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Content may be subject to copyright.
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
DOI: 10.24996/ijs.2022.63.4.7
___________________________________
*Email: osamaalways230@gmail.com 1464
Impact of Tharthar Arm on the Composition and Diversity of Rotifera in
Tigris River North of Baghdad, Iraq
Osama S. Majeed1* , Muhanned R. Nashaat2 , Ahmed J. M. Al-Azawi3
1 Directorate of Baghdad Education Karkh III, Ministry of Education, Baghdad, Iraq
2Ministry of Science and Technology, Baghdad, Iraq
3Department of Biology, College of Science, University of Baghdad, Baghdad, Iraq
Received: 12/7/2021 Accepted: 24/8/2021 Published: 30/4/2022
Abstract
This study was conducted to evaluate the effects of Tharthar Arm on the
composition and diversity of Rotifera in TigrisRiver. Six sampling sites were
selected, two on Tharthar Arm and four along the Tigris River, one before the
confluence as a control site and the others downstream of the confluence. Seventy-
seven species of Rotifera were identified in Tigris, whereas, 60 in the arm. The results
showed that low density of Rotifera in Tharthr Arm decreased the density in Tigris
from 239812.4 Ind./m3 upstream of the confluence to 223315.5 Ind./m3 at
immediate downstream of the confluence. It also declined the mean values of richness,
evenness and Shannon diversity indices from 5.19, 0.69 and 2.14 bit/Ind., before the
confluence to 3.97, 0.73 and 2.00 bit/Ind. below the confluence, respectively.
Moreover, the highest similarity value was between sites 1 and 6 reached 83.27%,
while the lowest value was between sites 1 and 2 recorded as 60.52%. For constancy
index, the highest value was 14 in site 1 and the lowest was 8 in site 2.
Keywords: Biodiversity, River Confluences, Rotifera, Tharthr Arm, Tigris River.
1*
2
3
*1
2
3
ISSN: 0067-2904
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
1. Introduction
Riverine confluences play an important role in the dynamics of all fluvial systems and are
ubiquitous and fundamental elements of natural drainage networks [1, 2]. Rivers at channel
confluences create a complex hydrodynamic and morphodynamic environment. Inside the
confluence, the tributaries flow mutually deflect each other. This deflection is the outcome of
pressure gradients created by the spatial pattern of water-surface elevations that steers the
confluent flows into the receiving channel [3]. Quite often two incoming flows have different
water properties, such as temperature, conductivity, pH, hardness, or if they are transporting
various types of suspended materials [3].
The term zooplankton comes from the Greek, zoon meaning living organism, and planktons
meaning wanderer or drifter that floats and drifts passively at the mercy of currents, waves, and
tides. Zooplankton (Rotifera, Cladocera and Copepoda) are tiny, often microscopic, water-
suspended species. They are present in both freshwater and marine ecosystems and form a vital
link in the aquatic food chains, grazing on phytoplankton, bacteria and non-living organic
matter, and in turn being eaten by secondary consumers like fish [4]. These animals groups,
especially Rotifera, provide a complete picture about the status of the water ecosystem because
they are bioindicators for pollution and eutrophication [5,6].
Rotifera, also known as wheel animals, are so-named because of the ciliated corona on their
head [7,8]. Rotifers are considered to be the smallest animals amongst the Metazoa. It’s mostly
of microscopic size. The adult rangefrom about 40-2,000 μm in length. They are made up of
about a thousand cells, unsegmented, bilaterally symmetrical, pseudocoelomates [7,8,9].
Based on Segers [10], rotifers are widely distributed geographically and contain about 2,030
species divided into three classes, the Monogononta composed of 1,570 species, Bdelloidea
with 461 species and the marine Seisonida involved only 3 species. Though, most rotifers live
in freshwater out of 1,948 species some species are also able to inhabit in saline waters [11,
12]. The objective of this study is to investigate the effect of Tharthar Arm on the density and
diversity of Rotifera in Tigris River north of Baghdad City during the 2020.
2. Material and Methods
2.1 Study Area
Tigris is one of the largest rivers in the western Asia, also considered as one of the two most
important twin rivers in Iraq. It rises from the south-eastern parts of Turkey on the southern
slopes of Touros mountains. It drains an area of 473103 Km2 which is shared by Turkey, Syria
and Iraq. It forms the Turkish-Syrian border for about 47 Km, before crossing Iraqi border 4
Km north of Faysh Khabur near Zakho City [13].
