Using benthic macroinvertebrates as indicators for assessment the water quality in River Nile, Egypt

ABSTRACT

Macrobenthic invertebrate’s species are differently sensitive to a biotic and biotic parameters in their environment. So they are used as bioindicators of stat and water quality of aquatic environment. The main objective of this research is using benthic invertebrates for biological assessment of water quality. Twenty-three stations along River Nile from Aswan to Cairo were selected for sampling of benthic macroinvertebrates. Benthic fauna were collected seasonally by a Naturalist Rectangle Dredge with a net 500 µm mesh size. During the monitoring period (four seasons), forty taxa were identified. They belong to benthos sensitive individuals (25%) and medium tolerant benthos (10%) and tolerant benthos individuals (65%). Relations between macrobenthic communities and circumstances of aquatic ecosystem have been lately used to perform the Biological Monitoring Water Quality (BMWQ) score to evaluate quality level in River Nile water. The total BMWQ (T-BMWQ) score and the average BMWQ (A-BMWQ) score are calculated, and their relations with MacArther, Margalef, Menhinick diversity indices and family richness are also examined. BMWQ scores are more subtle measures to assess the response of macroinvertebrates to organic pollution than diversity indices and total population density. However, the A-BMWQ score is more sensitive to changes in family composition than the T-BMWQ score, whereas T-BMWQ score is more subtle to family richness and size of sample. A-BMWQ score is suggested for the biological evaluation of freshwater quality. Also Trent Biotic Index (TBI) was calculated in each station. All these biological indices examined in this study using benthic macroinvertebrates proved that some stations in Nile River were classified as good water quality, most of studied stations were moderate water quality and very few stations were classified as poor water quality.

KEYWORDS:

• River Nile
• benthic macroinvertebrates
• biotic index
• BMWQ
• water quality

Introduction

Nile River is the longest river in the world. It runs from the lakes of Central Africa toward the north to Mediterranean Sea. Nile plays an important role in the life of Egyptians, in the river’s valley about 97% of Egypt’s population lives, 98% of water in Egypt comes from the Nile [1] and it provides Egypt with 44.73% of its annual fish production (9.86% wild fisheries and 34.87% from fish farming) [2]. Water pollution in River Nile caused by sewage, agriculture and industries affect aquatic community biodiversity and the species composition. The species composition reflects water pollution because the nature species changes to tolerant species [3]. Cao et al. [4] and Abdel Gawad [5] reported that high levels of pollutants reduce biodiversity because of reducing the species to tolerant species. For determination anthropogenic and natural effects on water resources, biological methods are used because biota respond to any changes from multiple spatial or time scales integratively [6]. Also, they save time and costs if compared with physico-chemical estimation of water quality [7], which provide little prudence into the temporal variation of conditions.

Water quality bioassessment is deduced by several methods, the most common one, diversity indices of macrobenthic invertebrate community, as species richness, abundance; and multimetric indices of different macroinvertebrate taxa and multienvironmental factors [8]. Macroinvertebrate taxa tolerance to pollution frequently depends on their life history characteristics and feeding behaviors [9]. Some taxa are indicators of pollutions, survive in a certain level of water quality and cannot live in other levels of water quality. For example, the existence and abundance of Arachnida, Oligochaeta and Gastropoda are indicators of organic pollution [10]. Some chironomid species are tolerant to pollution and can live in heavy polluted water [11–13].

Using biotic indices for pollution monitoring in rivers was developed in Europe and then in the United States. Indices have been developed by using many groups of organisms as, Protozoa [14,15]; Diatoms, Macrophytes and Fish [16–18]; Benthic invertebrates [19–23]. Macrobenthic invertebrates appears to be the best and preferred biological indicators for condition of aquatic ecosystem [24,25] then using this group in biotic indices facilitate the interpretation of great quantity of data obtained from the biological surveillance of water quality in fresh water [24,26]. Benthic invertebrates have been commonly regarded in this respect because they have several benefits including species diversity and habits. Many sedentary species can indicate effects at site of sampling. Respond to changes may occur for whole communities. Some species that have long life cycle can indicate pollution effects over time. Sampling of this group is easy and tools for collection are simple. Good taxonomic keys are present for identification of families [27,28].

