Document Type: Original Article

Authors

Department of Environmental Sciences, College of Science, Salahaddin University-Erbil, Erbil, Kurdistan Region, Iraq

Abstract

Ecological integrity and their properties of any aquatic environment are important to monitor its stability and any change to the ecological system. The current work was undertaken to study the community of aquatic insects and physio-chemical variables of the Shekh Turab stream in periods extended for two months, one in July and the other in November 2017. The aquatic insects’ samples collected from five sites with three replications/site. The physio-chemical parameters of water were water temperature, air temperature (˚C), pH, electrical conductivity EC (μS.cm-1), total dissolved solid TDS (mg.l-1), dissolved oxygen DO (mg.l-1), BOD5 (mg.l-1), alkalinity (mg CaCO3.l-1), bicarbonate HCO3 (mg.l-1), total hardness (mgCaCO3.l-1), calcium (mg Ca2+.l-1), magnesium (mg Mg2+.l-1), nitrate (mg NO3-N.l-1), chloride (mg.l-1), sodium (mg.l-1), potassium(mg.l-1) and sulfate (mg SO4.l-1). The correlation between physio-chemical parameters and different biological taxa were statistically tested. The correlation analysis showed significant relationship. In phylum Arthropoda, a total of 5 insect species belonging to 2 orders; Ephemeroptera and Diptera depicted the Shesk Turab stream macroinvertebrates. Depending on Shannon-Weiner index, species diversity varied from 0.365 to 0.755 at site 4 and 2 respectively.

Keywords

1. Introduction

     There are over 751,000 known insect species, which is about 75 percent of all known animal species on Earth.  Some of them are living in water ecosystem as benthic macroinvertebrates and they can be used for water quality monitoring (1). Despite the fact that most insects live in inland water; for instance, (swamps, ponds, lakes, springs, rivers and streams) these are referred to as water insects (2). Approximately 3% of all insect species have water phases in some inland water biotopes; insects can account for more than 95% of the complete macroinvertebrates population (3). Biosocial methods have recently been replaced or compensated for physical and chemical factors in evaluate water qualities (4). Furthermore, (5) concluded that the role of biota is usually the last point of water degradation and contamination and are therefore significant indicators of a healthy ecosystem. The biodiversity is the variety of living forms in a certain area and represented by the number of existing species. It is indicated that anthropogenic contamination and environmental stress will reduce the biological productivity of the wetland communities which will led to changes in their communities, reduction of their optimal nutritional activities, reduction in the richness and abundance of the endogenous species (6). However, highlighted five major impacts affecting on biodiversity in water general: (I) the fluctuation of the water levels; (II) The overexploitation; (III) water contamination; (IV) destruction of the habitat; (V) and the effect of the invasive species (7). Biodiversity implies the organisms that reside in a region, plus the ecological factors that are essential to maintain them, but also the relationship between these two factors that can be translated into the water system's capacity to support different forms of living organisms (8). The use of aquatic insects as biological indicators is supported by the fact that they are usually stable in time and place; thus, appearing the variations of the ecosystem had gone through (9). Aquatic insects are used to evaluate the “healthy status” of a stream, and also determined water quality by characterized by finding sensitive as well as tolerance organisms (10). In various researches, aquatic insects were used to assess the biological-ecological integrity of the lotic water environment. They estimated the biological integrity and to validate the Index of Biological Integrity based on macroinvertebrate assemblages in rivers (11 and 12). Conditions of aquatic ecosystems can be evaluated to assess the degradation of freshwater ecosystems, hence the current work has been completed to estimate the aquatic insects’ diversity in relation to physical and chemical characteristics of Shekh Turab stream in Erbil province.

2. Materials and Methods

2.1. Study Site

     Erbil is the capital city of Kurdistan and is situated in northeastern Iraq (figure 1A). It is bordered to the north-east and south-east the Upper and Lower Zabs. It is located between longitudinal 43º 58ˉ to 44º 03ˉ E and from latitude 36º 09ˉ to 36º 14ˉ N (13). Climate in the region is regarded a broad daily and annual temperature variation. The climate of the area is nearer to the sort of Iran-Turan. The average annual precipitation exceed 1000mm (14). Shekh Turab stream located about 20 km from the east of Erbil city, Kurdistan Regional of Iraq. The stream is mainly used for irrigation and drinking purposes. The riparian areas are occupied by residence and therefore it is exposed to domestic waste and agricultural runoff.  The locations of the sampling sites are shown in figure 1B.

