Didymosphenia geminata (Lyngbye) M.Schmidt, a threat for the Karaj River's ecosystem, Central Alborz, Iran

Diatoms are the most diverse group of single-celled algae that contain fucoxanthin, clorophyll a and c. They are the beginners at the food chain in aquatic ecosystems. Didymosphenia geminata (Lyngbye) M.Schmidt is a diatom species, considered as an invasive species which has caused many environmental problems in North America, Europe, New Zealand and Australia. In an investigation on diatom flora of the Karaj River, Didymosphenia geminata was found as a dominant species with a relative abundance of 10% in January 2011. The dominance of this species in the Karaj River is a threat for the ecosystem of the river. Therefore, to protect the river ecosystem, monitoring programs should be conducted annually and in case of high prevalence of the species, measures should be taken to clear the species from the river.