjusted to the eyepiece (magnification 150). Statistical procedures used in data analyses were taken from Steel and Torrie (1960).
Results and Discussion
Community structure of phytoplankton in the Nile River The examination of Nile water samples from Halwan to EI-Kanater showed various phytoplanktonic communities comprised largely of three major groups, namely, Chlorophyta (green algae), Cyanophyta (bluegreen algae), and Bacillariophyta (diatoms). Diatoms (especially Cyclotella, Melosira, Bacillaria and Synedra) were the most abundant algal group and were present in high numbers in all samples. Cyanophyta were dominant throughout the investigated period. Cylindrospermum was the most single abundant genus. Chlorophyta were present nearly throughout the entire year. Eudorina, Scenedesmus, and Ankistrodesmus were the dominant genera of green algae in this study. Figures 1-3 show that phytoplankton consists primar-
ily of Bacillariophyta, which represented 33070-96°70 of community structure, followed by Cyanophyta which ranged from 3070 to 67070 of phytoplankton composition during the investigated years. Chlorophyta represent the low percentage group and ranged from 0.2070 to 34070 during the entire year. When comparing the percentage distribution of the three groups in the three sites, some variation between different sites was detected. An exceptional case occurred in February at the Cairo site, when there was a sudden increase in the percentage of green algae due to the high numbers of Scenedesmus sp. The percentage distribution of blue-green algae and diatoms displayed a rather uniform percentage in all sites of Nile water. Yet a casual decline or rise may be spotted in the percentage in some months, especially at the Helwan site. The effect of industrial discharge was quite feasible at Helwan site (EI-Gohary et al., 1982) and its clear effect on algal counts and the recovery of algae was detected in the next site at Cairo. Statistical evaluation to segregate spatial and temporal variation of Nile water showed that hard deviations mainly in sign (+ vs. - ) and in magnitude from one locality to another would refer to pollution with industrial residue (Shehata et aL 1981).
36
32
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Helwan
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.
.
.
.
Fig. (1) Percentagedistributionof green algae in Nile water at Cairo district.
Effect of Nile River on algae
467
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am Hetwan Et-Gizera []
Et-Kanater
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Fig. (2) Percentage distribution of blue-green algae in Nile water at Cairo district.
100
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Helwan
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Fig. (3) Percentage distribution of diatoms in Nile water at Cairo district.
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468
S.A. Shehata and S. A. Bader
Community properties The phytoplankton community composition parameters of river Nile were measured using Shannon's equation:
H' = - ~
(n,/N) log, (n,/N),
i=1
where s is number of taxa samples, n, the number of individuals of ith taxan, and N is sample size. The information measure of diversity for the three major groups (Table 1) showed that the highest diversity was detected in green algae, followed by diatoms: The lowest one was blue-green algae. The mean values for diversity of green algae, diatoms, and blue-green algae was 1.22, 0.84, and 0.45, respectively. The lowest diversity of blue-green algae was found around the whole year, a phenomenon associated with the dominance of Cylindrospermum. Karentz and Mclntire (1977) found that the diversities of planktonic diatoms in the Yaquina river were remarkably similar during different seasons with a mean value of 2.25. Generally, phytoplanktonic diversity of Nile water ranged from 0.31 to 1.1. However, diversity was relatively high during the investigated period and the lowest value was detected only during the dominancy of the diatom Cyclotella during winter. Mitchell and Buzzell (1971) stated that oligotrophic water characteristically ranges in diversity from 0.7 to 1.0, while values of 0.3 or less more commonly occur in eutrophic conditions. Thus, the diversity of phytoplanktonic Nile water near Cairo districts indicates that it is relatively oligotrophic water.
Changes in phytoplanktonic numbers of the Nile River Total phytoplankton abundance during the investigated period ranges from 106 to 107 cells/L. When
Table 1. Range of values of diversity (H') of Nile water algae during 1978.
Month
Total Algal
Green Algae
Blue-Green Algae
Diatoms
January February March April May June July August September October November December
0.31-0.47 0.44-0.83 0.40--0.61 0.23-0.61 0.52-0.88 0.75-0.89 0.99-1.06 0.85-0.94 0.62-0.81 0.85-0.90 0.64--0.71 0.18-0.51
0.41-1.08 0.36-1.23 0.72-1.66 1.17-1.65 1.75-2.06 1.52-2.08 1.07-1.50 1.66-2.04 1.57-1.84 1.86-2.02 1.20-1.59 1.41-1.81
0.03-0.09 0.06-0.13 0.07-0.37 0.42-0.81 0.16-0.24 0.07-0.19 0.56-0.70 0.1-1~29 0.28-0.52 0.19-0.27 0.35-0.5 0.15-0.49
0.34-0.37 0.26-0.49 0.28-0.33 0.57-0.87 0.57-0.70 0.70-0.94 0.90--1.05 1.24-1.53 1.22-1.34 1.24-1.45 0.54-0.81 0.15-0.48
these results are compared with readings taken prior to the High Dam construction, one finds that clear changes in algal counts have taken place. Figure 4 shows average phytoplankton fluctuation between 1966 (i.e., before the High Dam construction) and 1974, 1978, and 1979 (i.e., after impoundment) (The data of years 1966 and 1974 are derived from Ramadan & Shehata, 1976a, b). In 1979, the greatest algal abundance was noted. However, the distinct rise in phytoplankton density is a feature of the water after the High Dam construction. This contributed to the low level of turbidity after impoundment (Ramadan and Shehata, 1976). In addition sharp reduction in flow rate of river Nile took place after High Dam construction as shown in Fig. 5.