 Figure 1: A- Map of Erbil province within Iraq, B- Map of studied sites within Erbil province (Shekh Turab Stream) (34)

2.2. Sample Collection and Analyses

     Five sites were homogenously distributed in the studied Shekh Turab stream. Water samples were taken in July and November 2017, when the responses of the systems to nutrient enrichments were more significant and growth and decay rates of macrobenthic species were at the highest (35). From upper stream (site 1) to downstream, each site was located 7 km from each other except site 4 was located 6 km from site 3. Temperature measured using alcohol thermometer, pH, EC (μS.cm-1) and total dissolved solids was directly measured with portable equipment (pH-EC-TDS meter, HI 9812, Hanna instrument), dissolved oxygen (mg.l-1), BOD5 (mg.l-1), alkalinity (mg CaCO3.l-1), HCO3 (mg.l-1), total hardness (mgCaCO3.l-1), calcium (mg Ca2+.l-1), magnesium (mg Mg2+.l-1), nitrate (mg NO3-N.l-1), chloride (mg.l-1), sodium (mg.l-1), potassium (mg.l-1) and sulfate (mg SO4.l-1) were estimated according to (15).  Aquatic macroinvertebrate insect samples were collected at each site by gathering the rocks using Surber sampler (16). The benthic invertebrate has been separated for the primary taxonomic group, and conserved in 4% formalin vials (17). Most samples were taxonomically identified at the generic level and some participants at the species level through the taxonomic key of (18, 19 and 20). The Tukey HSD multiple comparison test was used for the significant differences of means of physio-chemical variables between sites (one-way ANOVA; P < 0.05).  Pearson correlation coefficient analysis was performed to find out the relation between physio-chemical parameters versus taxonomic levels of diversity of aquatic insects. The aim was to find the strength of association between the two sets of variables (36). All statistical analyses were carried out using SPSS (version 19) and using a significant level of 0.05.

2.3. Biological indices

a- Species Richness: Species richness is a measure of the amount of species contained in a sample. This specific measure of species richness is known as D, the index of the Menhinick (21).

D=S/ √¯N

Where S is equal to the amount of distinct species in the sample, and where N is equal to the complete amount of individual sample organisms.

b- Species diversity: Species diversity differs from species richness by taking into consideration both the number of species current and species dominance or evenness in relation to each other. Shannon index was calculated as a measure of species diversity, H. (22).

𝑯 = ∑ (𝑷𝒊) /ln𝑷𝒊/

Where: Pi is the proportion of the total number of individuals in the population that are in species “i”.

c- Simpson dominance index: Simson’s Index is regarded as a dominance index because it weighs towards the most prevalent species ' abundance

Ds=∑si=10 (ni(ni-1)/N(N-1))

Where: ni is the number of species and N complete amount of species in the ith species (23).

3. Results and Discussions

      All the variables studied includes water temperature, air temperature, pH, EC, total dissolved solid, dissolved oxygen, BOD5, alkalinity, HCO3, total hardness, calcium, magnesium, nitrate, chloride, sodium, potassium and sulfate shows significant at different sites in the two different months (Table 1 and 2). Air and water temperatures varied between 12.40 Cº to 35.45Cº and 7.20 Cº to 26.30 Cº respectively. The pH values ranged from 7.89 to 8.38, this implies water samples are almost sub-alkaline in nature. The present results indicate a comparative coincidence with pH values of surface water which lie within the range of 6.5 to 8.5 (24). The values of Electrical Conductivity varied between 977 to 1198 µs/cm. The values of total dissolved solid (TDS) changed from 624 to 766 mg/l respectively. In drinking water, the most desirable limit for TDS is 500 mg/l according to WHO standard and all samples go beyond this limit (24).