Tharthar Arm or Tharthar-Tigris Canal is a human-mediated river that obtains it's
characteristics from Tharthar Lake. It is diverted from the left side of division regulator which
is located on Tharthar-Euphrates Canal. Then it continues to the east for 65 Km until the
confluence with Tigris River northern of Baghdad City. It is designed to discharge water up to
600m3/s into the Tigris River directly [14].
2.2 Study Sites Description
Six sites were selected for sample collection (Figure 1). The first site was located along the
main stream of the Tigris River about 2.4 km before the confluence Tharthar Arm with Tigris
River at 33°29'04.5"N latitude and 44°18'06.3"E longitude. This site was considered a reference
site, known as upstream Confluence Hydrodynamic Zone (CHZ). The second site was located
on Tharthar Arm above the entrance of Sabaa Al-Bour City at 33°28'27.2"N, 44°07'49.6"E
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
about 20 Km downstream the drop regulator on the arm. The third site was located on Tharthar
Arm before the entrance to the mainstream, leading up to Sabaa Al-Bour City (33°28'43.0"N,
44°14'06.9"E) about 7.5 km before the confluence of the arm with Tigris. The fourth was site
located on Tigris River, about 300 meters from the joining of Tharthar Arm with Tigris River,
known as immediately downstream the confluence Hydrodynamic Zone (CHZ) at 33°27'46.4"N
and 44°18'10.3"E. Fifth site lied in Al-Tajiy, near Al-Muthana Bridge area at 33°25'43.0"N,
44°20'39.4"E about 6 km below the confluence of Tharthar Arm with Tigris River. Sixth site
was located on Tigris River near Al-Graia’at Floating Bridge in Al-Kadhimiya City
(33°23'07.5"N, 44°20'15.1"E) about 12.6 Km downstream the confluence of Tharthar Arm with
Tigris River. Sites 5 and 6 were known as downstream CHZ.
Figure 1 - Iraq map showing the study sites on Tigris River and Tharthar Arm. Map Scale
1/10000.
The rates of water discharge ranged from 474 m3/s in April to 681 m3/s in July for Tigris
River. Whereas in Tharthar Arm the flow ranged from 83 m3/s in August to 250 m3/s in January
(Figure 2). The data was obtained from the Ministry of Water Resources, 2020 personal
communication.
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
Figure 2- Seasonal variation of water discharges in Tigris River and Tharthar Arm during 2020.
2.2 Sampling Method
Samples were collected monthly from January to December 2020. Samples collected by
passing 45 litres of surface water through vertical planktonic net with a mesh size of 55 microns,
mouth diameter 25 cm. All samples were preserved in 4% formalin. Following sample
condensation, the zooplankton was identified under a compound microscope to the lowest
possible taxonomic unit by using Sedgewick-Rafter chamber. The rectangular cavity slide
contained (50 mm long x 20 mm wide x 1 mm deep) exactly 1 ml of water sample [15]. The
sample was shaken well and was instantly transferred to the cavity by using a graduated pipette.
The coverslip was adjusted correctly to ensure that no air bubbles remained within.
The density was calculated depending on the formula contained in Baird et al. [15].
Rotifera Ind./L = 𝒏
𝐕𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐬𝐚𝐦𝐩𝐥𝐞X 1000
Where: n = No. of Rotifera.
Following diagnostic keys were used for identification, Edmondson [16], Pontin [17] and
Smith [18], and the results were expressed by the number of individuals in a cubic meter.
Ecological Indices were counted as follow:
Relative Abundance Index (Ra): This index calculated depending on the equation found in
Omori and Ikeda[19]: Ra% = (N/Ns) χ100
N: Number of individuals in each taxonomic unit in the sample;
Ns: Total number in the sample
Constancy Index (S): Calculate the presence and frequency of each species, the formula found
in Serafim et al [20]: S = (n/N) χ 100 where n = positive sample number; N = total sample
number.
The Species Richness Index (D): This index was calculated monthly, using the formula in
Margalef's book [21]: D = (S-1)/ log N
S: Species number; N: Individuals total numbers
Species Evenness Index (J): was measured based on the equation found in Neves et al. [22]:
E = H/Ln S
Ln S: Diversity largest theoretical value; H: Shannon Weiner value; S: Taxonomic unit number
in each site.
Shannon-Weiner Diversity Index (H): The values of this index were calculated monthly
according to the formula stated in Shannon and Weaver [23]: H =-∑ ni/n χ Ln (ni/n)
Where ni: Number of individuals per taxonomic unit; n: Total summation of individuals. The
results were expressed by a bit/individual unit
0
100
200
300
400
500
600
700
800
Water Disharge (m3/s)
Months
Tharthar Arm
Tigris River
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
The results are also represented as the unit bit/Ind. as a bit equal one piece of information.
