Small naviculoid species of Kobayasiella Lange-Bertalot, Adlafia Moser, Lange-Bertalot & Metzeltin, Nupela Vyverman & Compère and Sellaphora Mereschowsky from Tursujuq National Park, Hudson Bay region, Nunavik, Québec

Seven species from the genera Kobayasiella (K. madumensis Jørgensen, K. micropunctata Germain, K. parasubtilissima Kobayasi & Nagumo, K. pseudostauron Lange-Bertalot, K. subtilissima P.T.Cleve), Adlafia (A. bryophila Petersen) and Nupela (N. tenuicephala Hustedt) from oligotrophic lakes of the subarctic boreal zone in Tursujuq National Park in Nunavik (northern Québec, Canada), were studied by light and scanning electron microscopy and linked with environmental conditions. In addition, four new species, Kobayasiella tursujuqensis sp. nov., Adlafia umiujaqensis sp. nov., Adlafia ossiformis sp. nov., and Sellaphora vincentiana sp. nov., were observed and described. The new species are similar in light microscope observations to other species in their associated genera, but can be identified based on independent character traits under a combined LM and SEM analysis. Morphological structures of particular interest include valve outline, position of the central and terminal raphe fissures, orientation of the striae, and the structural formation of the areolae within the striae. Due to low taxon abundances, distribution patterns of these species in the park were difficult to identify. Kobayasiella parasubtilissima, K. subtilissima, K. tursujuqensis sp. nov. and N. tenuicephala were associated with acidic conditions while K. pseudostauron, A. bryophila and S. vincentiana sp. nov. were found in circumneutral waters. A better knowledge of small naviculoid species is necessary to document the circumpolar biogeography and ecology of diatoms for a better understanding of the dynamic of those organisms in changing environmental conditions within the context of rapid climate change in northern regions.