Biodiversity of carapace epibiont diatoms in loggerhead sea turtles (<i>Caretta caretta</i> Linnaeus 1758) in the Aegean Sea Turkish coast

Abstract

A total of 457 epizoic diatom taxa belonging to 86 genera were identified. Epizoic forms, e.g., <i>Achnanthes</i> spp., <i>Chelonicola</i> spp. or <i>Tripterion</i> spp. (also identified by SEM observations of the undisturbed pieces of the microbiome) dominated in terms of relative abundance, but the highest numbers of taxa were ubiquitously represented by <i>Navicula</i> (79), <i>Nitzschia</i> (45), <i>Amphora</i> (40), <i>Cocconeis</i> (32), <i>Diploneis</i> (25) and <i>Mastogloia</i> (23). <i>Navicula perminuta</i> and <i>Delphineis australis</i> were the most frequent taxa, present in 65% of the samples, both with an average relative abundance of 10%. The results of our study revealed that diatoms are an essential component of the loggerhead sea turtles' microbiome, in terms of high biodiversity and abundance. Although strict epibionts provide a signature of the turtle microbiome, the carapace as a solid substrate attracts numerous benthic diatom species which are considered opportunistic forms and can be found in the surrounding benthic habitats of the vast ocean littoral space.