Application of ordination technique in investigating Diatom populations and their relation with environmental factors (Case study: Masooleh Roudkhan)

Benthic diatom populations are highly diverse and ubiquitous، and consistently correlate with environmental variables. The present study was conducted to evaluate effects of some physical and chemical parameters on abundance of diatoms in a tributary of the Masooleh River in summer، autumn and winter in the year 2011. The samples were collected from surface layers of Epilithon، Epidendron، Epipssamon and Epipelon as natural substrates. The collected samples were processed and slides were prepared for LM examination. Masooleh River is located at 37o 22’ to 37o 23’ northern latitude and 49o17’- 49o19’ eastern longitude in Guilan Province، north of Iran. Five sampling sites were chosen along 15 km of the river In this study 23 genera of diatoms were identified. The analyses showed that pH and Fe were negatively correlated with Diploneis، Gomphonema، Cymbella and Surirella and positively with Amphora، Achnanthes، Diatoma، Melosira، Nitzschia، Cymatopleura and Rhoicosphenia (P<0. 05). The pH، Nitrate and EC were negatively correlated with Synedra، Navicula، Rhopalodia، Gyrosigma and positively with Nitzschia، Reimeria and Cocconeis (P<0. 05). Discussion and Effects of salinity and water temperature on the diatom populations (Group 1: Cymbella، Surirella، Gomphonema، Diploneis، Cocconeis) were higher than other agents and factors such as pH، iron (Fe2+) and silicate (SiO2) were second rate in terms of importance.