comparative studies of phytoplankton compositions as a...

Vol.:(0123456789)1 3

International Journal of Environmental Science and Technology https://doi.org/10.1007/s13762-019-02409-0

ORIGINAL PAPER

Comparative studies of phytoplankton compositions as a response of water quality at North El‑Manzala Lake, Egypt

M. A. Deyab1 · S. E. Abu Ahmed1 · F. M. E. Ward1

Received: 21 September 2018 / Revised: 2 May 2019 / Accepted: 11 May 2019 © Islamic Azad University (IAU) 2019

AbstractEl-Manzala Lake represents one of the most economical and valuable fish sources lakes in Egypt. This study aims to study the impact of physical and chemical properties of water on phytoplankton communities in North El-Manzala Lake. The number and biomass of phytoplankton, as well as physicochemical characteristics of surface water at the seven sites (Al-Baghdadi, Shatta, El-Deiba, Abo El-Ross, El Nafft, Towall Ibrahim, and Shatt Greba) representing North El-Manzala Lake—Damietta, Egypt, were studied from January to December 2017. Physicochemical properties of water exhibited seasonal and local vari-ations. Phytoplankton standing crop in North El-Manzala Lake—Damietta, Egypt, was varied in relation with water quality as follows: Al-Baghdadi > El Nafft > Shatt Greba > Shatta > El-Deiba > Towall Ibrahim > Abo El-Ross. Cyanophyta was the dominant class at all sites except at Al-Baghdadi and Towall Ibrahim where Bacillariophyta and Pyrrophyta were the predominant phytoplanktonic groups, respectively. The maximum crop density was recorded in winter, whereas the lowest values occurred in summer. Pearson’s correlation coefficient revealed that most of the phytoplankton groups were significantly correlated with water temperature, pH, total alkalinity, ammonia, nitrate, silica, and ortho-phosphorus.

Keywords Bacillariophyta · Biomass · Chlorophyta · Cyanophyta · Physicochemical analyses · Pyrrophyta

Introduction

El-Manzala Lake occupies the northeastern corner of the Nile Delta between the Suez Canal (East) and Damietta Branch (West) with a length of 50 km along the Mediter-ranean coast (Ahmed et al. 2009; Abd El-Karim 2008). El-Manzala Lake locates between latitudes 31°07′N and 31°30′N, and longitudes 31°48′E and 32°17′E (Elmorsi et al. 2017). Economically, El-Manzala Lake is one of the most valuable fish and salt sources in Egypt by about 36–50% of the total annual production of the Egyptian lakes (Rasmus-sen et al. 2009).

At the present time, El-Manzala Lake suffers from expo-sure to high inputs of industrial, domestic, and agricultural pollutants. Ismail and Hettiarachchi (2017) reported that the lake receives an annual 7.2 billion cubic meters of annual water inflow, of which agricultural drainage (96%), sewage (3.9%), and industrial drainage (0.1%). The northern coasts of the lake differ much more than the southern coasts along the whole year. The northern sites were strongly influenced by the Mediterranean seawater inflows, especially during the winter, and have many inlets by which great amounts of wastewater discharge carrying large amounts of particular matter, heavy metals, and organics (Elmorsi et al. 2017). Sood et al. (2015) reported dominance of Cyanophyta in habitats contaminated with sewage.

Water capacity to sustain heterotrophic communities, dynamic changes in pH, and concentrations of oxygen and inorganic nutrients (nitrate, phosphate, ammonia) were all closely associated with fluctuations in phytoplankton com-position (Hulyal and Kaliwal 2009). Phytoplankton is the largest group of primary producers in aquatic ecosystems which plays an important role in the biogeochemical cycle and climatic processes. Marine phytoplanktons contribute

Editorial responsibility: M. Abbaspour.

Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s1376 2-019-02409 -0) contains supplementary material, which is available to authorized users.

* F. M. E. Ward [email protected]

1 Department of Botany and Microbiology, Faculty of Science, Damietta University, New Damietta City 34517, Egypt

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International Journal of Environmental Science and Technology

1 3

about 95% of the primary production in the oceans (Arm-brust 2004).

Ecological conditions, pollution, and human impacts induce variations to biological features of water as it affects growth rate and behavior characteristics of phytoplankton species. The free-floating behavior of phytoplankton gave the opportunity to the community composition to change in response to environmental conditions (Hare et al. 2007). These variations depend mainly on the type and nature of the water area itself as well as runoff of minerals and chemi-cals from agriculture soils. Moreover, the physicochemical properties and nutrient status of the water play an important role in the production of phytoplankton, which is essential in maintaining productive aquatic organisms (Kumar and Sahu 2012). Therefore, phytoplankton composition is considered as natural bioindicators of water quality because of their sensitivity and rapid responses to changes in environmental conditions such as pH, temperature, salinity, turbidity, and nutrients with respect to industrial, municipal, and domestic pollution (Rimet and Bouchez 2012; Stanca et al. 2013).

The available works of the literature on phytoplank-ton composition at the different sites of El-Manzala Lake, Egypt, are scarce. Therefore, the aim of the present study is to follow up the impact of physicochemical properties of water on phytoplankton communities in North El-Manzala Lake during January–December 2017 and to investigate the correlation between physicochemical parameters and phytoplankton.

Materials and methods

Sampling sites

Water samples were monthly collected over 1 year (Janu-ary–December, 2017) from seven sites in North El-Manzala Lake. The chosen sites are represented in the following map (Fig. 1) where site I: Al-Baghdadi, site II: Shatta, site III: El-Deiba, site IV: Abo El-Ross, site V: El Nafft, site VI: Towall Ibrahim, and site VII: Shatt Greba.

Physicochemical and biological analyses of water

Temperature, pH, electrical conductivity (EC), salinity, and turbidity were measured in the field. The temperature of water samples was measured at collection point using the laboratory glass thermometer. Water pH was meas-ured using a pH meter (model HI 8314, Hanna Instruments Ltd). The pH meter was standardized with pH 4, 7, and 10 buffer solutions. It was then washed with distilled water, wiped, dipped into the water sample, and left for some seconds for the reading to stabilize. Finally, pH value was recorded from the display. Water EC was measured using Jenway conductivity meter model 470, 0.01 M of KCl solution. The conductivity meter was standardized with 0.01 M of KCl solution. The electrode was rinsed with deionized water, wiped, and immersed in the water sample

Fig. 1 A map showing the sampling sites


1 3

and retained for seconds. After the reading stabilizing, the EC value displayed on the screen was recorded in mmhos/cm. Water salinity was measured directly using Salt Meter SALT-3000. The meter was calibrated at 3000 ppm NaCl. After inserting the probe into the water sample up to the immersion level, the value was recorded from the display and was expressed as mg/L. Water turbidity was meas-ured directly using HANNA instruments microprocessor turbidity meter, and the results were expressed as NTU. Total alkalinity, dissolved oxygen (DO), ammonia, nitrate, nitrite, silica, and ortho-phosphorous were estimated in the laboratory according to APHA (Anonymous 1996). Each measurement was taken in triplicate.

Collections of phytoplankton were made using a conical net of bolting nylon of 0.069 mm mesh width and mouth ring diameter of 35 cm with the help of an outrigger canoe. The filtered samples were fixed with Lugol’s solution and 4% of formalin and enumerated using an inverted Olym-pus light microscope (Sharma 2002), the following sedi-mentation according to Utermohle (1936). Identification of the main phytoplanktonic groups was made using an EXACTA + OPTECH GmbH biological light microscope (Model B3)—Code K7161, Germany, with reference to Botes (2003), Krammer and Lange-Bertalot (1986), and

Tikkanen (1986). The phytoplankton biomass was calcu-lated according to Edler (1979).

Statistical analyses

Data were analyzed using two-way ANOVA. A2-tailed Pear-son product moment correlation was performed using SPSS version 22 to examine the relationship between all phys-icochemical and biological parameters at North El-Manzala Lake, Egypt. Mean separation was performed using the Dun-can’s multiple range test at p < 0.05.

Results and discussion

Physicochemical analysis of water

The effect of the main factors (site and month) and their interaction on physicochemical parameters of water along El-Manzala Lake was very highly significant (p < 0.05) as shown in Table 1. The effect of a site was stronger (with higher F ratio) than that of a month for all parameters, except for pH, temperature, nitrate, and silica for which the effect of a month was stronger.