Seasonal variation in phytoplanktonic pigment of the Nile River The seasonal distribution of chlorophyll-a in 1978 is shown in Fig. 6. Average chlorophyll-a ranged from 5 to 37 mg/m 3 during the investigation. The bigest concentration of chlorophyll-a was found during the summer, due to the most common forms together with the high value of chlorophyll-a content, namely, Cylindrospermum (a filamentous species) and Bacillaria (a pennate diatom). Tailing (1965) found that the large Kavirondo Gulf is highly eutrophic with 20 mg/m 3 chlorophyll-a. The total concentration of chlorophyll-a in the offshore surface water of Lake Victoria is not large (1.2-5.5 mg chlorophyll-a/m3; Tailing, 1966). No relationship could be detected between phytoplankton counts and chlorophyll content. This might be due to the changes in community structure of phytoplankton and the ratios between unicellular, colonial, and filamentous forms. In addition, chlorophyll-a content per cell depends on its physiological state (Glooschenko et al., 1974). A significant relationship between algal cell counts and chlorophyll-a content was observed by Karlstrom and Backlund (1977). However, we found that chlorophyll-a concentration and rate of phytosynthesis (oxygen production) were positively correlated (Table 2). Changes of primary production in Nile water The primary production of the river Nile ranged from 8.5 to 52 mg 0 2 / h , which is equivalent to 3.2 to 19.5 mg C/m 2 h. High primary production was detected during the spring and summer at all stations. These results agree with data given by Reamann (1978), who found that 02 production increased with increasing water temperature; the maximum was 18-30 °C. Also, the primary production in a shallow arctic pond was highest during August, when it reached 46 mg C / m 2 day (Robert et aL, 1975). Annual average primary production values for Helwan, E1-Gizera, and E1-Kanater were 37.6, 27.4, and 24.8 mg O2/m 2 h, respectively. Production was high at Helwan station, presumably because the Nile receives some organic waste at that site (E1-Gohary et aL, 1982).
Effect of Nile River on algae
469
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Fig. (4) Seasonal abundance of phytoplankton in Nile water at Cairo station during different years.
The primary production rate of Nile water was 2.6 times greater than the community respiration rate. This result is in agreement with data obtained in the river Khan, in which primary production was found to be 2.5 times greater than the community respiration (Rao et aL, 1979). These values are subject to slight variation during most months. However, values of primary production, which ranged between 0.08 and 0.5 g C/m 2 day, does not indicate a polluted condition in river Nile at Cairo district. Conceptionally low primary production could be due to low nutrients, high grazing, or low light intensity. Vollenweider (1971) stated that primary production values of 0-50 g C/m 2 day indicated oligo-
trophic conditions, while 150-200 g C/m 2 day could be expected for highly eutrophic waters• Chlorophyll-a and oxygen production were more strongly correlated than were chlorophyll and total algal counts (Table 2). This is due to the fact that both chlorophyll-a concentration and oxygen production depend upon the photosynthetic activity of phytoplankton. Nutrients in relation to phytoplankton in the Nile River Chemical analysis of the major phytoplanktonic nutrients, namely, phosphorus, silica and nitrogen, showed clear seasonal trends. Positive correlation was found between concentrations of dissolved phosphorus and
470
S.A. Shehata and S. A. Bader Table 2. Simple correlation and regression coefficients between chlorophyll-a and algal cell numbers values, oxygen production, dissolved phosphorous, and nitrate-N.
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Correlation Coefficient Correlated Items.
rxy
byx
bxy
f'\
Temporal changes Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs.
total cell number Oxygen production PO~nitrate
-.1287" -.1840* -.3153" + .0863*
-94.33 - 3.29 - 3.23 + 1.5105
8
+.9123" + .9624* + .6458* + .0422
+655.74* + 37.45* +9.0818" + .0025
+.0013 + .0247 + .0459 + .7190
+0.444 -.1836 + . 1151 -.0933
+24.13 - 5.04 2.14 -3.10
+ .0001 + .0067 + .0062 -356.31
l
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Discrepancy (function) Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs.
Total cell number Oxygen production PO~nitrate
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3_
*Denotes chlorophyll-a content.
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Total cell number Oxygen production PO]nitrate
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- .0103 - .0308 + .0049
Spatial changes Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs.
9
- .0002
I I
phytoplankton counts in this river (Fig. 7). In contrast, Jenkins and Ives (1973) found no decrease in soluble phosphorus when a large crop of phytoplankton occurs. Statistical analysis revealed a significant correlation between chlorophyll-a and phosphorus concentrations (Table 2). These results agree with those obtained by Pieterse and Toerien (1978), who found a statistically significant correlation between chlorophyll-a and phosphorus concentration in Roodep loat Dam. How-
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Fig. (5) Annual variation of flow rate at Caafra before and after High Dam.
Table 3. Range values of Nile water characters before and after High Dam construction. Year Parameters Temperature °C Turbidity NTU pH E.C umho Cm "1 Total Alkalinity as CaCO3 mg/L Total Hardness as CaCO~ mg/L Calcium Hardness as CaCO3 mg/L Magnesium Hard. mg/L Chlorides mg C1/L Sulfates mg SO,/L Ammonia mg N/L Nitrite mg N/L Nitrate mg N/L Total Organic nitrogen mg N/L Total phosphorous mg P / L Dissolved Phosphorous mg P / L Dissolve Silica SiO2 mg/L Dissolved oxygen mg O2/L *Turbidity rng/L **N.R. = Not Recorded
1964 19-30.5 "19-2950 7.2-8.3 208-420 78.8-177.9 76.6-114.6 46.1-72.5 24.3-59.8 6.4-24.6 N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. 7.11-10.07
1966 13-29 *25-200 7.9-8.2 N.R. 104-180 91-137 52-73 36-64 10--18 N.R. 0.002-0.07 0.0--0.02 N.R. 0.2-0.48 N.R. 0.09-0.2 8.6-14 5.9-13.3
1976
1977
1978
1979
14-29 5-30 7,2-8.8 311-402 124-140 120-145 44-90 28-62 14-28 13-20.8 Nil 0.0-0.015 0.01-0.25 0.6-3.3 0.065-0.2 0.025-0.12 2.4-10.6 N.R.
