Three new Cosmarium species from Nature Reserve Zwanenwater (North Holland, the Netherlands)

A study on diversity and distribution of desmids in the dune pools of Nature Reserve Zwanenwater revealed a number of forms of the genus Cosmarium that could not be satisfactorily identified with the pertaining literature, or led to taxonomic confusion with similar forms. Three species are described as new to science: Cosmarium lacuscygnei, C. jemtlandicoides and C. obscurum. Differences and similarities with related species are discussed. The ecology of these new species is described on the basis of the nature of the various sites in the area where they were encountered.