Do and BOD findings have never reached critical information in most of this study, indicating excellent circumstances of water quality. The smallest concentration of DO was 5.7 mg/l in accordance with WHO norms and is deemed good to sufficient for human consumption and most aquatic biota (25). A low alkalinity value was 113.0 mg CaCO3/l while an elevated alkalinity value was 178 mg CaCO3/l. (15) reports that sewage contamination and other pollution sources and its decomposition appear to be a probable cause of the peak alkalinity in water. Lowest value of calcium was 48 mg/l at site 4 in July and maximum value was 139 mg/l at site 1 in July, values for Ca+2 agree with (10 and 23). All Ca+2 values are within acceptable limit which is 200 mg/l according to the Iraqi Standard (24). The minimum 19.0 mg/l and maximum 51 mg/l values for Mg+2 were recorded at site 1 and site 3 in July respectively. Values for Mg+2 were acceptable according to Iraqi standard (24). Total hardness for this survey varied from 249 mg CaCO3/l in November at site 1 and 438 mg CaCO3/l in July at site 1. This value was unacceptable because the maximum limit is 200 mg/l according to WHO standard (24). Total hardness increases in water because pollution of surface water with industrial and domestic wastes and nature of salts content of the soil (24). Current water samples indicate that the sodium ion value ranged from the minimum value of 29.3 mg/l the highest value of 37.4 mg/l. These findings acquired agree with the outcomes of (26). Both sodium and potassium demonstrate resemblance in the timing of rise and reduce, according to the findings of (26). Chloride values were unstable through the study period. In July, the greater value 45 mg/l was calculated at site 1, while the smallest value 28 mg/l was recorded at site 1 in November. All values for chloride were within the acceptable range according to Iraqi standard (24). The most abundant form of nitrogen compounds was nitrate and the highest value was 23 mg/l in the course of this study, however, it still complies with the suggestions of the WHO (24). The possible sources of nitrate in the surface water of Shekh Turab water system are mainly from the atmosphere, surface runoff, sewage discharges, agricultural fertilizers and organic wastes (24). With respect to the study area's sulfate content, they show differences within 236 – 1054 mg/l. Aquatic insects are excellent indicators of water quality because they are influenced by the water body's physical, chemical and biological factors. They have little mobility and they are sensitive to local pollution (27).

Table 1: Physio-chemical parameters of Shekh Turab stream in July 2017 (numbers are mean ± SE).:

Sites

1

2

3

4

5

Water temperature (˚C)

23.9±0.05a

24.5±0.20a

24.5±0.30a

26.3±0.25b

24.5±0.20a

Air temperature (˚C)

32.5±0.40a

32.3±0.20a

34.6±0.30b

35.45±0.15b

35.15±0.35b

pH

7.89±0.07a

8.00±0.06a

8.07±0.07a

8.11±0.02a

8.15±0.12a

EC (μS.cm-1)

1198±18.50b

1155±34.50ab

1176±3.50ab

1159±5.50ab

1127±2.50a

TDS (mg.l-1)

766±11.84b

739±22.08ab

752±2.24ab

741±3.52ab

721±1.60a

DO (mg.l-1)

6.2±0.20a

6.6±0.40a

5.7±0.30a

6.35±0.05a

6.05±0.05a

BOD5 (mg.l-1)

2.15±0.65a

2.45±0.55a

1.55±0.15a

2.10±0.30a

1.10±0.10a

Alkalinity (mg CaCO3.l-1)

178±2.50a

175±1.50a

178±5.50a

171±1.00a

171±4.24a

HCO(mg.l-1)

217±3.05a

213±1.83a

227±4.29b

209±1.22a

213±0.19a

T. Hardness (mgCaCO3.l-1)

438±12.00c

342±12.00a

411±1.00bc

405±1.00b

408±0.50b

Ca2+ (mg Ca2+.l-1)

139±5.50c

76±8.40a

105±14.80b

48±1.50a

113±1.50bc

Mg2+ (mg Mg2+.l-1)

19±3.60a

48±9.36b

51±6.48b

36±10.56ab

27±2.88ab

NO3-(mg NO3-N.l-1)

19±0.20c

18±0.28c

17±0.20b

16±0.08a

16±0.18a

Chloride (mg.l-1)