Table 1 Two-way ANOVA showing the effect of the main factors (site and months) and their interaction on physicochemical parameters of water

Variable and source of variation

df F p Variable and source of variation

df F p

pH Ammonia Site 6 208.8 0.00 Site 6 35,658.9 0.000 Months 11 414.2 0.00 Months 11 11,361.1 0.000 Site × month 66 36.43 0.00 Site × month 66 3030.7 0.000

Temperature Nitrite Site 6 263.1 0.00 Site 6 5,195,629 0.000 Months 11 73,433.6 0.00 Months 11 1,461,653 0.000 Site × month 66 199.1 0.00 Site × month 66 2,144,479 0.000

Turbidity Nitrate Site 6 512,584 0.00 Site 6 19,160,612 0.000 Months 11 81,814.3 0.00 Months 11 6,808,235 0.000 Site × month 66 55,516.5 0.00 Site × month 66 4,070,999 0.000

Salinity Silica Site 6 2,466,507 0.00 Site 6 1719.8 0.000 Months 11 84,586.8 0.00 Months 11 2320.0 0.000 Site × month 66 23,029.9 0.00 Site × month 66 574.6 0.000

Conductivity ortho-P Site 6 37,222,114 0.00 Site 6 754,513 0.000 Months 11 2,283,620 0.00 Months 11 169,858 0.000 Site × month 66 543,691 0.00 Site × month 66 52,753 0.000

Total alkalinity DO Site 6 725.4 0.00 Site 6 551.5 0.000 Months 11 95.54 0.00 Months 11 18.0 0.000 Site × month 66 26.09 0.00 Site × month 66 24.3 0.000


1 3

The values of water temperature at different sites of the study area varied between 10 ± 0.1 °C and 30 ± 0.1 °C (Table 2). These variations of temperature are found to affect the diversity and succession of the phytoplankton groups. Both numbers and biomass of Cyanophyta, Bacillariophyta, Pyrrophyta, and Chlorophyta were correlated positively with water temperature. Similarly, Chellappa et al. (2009) reported a positive correlation between Cyanophyta group and temperature.

pH is an important factor in the aquatic system and con-sidered as the productivity index of the water quality. In this study, there are significant (p < 0.05) differences in the pH values of the water between sites as shown in Table 1. All sites occurred in the alkaline side where the pH values ranged between 7.0 at site VII (in August) and 9.8 at site III (in January) as shown in Table 2. It could be attributed to agriculture wastes or domestic wastes (such as soap, deter-gent, and other organic matters) mixed into the canal which agrees with the finding of (El-Kafrawy 2004). Moreover, biological activity (i.e., photosynthesis and respiration) and disposal of industries wastes carry out changes in the pH (Nassar et al. 2014). The variation in pH of water indicates a highly productive nature of the water body in El-Manzala Lake. As shown in Table 5, significant positive correlations were reported between the biomass of most phytoplankton groups (Cyanophyta, Bacillariophyta, Pyrrophyta, and Chlo-rophyta) and water pH. Water pH was significantly corre-lated with water temperature (r = − 0.513, p < 0.01), turbid-ity (r = − 0.236, p < 0.01), nitrate (r = − 0.200, p < 0.01), and DO (r = 0.265, p < 0.01). A similar correlation between pH and both temperature and DO value was also reported by Elmorsi et al. (2017) and Nassar et al. (2016).

In North El-Manzala Lake, there are high local variations (2.4–103.5 NTU) in turbidity values between sites as shown in Table 2. The minimum values of turbidity were recorded at site V in May; meanwhile, the maximum was recorded at site VII in April. The high turbidity may be due to resuspen-sion of sediment and high organic pollution of water. Total number of Conjugatophyta was correlated negatively with turbidity (r = − 0.128, p < 0.05). Whereas, the number and biomass of Euglenophyta were correlated positively with water turbidity (Table 5). Turbidity showed a moderate posi-tive correlation with total alkalinity (r = 0.317, p < 0.01) and silica (r = 0.184, p < 0.01), and negative correlation with DO (r = − 0.285, p < 0.01).

The present results showed that there was a wide range of changes in the salinity between sites with the lowest mean value (1.7 mg/L) at site VII, while salinity recorded its high-est mean annual value (58 mg/L) at site V (Table 3). High salinity at this site indicates that the discharged water con-tains a high amount of pollutants. There is evidence that the industrial discharges (Aziz et al. 1996), domestic wastes dis-charged, and agriculture runoff (Golterman 1999) increase

salinity in the water. High salinity at most sites in summer may be due to high evaporation rate (Herman and Adrienne 1995). Salinity was moderately correlated with conductivity (r = 0.949, p < 0.01), total alkalinity (r = − 0.673, p < 0.01), ammonia (r = − 0.401, p < 0.01), nitrite (r = 0.379, p < 0.01), silica (r = − 0.234, p < 0.01), and ortho-p (r = − 0.273, p < 0.01). Significant negative correlations were reported between the Bacillariophyta, Conjugatophyta, Chlorophyta, and Euglenophyta numbers and water salinity. Biomass of Euglenophyta and Chlorophyta was correlated negatively with water salinity (Table 5). Whereas, a significant posi-tive correlation was found between Pyrrophyta biomass and water salinity (r = 0.244, p < 0.01).

In most sites, electrical conductivity started to increase in summer reaching a maximum value of 94,000 ± 15 mmhos/cm in August at site V as shown in Table 3. It could be related to a decrease in phytoplankton population in summer leading to an increase in the availability of nutrients. The high annual mean value of conductivity (79,966.7 mmhos/cm) at site VI may be attributed to high dissolved solids and the relatively high rate of biodegradation, biogeochemical cycle, and human activities (Koçer and Şen 2012; Abdel-Satar 2005). Significant positive correlations (p < 0.01) were found between electrical conductivity with nitrite (r = 0.379) and site (r = 0.833). Also, negative correlation (p < 0.01) between electrical conductivity with total alkalin-ity (r = − 0.702), ammonia (r = − 0.547), silica (r = − 0.219), and ortho-P (r = − 0.321) was detected.

The annual mean value of total alkalinity was low at site IV (2.4 meq/L) and high at site II (4.6 meq/L) as shown in Table 2. This difference might be related to water qual-ity. Total alkalinity depends upon the type of discharged wastes. Moss (1973) reported that total alkalinity values greater than 1.4 meq/L indicate eutrophic conditions. There were positive significant correlations between numbers of most phytoplankton groups (Cyanophyta, Bacillariophyta, Chlorophyta, and Euglenophyta) and total alkalinity of water (Table 5). Total alkalinity has a weak correlation with DO (r = − 0.126, p < 0.05), and a moderate correlation with ammonia (r = 0.533, p < 0.01), nitrite (r = − 0.401, p < 0.01), nitrate (r = − 0.234, p < 0.01), silica (r = 0.324, p < 0.01), ortho-P (r = 0.419, p < 0.01), and site (r = − 0.717, p < 0.01). A similar correlation between total alkalinity and DO value was also reported by Elmorsi et al. (2017).

Ammonium is an active compound present in water as a normal biological degradation product of organic nitro-gen and represented 80% of dissolved inorganic nitro-gen (Salah and El-Moselhy 2015). The results showed significant positive correlations between numbers of Bacillariophyta, Conjugatophyta, and Euglenophyta and ammonia content in water (Table 5). Also, Chellappa et al. (2009) reported a positive correlation between Bacillari-ophyta group and ammonia. Biomass of Conjugatophyta,


1 3

Tabl

e 2

Mon

thly

var

iatio

ns in

pH

, tem

pera

ture

, tur

bidi

ty, a

nd to

tal a

lkal

inity

(mea

n ± S

D) a

t diff

eren

t site

s

Para

met

ers

Mon

ths

Site

Janu

ary

Febr

uary

Mar

chA

pril

May

June

July

Aug

ust

Sept

embe

rO

ctob

erN

ovem

ber

Dec

embe

r

pHSi

te I

9.2 ±

0.1

7.6 ±

0.1

7.9 ±

0.1

8.2 ±

0.1

8.2 ±

0.1

8.1 ±

0.1

7.8 ±

0.1

8.0 ±

0.1

7.7 ±

0.1

7.6 ±

0.1

7.9 ±

0.1

8.0 ±

0.1

Site

II7.

1 ± 0.

18.

1 ± 0.

17.

1 ± 0.

17.

3 ± 0.

17.

2 ± 0.

17.

1 ± 0.

17.

1 ± 0.

17.

2 ± 0.

17.

1 ± 0.

037.

6 ± 0.

17.

8 ± 0.

17.

4 ± 0.

1Si

te II

I9.

8 ± 0.

19.

4 ± 0.

18.

5 ± 0.

18.

1 ± 0.

017.

9 ± 0.

017.

5 ± 0.

17.

8 ± 0.

17.

7 ± 0.

17.

9 ± 0.

17.

6 ± 0.

17.

5 ± 0.

17.

9 ± 0.

