Effect of some physical and chemical factors on the aquatic annelida (Oligochaeta)‎ in al-Hilla river-Iraq

الملخص EN

This study was carried out to determine the effects of some physical and chemical factors on the qualitative and quantitative composition of the aquatic Oligochaeta in sediment of Al- Hilla Rive.

The samples were collected monthly from 3 sites for period from June 2014 to May 2015.In the present study 7 physical and chemical parameters were measured including (Water temperature (oC), Salinity (‰),pH, Dissolved Oxygen(Mg/L), Biological Oxygen Demand (Mg/L), percentage of organic matter (%) and Soil texture).The minimum and maximum values of Water temperature (oC), Salinity (‰), pH, Dissolved oxygen(mg/l) and Biochemical oxygen demand (BOD5) (Mg/L) were ( 10 - 24; 0.65-0.98; 6.21- 8.22; 5.53-11.93 and 1.45-4.67 ) respectively.

The range of percentage organic matter (%) was (1.11- 4.30) and the nature of the bottom is a mixture of sand, clay and silt with a small percentage of stones, especially at Site 2.

The results were recorded a total of 20 species belong to 5 families and 11 genus including 8 species from Tubificidae family,7 species from Naididae family,2 species from Aeolosomatidae family, 2 species from Lumbriculidae family, and 1 species from Lumbricidae family.

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The results were revealed that the highest density values of Oligochaeta were 1480 (Ind./m2 ) in July 2014 and lowest values were 120 (Ind./m2 ) in February 2015, these values showed significant correlation (positive and negative) with some studied factors which indicated significant positively correlation with each of water temperature,BOD5 and percentage of organic matter(r = 0.77, r =0.75,r = 0.79,P <0.05) respectively while significant negative correlation with dissolved oxygen (r = - 0.65 ,P <0.05) .

In the present study the family Tubificidae was recorded highest density among other families ranging from higher value 850 (Ind./m2 ) in June 2014 to lowest value 50 (Ind./m2 ) in February 2015, while The second family Naididae was recorded density values ranging from highest value 225 (Ind./m2 ) in March 2015 to lowest value 30 (Ind./m2 ) in January 2015 .The results were showed according to relative abundance index that the Limnodrilus hoffmeisteri, Tubifex tubifex and Branchuira sowerbyi were appeared as dominate species .while other species were appeared between few to rare species except species Peloscolex feroxand was abundant in all sites and species Dero sawayai in site1 .The results also showed that the highest biodiversity value according to Shannon-weaver Index was 2.125 (bit/Ind).

in October 2014 while the lowest value was 0.551( bit/Ind) in July2014.