18-26 N.R. 7.4-8.4 283-414 124-146 108-135 46-82 36-82 16-26 13-21 Nil 0.0-0.025 0.03-0.175 0.56-1.3 0.16-0.37 0.025-0.144 3.4-912 N.R.
15-28 1.5-18 7.5-8.8 271-401 124-150 104-128 60-80 34-54 18-30 7.8-23.2 Nil Nil-0.019 0.02-0.318 0.448-1.37 0.100-0.313 0.0-0.145 2.2-9.4 6.6-11.6
N.R.** N.R. 7.7-8.5 210-320 109-148 86-126 55-80 29-49 11-22 8-18.6 N.R. N.R. Nil-0.480 0.448-1.344 0.046-0.140 0.007-0.059 3.2-7.4 N.R.
Effectof NileRiveron algae
471
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ChLorophyll
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Fig. (6) Seasonalvariationof total algalcountsand chlorophyll-aconcentrationin Nilewaterduring 1978.
ever, Fayed and Shehata (1979) showed that phytoplankton growth in Nile water has been primarily limited by nitrogen and secondly by phosphorous contents. Dissolved silica is an important nutrient in the Nile River because diatoms dominate phytoplankton assemblages. Concentrations of dissolved silica were usually between 2.2 and 10.6 mg/L. The lowest values were associated with maximal growth of phytoplanktonic diatoms. However, there was a significant positive correlation between diatoms and dissolved silica (Fig. 8). More emphasis was given to diatoms than the other two groups. This is due to the fact that diatoms are the most dominant group during the whole year, whatever the physicochemical characteristics.
The concentration of nitrate showed seasonal fluctuating between 20 and 480 ttg/L. A marked burst of diatoms was detected during the winter, when nitrate reached a low level of 20 /~g/L. Statistical analysis revealed a highly significant correlation between phytoplankton density and nitrate concentration (Table 1). Trace amount of nitrite may be detected, actually falling from 0 to 25 #g/L. It may be worthwhile to note that Nile water does not contain any traces of free ammonia.
Physicochemical characteristics of Nile water Results of physicochemical characteristics of Nile water during the investigated period showed no clear variation between different years or between different
472
S. A. Shehata and S. A. Bader
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Fig. (7) Relationship between total algal counts and dissolved phosphorus in Nile water during 1978.
sites along the river (Table 3). Temperature fluctuated from 14 to 25 °C in each study year. The high temperature influenced the photosynthetic activity of the phytoplankton, especially during August when the concentration of chlorophyll-a reached a maximum (Fig. 6). Measurements of pH level during the same period ranged between 7.5 and 8.8. The turbidity measurements of Nile waters were consistently low (1.5 to 30 NTU), with the highest values being recorded during January, when phytoplanktonic counts were dominated by centric diatoms. Water clarity was improved with creation of the High Dam which controls particulate content by increasing sedimentation. The variation in salinity is indicated by records of specific conductivity, which attain maximal values of
414 #mho during the phase of lowest water level. Minimal conductivity (271 #mho) occurred during January. The concentration of alkalinity was closely correlated with conductivity; total alkalinity generally ranged between 124 and 150 mg CaCO3/L. Total hardness (expressed as CaCO3) fell within the range 104-145 mg/L. These results confirm that Nile water during that period was well buffered. The two major anions C1- and SO 2- showed different patterns of distribution. Concentrations of C1- fluctuated little (14-30 mg/L), while sulphate showed greater seasonal variation (7.8-23 mg/L). From a biological standpoint, the phytoplankton density in Nile water strongly influences the concentration of dissolved oxygen. Oxygen supersaturation (116%)
Effect of Nile River on algae
473
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Fig. (8) Relationship between total diatoms and dissolved silica in Nile water during 1978.
was observed during winters when phytoplankton were abundant. Also, in the Blue Nile supersaturation was found during the annual phytoplankton maximum (Tailing and Rz6ska, 1967). Pre-High Dam slight supersaturation developed during the winter season and values were above 70070 saturation throughout the year (Ramadan, 1972).
References American Public Health Association/American Water Works Association (1975) Standard Methods f o r the Examination o f Water and Wastewater, 14th ed. APHA/AWAVA, Washington, DC. EI-Gohary, F., Nawar, S., and Aub-E1-Ela, S. (1982)Changes in river Nile water quality and impact of waste water discharge. Symposium on Environmental Technology for Developing Countries. July, Istanbul, Turkey. Fayed, S. E. and Shehata, S. A. (1979)Nutritional status of Nile water
in relation to phytoplankton population, Z. Wasser-Abwasser Forsch. 13, 45-51. Fremling, C. R. (1960) Biology and possible control of nuisance caddisflies on the upper Mississippi river, Iowa State Agr. Home Econ. Exp. State Res. Bull. 483, 856-879. Garret, M. K., Weatherap, S. T. C. and Allan, M. D. B. (1978). Algal culture in a liquid phase of animal slurry. Effect of light and temperature upon growth and phosphorus removal, Environ. Pollut. 15, 141-154. Glooschenko, W. A., Moore, J. E., Munawar, M. and Vollenweider, R. A. (1974) Spatial and temporal distribution of ChlorophyU a and phaeopigments in surface water of Lake Erie, J. Fish-Res. Board Can. 31, 265-274. Jenkins, S. H. and Ives, K. J. (1973) Phosphorus in fresh water and the marine environment in Progress in Water Technology. Pergamon Press, Oxford. Karentz, D. and McIntire, C. D. (1977)Distribution of diatoms in the plankton of Yaquina estuary, Oregon, J. Phycol. 13, 379-388. Karlstrom, U. and Backlund, U. (1977) Relationship between algal cell number, chlorophyll a and fine particulate organic matter in a river in Northern Sweden, Arch Hydrobiol. 80, 192-199.