03Si

te IV

9.4 ±

0.1

8.9 ±

0.1

7.5 ±

0.1

7.2 ±

0.1

7.1 ±

0.1

7.1 ±

0.1

7.6 ±

0.1

7.5 ±

0.1

7.6 ±

0.1

7.8 ±

0.1

7.9 ±

0.1

8.8 ±

0.1

Site

V9.

3 ± 0.

19.

1 ± 0.

18.

5 ± 0.

17.

8 ± 0.

17.

7 ± 0.

17.

5 ± 0.

17.

8 ± 0.

17.

6 ± 0.

17.

7 ± 0.

17.

8 ± 0.

17.

9 ± 0.

18.

0 ± 0.

1Si

te V

I8.

8 ± 0.

18.

7 ± 0.

17.

7 ± 0.

17.

6 ± 0.

17.

5 ± 0.

17.

4 ± 0.

17.

8 ± 0.

17.

7 ± 0.

17.

8 ± 0.

17.

9 ± 0.

18.

0 ± 0.

18.

5 ± 0.

1Si

te V

II2.

8 ± 0.

012.

9 ± 0.

12.

8 ± 0.

12.

7 ± 0.

12.

2 ± 0.

12.

1 ± 0.

12.

0 ± 0.

12.

2 ± 0.

12.

3 ± 0.

12.

5 ± 0.

12.

6 ± 0.

12.

7 ± 0.

1Te

mpe

ratu

re (°

C)

Site

I10

± 0.

112

± 0.

120

± 0.

123

± 0.

124

± 0.

125

± 0.

127

± 0.

129

± 0.

129

± 0.

125

± 0.

121

± 0.

117

.5 ±

0.1

Site

II10

± 0.

112

± 0.

120

± 0.

123

± 0.

124

± 0.

125

± 0.

126

± 0.

128

± 0.

127

± 0.

122

± 0.

120

± 0.

118

± 0.

1Si

te II

I10

± 0.

112

± 0.

120

± 0.

123

± 0.

124

± 0.

126

± 0.

127

± 0.

126

± 0.

130

± 0.

124

± 0.

123

.5 ±

0.1

17 ±

0.1

Site

IV10

± 0.

111

± 0.

120

± 0.

122

± 0.

123

± 0.

125

± 0.

128

± 0.

129

± 0.

127

± 0.

125

± 0.

124

± 0.

117

.5 ±

0.1

Site

V11

± 0.

113

± 0.

120

± 0.

122

.5 ±

0.1

24 ±

0.1

25 ±

0.1

26 ±

0.1

28 ±

0.1

27 ±

0.1

25 ±

0.1

23 ±

0.1

18 ±

0.1

Site

VI

10 ±

0.1

11 ±

0.1

20 ±

0.1

22 ±

0.1

23 ±

0.1

25 ±

0.1

27 ±

0.1

29 ±

0.1

26 ±

0.1

24.5

± 0.

124

± 0.

119

± 0.

1Si

te V

II10

± 0.

113

± 0.

120

± 0.

121

± 0.

124

± 0.

126

± 0.

128

.5 ±

0.1

28 ±

0.1

27 ±

0.1

26 ±

0.1

24 ±

0.1

18 ±

0.1

Turb

idity

(NTU

)Si

te I

3.8 ±

0.1

6.3 ±

0.1

5.8 ±

0.1

13.5

± 0.

112

.1 ±

0.1

11.2

± 0.

19.

2 ± 0.

110

± 0.

116

± 0.

14.

6 ± 0.

14.

0 ± 0.

13.

3 ± 0.

1Si

te II

12 ±

0.1

18 ±

0.1

20 ±

0.1

41.4

± 0.

141

.1 ±

0.1

42 ±

0.1

19.4

± 0.

131

.5 ±

0.1

24.3

± 0.

110

± 0.

19.

0 ± 0.

17.

1 ± 0.

1Si

te II

I7.

0 ± 0.

15.

8 ± 0.

16.

0 ± 0.

16.

2 ± 0.

18.

6 ± 0.

117

.4 ±

0.1

12.7

± 0.

112

.0 ±

0.1

10.2

± 0.

16.

2 ± 0.

14.

3 ± 0.

13.

6 ± 0.

1Si

te IV

3.0 ±

0.1

4.5 ±

0.1

6.5 ±

0.1

5.8 ±

0.1

5.2 ±

0.1

4.9 ±

0.1

3.0 ±

0.1

3.4 ±

0.1

3.2 ±

0.1

3.3 ±

0.1

5.5 ±

0.1

2.8 ±

0.1

Site

V7.

9 ± 0.

14.

4 ± 0.

16.

6 ± 0.

19.

9 ± 0.

12.

4 ± 0.

18.

1 ± 0.

118

.3 ±

0.1

24.2

± 0.

125

± 0.

118

± 0.

110

.2 ±

0.1

3.2 ±

0.1

Site

VI

7.1 ±

0.1

7.2 ±

0.1

6.9 ±

0.1

7.3 ±

0.1

7.4 ±

0.1

7.6 ±

0.1

6.6 ±

0.1

6.5 ±

0.1

6.4 ±

0.1

6.8 ±

0.1

7.5 ±

0.1

7.4 ±

0.1

Site

VII

30.6

± 0.

16.

5 ± 0.

177

.8 ±

0.1

103.

5 ± 0.

160

.3 ±

0.1

50.8

± 0.

13.

8 ± 0.

142

± 0.

16.

4 ± 0.

15.

8 ± 0.

14.

1 ± 0.

157

.7 ±

0.1

Tota

l Alk

. (m

eq/L

)Si

te I

4.4 ±

0.01

4.8 ±

0.01

4.4 ±

0.1

4.0 ±

0.6

3.6 ±

0.01

3.8 ±

0.1

2.3 ±

0.1

2.9 ±

0.01

4.0 ±

0.01

5.6 ±

0.1

5.2 ±

0.1

4.7 ±

0.01

Site

II5.

2 ± 0.

15.

1 ± 0.

14.

9 ± 0.

13.

7 ± 0.

014.

4 ± 0.

14.

1 ± 0.

13.

4 ± 0.

13.

9 ± 0.

014.

5 ± 0.

015.

2 ± 0.

015.

0 ± 0.

015.

7 ± 0.

01Si

te II

I4.

6 ± 0.

13.

8 ± 0.

13.

7 ± 0.

13.

8 ± 0.

14.

0 ± 0.

63.

9 ± 0.

13.

4 ± 0.

13.

6 ± 0.

13.

8 ± 0.

14.

4 ± 0.

14.

2 ± 0.

14.

8 ± 0.

1Si

te IV

2.6 ±

0.1

2.1 ±

0.1

1.6 ±

0.1

2.2 ±

0.1

2.1 ±

0.1

2.0 ±

0.1

2.0 ±

0.01

2.1 ±

0.1

2.2 ±

0.01

5.5 ±

0.01

2.2 ±

0.01

2.6 ±

0.1

Site

V3.

2 ± 0.

012.

8 ± 0.

12.

8 ± 0.

12.

8 ± 0.

12.

0 ± 0.

62.

2 ± 0.

12.

0 ± 0.

012.

4 ± 0.

12.

2 ± 0.

13.

4 ± 0.

13.

6 ± 0.

013.

7 ± 0.

1Si

te V

I2.

8 ± 0.

012.

9 ± 0.

12.

8 ± 0.

12.

7 ± 0.

12.

2 ± 0.

12.

1 ± 0.

12.

0 ± 0.

12.

2 ± 0.

12.

3 ± 0.

12.

5 ± 0.

12.

6 ± 0.

12.

7 ± 0.

1Si

te V

II6.

5 ± 0.

17.

4 ± 0.

16.

0 ± 0.

68.

0 ± 0.

65.

2 ± 0.

16.

2 ± 0.

13.

0 ± 0.

66.

3 ± 0.

013.

1 ± 0.

014.

5 ± 0.

14.

2 ± 0.

19.

2 ± 0.

1


1 3

Tabl

e 3

Mon

thly

var

iatio

ns in

salin

ity, e

lect

rical

con

duct

ivity

, DO

, and

silic

a co

nten

ts (m

ean ±

SD

) at d

iffer

ent s

ites

Para

met

ers

Mon

ths

Site

Janu

ary

Febr

uary

Mar

chA

pril

May

June

July

Aug

ust

Sept

embe

rO

ctob

erN

ovem

ber

Dec

embe

r

Salin

ity (m

g/L)

Site

I10

± 0.

038 ±

0.03

9 ± 0.

0310

± 0.

112

.5 ±

0.1

13 ±

0.1

33 ±

0.1

26 ±

0.1

25 ±

0.1

38 ±

0.1

15 ±

0.03

10 ±

0.03

Site

II18

± 0.

0320

± 0.

122

± 0.

124

± 0.