The main purpose of this study was to assess the water quality biologically taking into consideration the presence, density and tolerance of macrobenthic invertebrate species. This study provides data about macrobenthic invertebrates as indicators of water quality in Nile River by calculating (1) some biotic indices as Trent Biotic Index (TBI), total biological monitoring water quality (T-BMWQ) and average biological monitoring water quality (A-BMWQ). (2) Diversity indices as MacArther, Margalef and Menhinick diversity indices. Also, the relations between the biotic and diversity indices were examined.

Materials and methods

Study area

The stretch of River Nile studied was about 1035 km from Aswan High Dam to El-Kanater Barrage in Cairo. Various levels of agricultural, domestic and industrial activities take place along River Nile, therefore some sites in the river are considerably polluted [29]. Twenty-three stations were selected for sampling to cover the Nile in this area. The location of selected sampling stations and their key feature were shown in Table1 and Figure 1.

Figure 1. Map showing sampling stations on River Nile.

Table 1. Sampling stations description on the River Nile.

Station	Location	Distance from high dam/km	Key feature	Lat.	Long.
N1	Aswan	1		24° 02′ 52.7″	32 ^o 51′ 37.3″
N2	Kema	10	Effluent from Kema factory for fertilizers and chemicals	24^o 9′ 09.5″	32^o 52′ 57.6″
N3	Kom Ombo	51	Sugar factory	24^o 25′ 25.8″	32^o 56′ 18″
N4	The Train station	85	Train station	24^o 41′ 06.8″	32^o 54′ 59.7″
N5	Edfo	110	Sugar factory effluent	24^o 58′ 42.9″	32^o 52′ 55.3″
N6		170		25^o 13′ 34″	32^o 38′ 57.2″
N7	Armant	225	Sugar factory effluent	25^o 35′ 16.1″	32^o 3′0 33.1″
N8	Luxor	260	Tourist city	25^o 50′ 29.2″	32^o 46′ 19.6″
N9	Qena	320	Major city	26^o 9′ 00.9″	32^o 42′ 6.3″
N10	Naga Hamady	380	Aluminum factory	26^o 8′ 45.9″	32^o 10′ 42.9″
N11	Balena city	410	Small city	26° 13′ 39.8″	32^o 00′ 22.2″
N12	Sohag	440	Major city	26^o 33′ 35.3″	31^o 42′ 29.4″
N13	El Hamamya	485		26^o 55′ 09.3″	31^o 28′ 17.1″
N14	Assute	540	Major city	27^o 10′ 50.7″	31^o 11′ 42.3″
N15	El Qusea	585		27^o 23 28.1″	30 55′ 19.2″
N16	El Maesara	640		27^o 42′ 57.8″	30^o 52′ 10.5″
N17	El Menia	690	Organic effluents	28^o 5′ 45.5″	30^o 45′ 42.7″
N18	Matai	730	Petrol station	28^o 24′ 15.5″	30^o 48′ 17.4″
N19	El Fashn	770		28^o 48′ 41.7″	30^o 54′ 14.2″
N20	Bani Seweef	820	Major city	29^o 4′ 30.4″	31^o 6′ 57.6″
N21	Atfeeh	895		29^o 23′ 12.0 ″	31^o 14′ 11.4″
N22	El Maesara	915	Industries region	29 ° 43′ 37.1″	31^o 15′ 24.4″
N23	El Kanater	960	End of main River	30 ° 16′ 8.3″	31^o 18′ 2.3″

Sampling

Samples were collected for four seasons (autumn 2016, winter, spring and summer 2017). A Naturalist Rectangle Dredge (1 m * 1 m area with a net 500 µm mesh size) was used to collect the macrobenthic invertebrates. Each sample was washed in the field and preserved with 10% formalin solution. In the laboratory, each sample was sorted under stereoscopic microscope. The number of organisms of each species and the number of families at each sampling station were counted.

Biotic indices

Diversity indices and four biological (biotic) indices: Taxa richness (S), Trent Biotic Index (TBI), total BMWQ score (T-BMWQ) and average BMWQ score (A-BMWQ) were used for biological evaluation of water quality.

Diversity indices

Diversity at selected stations was calculated using MacArther, Margalef and Menhinick formulas

• MacArthur’s diversity index [30]

  It depend on the relative abundance of each taxon in the community, and have been widely used in water pollution studies for evaluating changes in aquatic communities structure [25].

