Identification of phytoplankton communities, water quality and eutrophication status in the reservoir of Karun 4

One of the major problems of aquatic ecosystems is eutriphication or enrichment of water with nutrients. In this study, the phytoplankton communities in the Karun 4 reservoir were investigated in spring and summer in 2018.

Chlorophyll A and 19 water physicochemical parameters were measured and analyzed at the reservoir in 26 stations. Statistical analysis of data was done in SPSS software. In order to investigate the biological indicators, Simpson and Shannon-Wiener indices were used, and Trophic State Index (TSI) was used to determine the eutriphication status of the lake.

Among the 35 identified genera, the phytoplankton populations mostly belonged to the Nephrocitium, Oonephris, Peridinium, Pyrophacus, Dinobryon, Cyclotella, Diatoma, and Chlorella genera. Also, the population of phytoplankton was more in summer than in spring. The Simpson and Shannon-Wiener biodiversity indices were calculated as 0.835±0.031 and 2.01±0.174 in spring and 0.819±0.041 and 2.02±0.21 in summer, respectively. According to the TSI index, the trophic status of the studied reservoir was in the eutrophic range (50-75). The analysis of the main components of principal component analysis showed that in spring, six components explained 80.847% of the total variance, while in summer, eight components explained 83.287% of the total variance.

The results showed that the Karun 4 reservoir, which is an important water source in Iran, is in a eutrophic state. This may be due to the increase in temperature in spring and summer, the growth of phytoplankton populations, and the increase in the amount of released ions of industrial and agricultural wastewater, which leads to the eutrophic condition in the reservoir.