0329

± 0.

128

± 0.

122

.5 ±

0.1

24.5

± 0.

125

± 0.

0328

± 0.

0330

± 0.

0317

± 0.

1Si

te II

I28

± 0.

114

± 0.

0315

± 0.

113

± 0.

111

± 0.

0310

± 0.

127

± 0.

131

± 0.

125

± 0.

122

± 0.

0321

± 0.

0313

.5 ±

0.03

Site

IV34

.5 ±

0.1

36 ±

0.1

49 ±

0.1

43.1

± 0.

0345

± 0.

143

.5 ±

0.1

44 ±

0.1

48 ±

0.1

50 ±

0.1

66 ±

0.1

33 ±

0.1

34 ±

0.03

Site

V56

± 0.

0350

± 0.

152

± 0.

155

± 0.

148

± 0.

147

± 0.

158

± 0.

180

± 0.

172

± 0.

0365

± 0.

0360

± 0.

0352

.5 ±

0.1

Site

VI

50 ±

0.1

55 ±

0.03

47 ±

0.1

46 ±

0.1

45 ±

0.1

43 ±

0.03

59 ±

0.1

60 ±

0.1

58 ±

0.03

70 ±

0.03

79 ±

0.03

74 ±

0.1

Site

VII

3.0 ±

0.0

3.0 ±

0.0

2.0 ±

0.0

3.0 ±

0.0

1.0 ±

0.0

2.0 ±

0.0

1.0 ±

0.0

2.0 ±

0.0

1.0 ±

0.0

1.0 ±

0.03

0.65

± 0.

030.

5 ± 0.

0EC

(mm

hos/

cm)

Site

I80

00 ±

1812

,000

± 15

14,0

00 ±

1516

,000

± 15

20,0

00 ±

1922

,000

± 19

63,0

00 ±

1549

,000

± 15

39,0

00 ±

1771

,000

± 6

30,0

00 ±

8.8

15,0

00 ±

15Si

te II

34,4

00 ±

1535

,000

± 15

35,1

00 ±

1535

,500

± 19

43,5

00 ±

1540

,000

± 23

37,0

00 ±

1739

,500

± 6

39,6

00 ±

1740

,000

± 15

40,4

00 ±

1534

,000

± 15

Site

III

41,0

00 ±

1922

,000

± 15

23,5

00 ±

620

,000

± 15

17,5

00 ±

1517

,000

± 19

43,5

00 ±

1756

,000

± 15

39,5

00 ±

1725

,000

± 15

20,6

00 ±

1920

,000

± 15

Site

IV56

,600

± 15

60,0

00 ±

1570

,000

± 12

71,0

00 ±

1570

,500

± 15

69,0

00 ±

1960

,000

± 17

67,5

00 ±

370

,500

± 19

90,0

00 ±

1552

,160

± 9

56,5

00 ±

15Si

te V

46,5

00 ±

1542

,000

± 15

45,0

00 ±

1555

,000

± 15

44,0

00 ±

1944

,000

± 15

92,0

00 ±

1794

,000

± 15

90,0

00 ±

1570

,000

± 15

60,0

00 ±

5.8

43,5

00 ±

15Si

te V

I80

,000

± 19

72,0

00 ±

1569

,000

± 12

67,0

00 ±

1966

,500

± 15

65,0

00 ±

1590

,000

± 17

89,0

00 ±

1588

,500

± 3.

590

,100

± 8.

892

,000

± 15

90,5

00 ±

15Si

te V

II32

00 ±

1535

00 ±

1520

00 ±

1734

00 ±

1720

00 ±

1721

00 ±

718

00 ±

1625

00 ±

1.9

1800

± 15

1800

± 6

1700

± 19

1600

± 15

DO

(mg/

L)Si

te I

10 ±

0.6

8.8 ±

0.1

8.9 ±

0.1

9.1 ±

0.1

10 ±

0.6

8.7 ±

0.1

7.1 ±

0.1

7.2 ±

0.1

7.0 ±

0.6

7.9 ±

0.1

8.1 ±

0.1

8.2 ±

0.1

Site

II7.

0 ± 0.

67.

1 ± 0.

17.

2 ± 0.

15.

8 ± 0.

16.

0 ± 0.

65.

5 ± 0.

18.

1 ± 0.

17.

9 ± 0.

18.

0 ± 0.

65.

5 ± 0.

15.

6 ± 0.

15.

5 ± 0.

1Si

te II

I8.

1 ± 0.

18.

4 ± 0.

18.

2 ± 0.

19.

2 ± 0.

18.

0 ± 0.

68.

5 ± 0.

18.

0 ± 0.

17.

2 ± 0.

15.

6 ± 0.

17.

2 ± 0.

17.

1 ± 0.

17.

0 ± 0.

6Si

te IV

12.0

± 0.

68.

1 ± 0.

14.

1 ± 0.

18.

2 ± 0.

18.

1 ± 0.

18.

0 ± 0.

66.

9 ± 0.

17.

0 ± 0.

17.

1 ± 0.

17.

9 ± 0.

18.

0 ± 0.

18.

1 ± 0.

1Si

te V

7.4 ±

0.1

8.0 ±

0.1

7.6 ±

0.1

8.8 ±

0.1

4.0 ±

0.6

6.6 ±

0.1

6.8 ±

0.1

7.2 ±

0.1

7.3 ±

0.1

7.7 ±

0.1

7.6 ±

0.1

7.8 ±

0.1

Site

VI

5.9 ±

0.1

6.2 ±

0.1

6.3 ±

0.1

7.0 ±

0.6

7.2 ±

0.1

7.3 ±

0.1

5.2 ±

0.06

5.3 ±

0.1

5.4 ±

0.1

6.1 ±

0.1

6.2 ±

0.1

6.0 ±

0.6

Site

VII

2.8 ±

0.1

4.0 ±

0.6

0 ± 0

0 ± 0

0 ± 0

0 ± 0

6.6 ±

0.1

6.0 ±

0.6

4.0 ±

0.6

3.0 ±

0.6

2.2 ±

0.04

2.5 ±

0.1

Silic

a (m

g/L)

Site

I6.

1 ± 0.

016.

4 ± 0.

16.

9 ± 0.

16.

4 ± 0.

12.

8 ± 0.

14.

1 ± 0.

14.

0 ± 0.

18.

5 ± 0.

017.

4 ± 0.

017.

0 ± 0.

016.

5 ± 0.

10.

96 ±

0.01

Site

II5.

9 ± 0.

15.

7 ± 0.

15.

8 ± 0.

15.

6 ± 0.

12.

6 ± 0.

013.

5 ± 0.

13.

8 ± 0.

010 ±

07.

0 ± 0.

018.

2 ± 0.

110

.9 ±

0.01

0.8 ±

0.1

Site

III

5.6 ±

0.1

5.4 ±

0.1

5.5 ±

0.1

6.1 ±

0.1

3.2 ±

0.1

4.2 ±

0.1

4.2 ±

0.01

1.3 ±

0.01

7.8 ±

0.01

8.5 ±

0.1

13.4

± 0.

10.

6 ± 0.

01Si

te IV

1.3 ±

0.01

2.2 ±

0.1

2.4 ±

0.1

3.5 ±

0.1

3.6 ±

0.1

1.4 ±

0.1

2.1 ±

0.01

2.5 ±

0.1

2.2 ±

0.1

6.2 ±

0.1

6.7 ±

0.01

0.6 ±

0.01

Site

V4.

8 ± 0.

13.

2 ± 0.

13.

5 ± 0.

13.

2 ± 0.

12.

2 ± 0.

011.

6 ± 0.

013.

7 ± 0.

017.

8 ± 0.

017.

9 ± 0.

11.

3 ± 0.

11.

2 ± 0.

10.

64 ±

0.01

Site

VI

1.3 ±

0.1

1.5 ±

0.1

0.8 ±

0.1

2.6 ±

0.1

2.7 ±

0.1

2.9 ±

0.01

2.4 ±

0.1

2.5 ±

0.1

2.6 ±

0.1

10.5

± 0.

110

.4 ±

0.1

11 ±

0.6

Site

VII

6.3 ±

0.1

7.2 ±

0.1

7.2 ±

0.1

7.2 ±

0.1

2.9 ±

0.01

3.1 ±

0.1

4.0 ±

0.58

9.3 ±

0.01

7.5 ±

0.01

6.0 ±

0.1

13.6

± 0.

041.

1 ± 0.