474 Mitchell, D. and Buzzell, J. C. (1977) Estimating eutrophic potential of pollutants, J. Sanit. Eng. Div. 97, 453-465. Palmer, C. M. (1962) Algae in water supplies of Ohio, Jour. Sci. 62, 225 -244. Pieterse, A. J. H. and Toerien, D. F. (1978) The phosphorus chlorophyll a relationship in Roodep loat Dam, Water SA 4, 105-112. Ramadan, F. M. (1972) Characterization of Nile waters prior to High Dam, Z. Wasser Abwasser Forsch. 1, 21-24. Ramadan, F. M. and Shehata, S. A. (1976a) Studies on the Nile water plankton prior to High Dam. Symposium on Nile Waters and Lake Dam Projects. National Research Centre, Cairo. Ramadan, F. M. and Shehata, S. A. (1976b) Early changes in phytoplankton of Nile water (1965-1974). Symposium on Nile Water and Lake Dam Projects. National Research Centre, Cairo. Reamann, K. (1978) Oxygen production by phytoplankton depending on water temperature, Z. Wasser Abwasser Forsch. 11, 151-154. Ran, S. V. R., Singh, V. P. and Mall L. P. (1979) The effect of sewage and industrial waste discharges on the primary production of a shallow turbulent river, Water Res. 13, 1017-1021. Robert, S. G., Mohuiddin, M. and Johan, H. A. 0975) Phytoplank-
S.A. Shehata and S. A. Bader ton biomass composition and primary production during ice-free period in a tundra Ponda. Proc. Circumpolar Conf. North. Ecol. 3, 2-31. Shehata, S. A., Badr, S. A. and EI-Ballal, A. S. (1981) Physiological features of Nile water quality. A Parametric characterization of temporal and spatial environments. Acta Hort. Water Supply Irrig. 119, 267-269. Steel, R. G. D. and Torrie, J. H. (1960)Principles and Procedures o f Statistics with Special References to Biological Science. McGrawHill, New York. NY. Tailing, J. F. (1965) The photosynthetic activity of phytoplankton in east African lakes, Int. Rev. Ges. Hydrobiol. 50, 1-32. Tailing, J. F. (1966) Photosynthetic behavior in stratified and unstratified lake populations of a planktonic diatom, J. Ecol. 54, 99-127. Tailing, J. F. and Rz6ska (1967) The development of plankton in relation to hydrological regime in the Blue-Nile, J. Ecol. 55, 637-662. Vollenweider, R. A. (1971) A manual on methods for measuring primary production in aquatic environments IBP handbook No. 12. Blackwell Scientific Publications, Oxford.
0160-4120/85 $3.00 + .00 Copyright © 1985 Pergamon Press Ltd.
EFFECT OF NILE RIVER WATER QUALITY ON ALGAL DISTRIBUTION AT CAIRO, EGYPT Salwa A. Shehata and Sabah A. Bader Water Pollution Control Laboratory, National Research Center, Dokki, Cairo, Egypt (Received 23 June 1984; Accepted 5 July 1985) Changes of phytoplankton density and their relation to physicochemical characteristics along the Nile River have been noted in the Cairo district between 1976 and 1982. Three major phytoplankton groups were found to dominate the river Nile: green algae, blue-green algae, and diatoms. Diatoms represent the most dominant group and comprised from 42°70 to 96070 of the phytoplankton community during the investigated period. Blue,green algae comprised from 0.707o to 4807o of total cell number. Green algae represent the low percentage group, which ranges from 0.2070 to 41070 of Nile water algae. High species diversity (H') was detected in green algae (1.22) followed by diatoms (0.84); the lowest diversity was in blue-green algae (0.45). The density of total phytoplankton count fluctuated between 10' and 10' organism/L. The concentration of chlorophyll-a ranged from 5 to 37 mg/m 3. Primary production rates in the Nile River ranged from 8.5 to 52 mg O2/m 3 h. Statistical analysis revealed significant positive correlations between chlorophyll-a content, and concentrations of phosphorus and nitrate. Phytoplankton diversity, primary production, ammonia, and nitrite content revealed that there is no indication of pollution in the Nile.
Introduction
Cairo district during different years. In addition; the investigation covers the physicochemical changes relative to algal densities during various seasons.
