Comparative Investigation of Marine Benthic Diatom Assemblages with Morphological and Metabarcoding Approaches Along the Coasts of Istanbul Metropolis

The importance of sustainable bioassessment and management of coasts to maintain good trophic status is increasing due to the high anthropogenic impacts on marine ecosystems. Diatoms are one of the most important assemblages and useful tools for assessing the state of the environment due to their advantages over other organisms such as short life span and rapid reaction to environmental changes in aquatic systems. In this study, our objective was to investigate marine benthic diatoms and compare them using three different methods: light microscopy (LM), scanning electron microscopy (SEM), and molecular metabarcoding (MB). LM observations were supported by SEM; in addition, 18S rRNA metabarcoding was used to reveal the diatom flora. The results showed that the highest number of genera was observed with LM (49), followed by SEM (27) and MB (21). Eight genera were found to be common by all three methods. Although MB identified a small number of genera, it verified the presence of common taxa through a rigorous analysis. However, all the methods used gave consistent results in confirming that the diatom assemblages found along the coasts of Istanbul in the Sea of Marmara exhibited low diversity. Our results suggest that the morphological approach to the study of marine benthic diatoms can be complemented by the metabarcoding approach, which showed encouraging results, and that both approaches can be mutually supportive.