01


1 3

Chlorophyta, and Euglenophyta were correlated positively with ammonia. High contents of ammonia were detected throughout the year in site VII as shown in Table 4. The annual mean values of ammonia varied between 2.1 mg/L in July to 8 mg/L in November with local variations. Ammonia (6.5 mg/L) attained their maximum values dur-ing winter months. This is in agreement with the find-ings of El Gammal et al. (2017) who found a higher level of ammonia during winter. The high concentration of ammonia at site VII may be attributed to high pollution mainly due to domestic and agricultural wastes which in turn decomposed by the bacterial effect and produced a high amount of NH4 (Salah El Din 2005). Ammonia was moderately correlated with nitrate (r = − 0.225, p < 0.01), silica (r = 0.219, p < 0.01), ortho-P (r = 0.654, p < 0.01), DO (r = − 0.272, p < 0.01), site (r = − 0.387, p < 0.01), and months (r = 0.166, p < 0.01).

Nitrite concentrations in the aquatic system are useful due to its intermediate oxidation state between ammonia and nitrate (Nassar and Hamed 2003). A low annual mean value of nitrite was detected at site I, while high values were detected at sites IV and VI (Table 4). Nitrite concentrations in the aquatic environment were affected by bacterial activ-ity and oxidation–reduction reactions. There were no cor-relations between phytoplankton groups and nitrite content in water (Table 5). It may be related to the dependence of phytoplankton on nitrate and ammonia as nitrogen sources. Nitrite in the water at sites I, IV, V, and VII increased with increasing temperature in July–September as nitrifying bacteria became active. Nitrite showed a moderate correla-tion with site (r = 0.418, p < 0.01) and silica (r = − 0.189, p < 0.01) and a weak correlation with both nitrate and DO (r = − 0.127, p < 0.05).

Nitrate is considered the most stable and predominant inorganic nitrogen form in seawater and it is one of the main nitrogen sources for phytoplankton (Al-Qutob et al. 2002). Numbers of Bacillariophyta, Pyrrophyta, and Chlorophyta groups were correlated positively with nitrate content in water as a nitrogen source. Also, Chellappa et al. (2009) reported the same previous correlations in the Armando Ribeiro Goncalves reservoir, Brazil. The annual mean nitrate values ranged between 385.9 mg/L at site VI and 2060.2 mg/L at site III as shown in Table 4. Nitrate is var-iable in all sites of the lake because they are involved in biological processes and can be incorporated into structural compounds within living organisms. High values of nitrate during spring and summer could be attributed to the decom-position of organic matter at higher temperature and entry of nitrogen fertilizers from catchment areas (Ganai and Parveen 2014). Nitrate showed a significant correlation with months (r = 0.188, p < 0.01) and ortho-P (r = − 0.504, p < 0.01). A similar correlation between nitrate and phosphorus was also reported by Abbassi et al. (2017).

The results revealed that there was a local variation of Silica, ranged from 0.6 ± 0.01 mg/L at sites III and IV to 13.6 ± 0.04 mg/L at site VII (Table 3). The high annual mean value of Silica at site VII may be attributed to the agricul-tural activities, the decay of diatoms, and the decomposition of organic matter (Juttner et al. 1996; Elewa et al. 1995). In this study, the number and biomass of Bacillariophyta were correlated positively with silica content in water (Table 5). Cetin and Sen (1998) reported a clear relationship between the seasonal growth of phytoplankton and the silica con-centration of the water. Silica showed a significant positive correlation with ortho-P (r = 0.246, p < 0.01), and a negative correlation with site (r = − 0.34, p < 0.01).

Phosphorus is an important element for the growth and primary production of phytoplankton in the aquatic systems. In this study, positive correlations were reported between the biomass of most phytoplankton groups (Cyanophyta, Conju-gatophyta, Chlorophyta, and Euglenophyta) and ortho-phos-phorus content in water (Table 5). ortho-Phosphorus content in North El-Manzala Lake was negatively correlated with DO (r = − 0.276, p < 0.01) and site (r = − 0.203, p < 0.01) and ranged from 1.9 ± 0.01 mg/L at site IV (in August) to 400 ± 0.04 mg/L at site VII (in November) as shown in Table 4. The high content of ortho-P at site VII may be related to pollution with industrial and urbane sewage water. Margalef (1978) reported that phosphorus concentration between 0.2 and 2.8 mg/L is favorable for the growth of Cyanophyta and Bacillariophyta. In all sites, ortho-P was highest during October–December.

Dissolved oxygen is considered as an indicator of the ability of water body to support a well-balanced aquatic life (George et al. 2012; Salah and El-Moselhy 2015). The maximum value of DO (12.0 ± 0.6 mg/L) was recorded in January at site IV with a minimum value (2.2 ± 0.04 mg/L) in November at site VII (Table 3). Dissolved oxygen con-centrations above 5 mg/L were suitable to support aquatic animals (Baleta and Bolaños 2016). DO was not detected at site III in March–June. The high annual mean value of DO (8.4 mg/L) at the site I may be due to low pollution and low wave action. The higher values of DO (7 mg/L as an average) in the winter period can be attributed to the lower rate of decomposition and the capacity of water to hold high oxygen concentration at low temperature. The present results showed a significant difference (p < 0.05) in DO among the different sites (Table 1). DO was positively correlated with pH (r = 0.265, p < 0.01) and negatively correlated with months (r = − 0.175, p < 0.01), temperature, turbidity, total alkalinity, ammonia, nitrite, and ortho-phosphorus. Koralay et al. (2018) also reported the negative correlation between DO and water temperature.

From the above discussed physicochemical results, it is evident that there was marked regional variation in the physicochemical properties of the studied area. These


1 3

Tabl

e 4

Mon

thly

var

iatio

ns in

am

mon

ia, n

itrite

, nitr

ate,

and

ort

ho-P

con

tent

s (m

ean ±

SD

) at d

iffer

ent s

ites

Para

met

ers

Mon

ths

Site

Janu

ary

Febr

uary

Mar

chA

pril

May

June

July

Aug

ust

Sept

embe

rO

ctob

erN

ovem

ber

Dec

embe

r

Am

m. (

mg/

L)Si

te I

2.5 ±

0.1

2.2 ±

0.1

2.3 ±

0.1

2.0 ±

0.01

2.8 ±

0.1

2.1 ±

0.1

2.2 ±

0.01

1.8 ±

0.01

1.7 ±

0.01

2.1 ±

0.01

3.2 ±

0.1

2.4 ±

0.1

Site

II2.

5 ± 0.

12.

4 ± 0.

12.

3 ± 0.

012.

2 ± 0.

012.

5 ± 0.

012.

5 ± 0.

011.

8 ± 0.

012.

7 ± 0.

012.

5 ± 0.

013.

4 ± 0.

114

± 0.

12.

5 ± 0.

01Si

te II

I3.

4 ± 0.

13.

2 ± 0.

12.

9 ± 0.

012.

8 ± 0.

11.

96 ±

0.01

2.4 ±

0.1

1.7 ±

0.01

1.9 ±

0.01

2.0 ±

0.01

5.1 ±

0.1

7.0 ±

0.1

4.2 ±

0.01

Site

IV2.

3 ± 0.

12.

2 ± 0.

012.

2 ± 0.

011.

9 ± 0.

012.

1 ± 0.

12.

2 ± 0.

011.

7 ± 0.

011.

6 ± 0.

011.

7 ± 0.

012.

5 ± 0.

14.

5 ± 0.

012.

2 ± 0.

01Si

te V

3.1 ±

0.1

2.9 ±

0.1

3.4 ±

0.1

2.8 ±

0.1

3.4 ±

0.01

3.1 ±

0.1

1.6 ±

0.01

1.7 ±

0.01

1.8 ±

0.01

3.4 ±

0.1

4.5 ±

0.1

5.9 ±

0.01

Site

VI

2.1 ±

0.1

2.2 ±

0.1

2.3 ±

0.1

1.2 ±

0.1

1.5 ±

0.1

1.84

± 0.

011.

68 ±

0.01

1.92

± 0.

011.

78 ±

0.01

2.5 ±

0.1

3.36

± 0.

014.

2 ± 0.

1Si

te V

II4.

2 ± 0.

14.

3 ± 0.

14.

4 ± 0.

17.

0 ± 0.

19.

8 ± 0.

18.

1 ± 0.

063.

7 ± 0.

014.

9 ± 0.

014.

1 ± 0.

0121

± 0.

119

.2 ±

0.1

18.6

± 0.

1N

itrite

(mg/

L)Si

te I

1219

± 0.

612

00 ±

0.6

1197

± 0.

612

80 ±

0.6

1276

± 0.

612

69 ±

0.6

1325

± 0.

613

20 ±

0.6

1321

± 0.

696

0 ± 0.

697

0 ± 0.

697

5 ± 0.

6Si

te II

1800

± 0.

618

70 ±

0.6

1865

± 0.

624

00 ±

0.6

2425

± 0.

624

11 ±

0.6

1596

± 0.