The Nile system consists principally of two major streams, the White Nile and Blue Nile rivers, whose combined waters flow for 3080 km as the main Nile from Khartoum to the Mediterranean sea. The creation of Lake Nasser has had a marked affect on the river downstream by regulating flows and by modifying the physical, chemical, and biological characteristics of water. Mississippi River impoundments considerably influence the types and amounts of suspended matter downstream, and thus impact composition of communities downstream (Fremling, 1960). Because of a change in physicochemicai characteristics of Nile water, changes might be expected in phytoplankton communities. The number a n d variety of phytoplankton are determined by the amounts and kinds of nutrients that are available (Palmer, 1962). Biologically, temperature and solar radiation occupy an important role in the control of planktonic life. Temperature changes not only effect of physiological processes of cells but also influence the kind of life that is present in water. Garret et al. (1978) found that temperature was the major factor influencing both algal growth and phosphorous removal. The present investigation deals with the study of the phytoplankton community recovered from the Nile River at three stations along a 60-kin distance within the
Material and Methods The investigation started in January 1976 and extended to March 1982, and it included three stations: Helwan, E1-Gezira and EI-Kanater. Composite water samples were collected along a 60-km reach within the Cairo district at the above three stations. Standard sampling bottles with Kipp thermometers were employed to collect composite water samples at three different depths [subsurface (0.5 m), 5 m, and 7 m], and from the two littorals (right and left). Enumeration of phytoplankton, quantification of chlorophyll-a concentration, phytoplankton productivity, and physiochemical characteristics were accomplished according to Standards Methods (APHA, 1975). Determinations of physicochemical characters involved the pH of water, its turbidity, electric conductivity, total alkalinity, total hardness, calcium hardness, magnesium hardness, chlorides, sulphates, free ammonia, nitrite, nitrate total organic nitrogen, phosphorus, silica, and its dissolved content. Counting of phytoplankton (organism/L) was determined by Sedgwick-Rafter cell. From the well-mixed sample, a 1-mL sample was drawn 465
466
S.A. Shehataand S. A. Bader
and placed into the Sedgwick-Rafter cell. Counts were made from 50 fields using a calibrated micrometer adjusted to the eyepiece (magnification 150). Statistical procedures used in data analyses were taken from Steel and Torrie (1960).
Results and Discussion
Community structure of phytoplankton in the Nile River The examination of Nile water samples from Halwan to EI-Kanater showed various phytoplanktonic communities comprised largely of three major groups, namely, Chlorophyta (green algae), Cyanophyta (bluegreen algae), and Bacillariophyta (diatoms). Diatoms (especially Cyclotella, Melosira, Bacillaria and Synedra) were the most abundant algal group and were present in high numbers in all samples. Cyanophyta were dominant throughout the investigated period. Cylindrospermum was the most single abundant genus. Chlorophyta were present nearly throughout the entire year. Eudorina, Scenedesmus, and Ankistrodesmus were the dominant genera of green algae in this study. Figures 1-3 show that phytoplankton consists primar-
ily of Bacillariophyta, which represented 33070-96°70 of community structure, followed by Cyanophyta which ranged from 3070 to 67070 of phytoplankton composition during the investigated years. Chlorophyta represent the low percentage group and ranged from 0.2070 to 34070 during the entire year. When comparing the percentage distribution of the three groups in the three sites, some variation between different sites was detected. An exceptional case occurred in February at the Cairo site, when there was a sudden increase in the percentage of green algae due to the high numbers of Scenedesmus sp. The percentage distribution of blue-green algae and diatoms displayed a rather uniform percentage in all sites of Nile water. Yet a casual decline or rise may be spotted in the percentage in some months, especially at the Helwan site. The effect of industrial discharge was quite feasible at Helwan site (EI-Gohary et al., 1982) and its clear effect on algal counts and the recovery of algae was detected in the next site at Cairo. Statistical evaluation to segregate spatial and temporal variation of Nile water showed that hard deviations mainly in sign (+ vs. - ) and in magnitude from one locality to another would refer to pollution with industrial residue (Shehata et aL 1981).
36
32
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Helwan
[]
Et-Gizera
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EL- Kanater
28
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-
20
16
12
4
0
•
.
.
.
.
Fig. (1) Percentagedistributionof green algae in Nile water at Cairo district.
Effect of Nile River on algae
467
4
am Hetwan Et-Gizera []
Et-Kanater
60
50 Ut
0
u
40
~
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r
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Fig. (2) Percentage distribution of blue-green algae in Nile water at Cairo district.
100
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Fig. (3) Percentage distribution of diatoms in Nile water at Cairo district.
°l
,~
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468
S.A. Shehata and S. A. Bader
Community properties The phytoplankton community composition parameters of river Nile were measured using Shannon's equation:
H' = - ~
(n,/N) log, (n,/N),
i=1
where s is number of taxa samples, n, the number of individuals of ith taxan, and N is sample size. The information measure of diversity for the three major groups (Table 1) showed that the highest diversity was detected in green algae, followed by diatoms: The lowest one was blue-green algae. The mean values for diversity of green algae, diatoms, and blue-green algae was 1.22, 0.84, and 0.45, respectively. The lowest diversity of blue-green algae was found around the whole year, a phenomenon associated with the dominance of Cylindrospermum. Karentz and Mclntire (1977) found that the diversities of planktonic diatoms in the Yaquina river were remarkably similar during different seasons with a mean value of 2.25. Generally, phytoplanktonic diversity of Nile water ranged from 0.31 to 1.1. However, diversity was relatively high during the investigated period and the lowest value was detected only during the dominancy of the diatom Cyclotella during winter. Mitchell and Buzzell (1971) stated that oligotrophic water characteristically ranges in diversity from 0.7 to 1.0, while values of 0.3 or less more commonly occur in eutrophic conditions. Thus, the diversity of phytoplanktonic Nile water near Cairo districts indicates that it is relatively oligotrophic water.
Changes in phytoplanktonic numbers of the Nile River Total phytoplankton abundance during the investigated period ranges from 106 to 107 cells/L. When
Table 1. Range of values of diversity (H') of Nile water algae during 1978.
