Two Novel Diatoms in Connecticut and Comparisons of Morphological and Molecular Approaches of Species Diversity Estimation

ABSTRACT Diatoms (Bacillariophyta) are ubiquitous and can be found wherever there is water and are ecologically important eukaryotic microalgae. Because many diatom species have been shown to be associated with particular environmental conditions, these taxa are accepted as biological indicators for assessing water quality. In order to address water quality and other applications using diatoms, accurate taxonomic identification is essential. The dominant approach used to identify diatom species is morphological characterization with light (LM) and scanning electron microscopy (SEM). However, using morphology alone to distinguish diatom species can be challenging because the phenotype of a species is often influenced by the life cycle stage and the environment. DNA barcoding is a method that compares a short section of a genome region. There is an increasing use of DNA barcoding for biodiversity studies, although the information provided by DNA barcoding of diatoms has not yet been compared with that from morphology, except from cultured material. This research contrasted the performance of DNA barcoding and morphological methods to distinguish diatom taxa in a freshwater sample of the Eightmile River, Connecticut. The research examined the utility of DNA barcoding to identify and document the presence of nuisance diatoms Cymbella janischii (A. Schmidt) De Toni and other stalk forming diatoms in The West Branch Farmington River, Connecticut and reports on a putatively new species in the genus Didymosphenia