616

00 ±

0.6

1670

± 0.

615

20 ±

0.6

1498

± 0.

615

11 ±

0.6

Site

III

2511

± 0.

626

80 ±

0.6

2520

± 0.

616

80 ±

0.6

1530

± 0.

610

80 ±

0.6

791 ±

0.6

760 ±

0.6

780 ±

0.6

920 ±

0.6

930 ±

0.6

940 ±

0.6

Site

IV17

25 ±

0.6

1731

± 0.

617

20 ±

0.6

1569

± 0.

615

35 ±

0.6

1560

± 0.

625

20 ±

0.6

2760

± 0.

627

44 ±

0.6

2720

± 0.

627

30 ±

0.6

2731

± 0.

6Si

te V

1820

± 0.

618

31 ±

0.6

1800

± 0.

617

52 ±

0.6

1771

± 0.

617

60 ±

0.6

2212

± 0.

623

19 ±

0.6

2321

± 0.

619

30 ±

0.6

1941

± 0.

619

52 ±

0.6

Site

VI

1260

± 0.

612

40 ±

0.6

1300

± 0.

681

20 ±

0.6

2580

± 0.

625

91 ±

0.6

1543

± 0.

615

60 ±

0.6

1551

± 0.

614

00 ±

0.6

1420

± 0.

614

11 ±

0.6

Site

VII

1391

± 0.

614

00 ±

0.6

1415

± 0.

612

00 ±

0.6

1225

± 0.

612

11 ±

0.6

1749

± 0.

617

60 ±

0.6

1750

± 0.

616

50 ±

0.6

1566

± 0.

615

96 ±

0.6

Nitr

ate

(mg/

L)Si

te I

625 ±

0.6

640 ±

0.6

633 ±

0.6

130 ±

0.6

140 ±

0.6

135 ±

0.6

680 ±

0.6

678 ±

0.1

671 ±

0.6

653 ±

0.1

660 ±

0.6

655 ±

0.6

Site

II16

9 ± 0.

617

7 ± 0.

618

0 ± 0.

640

8 ± 0.

641

0 ± 0.

640

1 ± 0.

618

00 ±

0.6

1808

± 0.

618

10 ±

0.6

232 ±

0.6

521 ±

0.6

530 ±

0.6

Site

III

168 ±

0.6

162 ±

0.1

165 ±

0.1

3776

± 0.

637

50 ±

0.6

7762

± 0.

622

50 ±

0.6

2257

± 0.

122

51 ±

0.6

729 ±

0.6

732 ±

0.6

720 ±

0.6

Site

IV53

5 ± 0.

652

0 ± 0.

650

9.6 ±

0.6

301 ±

0.6

290 ±

0.6

281 ±

0.1

1050

± 0.

610

40 ±

0.6

1044

± 0.

617

0 ± 0.

117

1 ± 0.

617

3 ± 0.

6Si

te V

861 ±

0.6

863.

2 ± 0.

187

0 ± 0.

157

38 ±

0.6

3605

± 0.

636

80 ±

0.6

1031

± 0.

610

41 ±

0.1

1045

± 0.

622

5 ± 0.

623

4 ± 0.

624

0 ± 0.

6Si

te V

I40

0 ± 0.

639

1 ± 0.

639

6 ± 0.

613

0 ± 0.

612

5 ± 0.

612

3 ± 0.

183

0 ± 0.

684

0 ± 0.

683

9 ± 0.

5818

0 ± 0.

619

0 ± 0.

619

2 ± 0.

6Si

te V

II92

± 0.

692

.5 ±

0.1

93 ±

0.6

216 ±

0.6

219 ±

0.6

221 ±

0.6

790 ±

0.6

797 ±

0.1

798 ±

0.6

520 ±

0.6

511 ±

0.6

515 ±

0.6

orth

o-P

(mg/

L)Si

te I

7.4 ±

0.1

31.5

± 0.

125

± 0.

65.

6 ± 0.

010 ±

06.

2 ± 0.

13.

7 ± 0.

13.

3 ± 0.

012.

8 ± 0.

014.

4 ± 0.

014.

8 ± 0.

14.

9 ± 0.

01Si

te II

31 ±

0.6

29 ±

0.6

28 ±

0.6

7.4 ±

0.1

2.7 ±

0.01

2.9 ±

0.1

13 ±

0.01

7.0 ±

0.01

8.9 ±

0.01

56 ±

0.6

55.5

± 0.

156

.7 ±

0.1

Site

III

33.3

± 0.

133

.3 ±

0.1

33.5

± 0.

11.

9 ± 0.

010 ±

02.

9 ± 0.

015.

9 ± 0

2.6 ±

0.01

3.3 ±

0.01

69 ±

0.6

68.5

± 0.

169

.5 ±

0.1

Site

IV16

.6 ±

0.1

12.8

± 0.

16.

7 ± 0.

018.

9 ± 0.

19.

1 ± 0.

19.

3 ± 0.

012.

6 ± 0.

11.

9 ± 0.

012.

8 ± 0.

14.

4 ± 0.

0148

.2 ±

0.1

44.5

± 0.

1Si

te V

20.4

± 0.

113

.7 ±

0.1

18 ±

0.6

3.7 ±

0.1

0 ± 0

3.4 ±

0.1

7.4 ±

0.1

5.9 ±

0.1

6.3 ±

0.1

45.5

± 0.

148

± 0.

147

± 0.

6Si

te V

I23

± 0.

622

.8 ±

0.1

22.2

± 0.

111

.5 ±

0.1

10.9

± 0.

110

.4 ±

0.1

2.6 ±

0.01

2.8 ±

0.1

3.5 ±

0.1

48.2

± 0.

149

.9 ±

0.1

50.5

± 0.

1Si

te V

II15

0 ± 0.

612

4.1 ±

0.1

200 ±

0.1

166.

6 ± 0.

18.

88 ±

0.01

88.9

± 0.

114

.4 ±

0.1

55.5

± 0.

116

.7 ±

0.01

390 ±

0.6

400 ±

0.04

380 ±

0.6


1 3

Tabl

e 5

Pea

rson

’ s co

rrel

atio

n be

twee

n ph

ysic

oche

mic

al p

aram

eter

s and

phy

topl

ankt

on g

roup

s at N

orth

El-M

anza

la L

ake

Cy.

Cya

noph

yta,

Ba.

Bac

illar

ioph

yta,

Py.

Pyr

roph

yta,

Co.

Con

juga

toph

yta,

Ch.

Chl

orop

hyta

, Eu.

Eug

leno

phyt

a, N

o. n

umbe

r, bi

o. b

iom

ass

**St

atist

ical

ly si

gnifi

cant

cor

rela

tion

at p

< 0.

01, *

stat

istic

ally

sign

ifica

nt c

orre

latio

n at

p <

0.05

. Bol

d te

xt in

dica

tes n

egat

ive

corr

elat

ion

Cy.

No.

Ba.

No.

Py. N

o.C

o.

No.

Ch.

N

o.Eu

. No.

Cy.

bi

o.B

a.

bio.

Py.

bio.

Co.

bio.

Ch.

bi

o.Eu

. bi

o.pH

Tem

p.Tu

rbid

-ity

.Sa

lin-

ityEC

Tota

l A

lk.

Am

m.

Nitr

iteN

itrat

eSi

lica

orth

o-P

DO

Cy.

No.

1B

a. N

o.0.

062

1Py

. No.

0.21

1**

0.51

6**

1C

o. N

o.0.115

0.08

50.084

1C

h. N

o.0.

034

0.60

2**

0.37

5**

0.04

51

Eu. N

o.0.

064

0.19

0**

0.10

10.012

0.032

1C

y. b

io.

0.96

8**

0.05

40.

200*

*0.101

0.04

80.

081

1B

a. b

io.0.059

0.26

2**

0.00

40.

284*

*0.

082

0.00

30.041

1Py

. bio

.0.

308*

*0.

066

0.63

0**

0.127*

0.11

00.002

0.32

1**

0.045

1C

o. b

io.0.100

0.059

0.116

0.44

7**

0.086

0.062

0.116

0.08

10.

002

1C

h. b

io.

0.03

50.

138*

0.19

3**

0.010

0.23

7**

0.20

6**

0.00

60.

155*

0.20

5**

0.05

31

Eu. b

io.

0.05

50.

313*

*0.

164*

*0.015

0.037

0.96

3**

0.06

80.

006

0.02

00.023

0.22

2**

1pH

0.31

9**

0.01

40.

063

0.089

0.014

0.016

0.33

8**

0.16

4**

0.24

0**

0.09

70.

284*

*0.018

1Te

mp.

0.30

3**

0.30

4**

0.24

1**

0.06

90.

398*

*0.