45±1.00b

36±0.00a

36±2.00a

39±3.00ab

40±2.00ab

Na+ (mg.l-1)

30.1±0.01b

29.3±0.01a

31.3±0.26cd

31.2±0.01c

31.5±0.02d

K+ (mg.l-1)

2.4±0.02b

2.3±0.01a

2.4±0.02b

2.5±0.01c

2.9±0.01d

SO42- (mg SO4.l-1)

236±4.00a

264±4.00b

362±2.50c

353±7.50c

369±3.50c

 


Note: Values in each row with different letters are significantly different and values with same letters are not significantly different.

 

Table 2: Physio-chemical parameters of Shekh Turab stream in November 2017 (numbers are mean ± SE).

Parameters

Site 1

Site 2

Site 3

Site 4

Site 5

Water temperature (˚C)

12.1±0.10a

7.2±5.45a

13.68±0.02a

12.6±0.06a

13.9±0.05a

Air temperature (˚C)

12.4±0.03a

17.5±0.03c

15.3±0.10b

14.7±0.24b

19.2±0.11d

pH

8.36±0.03c

8.15±0.01a

8.22±0.05ab

8.38±0.06c

8.35±0.02bc

EC (μS.cm-1)

1015±4.50b

985±5.00a

994±5.00ab

1015±15.00b

977±2.50a

TDS (mg.l-1)

640±6.40ab

629±1.80a

6.33±0.30ab

650±9.60b

624±3.20a

DO (mg.l-1)

9.5±0.50d

7.9±0.10cd

6.5±0.50ab

6.2±0.20a

8.2±0.60cd

BOD5 (mg.l-1)

1.8±0.25bc

2.1±0.11c

1.6±0.05ab

1.2±0.05a

3.6±0.05d

Alkalinity (mgCaCO3.l-1)

131±0.50d

125±0.50c

119±0.50b

122±1.5bc

113±2.00a

HCO3 (mg.l-1)

159±0.45d

153±0.03c

145±1.22b

146±0.61b

138±2.44a

T. Hardness (mgCaCO3.l-1)

249±1.00a

255±1.00a

283±1.00b

254±2.50a

251±7.00a

Ca2+ (mg Ca2+.l-1)

59±0.80c

63±0.40d

53±0.80a

57±0.40bc

56±0.40b

Mg2+ (mg Mg2+.l-1)

25±0.18ab

24±0.01a

36±0.24c

26±0.96b

25±0.44b

NO3-(mg NO3-N.l-1)

23±0.06a

22±0.06a

21±0.02a

12±9.00a

20±0.08a

Chloride (mg.l-1)

28±0.40a

32±1.60ab

29±1.00ab

34±0.00b

30±0.00a

Na+ (mg.l-1)

35.4±0.26a

35.9±0.26a

36.9±0.26b

37.4±0.26b

36.9±0.26b

K+ (mg.l-1)

2.3±0.00a

2.3±0.04a

2.7±0.33a

2.8±0.02a

2.3±0.01a

SO42- (mg SO4.l-1)

966±13.44a

995±0.00a

1054±2.42b

1052±16.36b

997±9.60a

Note: Values in each row with different letters are significantly different and values with same letters are not significantly different.

Among aquatic insects identified in the studied area (Table 3), Baetiserhodani, Caenimacrura, Caenismeosta, Caenistardata of the order Ephemeroptera, and Stimulium of order Diptera of Phylum Arthropoda were discovered to be abundant in the Shekh Turab stream. The variety of aquatic insects at site 5 in July-2017 may be due to the existence of phytoplankton and algal blooms, because they are food resources for macroinvertebrates. They provide them with shelter and nesting grounds for breeding (28). It was observed that a number of aquatic insects in the studied area in July were more than in November. Biological diversity of the water system develops in response to the hydrological regime, physical and chemical characteristics and biological interactions (Table 4). Thus the Shekh Turab's complete environment is the consequence of interaction between a number of parameters including water temperatures and nutrients, some of which play a significant part in determining the structure and function of the water ecosystem (29). There are important relationships among the water characteristics and aquatic diversity. The nature of the lower substrates is one of the most important environmental parameters for influencing the biodiversity of the stream (30). Different variables have been known to affect the density and abundance of water insects, but the most significant variables are water temperature and dissolved oxygen in the study region

Table 3: Aquatic insects that recorded in Shekh Turab stream in July and November, 2017.

