Golestan Dam Lake is located ۱۲ kilometers east of Gonbad City and was constructed in ۱۳۷۹. The volume of the Golestan Dam reservoir is ۵۲ million cubic meters and its area is ۱۵۰۰ hectares, which was built for the purposes of agricultural and aquaculture operations. The present study on phytoplankton biodiversity and its relationship with the primary productivity of the Golestan Dam reservoir was conducted from April to July ۲۰۱۹. Furthermore, water quality parameters such as transparency, pH, alkalinity, free carbon dioxide, air and water temperature, dissolved oxygen, primary productivity, conductivity, nitrate-nitrogen, and orthophosphate were analyzed along with the qualitative and quantitative estimation of phytoplankton. The results indicated that the average primary productivity or Gross primary production (GPP) was ۰.۳۹۹ ± ۰.۰۸۱ gcm۳h-۱, Net Primary Production (NPP) (۰.۳۰۷±۰.۰۶۱ gcm۳h-۱), and Community Respiration (CR) ۰.۰۹۴±۰.۰۲۴ gcm۳h-۱ in the surface. Algae in freshwater have numerous environmental functions and are based upon the recycling of nutrients. Totally ۷۳ species of phytoplankton belonging to the different taxonomic groups were identified. which belong to ۳۲ genera Among these ۳۲ genera, ۱۲ belong to Cyanophyceae,۸ belong to Chlorophyceae, ۱۰ belong to Bacillariophyceae, and ۲ belong to Euglenophyta. On the basis of mean primary productivity, the fish production potential of reservoir Golestan Dam showed considerable scope for the enhancement of current average production.

Golestan Dam, Phytoplankton Diversity, Primary Productivity