engleski

DNA metabarcoding and morphological analyses of the diatom biofilm associated with loggerhead sea turtles in the Mediterranean Sea

The external surfaces of large marine vertebrates, including sea turtles, provide hard substrata suitable for the development of rich microbial photoautotrophic biofilms. Among microeukaryotes, diatoms constitute the main biofilm component, with densities sometimes exceeding those known from other marine substrata. While some of the sea turtle- associated diatom taxa seem to be exclusively epizoic, others may also be common in habitats occupied by turtles thriving on both biotic and abiotic hard surfaces of, for instance, seagrass blades or sand grains. Many aspects of sea turtle ecology and behavior remain unknown, and micro- epibionts can be used as indicators of their behavioral patterns or as proxies of the anthropogenic impact on coastal marine habitats where sea turtles reside. Notably, these micro- communities are largely unexplored and there is a need to assess their taxonomic composition. In recent years, a DNA metabarcoding approach using rbcL marker has been applied to characterize diatom communities in different habitats. However, the lack of a reliable DNA reference database represents a serious impediment to the exclusive usage of molecular tools for the taxonomic assessment and they should be complemented with microscopical analyses. In this study, we aimed to use both molecular and morphology-based approaches to provide a detailed description of diatom communities associated with Mediterranean loggerhead sea turtles. We present the results of the analyses of the carapace and skin biofilm samples from ten loggerhead turtles collected from distinct habitats in the Mediterranean Sea including Croatian and Italian coastal areas within the Adriatic Sea and Amvrakikos Gulf in Greece.

diatoms ; molecular biology ; metabarcoding

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