Assessment of eutrophication in the Lake Zribar, Western Iran: analysis of temporal trophic variations – JBES

Mohammad Tahsin Karimi Nezhad, Fardin Mir Ahmadi, Mehdi Balideh

Department of Agronomy, Faculty of Agriculture and Natural Resources, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

Department of Food Science, Faculty of Agriculture and Natural Resources, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

Department of Environmental Protection, Kurdistan Province, Iran

Key words: Eutrophication, Lake Zribar, temporal variations, trophic state index.

Abstract

Lake Zribar, which is located in Kurdistan province, is one of the most productive lakes in Iran. Due to concerns about potential pollution resulting from watershed sources and adjacent agricultural lands, a study of the trophic state of Lake Zribar was conducted during the period December 2005 to October 2012. Total nitrogen (TN), total phosphorus (TP), Secchi disc depth (SD), Chemical Oxygen Demand (COD) and chlorophyll a (Chl a) were analyzed in order to assess the trophic state of the lake. The results indicated that COD, TN and TP are the key factors controlling the lake’s TSI level. The eutrophication level of the lake has been increasing and has reached the hypereutrophic level. Changes in N:P mass ratio indicated that phosphorus was the limiting nutrient for the algae proliferation at 65% of the sampling times; suggesting Bacillariophyta were the dominant taxonomic group. Soil analysis results showed that agricultural lands, especially tobacco farms, have a major contribution of nitrogen and phosphorus supply to the Lake.