Month
Total Algal
Green Algae
Blue-Green Algae
Diatoms
January February March April May June July August September October November December
0.31-0.47 0.44-0.83 0.40--0.61 0.23-0.61 0.52-0.88 0.75-0.89 0.99-1.06 0.85-0.94 0.62-0.81 0.85-0.90 0.64--0.71 0.18-0.51
0.41-1.08 0.36-1.23 0.72-1.66 1.17-1.65 1.75-2.06 1.52-2.08 1.07-1.50 1.66-2.04 1.57-1.84 1.86-2.02 1.20-1.59 1.41-1.81
0.03-0.09 0.06-0.13 0.07-0.37 0.42-0.81 0.16-0.24 0.07-0.19 0.56-0.70 0.1-1~29 0.28-0.52 0.19-0.27 0.35-0.5 0.15-0.49
0.34-0.37 0.26-0.49 0.28-0.33 0.57-0.87 0.57-0.70 0.70-0.94 0.90--1.05 1.24-1.53 1.22-1.34 1.24-1.45 0.54-0.81 0.15-0.48
these results are compared with readings taken prior to the High Dam construction, one finds that clear changes in algal counts have taken place. Figure 4 shows average phytoplankton fluctuation between 1966 (i.e., before the High Dam construction) and 1974, 1978, and 1979 (i.e., after impoundment) (The data of years 1966 and 1974 are derived from Ramadan & Shehata, 1976a, b). In 1979, the greatest algal abundance was noted. However, the distinct rise in phytoplankton density is a feature of the water after the High Dam construction. This contributed to the low level of turbidity after impoundment (Ramadan and Shehata, 1976). In addition sharp reduction in flow rate of river Nile took place after High Dam construction as shown in Fig. 5.
Seasonal variation in phytoplanktonic pigment of the Nile River The seasonal distribution of chlorophyll-a in 1978 is shown in Fig. 6. Average chlorophyll-a ranged from 5 to 37 mg/m 3 during the investigation. The bigest concentration of chlorophyll-a was found during the summer, due to the most common forms together with the high value of chlorophyll-a content, namely, Cylindrospermum (a filamentous species) and Bacillaria (a pennate diatom). Tailing (1965) found that the large Kavirondo Gulf is highly eutrophic with 20 mg/m 3 chlorophyll-a. The total concentration of chlorophyll-a in the offshore surface water of Lake Victoria is not large (1.2-5.5 mg chlorophyll-a/m3; Tailing, 1966). No relationship could be detected between phytoplankton counts and chlorophyll content. This might be due to the changes in community structure of phytoplankton and the ratios between unicellular, colonial, and filamentous forms. In addition, chlorophyll-a content per cell depends on its physiological state (Glooschenko et al., 1974). A significant relationship between algal cell counts and chlorophyll-a content was observed by Karlstrom and Backlund (1977). However, we found that chlorophyll-a concentration and rate of phytosynthesis (oxygen production) were positively correlated (Table 2). Changes of primary production in Nile water The primary production of the river Nile ranged from 8.5 to 52 mg 0 2 / h , which is equivalent to 3.2 to 19.5 mg C/m 2 h. High primary production was detected during the spring and summer at all stations. These results agree with data given by Reamann (1978), who found that 02 production increased with increasing water temperature; the maximum was 18-30 °C. Also, the primary production in a shallow arctic pond was highest during August, when it reached 46 mg C / m 2 day (Robert et aL, 1975). Annual average primary production values for Helwan, E1-Gizera, and E1-Kanater were 37.6, 27.4, and 24.8 mg O2/m 2 h, respectively. Production was high at Helwan station, presumably because the Nile receives some organic waste at that site (E1-Gohary et aL, 1982).
Effect of Nile River on algae
469
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Fig. (4) Seasonal abundance of phytoplankton in Nile water at Cairo station during different years.
The primary production rate of Nile water was 2.6 times greater than the community respiration rate. This result is in agreement with data obtained in the river Khan, in which primary production was found to be 2.5 times greater than the community respiration (Rao et aL, 1979). These values are subject to slight variation during most months. However, values of primary production, which ranged between 0.08 and 0.5 g C/m 2 day, does not indicate a polluted condition in river Nile at Cairo district. Conceptionally low primary production could be due to low nutrients, high grazing, or low light intensity. Vollenweider (1971) stated that primary production values of 0-50 g C/m 2 day indicated oligo-
trophic conditions, while 150-200 g C/m 2 day could be expected for highly eutrophic waters• Chlorophyll-a and oxygen production were more strongly correlated than were chlorophyll and total algal counts (Table 2). This is due to the fact that both chlorophyll-a concentration and oxygen production depend upon the photosynthetic activity of phytoplankton. Nutrients in relation to phytoplankton in the Nile River Chemical analysis of the major phytoplanktonic nutrients, namely, phosphorus, silica and nitrogen, showed clear seasonal trends. Positive correlation was found between concentrations of dissolved phosphorus and
470
S.A. Shehata and S. A. Bader Table 2. Simple correlation and regression coefficients between chlorophyll-a and algal cell numbers values, oxygen production, dissolved phosphorous, and nitrate-N.
12
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rxy
byx
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total cell number Oxygen production PO~nitrate
-.1287" -.1840* -.3153" + .0863*
-94.33 - 3.29 - 3.23 + 1.5105
8
+.9123" + .9624* + .6458* + .0422
+655.74* + 37.45* +9.0818" + .0025
+.0013 + .0247 + .0459 + .7190
+0.444 -.1836 + . 1151 -.0933
+24.13 - 5.04 2.14 -3.10
+ .0001 + .0067 + .0062 -356.31
l
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Total cell number Oxygen production PO~nitrate
I I I
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3_
*Denotes chlorophyll-a content.
