Odontidium mesodon (Ehrenb.) Kützing, an indicator diatom species for high water quality (a case study: Damavand River basin, Iran)

Diatoms are robust indicators of water quality in aquatic ecosystems. So far, many diatom indices have been defined based on the diversity of diatoms in different countries. Studying diatom biodiversity in the reference conditions, under no human pressure and pollution, is necessary for evaluating the water quality in rivers. Cheshme-Ala is one of the springs of the Damavand River basin with high water quality. In this study, Cheshme-Ala is considered as a reference site for the Damavand River. This study aims to study sensitive diatom species to organic pollution and introduce Odontidium mesodon (Ehrenb.) Kützing as the indicator species for high water quality in Cheshme-Ala. Samples were collected from the substrates of the Damavand River and Cheshme-Ala in eight stations seasonally. Results showed that Odontidium mesodon was observed as a dominant species in Cheshme-Ala in March. The high abundance of this species indicates the favorable habitat for growth in Cheshme-Ala. Furthermore, this species was not observed in the polluted sites along the river seasonally. Therefore, this study demonstrated that Odontidium mesodon was the indicator of high water quality. Our data are congruent with the researches in the USA, Europe, and Russia, introducing this species as a sensitive species to organic pollution. The information can be used in water quality monitoring projects of the rivers.