  $\mathrm{D}=1/{\sum }_{i=1}^{s}P{i}^2$

  Pi = relative abundance of each taxon; S = number of taxa recorded

  The following two indices based on the number of specie (S) and the total number of organisms (N).

• Margalef’s diversity index [31]

  $D=\left(S-1\right)/\mathrm{l}\mathrm{n}N$

• Menhinick’s diversity index [32]

  $D=S/{\left(N\right)}^{1/2}$

Trent Biotic Index (TBI)

This index is widely useful for quick assessments and can indicate organic and nutrient pollution. Tolerance values of organisms range from 0 to 10 and defined as

$\mathrm{T}\mathrm{B}\mathrm{I}{=}_{\mathrm{i}}{\sum }^{\mathrm{F}}{n}_{\mathrm{i}}{t}_{\mathrm{i}}/N$

Where F is the number of families, n_i is the individuals number in each family, t_i is the tolerance score of each family, and N is the total number of individuals in all the families [33]. The tolerance scores of most families of macrobenthic invertebrates were found in Hilsenhoff [33], and a few of families scores were found in Duan [34]. According to the Stroud Water Research Center, TBI values from 0 to 3.75 indicate very good water quality, 3.76–5.0 good water quality, 5.1–6.5 indicate medium water quality and 6.6–10.0 indicate poor level of water quality.

Biological monitoring water quality (BMWQ score)

This is sensitive to changes in taxa composition and richness. The score values for families reflect their tolerance to organic pollution [35]. The BMWQ score for families ranges between 1 and 15 [35,36]. The value of total biological monitoring water quality (T-BMWQ) is obtained by summing all families BMWQ scores that recorded in the sample. The average biological monitoring water quality (A-BMWQ) score is calculating by dividing T-BMWQ value by the number of families. According to Camargo [35] ‘A-BMWQ values ≥12 excellent water quality, 10–12 indicate good water quality, 7–10 moderate water quality, 4–7 poor water quality and < 4 very poor water quality’.

Results and discussion

Community composition of macroinvertebrates in River Nile

According to Environmental Protection Agency- USA (EPA-USA) benthic invertebrates have been classified into three main groups based on their tolerance level (Table 2). This classification was used to assess the water quality level in River Nile.

Table 2. Aquatic biological indicators of macrobenthic invertebrates based on their tolerance level (EPA-USA).

Benthos tolerant	Medium benthos tolerant	Benthos sensitive
Insecta/Diptera/Chironomidae	Insecta/Odonata	Insecta/Plecoptera
Annelidae	Arthropoda/Decapoda	Insecta/Ephemeroptera
Annelidae/Hirudidae	Crustacea/Amphipoda	Insecta/Coleoptera
Molusca/Gastropoda	Arthropoda/Isopoda	Insecta/Megaloptera
	Insecta/Diptera/Tipulidae	Insecta/Diptera/Athericidae
		Insecta/Tricoptera
		Molusca/Bivalvia

Based on the individual percentages and its presence or absence in the collected samples, the total value and percentages of the three main groups in the Nile River was calculated. (1) Sensitive benthos individuals, (2) medium benthos tolerant individuals and (3) tolerant benthos individuals (Figure 2). From the calculations the highest percentage was for tolerant individuals 65% and this group was consisted of gastropods, the major group with 9570 individuals, Annelida with 2434 individuals and Diptera/Chironomidae with 3308 individuals (Table 3). Medium benthos tolerant individuals constituted about 10% and it consisted of insect/Odonata 170 individuals, crustaceans 141 individuals and Diptera/Tipulidae with 2127 individuals. The third one, sensitive benthos individuals constituted about 25% and it consisted of group of three orders of insects, Ephemroptera, Plecoptera, Tricoptera (EPT) with 320 individuals and Mollusca/bivalves 5576 individuals (Table 3).

Figure 2. Benthic group’s percentage classified according to their tolerance in River Nile.

Table 3. Total individuals number and percentages of groups in the whole area of investigation.