I l
J
Total cell number Oxygen production PO]nitrate
I
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- .0103 - .0308 + .0049
Spatial changes Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs. Chlorophyll-a vs.
9
- .0002
I I
phytoplankton counts in this river (Fig. 7). In contrast, Jenkins and Ives (1973) found no decrease in soluble phosphorus when a large crop of phytoplankton occurs. Statistical analysis revealed a significant correlation between chlorophyll-a and phosphorus concentrations (Table 2). These results agree with those obtained by Pieterse and Toerien (1978), who found a statistically significant correlation between chlorophyll-a and phosphorus concentration in Roodep loat Dam. How-
1
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Fig. (5) Annual variation of flow rate at Caafra before and after High Dam.
Table 3. Range values of Nile water characters before and after High Dam construction. Year Parameters Temperature °C Turbidity NTU pH E.C umho Cm "1 Total Alkalinity as CaCO3 mg/L Total Hardness as CaCO~ mg/L Calcium Hardness as CaCO3 mg/L Magnesium Hard. mg/L Chlorides mg C1/L Sulfates mg SO,/L Ammonia mg N/L Nitrite mg N/L Nitrate mg N/L Total Organic nitrogen mg N/L Total phosphorous mg P / L Dissolved Phosphorous mg P / L Dissolve Silica SiO2 mg/L Dissolved oxygen mg O2/L *Turbidity rng/L **N.R. = Not Recorded
1964 19-30.5 "19-2950 7.2-8.3 208-420 78.8-177.9 76.6-114.6 46.1-72.5 24.3-59.8 6.4-24.6 N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. 7.11-10.07
1966 13-29 *25-200 7.9-8.2 N.R. 104-180 91-137 52-73 36-64 10--18 N.R. 0.002-0.07 0.0--0.02 N.R. 0.2-0.48 N.R. 0.09-0.2 8.6-14 5.9-13.3
1976
1977
1978
1979
14-29 5-30 7,2-8.8 311-402 124-140 120-145 44-90 28-62 14-28 13-20.8 Nil 0.0-0.015 0.01-0.25 0.6-3.3 0.065-0.2 0.025-0.12 2.4-10.6 N.R.
18-26 N.R. 7.4-8.4 283-414 124-146 108-135 46-82 36-82 16-26 13-21 Nil 0.0-0.025 0.03-0.175 0.56-1.3 0.16-0.37 0.025-0.144 3.4-912 N.R.
15-28 1.5-18 7.5-8.8 271-401 124-150 104-128 60-80 34-54 18-30 7.8-23.2 Nil Nil-0.019 0.02-0.318 0.448-1.37 0.100-0.313 0.0-0.145 2.2-9.4 6.6-11.6
N.R.** N.R. 7.7-8.5 210-320 109-148 86-126 55-80 29-49 11-22 8-18.6 N.R. N.R. Nil-0.480 0.448-1.344 0.046-0.140 0.007-0.059 3.2-7.4 N.R.
Effectof NileRiveron algae
471
c
o -- -4
Total
aLgaL
ChLorophyll
counts "a"
14 -
-28
X
I
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, ! o
20 :
8
//f
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-
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0
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I I
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Fig. (6) Seasonalvariationof total algalcountsand chlorophyll-aconcentrationin Nilewaterduring 1978.
ever, Fayed and Shehata (1979) showed that phytoplankton growth in Nile water has been primarily limited by nitrogen and secondly by phosphorous contents. Dissolved silica is an important nutrient in the Nile River because diatoms dominate phytoplankton assemblages. Concentrations of dissolved silica were usually between 2.2 and 10.6 mg/L. The lowest values were associated with maximal growth of phytoplanktonic diatoms. However, there was a significant positive correlation between diatoms and dissolved silica (Fig. 8). More emphasis was given to diatoms than the other two groups. This is due to the fact that diatoms are the most dominant group during the whole year, whatever the physicochemical characteristics.
The concentration of nitrate showed seasonal fluctuating between 20 and 480 ttg/L. A marked burst of diatoms was detected during the winter, when nitrate reached a low level of 20 /~g/L. Statistical analysis revealed a highly significant correlation between phytoplankton density and nitrate concentration (Table 1). Trace amount of nitrite may be detected, actually falling from 0 to 25 #g/L. It may be worthwhile to note that Nile water does not contain any traces of free ammonia.
Physicochemical characteristics of Nile water Results of physicochemical characteristics of Nile water during the investigated period showed no clear variation between different years or between different
472
S. A. Shehata and S. A. Bader
16
160 0
0
e--~
14 tO
0 x
I
\
120
\
,I'
c~
a,
/
/
10
- 100
/
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/
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80
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/
6
o rQ.
60
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4
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o I-
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~
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q
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I.
