Contrasting morphological and DNA barcoding methods for diatom (Bacillariophyta) identification from environmental samples in the Eightmile River in Connecticut U.S.A.

Authors: KHAN-BUREAU, DIBA - Department Of Natural Resources; ECTOR, LUC - Luxembourg Institute Of Science & Technology; MORALES, EDUARDO - Universidad Católica Boliviana; Wade, Elizabeth; LEWIS, LOUISE - University Of Connecticut

Submitted to: Nova Hedwigia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2017
Publication Date: 1/3/2018
Citation: Khan-Bureau, D.A., Ector, L., Morales, E.A., Wade, E.J., Lewis, L.A. 2018. Contrasting morphological and DNA barcoding methods for diatom (Bacillariophyta) identification from environmental samples in the Eightmile River in Connecticut U.S.A.. Nova Hedwigia. doi:10.1127/1438-9134/2017/279.
DOI: https://doi.org/10.1127/1438-9134/2017/279

Interpretive Summary: Diatoms are a major group of algae and many species are found in fresh water. These unicellular organisms are being more commonly used in water quality bio-assessment studies, however, they can be very difficult to identify to species. A scientist at the USDA-ARS, in conjunction with researchers from the US, Bolivia and Luxembourg contrasted traditionally used morphological species identification with DNA barcoding. They determined that both approaches identified many species not found with the other method and using both methods simultaneously provides the most accurate species assessment.

Technical Abstract: The dominant and traditional 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. There is an increasing use of DNA barcoding for biodiversity studies and water quality monitoring, although the information provided by DNA barcoding of diatoms has not been compared comprehensively with that from morphology, except from cultured material. This study contrasted the performance of morphology and molecular data to distinguish diatom taxa from a single sample of the Eightmile River in Connecticut. Using a portion of the sample for morphological analysis with LM and SEM, the number of species, genera, and their taxonomic identities were evaluated. Three approaches for analysis of barcode data were compared. In total, the morphological approach yielded 60 taxa, and the molecular approaches yielded from 23 to 92 taxa, depending on analysis method. Some morphologically detected taxa were not detected by molecular means and some molecularly detected species were not detected morphologically. Using DNA barcoding and morphological methods simultaneously provides more information on species diversity within an environmental sample.