Sediment Assessment of Al-Hindyia and Al-Abbasyia River / Iraq by aquatic oligocheata community as bioindicators

: Bioindicators have an important role in assessing the quality of water bodies. Aquatic oligocheates, was used as a bioindicator to assess the sediment quality of Al-Hindyia and AL-Abbasyia river (branches of Euphrates River in Iraq). Two sites in each river have been chosen for this purpose, site S1 was located at Al-Hindyia River and S2 at Al-Abbasyia River. Some kinds of biological indices were used in this study, comprising the percentage of oligochaetes in benthic invertebrates, ranged from 20.3-60.16%. While the percentage of Tubificidae within benthic invertebrates was close 43.3-43.9%.Index of pollution D ranged from 0.13-0.21. The maximum percentage of aquatic oligochaetes to insects larvae of family Chironomidae larvae was recorded at S2 90% while at S1 60%. I 0 was scored high value at S1 36.06 whilst only 30.56 at S2.E 0 was A 8 at S1 and A 9 at S2.while IOBS was 15.26 at S2 and 7.07 at S1.The percentage of subfamily Tubificidae (TUSP) showed the highest value 21.21% at S1 while 11.79%at S2 .


Introduction:
Bioindicators are qualitative situation of the environment; they are responsible for different types of pollutants gradually. They play a key role in monitoring changes in the environments and can discover the effects of incidental as well as cumulative pollution and habitat shifts 1 .
Many organisms such as plants, planktons, fishes are used as bioindicators 2 . The benthic macro invertebrates like Oligochaeta are most commonly used to evaluate the water health, they are subclass of class Clitellate, phylum Annelida, predominantly aquatic and terrestrial, used as an indicator for water and sediment quality 3. About 1700 rightful species of Oligochaetes are recognized to date; of these nearly 1,100 are freshwater. The most group is the Tubificidae, with more than 1000 described species including 582 being considered as freshwater inhabitants, Tubificid worms which belong to Naididae family were the most group of aquatic oligochaetes used as bioindicator to assess water quality 4 .
In Iraq, many studies refer to Oligochaeta in Euphrates River such as [5][6][7][8] , and in Tigris River 9-12 . The present study adds a new scope on the relevance between the aquatic oligochaetes and quality of sediment in both of Al-Hindyia, at Al-Kifil region and AL-Abbasyia rivers, both of these two rivers are branches of Euphrates River in Iraq run through agricultural places.

Material and Methods:
Sediment samples were collected monthly during the period from March to August 2020 by sediment sampler as three replicates for each site as in (Fig.1) by using an Ekman grab 15X15cm with a total area of 225 cm2 just 1 m from river edge. The samples were collected in suitable size plastic containers filled with river water. Site one (S1) located at Al-Hindyia River, (32°13'26.15"N , 44°21'46.40"E) which is a main branch of Euphrates River after Al-Hindyia dam. It passes through Karbala and Babil Provinces to wide spaces of farm lands and palm trees orchards in Al-Kifil region at the south of Iraq / Babil province and (S2) at Al-Abbasyia River (32°07'11.09"N, 44°23'43.07"E), other branches of Euphrates River, about five kilometer after AL-Kifil city. It passes through Babil and Al-Najaf provinces to wide spaces of farmlands, and there is a barrage on it known as AL-Abbasyia barrage which was constructed in 1984. By using 0.5 mm sieve, the sediment samples have been checked in lab that by circulate on the white plate, and big worms can easily be sorted from the remains, using enlargement hand lens, divided into groups 13 . Different indices as in [14][15][16][17][18]

Result and Discussion:
Depending to the information illustrated in (Table 1), the dominance was to the tubificid worms that have no hair setae at the both study sites, which are known as pollution tolerant organisms 19 , where tubificid worms with hair chaetae occurred in rare number.
The data used to calculate some of biological indices are represented in (Table 2). To overall benthic invertebratesm, the oligochaeta percentage was extending from (60. 16-20.3) % if (Olig.%) ˂ 60% Good water quality; 60-80 % Dubitable; 80 % hardly polluted, whether organic or industrial that mean. The percentage of tubificid worms to total benthic invertebrates were almost close in study sites (43.3-43.9) %.the percentage of oligocheates to Chironomidae larvae stretched between 60% in (S1) and 90% in (S2). Both groups are considered as pollution tolerant 20,21 . Pollution index (D) was extend between (0.21-0.13) and that indicate the Euphrates river is good according to 16 , if values  0.30 considered good ; 0.30-0.55 a little polluted; 0.56-0.80 polluted and; 0.81-1 hardly polluted. Io index value was (36.06) recorded in (S1), and reduce gradually as proceed downstream to reach its lowest value of (30.56) recorded in (S2). This point depends upon the turnout of hairless tubificid worms associated with total benthic species, because they are more resistant to oxygen nude created by various types of pollutants such as organic pollution 17,22 . The highest value was showed shown at (S2) 15.26 and the lowest value at (S1) 7.07 according to IOBS which represented the tubificid worms relative abundance jointly with or without chaetae to total oligocheates worms. TUSP index reached the highest percentage at (S1) 21.21% and the lowest at (S2) 11.79%. Eo index, represents by A8 and A9 for (S1) and (S2) respectively.

Conclusion:
Further biological indices indicate that the sediment of Euphrates River at the study sites (S1, S2) is slightly polluted and may be that pollution is related with the activities of humans and presence of some animals such as buffalo and ducks that were seen in those sites, pollution reduction can occur by increasing the water supply from the Hindyia dam towards the Abbasyia River in some months, where pollutants are pushed or diluted and the opposite can happen with a lower water levels.