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Diatoms of Krka River, Croatia

Krka River is a unique freshwater ecosystem situated in Dinaric karstic area of Croatia. Knowledge concerning diatom diversity, ecology and community associations especially of karstic environments in Croatia is still very scarce. Diversity of benthic diatom species from various habitats, both lotic and lentic, from springhead to the Krka River estuary was studied in September 2017. A total of 44 samples were collected and examined for taxonomic analyses using light and scanning electron microscopy. Altogether, 276 taxa (species, varieties and forms) from 69 genera were identified by traditional morphology analyses. Flora dominated by genera Navicula Bory sensu stricto, Nitzschia Hasall and Gomphonema Ehrenberg was observed. The most frequent species were Navicula cryptotenella Lange-Bertalot, N. radiosa Kützing, Pantocsekiella ocellata (Pantocsek) K.T. Kiss & E. Ács, Encyonopsis minuta Krammer & E.Reichardt, and Achnanthidium minutissimum (Kützing) Kützing. Species with unclear taxonomic status (Reimeria sp. aff. uniseriata, Aneumastus aff. tusculus, Aneumastus aff. stroesei, Diploneis submarginestriata) were also recorded together with Gomphosphaenia plenkoviciae Gligora Udovič & Žutinić, a newly described diatom species from Crveno jezero, Croatia. For molecular analyses, 38 samples were exposed using the universal eukaryotic primer pair for the hypervariable V9-region. When comparing morphological and genetic results of represented Operational Taxonomic Units (OTUs), the most frequent species were Aulacoseira ambigua (Grunow) Simonsen, Cocconeis placentula Ehrenberg, Cymatopleura elliptica (Brébisson) W.Smith, Aulacoseira granulata var. angustissima (Otto Müller) Simonsen, Staurosirella pinnata (Ehrenberg) D.M.Williams & Round, and Achnanthidium minutissimum (Kützing) Kützing. These preliminary results of V9 region performed high number of OTUs for diatom species, but OTUs didn’t show high resolution of overlap with traditional morphological-based identification. In order to obtain a better resolution, further research will include primers for the highly conserved rbcl gene.

Krka River ; diatom diversity ; traditional morphology analyses ; molecular analyses

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