053

0.32

1**

0.19

6**

0.31

0**

0.01

80.

286*

*0.

045

0.51

3**

1Tu

rbid

-ity

0.06

30.021

0.059

0.128*

0.05

00.

246*

*0.

116

0.085

0.087

0.094

0.11

20.

200*

*236**

0.17

2*1

Salin

ity0.050

0.234*

*0.

010

0.356*

*0.261*

*0.193*

*0.109

0.123

0.24

4**

0.063

0.199*

*0.173*

*0.

104

0.12

6*0.157*

1EC

0.099

0.211*

*0.

094

0.363*

*0.215*

*0.189*

*0.148*

0.134*

0.20

6**

0.138*

0.208*

*0.171*

*0.

034

0.18

9*0.157*

0.94

9**

1To

tal

Alk

.0.

127*

0.27

8**

0.07

50.

092

0.25

8**

0.43

4**

0.20

0**

0.08

90.067

0.009

0.37

1**

0.41

9**

0.001

0.290*

0.31

7**

0.673*

*0.702*

*1

Am

m.

0.02

00.

291*

*0.

045

0.46

9**

0.03

90.

474*

*0.

042

0.014

0.022

0.18

2*0.

153*

0.51

4**

0.09

00.320*

0.03

10.401*

*0.547*

*0.

533*

*1

Nitr

ite0.

075

0.055

0.055

0.099

0.039

0.073

0.05

40.087

0.00

90.010

0.070

0.065

0.078

0.05

10.144*

0.37

9**

0.38

9**

0.401*

*0.134*

1N

itrat

e0.091

0.13

5*0.

144*

0.082

0.14

2*0.019

0.099

0.037

0.138*

0.116

0.080

0.043

0.200**

0.45

5*0.103

0.13

2*0.

074

0.234*

*0.225*

*0.127*

1Si

lica

0.058

0.23

2**

0.122

0.16

2*0.

143*

0.088

0.030

0.16

9**

0.270*

*0.

070

0.06

00.

022

0.003

0.09

80.

184*

*0.23

4**

0.219*

*0.

324*

*0.

219*

*0.189*

*0.092

1or

tho-

P0.

060

0.10

60.024

0.43

8**

0.12

10.

457*

*0.

128*

0.046

0.013

0.14

4*0.

287*

*0.

429*

*0.

134*

0.486*

0.05

90.273*

*0.321*

*0.

419*

*0.

654*

*0.117

0.504*

*0.

246*

*1

DO

0.020

0.03

50.034

0.112

0.027

0.177*

*0.092

0.16

1*0.

012

0.05

20.227*

*0.165*

*0.

265*

*0.155*

0.285*

*0.

056

0.06

50.126*

0.272*

*0.127*

0.07

40.093

0.276*

*1


1 3

variations were attributed to the effects of the different pol-lution sources. Site VII received a considerable amount of industrial and agricultural pollutants. Meanwhile, site I was comparatively less polluted as compared to other sites.

Biological analysis

Six of phytoplankton groups were identified in North El-Manzala Lake—Damietta, Egypt, and their photographs are shown in Fig. 2. Cyanophyta, Bacillariophyta, and Pyr-rophyta were the dominant classes that together constitute 98.5% and 97.3% of the total phytoplankton cell number and biomass, respectively. Other groups were present like Conjugatophyta, Chlorophyta, and Euglenophyta. Accord-ing to Abd El-Karim (2008), the dominant classes at El-Manzala Lake in 2004 were Chlorophytes, Bacillariophytes, and Cyanophytes.

The results revealed that the maximum cell number of total phytoplankton was recorded at site V (445.394 × 106). It is mainly due to the high growth of Cyanophytes, Pyr-rophytes, and Bacillariophytes as a result of the high trophic status of water and slightly stagnant water. This was in agreement with Latasa et al. (2016). Meanwhile, site VI has the lowest cell number of total phytoplank-ton (166.153 × 106) due to low nutrient content and high

movement of water (Kimmerer et al. 2018). Phytoplankton standing crop biomass was as follows: I > V > VII > II > III > VI > IV.

The results revealed that Cyanophyta dominated phyto-plankton communities along North El-Manzala Lake with an annual relative abundance of 92.9% and 44.9% based on cell number and biomass, respectively. The highest predomi-nance of Cyanophyta number was recorded at site V fol-lowed by site III and VII. The predominance of Cyanophyta may be due to the high N and P content; these elements co-limit primary productivity of algae in lakes (Carstensen et al. 2018; Filstrup and Downing 2017). While Bacillariophyta ranked the second position of dominance with an annual relative abundance of 4.1% and 32.1% based on cell number and biomass, respectively, the dominance of Bacillariophyta over Chlorophyta during all seasons of the year may be due to the competition for silica which leads to the flourishing of a large number of diatoms over the green species (Fathi and Kobbia 2000). At North El-Manzala Lake, Pyrrophyta, Conjugatophyta, Chlorophyta, and Euglenophyta constitute 1.5%, 0.20%, 1.15%, and 0.12%, respectively, of the annual phytoplankton cell number, and 20.3%, 0.83%, 0.87%, and 1.0%, respectively, of the annual biomass of phytoplankton. The highest growth of Bacillariophyta and Pyrrophyta was reported at sites I and VI, respectively.

Fig. 2 Photographs of phytoplanktons, Cyanophyta (a), Bacillariophyta (b), Pyrrophyta (c), Conjugatophyta (d), Chlorophyta (e), and Eugleno-phyta (f) cell numbers in North El-Manzala Lake


1 3

As shown in Table 5, a moderate positive correlation was reported between numbers of both Cyanophyta and Pyrro-phyta groups (r = 0.211, p < 0.01), and between the biomass of the same group (r = 0.321, p < 0.01). Bacillariophyta number is correlated significantly with numbers of Pyrro-phyta (r = 0.516, p < 0.01), Chlorophyta (r = 0.602, p < 0.01), and Euglenophyta (r = 0.190, p < 0.01). Positive significant correlations were observed between Pyrrophyta and Chlo-rophyta (both numbers and biomass). Similarly, positive significant correlations were found between Chlorophyta and both Bacillariophyta and Pyrrophyta (both numbers and biomass). Euglenophyta numbers were correlated signifi-cantly with Bacillariophyta numbers (r = 0.190, p < 0.01). Euglenophyta numbers were correlated significantly with Bacillariophyta numbers (r = 0.190, p < 0.01).

The results showed a temporal variation in phytoplankton community in North El-Manzala Lake—Damietta, Egypt. The maximum number of Bacillariophyta, Chlorophyta, and Pyrrophyta were reported in winter and early spring. The abundant growth of Bacillariophyta during winter may be favored by the low temperature (Ganjian et al. 2010). Meanwhile, the high standing crop of Chlorophyta in winter and early spring may be attributed to high nutrient content, especially nitrogen (Deyab et al. 2001). By contrast with this result, Rajagopal et al. (2010) pointed out that the pro-ductivity and periodicity of Chlorophyta increased at higher water temperature. The results showed that the maximum standing crop of Euglenophyta was recorded during autumn and early winter. Similar results were obtained by Ganjian et al. (2010) who reported that the maximum cell abundance and biomass of Euglenophyta was in winter. Meanwhile, in summer, Euglenophyta was rarely found at sites I, III, V, and VII, and completely absent at sites II, IV, and VI. These results were in agreement with Salah El Din (2005), who reported the absence of Euglenophyta during the summer season. Euglena genus is known as an indicator of organic pollution and is found commonly in polluted sites. Conju-gatophyta has a great fluctuation in the studied sites over the months. No significant correlations were found between numbers of Conjugatophyta and other phytoplankton groups (Table 5). Conjugatophyta was completely absent at site III throughout the year and was found only in autumn at site IV and in winter at site V. In general, the maximum stand-ing crop of Conjugatophyta was recorded during winter and autumn. Similar results were obtained by López-Archilla et al. (2001) who reported high growth of Conjugatophyta during autumn.

Pearson’s correlation coefficient calculated between physicochemical parameters and density of phytoplank-ton revealed that total number of phytoplankton has mod-erately positive correlation with phytoplankton biomass (r = 0.857, p < 0.01). The total number of phytoplankton was significantly correlated with pH (r = 0.325, p < 0.01),

turbidity (r = 0.183, p < 0.01), total alkalinity (r = 0.245, p < 0.01), ammonia (r = 0.178, p < 0.01), and water tem-perature (r = -358, p < 0.01). Meanwhile, phytoplank-ton standing crop biomass was significantly correlated with pH (r = 0.403, p < 0.01), total alkalinity (r = 0.216, p < 0.01), ammonia (r = 0.192, p < 0.01), ortho-phospho-rus (r = 0.166, p < 0.01), water temperature (r = − 0.445, p < 0.01), and silica content (r = − 0.165, p < 0.01). Simi-lar relationships between phytoplankton biomass and both temperature and ortho-phosphorus were also reported by Suresh et al. (2013).