 

July

November

Taxa

Site 1

Site 2

Site 3

Site 4

Site 5

Site 1

Site 2

Site 3

Site 4

Site 5

Phylum Arthropoda

 

 

 

 

 

 

 

 

 

 

Class Insecta

 

 

 

 

 

 

 

 

 

 

Order Ephemeroptera

 

 

 

 

 

 

 

 

 

 

Family Baetidae

 

 

 

 

 

 

 

 

 

 

Baetisrhodani (Pictet, 1845)

 

4

 

 

1

 

2

 

 

 

Family Caenidae

 

 

 

 

 

 

 

 

 

 

Caenismacrura(Stephens, 1835)

4

6

11

6

9

1

 

2

 

3

Caenismeosta (Bengtsson, 1917)

21

18

26

22

33

2

 

4

1

10

Caenistardata(McDunnough, 1931)

2

1

 

2

3

 

 

 

 

 

Order Diptera

 

 

 

 

 

 

 

 

 

 

Family Simuliidae

 

 

 

 

 

 

 

 

 

 

Subfamily Simuliini

 

 

 

 

 

 

 

 

 

 

Simulium sp.

 

 

 

 

 

 

8

 

 

 

Total

27

29

38

30

46

3

10

8

1

13

 

Table 4: Pearson correlation coefficient between water parameters, (Shannon index and Taxa richness).

Water parameter

H

P-Value

S

P-Value

Water temperature

0.666*

0.050

-0.647*

0.043

PH

-0.438

0.238

0.592

0.072

EC

0.602

0.086

-0.545

0.104

TDS

0.611

0.081

-0.545

0.104

DO

-0.447

0.228

0.484

0.256

BOD5

-0.165

0.671

-0.418

0.229

Alkalinity

0.654

0.056

-0.534

0.112

HCO3

0.651

0.058

-0.549

0.100

T.H

0.674*

0.047

-0.599

0.067

Ca

0.409

0.275

-0.391

0.264

Mg

0.413

0.269

-0.366

0.299

NO3

-0.530

0.142

0.661*

0.037

Cl

0.677*

0.045

-0.474

0.166

Na

-0.724*

0.027

0.508

0.134

K

0.102

0.794

-0.461

0.180

SO4

-0.676*

0.046

0.572

0.084

* Correlation is significant at the 0.05 level (two-tailed).

In the Shekh Turab water there were several variables responsible for more aquatic ecosystems, including water temperature, EC, TDS, DO, alkalinity, hardness and other ions. Periphyton development in relation to geology and velocity parameters was investigated in New Zealand (31). The nature of the underlying substratum of Shekh Turab stream is another one, too important factors affects the variety water insects. Species variety ranged from 0.365 to 0.755 bits/ind according to the Shannon-Weiner index. The highest diversity value recorded at site 2 whereas the minimum diversity calculated at site 4 (Table 5).

Table 5: Diversity and other indices of aquatic insects in the study stations of Shekh Turab stream.

 

Site 1

Site 2

Site 3

Site 4

Site 5

Number of taxa

3

5

2

3

4

Taxa richness / Menhinick’s index

0.866

0.6875

0.5725

0.774

0.5725

Shannon-Wiener diversity (H)

0.653

0.755

0.622

0.365

0.68

Simpson dominance

0.476

0.537

0.519

0.284

0.582

In general, sites diversities 1, 2, 3 and 5 were greater; this can be ascribed to greater human activity at site 1 sewage disposal containing more water nutrients and other ions used as food from phytoplankton cells and aquatic insects dominated at this site.  Organically enhanced environments have a reduced diversity, with some dominant species, according to (32). Meanwhile, (33) wrote that, in many instances, diversity at intermediate polluted locations is greater than at clean locations. Menhinick's richness index disclosed the largest richness calculated in site 1 and the lowest in locations 3 and 5, which likely linked to the amount of taxa recognized in each site for the region studied. Taxa dominance in this study ranged from 0.284 at site 4 to 0.582 at site 5.