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1
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t/t
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Fig. (7) Relationship between total algal counts and dissolved phosphorus in Nile water during 1978.
sites along the river (Table 3). Temperature fluctuated from 14 to 25 °C in each study year. The high temperature influenced the photosynthetic activity of the phytoplankton, especially during August when the concentration of chlorophyll-a reached a maximum (Fig. 6). Measurements of pH level during the same period ranged between 7.5 and 8.8. The turbidity measurements of Nile waters were consistently low (1.5 to 30 NTU), with the highest values being recorded during January, when phytoplanktonic counts were dominated by centric diatoms. Water clarity was improved with creation of the High Dam which controls particulate content by increasing sedimentation. The variation in salinity is indicated by records of specific conductivity, which attain maximal values of
414 #mho during the phase of lowest water level. Minimal conductivity (271 #mho) occurred during January. The concentration of alkalinity was closely correlated with conductivity; total alkalinity generally ranged between 124 and 150 mg CaCO3/L. Total hardness (expressed as CaCO3) fell within the range 104-145 mg/L. These results confirm that Nile water during that period was well buffered. The two major anions C1- and SO 2- showed different patterns of distribution. Concentrations of C1- fluctuated little (14-30 mg/L), while sulphate showed greater seasonal variation (7.8-23 mg/L). From a biological standpoint, the phytoplankton density in Nile water strongly influences the concentration of dissolved oxygen. Oxygen supersaturation (116%)
Effect of Nile River on algae
473
14
14 o
12
8
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v 6
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0
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o-----.o
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Fig. (8) Relationship between total diatoms and dissolved silica in Nile water during 1978.
was observed during winters when phytoplankton were abundant. Also, in the Blue Nile supersaturation was found during the annual phytoplankton maximum (Tailing and Rz6ska, 1967). Pre-High Dam slight supersaturation developed during the winter season and values were above 70070 saturation throughout the year (Ramadan, 1972).
References American Public Health Association/American Water Works Association (1975) Standard Methods f o r the Examination o f Water and Wastewater, 14th ed. APHA/AWAVA, Washington, DC. EI-Gohary, F., Nawar, S., and Aub-E1-Ela, S. (1982)Changes in river Nile water quality and impact of waste water discharge. Symposium on Environmental Technology for Developing Countries. July, Istanbul, Turkey. Fayed, S. E. and Shehata, S. A. (1979)Nutritional status of Nile water
in relation to phytoplankton population, Z. Wasser-Abwasser Forsch. 13, 45-51. Fremling, C. R. (1960) Biology and possible control of nuisance caddisflies on the upper Mississippi river, Iowa State Agr. Home Econ. Exp. State Res. Bull. 483, 856-879. Garret, M. K., Weatherap, S. T. C. and Allan, M. D. B. (1978). Algal culture in a liquid phase of animal slurry. Effect of light and temperature upon growth and phosphorus removal, Environ. Pollut. 15, 141-154. Glooschenko, W. A., Moore, J. E., Munawar, M. and Vollenweider, R. A. (1974) Spatial and temporal distribution of ChlorophyU a and phaeopigments in surface water of Lake Erie, J. Fish-Res. Board Can. 31, 265-274. Jenkins, S. H. and Ives, K. J. (1973) Phosphorus in fresh water and the marine environment in Progress in Water Technology. Pergamon Press, Oxford. Karentz, D. and McIntire, C. D. (1977)Distribution of diatoms in the plankton of Yaquina estuary, Oregon, J. Phycol. 13, 379-388. Karlstrom, U. and Backlund, U. (1977) Relationship between algal cell number, chlorophyll a and fine particulate organic matter in a river in Northern Sweden, Arch Hydrobiol. 80, 192-199.
474 Mitchell, D. and Buzzell, J. C. (1977) Estimating eutrophic potential of pollutants, J. Sanit. Eng. Div. 97, 453-465. Palmer, C. M. (1962) Algae in water supplies of Ohio, Jour. Sci. 62, 225 -244. Pieterse, A. J. H. and Toerien, D. F. (1978) The phosphorus chlorophyll a relationship in Roodep loat Dam, Water SA 4, 105-112. Ramadan, F. M. (1972) Characterization of Nile waters prior to High Dam, Z. Wasser Abwasser Forsch. 1, 21-24. Ramadan, F. M. and Shehata, S. A. (1976a) Studies on the Nile water plankton prior to High Dam. Symposium on Nile Waters and Lake Dam Projects. National Research Centre, Cairo. Ramadan, F. M. and Shehata, S. A. (1976b) Early changes in phytoplankton of Nile water (1965-1974). Symposium on Nile Water and Lake Dam Projects. National Research Centre, Cairo. Reamann, K. (1978) Oxygen production by phytoplankton depending on water temperature, Z. Wasser Abwasser Forsch. 11, 151-154. Ran, S. V. R., Singh, V. P. and Mall L. P. (1979) The effect of sewage and industrial waste discharges on the primary production of a shallow turbulent river, Water Res. 13, 1017-1021. Robert, S. G., Mohuiddin, M. and Johan, H. A. 0975) Phytoplank-
S.A. Shehata and S. A. Bader ton biomass composition and primary production during ice-free period in a tundra Ponda. Proc. Circumpolar Conf. North. Ecol. 3, 2-31. Shehata, S. A., Badr, S. A. and EI-Ballal, A. S. (1981) Physiological features of Nile water quality. A Parametric characterization of temporal and spatial environments. Acta Hort. Water Supply Irrig. 119, 267-269. Steel, R. G. D. and Torrie, J. H. (1960)Principles and Procedures o f Statistics with Special References to Biological Science. McGrawHill, New York. NY. Tailing, J. F. (1965) The photosynthetic activity of phytoplankton in east African lakes, Int. Rev. Ges. Hydrobiol. 50, 1-32. Tailing, J. F. (1966) Photosynthetic behavior in stratified and unstratified lake populations of a planktonic diatom, J. Ecol. 54, 99-127. Tailing, J. F. and Rz6ska (1967) The development of plankton in relation to hydrological regime in the Blue-Nile, J. Ecol. 55, 637-662. Vollenweider, R. A. (1971) A manual on methods for measuring primary production in aquatic environments IBP handbook No. 12. Blackwell Scientific Publications, Oxford.