Abstract
During recent observations of the diatom flora of Lake Ohrid, fifteen new species were found, each possessing unique morphological features: Odontidium minutum, Staurosirella pulchella, Staurosirella lata, Fragilaria micra, Navicula subviridula, Prestauroneis tumida, Placoneis pseudabundans, Placoneis subelegans, Cymbopleura tumida, Gomphosphenia tenuis, Gomphonema mihoi, Gomphonema subaequale, Gomphonema perolivaceolacuum, Gomphonema linearoides and Gomphonema densistriatum. We provide detailed descriptions for all fifteen species based on light and electron microscopy observations. Noteworthy is the high diversity recorded in the Gomphonema olivaceum species complex, which comprises eight species in total, three of which are described as new. We also provide a key for identification of species in the G. olivaceum complex in Lake Ohrid and a compilation of published data detailing the infraspecific diversity of this complex.