4. Conclusion

     From the results throughout this study, a total of 3 families representing 2 orders were recorded in this survey. Caenis macrura and Caenis meosta were present in the large amount of individuals at all sampling sites. This indicates the richness and diverse group of aquatic insects in the study area. It reinforces to the fact that the habitat quality is most suitable for insects to breed and multiply under the natural ecosystem. Furthermore, the river’s environmental factors had directly and/or indirectly affected aquatic insect assemblages, showing that aquatic insects were useful indicators of water quality in the Shekh Turab Stream. All sampling stations in the study came out as moderately polluted by indication of diversity index.

Conflict of interest

None

  1. Majumder, J., Das, R. K., Majumder, P., Ghosh, D. and Agarwala, B. K. (2013) Aquatic Insect Fauna and Diversity in Urban Fresh Water Lakes of Tripura, Northeast India. Middle-East Journal of Scientific Research13 (1): 25-32
  2. Voshell, J. R. A. (2002) Guide to Common Freshwater Invertebrates of North America. McDonald and Woodward Publishing Co., Blacksburg, Virginia: 442
  3. Ward, J.V. (1992) Aquatic insect ecology: 1. biology and habitat John Wiley & Sons, Inc., New York
  4. Wright, J. F. (1995) Development and use of a system for predicting macroinvertebrates in flowing waters. Austral Ecology. 20, 181-197
  5. Norris, R. H., Thomas, M. C. (1999) What is river health? Freshwater Biology41, 197-209
  6. Dudgeon, D., A. H. Arthington, M. O. Gessner, Z-I. Kawabata, D. J. Knowler, C. Lévêque, R. J. Naiman, AH. Prieur-Richard, D. Soto, M. L. J. Stiassny, and C. A. Sullivan (2006) Freshwater biodiversity: importance, threats, status and conservation challenges. Biological Reviews 81:163–182
  7. Rader, R. B., D. P. Batzer, and S. A. Wissinger (2001) Bioassessment and Management of North American Freshwater Wetlands. John Wiley and Sons, New York, NY, USA. 489pp
  8. Galdean, N., Staicu, G. (1997) The carrying capacity assessment of the lotic system Crisul Repede (Tisa Area Catchment, Romania), based on statistical analysis. Travaux du Museum National d’Histoire Naturelle “Grigore Antipa”37, 237-254
  9. Rosenberg, D. M., Resh, V. H. (1993) Freshwater Biomonitoring and Benthic Macroinvertebrates. Chapman and Hall, New York
  10. Zakir, H.M., Sharma, S. and Shikazono, N. (2006) Heavy metal pollution assessment in water and sediments of Turag River at Tongi area in Bangladesh. International Journal of Lakes and Rivers 1, 85-96
  11.  Duran, M and Suicmez, M. (2007) Utilization of both benthic macroinvertebrates and physico-chemical parameters for evaluating water quality of the stream Cekerek (Tokat, Turkey). Journal of Environmental Biology. 28, 231-236
  12. Torres-Olvera, M. J., Durán-Rodríguez, O. Y., Torres-García, U, Pineda-López, R. and Ramírez-Herrejón, J. P. (2018) Validation of an index of biological integrity based on aquatic macroinvertebrates assemblages in two subtropical basins of central Mexico. Latin American Journal of Aquatic Resources46 (5): 945-960
  13. Rzoska, J. (1980) Euphrates and Tigris, Mesopotamian Ecology and Destiny. Vol: 38. Mongr. Biol.W. Junk. The Hague-Boston. London. 122
  14. Zohary, M. (1950) The flora of Iraq and its phytogeographical subdivisions. Directorate-General of Agriculture, Bulletin. 31, 197-201
  15. APHA (American Public Health Association) (2005) Standard Methods for Examination of Water and Wastewater. 21st Edition. APHA, Washington DC
