engleski

Microbial Diversity Associated with Loggerhead Sea Turtles: Cyanobacterial Community Composition

Background: Loggerhead sea turtles carry rich microbial communities within their guts but also on their skins and carapaces. Studies of bacterial microbiota from the guts show that its composition is heavily influenced by the geographical location of turtles. Geographical variation has also been reported to influence diatom composition in epizoic surface loggerhead biofilms. However, the prokaryotic component of a loggerhead’s epizoic microbial biofilm is understudied. Advances in research on epizoic diatoms from the sea turtle biofilms have led to several newly described diatom taxa known to live only on the sea turtle host. This raises the question of habitat specificity of other prokaryotic organisms like Cyanobacteria ; are turtle-associated Cyanobacteria specific to their host or are they similar to species found in marine benthic environments? Objectives: Our goal is to identify the composition of epizoic microbial communities of Mediterranean loggerhead sea turtles and gain insight into their cyanobacterial counterparts for the first time. Methods: Carapace and skin scrapings from 54 loggerheads from the Adriatic and the Ionian Sea were collected in 2018 and 2019. We used high throughput sequencing and metabarcoding of 16S rRNA gene (V4 region) to investigate overall microbial diversity and get insight into cyanobacterial taxa composition. Data analysis was performed using the QIIME2 pipeline and SILVA 138 as the reference database. Results: More than 90 prokaryotic phyla were identified in our samples, and the most abundant were Proteobacteria, Bacteroidota, Bdellovibrionota and Cyanobacteria. The four most abundant cyanobacterial families were Phormidesmiaceae, Paraspirulinaceae, Xenococcaceae, and Limnotrichaceae. Alpha diversity indices show a significant difference in samples based on locality (Adriatic vs. Ionian Sea). Loggerhead sea turtles are anthropogenically threatened and our research complements the knowledge about their behaviour and migration routes and aids in their protection.

epibiotic, microbiome, cyanobacteria ; 16S rRNA gene

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