Effect of some environmental factors on the occurrence and distribution of Polychaeta Namalycastis indica (Southern, 1921) in the intertidal region of Shatt Al-Arab River Basrah Iraq

The current study was conducted on N. indica in three stations for the period from December 2017 to November 2018 (Al-Sharsh, Al-Salhiya and Al-Dweab), as samples were collected monthly. Some environmental factors calculated, such water temperature. lowest temperature 12 °C during January highest 33 July, both station. value of salinity 0.5‰ reached April Al-Sharsh station, while ‰ 39.3 recorded July Al-Dweab light transmittance values ranged between (63-18) cm, stations, respectively. As dissolved oxygen, it (12.1-5.1) mg/liter August May two stations. Al- Salhiya Al-Sharsh, bottom sediments all they alluvial with few different percentages sand clay. showed that studied have an impact distribution spread this species within horizontal vertical sections tidal zone. total density measured pattern each station monthly ranges 592-32 individuals/m2. calculated after dividing area into results indicated there significant differences at level P<0.05 densities first second indica, third sections.