  16. Pacific Northwest Aquatic Monitoring Partnership (PNAMP) (2007) Methods for the collection and analysis of benthic macroinvertebrate assemblages in wadeable streams of the Pacific Northwest. Pacific Northwest Aquatic Monitoring Partnership, Cook, Washington
  17. Lind, O. T. (1979) Handbook of common methods in limnology. C.V. Company. USA 
  18. Edmonson, W. T. (1959) Freshwater biology. 2nd Ed. John Wiely and Sons, Inc. 1248pp
  19. Macan T. T. (1979) A key to the nymphs of the British species of Ephemeroptera with notes on their ecology. 3rd Ed. Freshwater Biological Association. No. 20. pp, 79
  20. Quigley, M. (1977) Invertebrates of Streams and Rivers: A key to Identification. Edward Arnold Publication UK. pp, 84
  21. Maret, T. R. (1988) A water-quality assessment using aquatic macroinvertebrates from streams of the Long Pine Creek watershed in Brown County, Nebraska. Transactions of the Nebraska Academy of Science. 1, 69-84
  22. Shannon, C. E. and Wiener, W. (1963) The mathematical theory of Communication Univ. Illinois press, Urbana. pp, 36
  23. Hellawell, J. M. (1978) Biological surveillance of rivers. Water Res. Centre, Stevanage. pp, 332
  24. World Health Organization (WHO) (2004) “Guidelines for Drinking-Water Quality,” 3rd Edition, Geneva
  25.  Wilcock, R. J, McBride G. B., Nagels J. W and Northcott G. L. (1995) Water Quality in a Polluted Lowland Stream with Chronically Depressed Dissolved Oxygen: Causes and Effects. New Zealand J Mainer and Freshwater Research, 29, 277-288
  26. Rasheed, R.O. (2008) Evaluation of heavy metals and polyaromatic hydrocarbons in water, fish, and sediments within Derbendikhan reservoir. Ph.D. Thesis, University of Sulaymaniyah, Sulaymaniyah
  27. Tachet, H., Richoux, P., Bourneau, M. and Usseliopolatera, P. (2003) Invertebrates‟ eaudouce; systematique, biologie, ecologie. Fresh water invertebrates; systematic, biology, ecology. CNRS edition, Paris
  28. Ruitton, S.; Francou, P.  and Boudouresque, C. F. (2000) Relationships between Algae, Benthic Herbivorous Invertebrates and Fishes in Rocky Sublittoral Communities of a Temperate Sea (Mediterranean). Estuarine, Coastal and Shelf Science. 50: 217–230
  29. Gupta, N., Sharma, R. C. and Tripathi, A. K. (2008) Study of bio-physio-chemical parameters of Mothronwala swamp, Dehradun (Uttarakhand). Journal of Environmental Biology. 29, 381-386
  30. Minshall, G.W. (1984) Stream ecosystem theory: A global perspective. Journal of the North American Benthological Society. 7, 263-288
  31. Biggs, B. J. F. and Periphyton, M. E.  (1989) Biomass dynamics in gravel bed rivers, the relative effects of flows and nutrients. Freshwater Biology 22, 209-231
  32. Neves, I. F.; Roche, K. F. and Pinto, A. A. (2003) Zooplankton community structure of two marginal lakes of the river Cuiaba with analysis of Rotifera and Cladocera diversity. Brazilian Journal of Biology. 63, 329- 343
  33. Mercado, L. M. (2003) A comparative analysis of the phytoplankton from six pampean lotic system (Buenos Aires, Argentina). Hydrobiology. (1-3), 103-117
  34. Hanna, N. S.,  Jarjes, F. Z. and  Toma, J. J. (2018) Assessing Shekh Turab Water Resources for Irrigation Purposes by Using Water Quality Index . Zanko Journal. 30 (5); 17-28
  35. Christia, C., Giordani, G. and Papastergiadou, E. (2014) Assessment of ecological quality of coastal lagoons with a combination of phytobenthic and water quality indices. Marine Pollution Bulletin, 86(1-2), 411-423
  36. Gómez, A., Juanes, J., Ondiviela, B. and Revilla, J. (2014) Assessment of susceptibility to pollution in littoral waters using the concept of recovery time. Marine Pollution Bulletin, 81(1), 140-148