Types of benthic fauna and its groups	Total number	%
Benthos tolerant taxons
Annelida (Olighocheta and Hirudinea)	2434	10.3%
Gastropoda	9570	40.5%
Chironomidae/Diptera	3308	14.0%
Medium benthos tolerant taxons
Odonata (Zigoptera and anisoptera)	170	0.7%
Crustacea (decapoda)	141	0.6%
Tpulidae/Diptera	2127	9.0%
Benthos sensitive taxons
Ephemroptera, Plecoptera and Tricoptera (EPT)	320	1.4%
Bivalves	5576	23.6%

There were differences among the different stations. Stations N1, N2, N3, N4, N5, N6, N7 have higher percentages of tolerant individuals than the other stations (Table 4). These differences express a better quality of water in stations from N8 to N23 than the others. This may be due to effluent of Kema factory for fertilizers and chemicals and sugar factories at southern stations N2, N3, N5, N7. Stations N15, N16 and N18 at El Qusea, El Maesara and Matai respectively have low percentage of tolerant benthos and have high percentage of sensitive benthos (Table 4). Thus, they may be classified as a clean water. This agrees with Keçi et al. [37] who found that a sampling station in Prespa Lake basin (Albania) has higher total tolerant individuals than another one at the same lake and referred these differences between the two stations express a better quality of water in the second station than in first one. EPT have high sensitivity to pollution [38]. Keçi et al. [39] found that sensitive benthos shows low tolerance toward water pollutants scored and referred that to these organisms may occur in clean and well oxygenated waters.

Table 4. Total number of individuals and percentages of three main groups in each station.

Station	Total number of individuals	Tolerant B.M.I. %	Medium tolerant B. M. I. %	Sensitive B. M. I. %
N1	529	95.0	0.5	4.0
N2	175	99.5	0.0	0.0
N3	1297	98.0	1.0	1.0
N4	1264	85.9	6.6	7.4
N5	1088	93.0	0.5	6.8
N6	994	94.4	1.8	6.3
N7	2363	94.3	0.8	5.2
N8	2251	66.1	0.0	34.2
N9	805	69.3	0.3	30.0
N10	927	69.2	1.2	26.4
N11	1726	71.3	0.7	28.1
N12	891	65.8	13.1	21.0
N13	614	88.0	9.0	2.0
N14	523	77.5	0.4	21.8
N15	375	47.6	4.3	47.7
N16	384	28.7	0.5	71.2
N17	1583	74.3	0.7	25.0
N18	1898	54.1	0.5	44.0
N19	127	93.0	0.0	7.1
N21	279	69.0	0.0	31.0
N22	2851	64.0	0.0	36.4
N23	704	55.6	13.4	31.4

(B. M. I. = benthic macroinvertebrates, N20 not collected).

Trent biotic index (TBI)

According to Trent Biotic index, densities of each taxonomic group at each site in Nile River listed in Table 5. Abundance of plecopterans, ephemeropterans, coleopterans, trichopterans, decreased or absent at most sampling stations, whereas tubificid worms and chironomid larvae increased and abundant at sampling sites. The total nitrogen (TN) ranged from 0.334 to 1.189 mg/l and total phosphate (TP) ranged from 0.044 to 0.073 mg/l in the area investigated. This increase in concentrations of N and P compounds could be the important causes for ‘potamonization’ (enhancement of potamic conditions) in macrobenthic community structure because some effluents cause a real organic pollution generating high concentration in compounds of N and P [35]. The siltation of suspended solids (mainly organic matter) credit on the stream bottom would be the main cause of changes in the macrobenthic community structure where the tubificid worms and chironomids larvae were dominant. These two groups (tubificid and chironomids) of macrobenthic invertebrates have been recorded to be distinctive organisms in this sediment type [40].

Table 5. Nile Pollution tolerance values for each group, the total tolerance scoring taxa and resulting Trent Biotic Index (TBI) Scores for each station.