Low diversity is indicated by values less than 1 bit/Ind. whereas, high diversity is indicated by
values more than 3 bits/Ind. [24]
Some physicochemical characteristics, such as water temperature, salinity, pH and
turbidity, were conducted in the study sites directly. Water temperature, salinity and pH were
measured by HANA (HI9811). Turbidity was measured by the turbidity meter, Jenwaw
company Model-6035. Dissolved and biological oxygen demands were measured by using
Azide modification of Winkler titration method [15]. Total Suspended Solids (TSS), total
hardness, reactive phosphate and nitrate were determined as described in standard methods [15].
Table 1- Some physical and chemical characteristics for Tigris River and Tharthar Arm during
2020. Minimum and maximum (First Line) mean and standard error (Second Line).
Site
Parameter
TigrisRiver
Tharthar Arm
Tigris River
LSD
Value
S1
S2
S3
S4
S5
S6
Water
Tempe. (˚C)
10-27
18.90±1.717
12.1-28.2
21±1.8078
12.4-28.4
21.34±1.837
10.7-28.7
20.916±1.838
10.3 - 28.5
20.23±1.78
10.6 - 28.5
20.35±1.819
2.72
NS
Turbidity
(NTU)
8.16-131
34.75±9.603
a
6.2-18.37
11.53±1.300
b
3.68-22.33
13.503±1.71
b
10.9-114
28.65± 8.094
a
11.73-118
32.49±8.238
a
12.2-137
34.26±9.636
a
8.55 *
Salinity
(‰)
0.339-0.710
0.504±0.031
0.4224-1.324
0.718±0.074
0.4224-1.286
0.7382±0.07
0.4224-0.704
0.603 ± 0.027
0.4352-
0.6208
0.531 ± 0.015
0.396-0.6144
0.519 ± 0.01
0.281
NS
pH
7.38-7.91
7.64 ± 0.049
7.35-7.88
7.66 ± 0.055
7.34-7.93
7.68 ± 0.061
7.44-7.89
7.692 ±0.051
7.51-7.91
7.69 ± 0.425
7.41-7.84
7. 63]±0.044
0.944
NS
DO
(mg/L)
8 - 13.1
9.891 ± 0.49
7.7 - 13.6
10.35 ± 0.499
7.8 - 11.9
9.691 ± 0.428
7.5 - 12.8
9.96 ± 0.468
7 - 11
9.1 ± 0.38
6.5 - 11.3
9.35 ± 0.44
1.26
NS
POS (%)
93.61-122.3
104.82±2.49
91.44-131.74
114.88±3.44
94.43-124.70
107.96±2.58
94.10-123.68
110.20±2.67
90.90-110.54
100.20±1.67
84.41-131.85
102.75 ±3.94
13.94
NS
BOD5
(mg/L)
1.4-3.6
2.35 ± 0.23
0.9-3.5
2.4 ± 0.197
1-2.9
2.108 ± 0.21
1.5-3.6
2.38 ± 0.193
0.9 -4.1
2.18 ±0.228
1.1-4.3
2.2083±0.239
0.579
NS
Total
Hardness
(mg CaCO3/ /L)
284-440
354.66±13.2
b
304-800
516.66±42.96
a
288-960
518.33±51.40
a
300-556
431.33±27.16
ab
288-468
369.33
±13.45
b
320-380
358.25±5.57
b
142.3
*
𝐍𝐎𝟑
−
(mg/L)
0.6817-
1.074
0.965±0.038
0.317-1.293
0.588±0.0865
0.2698-1.226
0.533±0.082
0.2913-0.93
0.497±0.055
0.49-0.911
0.6577±0.033
0.58-0.998
0.7704±0.033
0.366
NS
𝐏𝐎𝟒
𝟐 −
(mg/L)
0.00337-
0.02
0.011±0.001
0.0002-
0.0193
0.0061±0.004
0.0002-0.016
0.0070±0.001
0.0015-0.019
0.0064±0.001
0.0015-
0.0237
0.0099±0.001
0.00025-0.022
0.0125±0.001
0.0109
NS
TSS
(mg/L)
1-118
34.25±8.615
a
4-22
12.25±1.557
b
6-29
15.16±1.650
b
2-102
25.91±7.753
a
4-109
34.91±8.056
a
1-125
34±8.934
a
9.516
*
Means having with the different letters in same column differed significantly.
* (P≤0.05), . NS: Non-Significant.
