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. This group is considered as algae, the first group of food chain in aquatic ecosystems, however, a species of them with the scientific name Didymosphenia geminata (Lyngbye) M. Schmidt as an invasive species in North America, Europe, New Zealand and Australia are known to cause many environmental problems. During 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.