Ecological assessment of organic pollution of Bustan dam reservoir using Palmer and Carlson indexes

In this study, the trophic status of the Bustan dam reservoir was investigated using Palmer and Carlson indices. Biological parameters including phytoplankton and environmental factors such as phosphate, nitrate and chlorophyll were sampled at the depth of 0.5 meter in five stations in three replicates seasonally in 2019, repetitions and Then the Palmer and Carlson indices were determined. The Palmer index in Bustan dam was estimated as 24, 31, 27.6, and 28.8in spring, summer, autumn, and winter, respectively.  According to the Palmer index classification, in all four seasons, Bustan dam water is in the category of water with high organic matter. The highest value of Palmer's index was obtained in summer (31) and its lowest value was obtained in spring (24). The highest nutritional status of Carlson's index was related to summer (60.46 eutrophication) and the lowest level was found inwinter (52.44 eutrophication), which indicates that the reservoir has moved to semi-nourishing condition in winter season. Also, the highest nutritionism status was observed in station 3 (54/23). According to Palmer's and Carlson's indices and the ratio of phosphate to total nitrogen, the main factor of nutritionism in the reservoir of Bustan dam was phosphorus compounds that enteres the reservoir from external sources of the dam and ultimately causes the decrease of water quality.