Özet:

To define the biological features of phytoplankton in Mosul Dam Lake, monthly samples were collected along a year from September 2003 to August 2004. Consisting thermal stratification and turn over periods from four locations in the main lake and another location in the regulating lake. Total numbers of algae reached 2300 cell/ml in the main lake and 1100cell/ml in the regulating lake. Bacillariophyta were dominant with a maximum number of 1400 cell/ml in autumn. Chlorophyta were dominant in autumn also with 550 cell/ml. Ten genus of Chlorophyta were appeared in this water body: Cosmarium, Chlorella, Spirogyra, Scendesmus, Pediastrum, Tetraedron, Quadrigula, Ankiseradosm, Pandorina, and Straurastrum. Seven genus of Bacillariophyta were noticeable. Some genus of Cyanophyta was recorded as Aphanocapsa. In addition some Euglenophyta spp. were occurred in the main lake and the regulating lake also. On the basis of these algae abundance, the lake is undergoing cultural Eutrophication. It has passed in mesotrophic state (the middle trophic state of Eutrophication). Some genera which were appeared are the indication of eutrophic state. Total plate count bacteria ranged from 400-1700 cell/ ml in the main lake and 200- 950 cell/ml in the regulating lake were also recorded. Coliform bacteria were founded with most probable number reached 460 cell/100ml in the main lake and 150 cell/100ml in the regulating lake. Therefore, the lake water is classified as moderate pure and considering a good source of raw water supply with all treatment units and safe for swimming and recreational uses.

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