At the site I, Phytoplanktonic communities were identi-fied and represented as cell number and biomass. Based on cell number, the phytoplankton belonging to Cyanophyta (93.1%) was dominant followed by Bacillariophyta (4.2%), Pyrrophyta (1.2%), Conjugatophyta (0.3%), Chlorophyta (1.1%), and Euglenophyta (0.1%) (Fig. 3). Whereas based on biomass standing crop, the phytoplankton belonging to Bacillariophyta (71.2%) was dominant followed by Cyano-phyta (22.3%), Pyrrophyta (5.6%). Conjugatophyta, Chloro-phyta, and Euglenophyta formed only 1% of total biomass standing crop as shown in Fig. 4d–f. The high biomass standing crop at the site I was observed in winter, especially in January (Fig. 4b). Meanwhile, the low standing crop of phytoplankton was observed in some months, especially in August, as it might be attributed to a mix of the brackish water of El-Manzala Lake with high saline brackish water from triangle region of Damietta resulting in inhibition of growth of most flora of water mass.

The seasonal succession of phytoplankton at site II showed no obvious pattern of variation with a predominance of Cyanophyta group in most months. Cyanophyta repre-sents 87.2% and 59.7% of the total number and biomass standing crop, respectively. Kobbia et al. (1993) reported that Cyanophyta has the ability to grow under a wide range of chemical variability. At site II, Bacillariophyta, Pyrro-phyta, and Chlorophyta represent 21.8%, 15.2%, and 0.7% of total biomass standing crop. The total number of phyto-plankton standing crop at site II was greatly higher in spring especially in April (Fig. 3a). Meanwhile, the low standing crop of phytoplankton was observed in September.

At site III, Cyanophyta predominated phytoplankton com-munity forming 65.6% of total biomass standing crop and represented the first group throughout the year except in June and December (Fig. 4a). An absence of Euglenophyta at site III in low-temperature months was in agreement with Enawgaw and Lemma (2018) who reported low biovolume of Euglenophyta in winter. Phytoplankton standing crop was highest at site III during winter, especially in January, while the lowest biomass was observed in June. It might be attributed to the high turbidity of water in June (17.4 NTU) which prevents sufficient light required for phytoplankton growth (Boyd, 1990).


1 3

0

20

40

60

80

100

120

140

160

180

200

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

emb…

Oct

ober

Nov

embe

r

Dec

embe

r

Cell

num

ber ×

106

Month

A Site I Site IISite III Site IVSite V Site VI

0

2

4

6

8

10

12

14

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

emb…

Oct

ober

Nov

embe

r

Dec

embe

r

Cell

num

ber ×

106

Month

B Site I Site II Site IIISite IV Site V Site VISite VII

0

1

2

3

4

5

6

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

em…

Oct

ober

Nov

emb…

Dec

embe

r

Cell

num

ber ×

106

Month

C Site I Site IISite III Site IVSite V Site VISite VII

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

em…

Oct

ober

Nov

emb…

Dec

embe

r

Cell

num

ber ×

106

Month

D Site I Site IISite III Site IVSite V Site VISite VII

2.5

3.0

3.5

4.0

4.5

um

ber

×10

6

E Site I Site II Site IIISite IV Site V Site VISite VII

0.8

1

1.2

1.4

num

ber ×

106

F Site I Site IISite III Site IVSite V Site VISite VII

0.0

0.5

1.0

1.5

2.0

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

em…

Oct

ober

Nov

emb…

Dec

embe

r

Cell

nu

Month

0

0.2

0.4

0.6

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

em…

Oct

ober

Nov

emb…

Dec

embe

r

Cell

n

Month

Fig. 3 Monthly and spatial variations of Cyanophyta (a), Bacillariophyta (b), Pyrrophyta (c), Conjugatophyta (d), Chlorophyta (E), and Eugle-nophyta (f) cell numbers in North El-Manzala Lake


1 3

0

5

10

15

20

25

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

embe

r

Oct

ober

Nov

embe

r

Dec

embe

r

Biom

ass

(mg/

l)

Month

A Site I Site IISite III Site IVSite V Site VISite VII

0

15

30

45

60

75

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

embe

r

Oct

ober

Nov

embe

r

Dec

embe

r

Biom

ass

(mg/

l)

Month

B Site I Site IISite III Site IVSite V Site VISite VII

0

2

4

6

8

10

12

14

16

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

embe

r

Oct

ober

Nov

embe

r

Dec

embe

r

Biom

ass

(mg/

l)

Month

C Site I Site II Site IIISite IV Site V Site VISite VII

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

embe

r

Oct

ober

Nov

embe

r

Dec

embe

r

Biom

ass

(mg/

l)

Month

D Site I Site II Site IIISite IV Site V Site VISite VII

0.2

0.3

0.4

0.5

0.6

0.7

iom

ass

(mg/

l)

E Site I Site II Site IIISite IV Site V Site VISite VII

0.4

0.6

0.8

1

1.2

1.4

1.6

Biom

ass

(mg/

l)

F Site I Site II Site IIISite IV Site V Site VISite VII

0

0.1

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

embe

r

Oct

ober

Nov

embe

r

Dec

embe

r

Bi

Month

0

0.2

Janu

ary

Febr

uary

Mar

ch

Apri

l

May

June July

Augu

st

Sept

embe

r

Oct

ober

Nov

embe

r

Dec

embe

r

Month

Fig. 4 Monthly and spatial variations of Cyanophyta (a), Bacillariophyta (b), Pyrrophyta (c), Conjugatophyta (d), Chlorophyta (e), and Eugleno-phyta (f) biomasses (mg/L) in North El-Manzala Lake


1 3

At site IV, Cyanophyta represented the first group form-ing 89% and 42% of cell number and biomass, respectively (Figs. 3a, 4a). The high standing crop of phytoplankton at site IV was recorded during winter months.

At site V, the seasonal succession of phytoplankton showed no obvious pattern of variation with a predomi-nance of Cyanophyta group in most months. Cyanophyta represents 97.3% and 54% of the total number and biomass standing crop, respectively (Figs. 3a, 4a). The present result agreed with Ranković et al. (2006) who reported the absence of Euglenophyta in winter months as shown in Figs. 3f, 4f.

Based on cell number at site VI, Cyanophyta (88.9%) was dominant followed by Pyrrophyta (5.1%), Bacillario-phyta (4%), Chlorophyta (1.9%), Conjugatophyta (0.06%), and Euglenophyta (0.02%). Pyrrophyta represented the first group at site VI in winter and summer (Figs. 3c, 4c). Conju-gatophyta was found at site VI only in spring (Figs. 3d, 4d).

At site VII, Cyanophyta represented the first group throughout the year (95% and 67.2% of total cell number and biomass, respectively) except in summer as shown in (Figs. 3a, 4a). A maximum standing crop of phytoplankton at site VII was recorded in winter months. Pyrrophyta, Con-jugatophyta, Chlorophyta, and Euglenophyta were absent in spring as shown in Fig. 3c–f.

Conclusion

The present study was conducted to investigate the correla-tion between physicochemical parameters and phytoplankton at North El-Manzala Lake—Egypt, during 2017. Pearson’s correlation coefficient revealed that phytoplankton distribu-tion depends on the variability of physicochemical param-eters and had a significant positive relationship with water temperature, pH, total alkalinity, ammonia, nitrate, silica, and ortho-phosphorus. Six of phytoplankton groups (Cyano-phyta, Bacillariophyta, Pyrrophyta, Conjugatophyta, Chlo-rophyta, and Euglenophyta) were identified in most study sites and can be considered as bioindicators of pollution and water status due to their low cost and ease of handling. Thus, it is necessary to control the disposal of industrial, domestic, and agricultural pollutants and to apply biological control technologies to solve pollution problems into El-Manzala Lake.

Acknowledgements The authors thank all members of the faculty of Science, Damietta University, for their valuable guidance, continuous and unlimited support throughout the whole work. This work did not receive any specific grant from funding agencies in the public, com-mercial, or not-for-profit sectors.

Compliance with ethical standards

Conflict of interest The authors declare that they have no conflict of interest.

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Comparative studies of phytoplankton compositions as a response of water quality at North El-Manzala Lake, EgyptAbstractIntroductionMaterials and methodsSampling sitesPhysicochemical and biological analyses of waterStatistical analyses

Results and discussionPhysicochemical analysis of waterBiological analysis

ConclusionAcknowledgements References

comparative studies of phytoplankton compositions as a...

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