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
3. Results and Discussion
Our results showed that Rotifera density varied spatially and temporally. At site 1 upstream
CHZ, the values of rotifers densities ranged from 3407.5 Ind./m3 to 54879.2 Ind./m3 in May
and December respectively. In Tharthr Arm, the values varied from 2367.9 Ind./m3 in May to
37360.4 Ind./m3 in March. Whereas, the minimum density was 2080 Ind./m3in July and the
maximum density recorded was 71675.2 Ind./m3 in March at immediately downstream CHZ.
As well as, it ranged from 4332 to 92271.3 Ind./m3 in January and December, respectively
downstream CHZ (Figure 3).
In general, the low density of Rotifera in Tharthar Arm decreased its total density in Tigris
River from 239812.4Ind./m3 upstream CHZ down to 223315.5 Ind./m3 at immediately
downstream the CHZ (Table 3). This finding agreed with Rabee [25], pointed that low density
of rotifers in Tharthar-Euphrates Canal also reduced its density in Euphrates River downstream
the confluence zone. Conversely, with Czerniawski and Domagała [26], they found out that the
high density of Rotifera in Stary Potok Tributary increased its density in Drawa River after the
confluence of two rivers.
Figure 3 -Total densities of Rotifera in Tigris River and Tharthar Arm during 2020.
In the spatial aspect, the minimum value of Rotifera density recorded at site 2 on Tharthar Arm,
whereas the maximum value was recorded on site 5. Low density in the arm could return to the
high level because of low salinity. This fact is supported by Czerniawski and Sługocki [27],
Yuan et al. [28] and Nguyen et al. [29] they found that Rotifera density decreases with
increasing the salinity. Whereas, the high density in site 5 may be related to several favorable
conditions for rotifers growth such as low values of salinity, high percentage of oxygen
saturated (Table 1) [30], high discharge rate and the presence of macrophytes [27].
In the temporal aspect, Figure 3 shows that two peaks of rotifers density recorded during spring
and autumn. This case may coincide with suitable environmental conditions such as the
nutrients and water temperature which have an essential supporting role for increasing
microalgae as an important feeding resource. This consequently increased the density of
Rotifera in the river [31].
The relative abundance index of rotifers indicated that Brachionus angularis followed
were: Syncheta oblonga, Polyarthra dolicoptera, Keratella cochlearis, K. valga, K. tropica and
B. plicatlus were the most abundant species in Tigris River. Whereas, S. oblonga, B. angularis,
K. cochlearis, Trichocerca similis, Rotaria neptunia and Polyarthra dolicoptera were the most
abundant species in the arm as shown in Table 2 and Figure 4.
As well as, the higher abundance of Rotifera in site 1 upstream CHZ, were B. angularis 36%,
K. tropica 9%, K. valga 5%, B. urceolaris 5%. Whereas, on the arm at site 2, B. angularis, E.
S1
S2
S3 S4 S5 S6
0
20000
40000
60000
80000
100000
Sites
Ind./m3
Months
S1
S2
S3
S4
S5
S6
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
delatata, K. cochlearis,R. neptunia, P. dolicoptera, were recorded, 14%, 9%, 9%, 7% and 6%,
respectively. At site 3, S. oblonga,K. cochlearis, T. similis, K. valga, P. dolicoptera were
recorded 42%, 11%, 7%, 6% and 5%, respectively. While in site 4, the relative abundance
distributed as follows: P. dolicoptera 25%, S. oblonga 22%, K. cochlearis 11% and B. angularis
10%. Also, at site 5 downstream CHZ, the values of relative abundance of S. oblonga, B.
angularis, K. cochlearis, K. valga and B. plicatlus were recorded 31%, 20%, 10%, 7%, and 5%,
respectively. Furthermore, that on site 6 B. angularis, B. plicatlus, K. valga, K. tropica and R.
neptunia were recorded as 31%, 14%, 9%, 8% and 7%, respectively.
In the present study seventy-eight species of Rotifera were identified, 77 species in Tigris
River and 60 species in Tharthar Arm (Table 2). Our results contrasted with other previous
studies implemented in the river Tigris and Tharthar water [25, 32, 33]. These differences could
be related to several reasons such as the level of classification, size of planktonic net, sampling
sites and nature of environmental conditions.
Figure 4 - The most dominant Rotifera in Tigris River and Tharthar Arm during 2020.