Station		N1		N2		N3		N4		N5		N6
Groups	Tolerance value	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance
Gastropoda	7	223	1561	109	763	867	6069	695	4865	400	2800	370	2590
Bivalves	6	41	246	0	0	19	114	60	360	29	174	8	48
Hirudinea	8	155	1240	0	0	0	0	4	32	0	0	0	0
Oligochaeta	8	0	0	6.5	52	232	1856	114	912	300	2400	320	2560
Decapoda	5	0	0	0	0	0	0	38	190	0	0	3	15
Ephemroptera	3.6	0	0	0	0	1	3.6	38	136.8	55	198	27	97.2
Trichoptera	2.8	0	0	0	0	0	0	8	22.4	0	0	1	2.8
Ishniedae	3	0	0	1	3	0	0	17	51	9	27	13	39
Gomphaida	1	20	20	0	0	0	0	0	0	0	0	0	0
Chironomid	6	6	36	58	348	100	600	183	1098	200	1200	150	900
Tipulidae	3	55	165	0	0	60	180	107.5	322.5	100	300	100	300
Total		500	3268	175	1166	1279	8822.6	1264.5	7989.7	1093	7099	992	6552
TBI		6.5		6.7		6.9		6.3		6.5		6.5
station		N7		N8		N9		N10		N11		N12
Groups	Tolerance value	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance
Gastropoda	7	1330	9310	1364	9548	465	3255	150	1050	426	2982	530	3710
Bivalves	6	123	738	775	4650	225	1350	225	1350	457	2742	250	1500
Hirudinea	8	10	80	0	0	13	104	12	96	0	0	5	40
Oligochaeta	8	80	640	105	840	0	0	225	1800	57	456	62	496
Decapoda	5	0	0	0	0	0	0	0	0	0	0	11.5	57.5
Ephemroptera	3.6	8	28.8	0	0	3	10.8	8	28.8	25	90	0	0
Tricoptera	2.8	0	0	0	0	0	0	0	0	3.5	9.8	5	14
Ishniedae	3	8	24	0	0	14	42	6.5	19.5	12	36	0	0
Gmphaida	1	0	0	0	0	0	0	0	0	0	0	0	0
Chironomid	6	499	2994	10	60	86	516	300	1800	497	2982	30	180
Tipulidae	3	307	921	0	0	0	0	0	0	275	825	16	48
Total		2365	14735.8	2254	15098	806	5277.8	927	6144.3	1752	10122.8	910	6045.5
TBI		6.2		6.7		6.5		6.6		5.8		6.6
station		N13		N14		N15		N16		N17		N18
Groups	Tolerance value	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance
Gastropoda	7	290	2030	315	2205	115	805	76	532	635	4445	585	4095
Bivalves	6	2	12	122	732	164	984	277	1662	400	2400	875	5250
Hirudinea	8	2	16	0	0	0	0	0	0	0	0	0	0
Oligochaeta	8	3	24	40	320	22	176	14	112	225	1800	360	2880
Decapoda	5	2	10	0	0	4	20	1	5	18	90	0	0
Ephemroptera	3.6	8	28.8	0	0	7	25.2	0	0	0	0	10	36
Tricoptera	2.8	0	0	1	2.8	0	0	0	0	7	19.6	2	5.6
Ishniedae	3	42	126	2	6	8	24	1	3	15	45	5	15
Gmphaida	1	0	0	0	0	0	0	0	0	0	0	0	0
Chironomid	6	13	78	26	156	30	180	9	54	170	1020	27	162
Tipulidae	3	250	750	17	51	23	69	5	15	100	300	4	12
Total		612	3074.8	523	3472.8	373	2283.2	383	2383	1570	10119.6	1868	12455.6
TBI		5.0		6.6		6.1		6.2		6.4		6.7
Station		N19		N21		N22		N23
Groups	Tolerance value	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance	T.N.I.	Total tolerance
Gastropoda	7	22	154	85	595	636	4452	322	2254
Bivalves	6	9.5	57	87	522	1046	6276	199	1194
Hirudinea	8	0	0	1	8	5.7	45.6	16	128
Oligochaeta	8	43	344	65	520	445	3560	35	280
Decapoda	5	0	0	0	0	0	0	46	230
Ephemroptera	3.6	0	0	0	0	0	0	11	39.6
Tricoptera	2.8	0	0	0	0	0	0	10.5	29.4
Ishniedae	3	0	0	0	0	0	0	37	111
Gmphaida	1	0	0	0	0	0	0	0	0
Chironomid	6	28	168	25	150	342	2052	21	126
Tipulidae	3	25	75	14	42	228	684	12	36
Total		127	798	277	1837	2703	17069.6	710	4428
TBI		6.3		6.6		6.3		6.2

(T.N.I. = total number of individuals, station N20 not collected)

By using Trent biotic index, TBI in the whole area was 6.27, so the water in River Nile from Aswan to Cairo was classified as medium water quality according to the Stroud Water Research Center [39]. This means, some organic pollution found. Table 5 shows TBI for each station (23 stations), it was found that TBI was equal or more than 6.6 in stations N2, N3, N8, N10, N12, N14 and N18, consequently, these stations were classified as poor water quality. This may be due to pollution from Kema Factory at station N2, and Sugar factories at station N3, effect of tourism and organic wastes entering the Nile from sewage drain at other stations. The lowest value of TBI (5.0) was calculated at station N13 and it was classified as good water quality. Other stations N1, N4, N5, N6, N7, N9, N11, N15, N16, N17, N19, N21, N22 and N23 were classified as medium water quality level where TBI ranged between 6.2 and 6.6 (Table 5).

