Author(s)： Fikrat M. Hassan, Ali Obaid Shaawiat
The study was conducted on epipleic diatoms in a lotic ecosystem. The Al-Shamiyah River was selected which is a distance from industrial activities. Four sites along the river were selected for sampling during the period from March 2013 to February 2014. A total of 173 species of epipelic diatoms were identified. The pennate diatoms predominated and represented about 92.49% of the total diatoms, while centric diatoms formed only 7.51%. The total number of diatoms ranged between 185.1 – 422.34 cell × 104/cm2. Some of the pennate diatom species were Achnanthes affinis Grunow, Achnanthes mintussima Küetzing, Cocconeis placentula var. euglypta (Ehr.) Cleve, Cymbella affinis Küetzing, Diatoma vulgare Bory, Fragilaria capucina Desmazieres, Gomphonema angustatum var. productu Grun., Navicula lanceolata (Ag.) Kuetzing, Navicula radiosa Küetzing, Navicula viridula Küetzing, Nitzschia palea (Kutz.) W. Smith, Nitzschia romana Grunow. The physicochemical and epipelic algae species indicated that the water quality of the river was clean to moderate water quality.
The importance of benthic algae in Iraqi aquatic ecosystems was subjected to investigations recently -. Many authors have previously recognized benthic algae as bioindicators in different aquatic ecosystems of Iraq -.
Benthic algae play a role as energy source for many benthic fauna. Moreover, their roles in recycling nutrients (through the water column and sediment) and transformation of inorganic material into organic via photosynthesis in sediment were also known. Also, it was considered as oxygen sources for the water and sediment -. The benthic algae were considered as resistant to alterations of the environment and pollution due to their ability to attach to benthic substrates .
The abundance of diatomic algae was also observed in different studies. The abundance of some diatomic species may reflect the status of the aquatic ecosystem such as the trophic status  or extent of organic pollution   and to water quality . Many authors have pointed out the abundance of diatoms and explained that the diatomic algae had the ability to alter the conditions of their environment, but their community structure responded to altered physicochemical and biological variables in the ecosystem -.
Al-Lami et al.  observed high diversity of epipelic algae in four aquatic systems having a gradient of salinity in central of Iraq. Essa  used diatoms as bioindicators in some aquatic systems in Basra region, Iraq, where the author stated that the status of these sites ranged between oligo-mesotrophic and mesotrophic except only one site which was trophic.
This investigation is the first attempt to fill the gap of information about epipelic algal ecology in Al-Shamiyah River and the possibility to use epipelic algae as bioindicators.
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