Brachionus angularis
36%
S1
S2
Syncheta oblonga
42%
Others Rotifers
29%
S3
Polyarthra dolicoptera
25%
Other Rotifers
32%
S4
Syncheta oblonga
31%
Others Rotifers
27%
S5
Brachionus angularis
31%
Others Rotifers
31%
S6
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
Table 2 - Rotifers distribution, Relative abundance (Ra) and Constancy index (S) in Tharthar
Arm and Tigris River
Sites
Taxa
Relative abundance
Constancy
1
2
3
4
5
6
1
2
3
4
5
6
1
Anuroaeopsis fissa
(Gosse, 1851)
R
R
R
R
R
R
C
Ac
A
A
Ac
A
2
Asplanecna brightwelli
(Gosse, 1850)
-
-
-
-
-
R
-
-
-
-
-
Ac
3
A. priodonta (Gosse, 1850)
R
R
R
R
R
R
Ac
Ac
Ac
Ac
C
4
Ascomorpha sp..Perty, 1850
-
R
-
-
-
R
-
A
-
-
-
A
5
Ascomorpha saltans Bartsch, 1870
-
R
R
R
R
-
-
A
A
A
A
-
6
Aspelta bidentate
(Wulfert, 1961)
R
R
R
R
R
-
A
-
A
A
A
-
7
Brachionus angularis
(Gosse, 1851)
La
La
R
R
La
R
C
C
C
C
C
C
8
B. bennini (Pallas, 1766)
-
-
-
-
-
R
-
-
-
-
-
A
9
B. calcyflorus calcyflorus
(Pallas, 1766)
R
R
R
R
R
R
C
Ac
Ac
A
C
C
10
B. calcyflorus amphecerus
(long spin) (Ehrenberg 1838)
R
-
R
R
R
R
C
-
A
A
A
A
11
B. calcyflorus amphecerus
(short spin) (Ehrenberg 1838)
R
R
R
R
R
R
C
A
A
A
Ac
C
12
B. falcatus (Zacharias, 1898)
R
R
R
R
R
R
Ac
A
A
A
Ac
A
13
B. forficula (Pallas, 1766)
R
R
R
R
R
R
Ac
A
A
A
C
Ac
14
B. havanaensis (Rousselet, 1913)
R
-
R
R
R
R
A
-
A
A
Ac
A
15
B. quadridentatus (Hermann,1783)
R
R
R
R
R
R
Ac
Ac
A
A
Ac
Ac
16
B. quadridentatus (long spin)
(Hermann,1783)
-
-
-
R
-
R
-
-
-
A
-
A
17
B. quadridenta Gtus (short spin)
(Hermann,1783)
R
-
R
R
R
-
A
-
A
A
A
-
18
B. plicatlus (Müller,1786)
La
R
R
R
R
La
C
Ac
C
Ac
C
C
19
B. rubens (Ehrenberg, 1838)
R
R
-
-
-
-
A
A
-
-
-
-
20
B. urceolaris(Müller, 1773)
R
R
R
R
R
R
C
C
A
C
C
C
21
Cephalodella aureculata
(Wulfert, 1938)
R
R
R
R
R
-
A
Ac
A
A
A
-
22
C. forficula (Wulfert, 1938)
-
-
-
-
R
R
-
-
-
-
A
A
23
C. gibba (Wulfert, 1938)
R
R
R
R
R
R
Ac
Ac
A
Ac
A
Ac
24
Colurella obtuse (Gosse, 1886)
-
-
-
-
R
-
-
-
-
-
A
-
25
Colurella adriatica (Ehrenberg,
1831)
R
R
R
R
R
R
Ac
A
C
Ac
A
C
26
Dipleuchlanis propatula (Gosse,
1886)
R
R
R
R
R
R
A
A
A
A
A
A
27
Euchlanis delatat (Ehrenberg,
1832)
R
R
R
R
R
R
C
C
C
C
Ac
Ac
28
Filinia longiseta (Ehrenberg,
1834)
R
R
R
-
R
R
Ac
A
A
-
A
Ac
29
F. opliensis (Zacharias, 1898)
R
R
R
-
R
R
Ac
A
A
-
A
A
30
F. brachiate
(Rousselet, 1901)
-
-
-
-
-
R
-
-
-
-
-
A
31
Hexarethra mera (Hudson,1871)
R
R
R
R
R
R
Ac
Ac
Ac
A
Ac
Ac
32
Keratella cochlearis (Gosse,
1851)
R
R
La
La
La
R
C
Ac
C
C
Ac
C
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
33
K. tropica (Apstein, 1907)
R
R
R
R
R
R
C
Ac
C
Ac
Ac
Ac
34
K. quadrata (Müller, 1786)
-
-
-
-
R
R
-
-
-
-
A
A
35
K. quadrata (logn spin)
(Müller,1786)
R
R
R
R
R
R
Ac
Ac
Ac
Ac
C
Ac
36
K. quadrata (short spin)
(Müller,1786)
R
R
R
R
R
R
Ac
A
A
Ac
Ac
C
37
K. valga (Ehrenberg, 1834)
R
R
R
R
R
R
C
C
