عنوان مقاله [English]
To study the density and distribution of phytoplankton, sampling was conducted in 6 stage from April till March 2016. Phytoplankton samples horizontally and vertically from different depths (0, 5, 10 and 20 m) by harvesting water with Ruthner and bring to a volume of 10 liters, homogenize and finally picked it took a liter. Samples 4% formalin fixed and in the laboratory using 5 ml containers and inverted microscope were identified and counted. Investigate totally distinguished 35 genus in 6 Phylums among of genus, Bacillariophyta, Euglenophyta. Chlorophyta, Pyrophyta, Chrysophyta and Cyanophyta had 8 genus, 1 genus, 13 genus, 3 genus, 2 genus and 5 genus respectively. In this reservoir dam the Phylum of Bacillariophyta was dominant of Phytoplankton with 73.8 % of population annually and genus Cyclotella , Navicula and Synedra were dominant samples. The Phylum of Chrysophyta has been located the second position with genus of Dinobryon and Synura and frequency 12.2 % . Other of Phytoplankton phylums were least population such as Chlorophyta with genus of Scenedesmus, Cosmariumand Tetraedronwith frequency 8.2 %. In all of the sampling months, mean of the most of Phytoplanktonic density belonged to Phylum of Bacillariophyta 69500449±11456 number in liter that in the spring with an abundance of 25044064 ± 467892 showed the highest density per liter. Phytoplankton abundance of phylum in summer, autumn and winter seasons with a lot of density 17323830, 10786088 and 16346467 per liter respectively. The maximum abundance of phytoplankton in a station 1 (crest dam) with an abundance 7,589,932, station 3 (end lake) with a frequency of 6637800 and two station (the middle section lake) with a frequency of 5,495,732 per liter respectively. According to the tropic index and according to the degree of transparency, the phosphate, nitrogen and chlorophyll a values obtained from physical and chemical data, Karde reservoir located at the level of Meso-trophic lakes.According to non-parametric analysis Kruskal-Wallis and Mann-Whitney there were statically significant difference between Phytoplanktonic frequency in different stations and months (P<0.05). The study also spring seasons showed significant differences with the other three seasons (P>0.05).