A review of Ulva intestinalis, the only macroscopic alga of Urmia Lake

There are little data on the presence of Ulva intestinalis, as the only macroscopic alga of Urmia Lake. This study tries to illuminate some historical, taxonomical, and ecological aspects of this macro alga of Urmia Lake which has not been observed in the lake since the late 1990s. Ulva intestinalis is a macroscopic alga that was previously recorded from Urmia Lake but disappeared from the lake flora in the late 1990s. This study is based on multiple visits to Urmia Lake since 1998 and a literature review. During many visits to Urmia Lake, we did not observe any samples of Ulva intestinalis. The reason remains unclear until now; natural or anthropogenic. However, it is a green alga belonging to the genus Ulva in Ulvaceae, with high carotene contents. Considering the human impacts on ecosystems and the probable extinction of some species, this study reviews the history of the occurrence of Ulva intestinalis in Urmia Lake and the possibility of its extinction. We believe that the documentation of the algal flora in an herbarium is very important in the interpretation of the presence, population decrease, or extinction of species. Therefore, we suggest the foundation of algal herbaria in institutions close to aquatic habitats, to keep records and monitor the algal and other aquatic flora.