C
C
C
C
38
K. testudo (Ehrenberg, 1832)
R
-
-
-
R
-
A
-
-
-
A
-
39
L. ovallus (Müller, 1786)
R
-
-
R
R
-
A
-
-
A
A
-
40
L. salpina (Donner, 1943)
R
R
R
R
R
R
Ac
Ac
Ac
Ac
A
A
41
Lecane donneri (Chengalath &
Mulamoottil, 1974)
R
R
R
-
-
-
A
A
A
-
-
-
42
L. depressa (Bryce, 1891)
-
-
-
R
-
-
-
-
-
A
-
-
43
L. elasma (Harring & Myers,
1926)
R
R
R
R
R
R
A
Ac
A
Ac
Ac
A
44
L. luna (Müller, 1776)
R
R
R
R
R
R
Ac
Ac
Ac
C
Ac
Ac
45
L. leudg (Eckstein, 1883)
-
-
-
R
-
-
-
-
-
A
-
-
46
L. stichaea (Harring, 1913)
R
R
-
-
-
R
A
A
-
-
-
A
47
L. crepida (Harring, 1914)
-
-
R
-
-
-
-
-
A
-
-
-
48
Macrochaetus subquadratus
(Perty, 1850)
-
R
-
R
-
R
-
A
-
A
-
A
49
Macrotrachela quadri cornifera
(Milne, 1886)
R
-
-
-
-
-
A
-
-
-
-
-
50
Manfredium eudactylotum (Gosse,
1886)
-
-
R
R
R
-
-
-
A
A
A
-
51
Mikrodades chlaena (Gosse,1886)
-
R
-
-
-
-
-
A
-
-
-
-
52
Monostyla bulla (Gosse, 1851)
R
R
R
R
R
R
C
A
Ac
C
C
C
53
M. closterocerca (Schmarda, 1859)
R
R
R
-
R
R
Ac
A
A
-
Ac
Ac
54
M. hamata (Stokes, 1896)
R
R
-
R
R
R
A
A
-
A
A
A
55
M. quadridentata
(Ehrenberg, 1832)
R
R
R
R
-
R
A
A
A
A
-
A
56
M. lunaris (Ehrenberg, 1832)
R
R
R
R
R
R
A
A
A
A
Ac
A
57
M. stenroosi (Meissner, 1906)
R
R
R
R
R
R
Ac
A
Ac
Ac
C
A
58
M. thalera (Harring & Myers,
1926)
-
R
-
-
R
R
-
A
-
-
A
A
59
M. thionemanni (Hauer, 1938)
-
R
R
R
R
R
-
A
A
A
A
A
60
M. scutata (Harring & Myers,
1926)
R
R
-
-
-
-
Ac
A
-
-
-
-
61
Mytilina nucronata (Müller, 1773)
-
-
-
R
-
-
-
-
-
A
-
-
62
Notholca acuminate (Ehrenberg,
1832)
R
-
-
-
R
-
A
-
-
-
A
-
63
N. squamula (Müller, 1786)
R
R
R
R
R
R
A
A
A
A
A
A
64
Philodina paradoxus (Murray,
1905)
-
-
-
-
R
R
-
-
-
-
A
A
65
Polyarthra dolicoptera
(Idelson,1925)
R
R
R
La
R
R
C
C
C
C
C
Ac
66
P. vulgaris (Carlin, 1943)
R
R
R
R
R
R
A
Ac
Ac
Ac
Ac
Ac
67
Pomopholyx sulcate (Gosse, 1851)
R
R
R
R
R
R
A
A
A
Ac
A
Ac
68
Platyias quadricornis (Ehrenberg,
1832)
-
-
R
-
R
R
-
-
A
-
A
A
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
69
P. patulus (Müller, 1786)
R
-
-
R
R
R
A
-
-
A
A
A
70
Rotaria neptunia (Ehreberg,1830)
R
R
R
R
R
R
C
C
C
C
C
C
71
Syncheta oblonga
(Ehrenberg,1831)
R
La
A
La
La
R
Ac
C
C
Ac
C
Ac
72
S. pectinata ( Ehrenberg,1832)
R
R
-
-
R
-
A
A
-
-
A
-
73
Testudinella patina
(Hermann, 1783)
R
-
R
R
R
R
A
-
A
A
A
A
74
Trichotria tetractis (Ehrenberg,
1830)
R
R
R
R
R
R
Ac
C
Ac
C
A
C
75
Trichocerca bicristata (Gosse,
1887)
R
R
R
R
R
R
Ac
Ac
A
A
A
A
76
T. capucina
(Wierzejski&Zacharias,1893)
-
-
-
R
-
-
-
-
-
A
-
-
77
T. rousseleti (Voigt, 1901)
R
R
R
R
R
R
A
Ac
Ac
Ac
Ac
A
78
T. similis (Wierzejski, 1893)
-
R
R
R
R
R
-
A
A
A
Ac
A
Where (D): Dominant species, more than 70%, (A) Abundant species 40-70 %, (La) Less
abundant 10-39 %, (R) Rare species less than 10 %. Whereas, for constancy: (C) Constant
species more than 50%, (Ac) Accessory species 26%-50%, (A) Accidental species 1-25%.