Biological monitoring water quality (BMWQ)

Tables 6 and 7 list BMWQ score for each family [35] and the families recorded in this study which used to calculate T-BMWQ and A-BMWQ for each station respectively. Generally, species richness and species composition are the most affected biological parameters by anthropogenic pollution [24], so the biological indices must be affected by changes in these two previous parameters. T-BMWQ and A-BMWQ scores appear to be more subtle measurements to measure macroinvertebrates response to pollution in freshwater than total population density and diversity indices, showing high sensitivity to any change in family composition and family richness. Camargo [35] stated ‘The A-BMWQ appears to be more sensitive to the potamonization in family composition than the T-BMWQ, whereas this latter score is more sensitive to family richness and sample size’. A-BMWQ shows low values at stations N2, N3, N8, N10, N18, N19 (≤7) (Table 8) therefore the water at these sites classified as poor water quality. A-BMWQ was more than 7 in all remaining stations (Table 8) so, they were classified as moderate water quality according to Camargo [35]. The use of A-BMWQ and T-BMWQ are recommended for assessment of freshwater quality biologically through organic pollution studies. Less efforts with more information is obtained by using A-BMWQ regarding to other scores. A similar deduction was reported by Balloch et al. [41] and Armitage et al. [42]. Classification of water in the studied stations by BMWQ was similar with the results of classification by TBI in this area.

Table 6. Biological monitoring water quality score (BMWQ), a score for each taxon recorded in River Nile [35].

Family	BMWQ score	Family	BMWQ score	Family	BMWQ score
Valvatidae	7	Unionidae	9	Oligoneuriidae	12
Planorbidae	5	Sphaeriidae	6	Coenagrionidae	10
Physidae	4	Corbiculidae	9	Gomphidae	10
Thiaridae	8	Mutelidae	7	Hydropsychidae	9
Neritidae	10	Glossiphoniidae	5	Dytiscidae	7
Bithyniidae	8	Salifidae	5	Corixidae	8
Viviparidae	9	Tubificidae	2	Chironomidae	2
Lymnaeidae	7	Decapoda	11	Tipulidae	9
Hydrobiidae	8	Caenidae	9
Ancylidae	9	Baetidae	8

Table 7. Taxa recorded at each station in River Nile for biological data.

stationsFamily	N1	N2	N3	N4	N5	N6	N7	N8	N9	N10	N11	N12	N13	N14	N15	N16	N17	N18	N19	N21	N22	N23
Valvatidae	+	+	+	+		+			+	+			+	+			+				+	+
Planorbidae	+	+	+	+	+	+	+		+	+	+		+	+	+							+
Physidae	+		+	+		+			+	+												+
Thiaridae	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+
Neritidae	+		+	+	+	+	+	+	+		+	+	+	+	+		+			+	+
Bithyniidae	+			+	+	+	+	+	+	+		+	+	+				+		+		+
Viviparidae										+	+	+		+	+	+	+		+	+	+	+
Ampullariidae
Lymnaeidae									+
Hydrobiidae				+		+				+		+					+
Ancylidae				+	+	+	+		+								+
Unionidae				+		+	+	+	+	+	+	+		+	+	+	+	+	+	+	+	+
Sphaeriidae	+		+	+	+		+	+	+		+		+									+
Corbiculidae	+			+	+		+	+	+	+	+	+		+	+	+	+	+	+	+	+	+
Mutelidae																		+
Glossiphoniidae	+			+			+			+		+	+							+	+	+
Salifidae	+
Tubificidae		+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+
Decapoda				+		+						+	+		+	+						+
Caenidae			+	+	+	+					+				+		+	+
Baetidae				+	+	+	+		+		+		+		+							+
Oligoneuriidae				+	+	+	+		+	+	+				+							+
Coenagrionidae		+		+	+	+	+		+	+	+		+	+	+	+	+	+				+
Gomphidae						+								+
Hydropsychidae									+		+	+						+				+
Dytiscidae									+
Corixidae				+													+
Chironomidae	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	+	++	+	+	+	+
Tipulidae	+		+	+	+	+	+	+			+	+		+	+	+	+	+		+	+	+

