Mesopotamia Environmental Journal ISSN 2410-2598 Mesop. environ. j. 2015, Vol.1, No.3:44-56. www.bumej.com 44 Assessment of eutrophication and organic pollution status of Shatt Al- Arab River by using diatom indices Amal M. Eassa 1 Wesal F. H. Jassim, H. Al-Maliki 2 Rana T. Al-Saad 1 Nadia, K. Mehson 1 1 Marine Science Center/ Department of Marine Chemistry/University of Basrah 2 Directorate of Basrah agriculture/Department of fisheries Corresponding author: amal_0770@yahoo.com To cite this article: Eassa, A. M., Al-Maliki, W. F.; Al-Saad, R. T.; Mehson, N. K. Assessment of eutrophication and organic pollution status of Shatt Al-Arab River by using diatom indices. Mesop. environ. j., 2015, Vol. 1, No.3, pp. 44-56. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivaves 4.0 International License . Abstract Many fish cages have been established along Shatt Al-Arab River by Directorate of Basrah agriculture in which the synthetic food supplied to fish may contribute in entrance of organic materials into Shatt Al-Arab water and it might be distributed for a wide distants by tide and waves. So, the present study was conducted to assess the environmental affect of fish cages on Basrahʼs Rivers. Four diatom indices were applied so as to assessment the potential impact of fish cages on water quality (trophic & organic pollution) at the studied sites. They are: Polluton tolerance index (PTI); Watanebe diatom index (DAIpo); Saprobic index (S) & biological diatom index (IBD). Diatom indices values except DAI PO ones showed that the studied sites were neither very clean nor severe polluted during the study period. PTI values indicated ecological status ranged from beta-mesosaprobic condition to alpha-mesosaprobic one for the studied sites. DAIpo values indicated good conditions for all sites. IBD values indicated ecological status ranged from good to bad condition. S values indicated ecological status ranged from beta-mesosaprobic condition to alpha- mesosaprobic one. In conclusion, our results showed that DAI PO was unsuitable as an index of trophic and saprobity status because its calculation comprised few number of diatom taxa that represent trace percentage of the total abundance of diatom. Both PTI and IBD indices indicated to the presence of eutrophication phenomenon resulting from self-purification process. While Saprobic index gives an obvious picture of the organic & trophic status for the studied sites. Keywords; fish cags-eutrophication- organic pollution-diatom indices. Introduction Aquaculture has become one of the fastest growing food industries in the world. Like many other industries, aquaculture, and especially fish farms may cause negative effects on the environment, such as