3.1 Ecological indices
3.1.1 Richness index (D)
Figure 5 depicted the value richness index of Rotifera during the study period. At site 1
upstream CHZ, the values ranged from 3.58 to 7.58 in December and January, respectively. In
the arm, the value ranged from 1.94 in April to 5.67 in July. Whereas at the immediate
downstream of CHZ, the minimum and maximum values were 2.41 and 6.74 in July and
August, respectively. While downstream of CHZ, the lowest value of 3.01 was recorded in
February and the highest value of 7.03 was recorded in August.
In other words, the low mean values of species richness index in Tharthar Arm reduced the
richness of Rotifera in Tigris River from 5.19 in site 1 upstream CHZ to 3.97 in site 4 at
immediately downstream CHZ, as can be seen in Table 3.
For spatial variations, the highest values of richness index were recorded in Tigris River at sites
1 and 6. While, the lowest value was recorded on the Tharthar Arm. The high values of this
index in Tigris River could be related to the high water discharge rates [27]. Whereas, low
values in Tharthar Arm could be attributed to the high amount of salinity (Table 1) [28].
Seasonally, the minimum value of species richness index of Rotifera was reported during the
spring season. While, the maximum value was recorded during winter season (Figure 5). The
increase in this value in winter could be associated to the increase of dissolved oxygen in cold
months which in turn increased the value of species richness of Rotifera. This finding is
corresponded with [25, 32]. Whereas, Rasheed et al. [35] showed that the value of richness
index for Rotifera in Al-Shamyiah River, increased during spring and autumn seasons. It was
related that to the increase of phytoplankton in these seasons. While, Abed and Nashaat [36]
found that the lowest values of richness index for total Zooplankton and Rotifera in Dejiala
River in winter was related that to the low density of phytoplankton.
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
Figure 5 - Seasonal variations of richness index of rotifers in Tigris River and Tharthar Arm
during 2020.
3.1.2 Species Evenness Index (J)
At site 1 upstream CHZ, the values of evenness index ranged from 0.52 in November
to 0.90 in May. In the Tharthar Arm, the lowest value was 0.24 in April and the highest value
was 0.93 in December. Whereas the minimum and maximum values of this indexranged from
0.38 to 0.95 in January and November respectively at immediately downstream of CHZ. While
it ranged from 0.22 in January 0.86 in April, downstream of CHZ (Figure 6).
In other terms, the mean value of Rotifera homogeneity in Tigris River increased slightly
from 0.69 upstream of CHZ to 0.73 at immediately downstream of CHZ, due to the lower of
evenness index in Tharthar Arm as can be seen in Table 3.
Figure 6 - Seasonal variations of Evenness index of rotifers in Tigris River and Tharthar Arm
during 2020.
S1
S2
S3 S4 S5 S6
0
2
4
6
8
Sites
D. Index of Rotifera
Months
S1
S2
S3
S4
S5
S6
S1
S2
S3 S4 S5 S6
0
0.2
0.4
0.6
0.8
1
Sites
J. Index of Rotifera
Months
S1
S2
S3
S4
S5
S6
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
Seasonally, the highest values were recorded in spring and summer seasons while, the lowest
values were reported in winter (Figure 6). This could be related to the favorable temperatures
and phytoplankton abundance [37]. In addition to the increasing of nutrients and Chlorophyll-
A during summer and spring seasons [38]. These results are consistent with Abdulwahab and
Rabee [32] that showed the evenness values of Rotifera in Tigris River ranged from 0.41 to
0.93.
3.1.3 Shannon Wiener Diversity Index (H')
The values of this index ranged from 1.63 bit/Ind. in November to 2.60 bit/Ind. in January at
site 1 upstream of CHZ. While, in the arm the values ranged from 0.53 to 2.65 bit/Ind. in April
and June respectively. Whereas, the minimum and maximum values were 1.17 bit/Ind. in
January and 2.71 bit/Ind. in August at immediately downstream of CHZ. While, the lowest
value was 0.76 bit/Ind. in January and the highest value recorded was 2.62 bit/Ind. in August
downstream of CHZ (Figure-7).
