تركيب گونه اي و تعيين تراكم فيتوپلاني در درياچه پشت سد لار

Identification and comparison of seasonal phytopiankton density in Lar dam lake

In this study, in order to investigate limnologica! and biological parameters of Lar dam lake such as indentification of density and distribution of phytopiankton, sampling were done during 6 months from different depths (layers 0,5,10,20,30 m) by Ruttner and fixed in formalin 4% and transferred to laboratory for further investigation under inverted microscope. In this study, 28 genera which belonged to 6 phytopianktonic phylla were identified. Among these genera, 14 were belonged to Bacillariophyta, 1 genus was belonged to Euglenophyta, 7 genera were belonged to chlorophyta, 3 genera were belonged to phvrophyta, 1 genus was belonged to chrysophyta and 2 genera were belonged to cyanophyta. In this reservoir dam, Bacillariophyta was the dominant phytoplanktom phylum with annually 74.83% of population and following genera cyclotella, Navicula and Nitzchia were dominat samples. The others phytoplank tonic phylla were: chlrophyta, chiysophyta, Pryophvta, Euglenophyta and cyanophyta with following frequencies: 17.10%, ʹ 3.60%, 2.73%, 0.83% and 0.83% respectively and following genera: (Oocystis, Padiastrum, Scendemus and Chlorella), (Dinobryon and Malomonas), (Ceratium and Peridinium) and (Occillatoria and Anabeana). In all of the sampling months, the highest average density was belonged to Bacillariophyta with 437500± 37.740 number per liter and the dominant genus of this phyllum which was observed in high number during a year was cyclotella. After that was Chlorophyta with average number of 268750± 39.753 per liter and its dominant genera were Oocystis, Pediastrum, Scenedesmus and Chlorella respectively. According to non-parametric analysis Kruskal-Wallis and Mann-Whitney, there were statically significant difference (P<0.05) between Phytoplanktonic frequency in different stations and months but there was not observed any statical significant difference between different depths (P>0.05). Biological studies indicated that this reservoir had low Planktonic generation potential. Keyword: Identification, Phytopiankton, Lar reservoir dam, Comparison