(N20 not collected)

Table 8. Values of indices and biological parameters estimated at each sampling station.

stations	N1	N2	N3	N4	N5	N6	N7	N8	N9	N10	N11	N12	N13	N14	N15	N16	N17	N18	N19	N21	N22	N23
Number of family	11	6	10	21	14	18	15	9	18	14	15	13	12	13	13	9	14	12	6	10	10	18
Number of species	10	11	15	26	20	22	21	13	23	19	19	17	17	18	16	11	18	16	10	12	16	22
Total number of individuals.	500	175	1279	1264	1088	994	2363	2251	805	927	1752	891	614	523	375	384	1583	1898	127	279	2851	704
T-BMWQ	78	34	63	159	117	141	112	63	132	98	117	99	91	98	113	69	109	82	39	71	70	133
A-BMWQ	7.09	5.67	6.3	7.57	8.36	7.83	7.47	7	7.33	7	8.36	7.62	7.58	7.54	8.07	7.67	7.79	6.83	6.5	7.1	7	7.39
TBI	6.536	6.62	6.89	6.32	6.52	6.59	5.23	6.70	6.55	6.63	5.86	6.78	5.01	6.64	6.08	6.21	6.45	6.63	6.28	6.60	6.20	6.29
Mac.D.I.(1972)	3.175	2.04	2.00	2.92	3.90	3.62	2.63	2.05	2.36	4.02	4.27	2.38	2.51	2.35	3.31	1.77	3.79	2.83	1.70	3.88	3.92	3.38
Mar.D.I. (1958)	1.45	1.94	1.96	3.50	2.72	3.04	2.57	1.55	3.29	2.64	2.41	2.36	2.49	2.72	2.53	1.68	2.31	2.12	1.86	1.95	1.88	3.20
Menh. D. I. (1964)	0.45	0.83	0.42	0.73	0.61	0.70	0.43	0.27	0.81	0.62	0.45	0.57	0.69	0.79	0.83	0.56	0.45	0.37	0.89	0.72	0.30	0.83

T-BMWQ = total biological monitoring water quality, A-BMWQ = average biological monitoring water quality, TBI = Trent Biotic Index, Mac.D.I. = MacArther’s diversity index, Mar.D.I. = Margalif’s diversity index, Menh. D. I = Menhinick’s diversity index, N20 not collected.

Diversity indices

Positive and significant correlation coefficient (r = 0.7, P = 0.05) between T-BMWQ and A-BMWQ, and between these two scores and family richness (r = 0.98 and 0.56 respectively) were calculated. Positive significant correlation between Margalef’s diversity index and T-BMWQ, A-BMWQ (r = 0.87 and 0.52 respectively, P = 0.05) were detected. Margalef’s diversity index appeared to be the most sensitive diversity index in assessing structural changes in macrobenthic communities. However, the relation between the two indices (T-BMWQ and A-BMWQ) and MacArthur’s index were positive and lower (r = 0.43 and 0.42 respectively). Thus Margalef’s index is nearly similar to that of family richness and biotic indices. This might indicate that Margalef’s index is more affected by changes in the number of species than MacArthur’s index and Menhinick’s diversity index. In contrast, MacArthur’s diversity index appeared less affected by the number of species and more affected by relative abundances of species. This result has been also reported by some investigators [41,43–45].

Conclusion

It is concluded that using macrobenthic invertebrates in biotic indices appears to be among the best indicators and have been extensively regarded in this regard.

Diversity and variety of benthic macroinvertebrates (40 species) demonstrated in the River Nile from Aswan to Cairo was not much. This may be due to most of the Nile is fast flowing and coarser sediment in some stations constitute an unstable inhospitable habitat. Studies of organic pollution on family richness in the region of the Nile below Cairo, that receives large amount of wastes from sewage drains, will be needed to discuss in the future studies.

Disclosure statement

No potential conflict of interest was reported by the author.