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Knowledge on benthic diatom taxonomy and hence biodiversity from Arctic locations is rare, though the few existing analyses address morphological characteristics only. Morphological treatment is a time-consuming process and just allows the taxonomic identification of a low sample volume. In contrast, molecular sequencing is a faster and universally applicable approach, and also has the potential for refined analyses. Unfortunately, a lot of molecular information in databases is not trustable, and often existing genetic data do not fit together with morphological aspects. Therefore, the main goal of our study was for the first time to combine both morphological features and DNA information on benthic Arctic diatoms. In a first step, we studied the morphology of 26 strains from the Rostock Culture Collection of Arctic diatoms via light and electron microscopies. Secondly, we addressed their molecular taxonomy by sequencing the DNA barcode 18S V4 and the chloroplast marker rbcL. As a result, we could identify five species. Seven of the altogether twelve taxa could not be attributed to any known species, because listed sequences and morphology did not fit together. From these, three species were described as new to science here. Although the studied strains represent only a minor fraction of the diatom flora of Svalbard, this study is a first milestone in coupling morphological and molecular data of benthic diatoms in such high latitudes. By making these data available online, they contribute to a taxonomic reference library for Arctic benthic diatoms and are available for comparative studies.

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