Biodiversity of diatom population in the Masouleh stream,Guilan, Iran

Studies of stream and river ecosystems in Iran are very sketchy and their information is rather general and vague. Understanding various aspects of river systems is vital for their management and protection. The present study was aimed to obtain and present information on key stream populations and evaluate their responses to arrays of environmental gradients as a model for other north Iran (Guilan) streams. During the study, in the period of 6 months (summer - autumn 2010) 23 diatom genera were identified from Masouleh stream. Physical and chemical parameters including temperature, electron conductivity (EC), pH, Fe, salinity, nitrate and orthophosphate were measured and analyzed in water column simultaneously. CCA test showed that EC, pH, Fe and salinity were the most important factors controlling diatom distribution. Values of two major components of CCA differed significantly (P<0.05). DCA analysis was used to observe taxonomic differences and similarities between diatom genera in different sites. We found that chemical parameters exert stronger impacts on diatom population than physical factors although studying of both parameters were essential to have an accurate understanding of stream health assessment and status. Diatom indices (diversity, evenness, TDI and PTI) provided useful information on biosenosis of the Masouleh stream and therefore application of this index is recommended for other streams in northern Iran.