Assessment of eutrophication and organic pollution status of Shatt al-Arab River by using diatom indices

الملخص EN

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 Basrah s Rivers.

Four diatom indices were applied so as to assessment the potential impact of fish cages on water quality (trophic and organic pollution) at the studied sites.

They are: Polluton tolerance index (PTI) ; Watanebe diatom index (DAIpo); Saprobic index (S) and biological diatom index (IBD).

Diatom indices values except DAIPO 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 alphamesosaprobic one.

In conclusion, our results showed that DAIPO 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 and trophic status for the studied sites.