In other words, the diversity of Rotifera slightly impacted by Tharthar Arm and the average
values reduced from 2.1 bit/Ind. before the confluence to 1.99 bit/Ind. at immediately
downstream of CHZ. Then it returned to its first state (Table 3).
For seasonal variations, the highest values of diversity index were reported during summer.
While, the lowest values were during winter (Figure 7). This could be associated to increase in
temperature, transparency and Chlorophyll-A, These factors are important for the availability
of phytoplankton as a food for zooplankton [39]. Whereas, the values of this index decreased
in winter probably due to the higher amount of turbidity and suspended matter which effects
the diversity of rotifers as mentioned by [32].
For spatial variation, the highest values were in Tigris River at sites 1 and 6 recorded 2.6 bit/Ind.
for each site. Whereas, the lowest value recorded was 0.53 in the Tharthar Arm (Figure 7). The
high values of this index in Tigris River could be related to the high discharge rates (Figure 1).
This view is supported by Czerniawski and Sługocki [27]. The low values in Tharthar Arm
could be attributed to high amount of salinity, as shown in Table 1. This fact was proved by
Yuan et al. [28].
Figure 7 - Seasonal variations of Shannon-Weiner diversity index of rotifers in Tigris River
and Tharthar Arm during 2020.
S1
S2
S3 S4 S5 S6
0
0.5
1
1.5
2
2.5
3
Sites
bit./ Ind.
Months
S1
S2
S3
S4
S5
S6
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
The results of present study were confirmed by other previous studies. Rabee [25] observed
that Al-Tharthar-Euphrates Canal impacts the diversity index of rotifer in Euphrates River that
decreased the diversity values downstream the confluence of two rivers. Also, Bolotov et al.
[40] mentioned that the diversity index of Rotifera in the Savala tributary declined after junction
with Khoper River, related that to the differences in hydrological and physiochemical
characteristic as velocity of current, salinity and water temperature between the two sites.
According to Hussain classification [41], species richness index ranged from moderate to
the perfect. Whereas that for the evenness index, values ranged from unbalanced to high.
Shannon index fluctuated between very poor and moderate both in Tharthar Arm and the river
Tigris.
Table 3 - The average values of species index, evenness index and Shannon-Weiner index with
total density of Rotifera.
Sites
6
5
4
3
2
1
Index
D
0.72
0.63
0.73
0.71
0.68
0.69
J
H
5.5
154757
2.4
Total Rot.
3.2 Jaccard Presence-Community Index
The highest similarity index value for Rotifera between sites 1 and 6 reached 83.27% (Figure
8). This could be attributed to the fact that the two sites were located on river Tigris and were
away from the influence of Tharthar Arm. Site1 was placed about 2.4 km before the confluence
of Tharthar Arm with Tigris River while, site 6 was placed around 12.6 Km away from the
confluence of two rivers. While, the lowest similarity index value of Rotifera was between sites
1 and 2 recorded 60.52% (Figure 8). This is probably was due to the fact that each site was
located on a different river, and each river was characterized with distinct hydrological,
morphological and geological features (Table 1). Similar results were reported by Abed and
Nashaat [36] which showed that the highest percentage of similarity for Rotifera in Dejiala
River was 60% between Wafidea District and the last stretch of river. They attributed to the
similar environmental and hydrological factors for both sites. Also, Al-Bahathy and Nashaat
[42] found that the highest percentage value of similarity index for Rotifera in the Euphrates
River, was 76.27 between the sites upstream and downstream of the Hindiya Dam. It was
attributed to the similarity of physicochemical characteristics of Euphrates River for these sites.
Whereas Mirza and Nashaat [43] showed that the lowest percentage of this index for Mollusca
groups in the Gharaf River was 33.17% between the sites located near Al-Kut Barrage 10 Km
down to Al-Moafaqya. It was related to the differences in the waste discharge between the sites
that generates different environmental conditions in each site.
Majeed et al. Iraqi Journal of Science, 2022, Vol. 63, No. 4, pp: 1464-1479
Figure 8- Dendrogram of Jaccard׳s index percentages of Rotifer.
In view of all that has been mentioned from our findings and other previous agreed studies
we can conclude that
Tharthar Arm reduced the density and diversity of Rotifera immediately downstream of the
confluence. The values then raised with the increase in the distance downstream of the main
river. Also, the density fluctuated seasonally depending on climatic change and the composition
of Rotifera in both rivers didn't change since a long time.
Environmental conditions and hydrological regimes were the most important factors which
affected Rotifera density.
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