An exploratory investigation into the microbial and cyanobacterial presence on skin epibiotia and orofacial lesions in estuarine common bottlenose dolphins (Tursiops truncatus) through metabarcoding

Estuarine common bottlenose dolphins (Tursiops truncatus) inhabiting the Indian River Lagoon (IRL) have been documented with light brown skin lesions, loosely categorized as "algal sheens". In recent years, dolphins from the IRL have also exhibited unusual necro-ulcerative orofacial lesions. To date, no metabarcoding investigation has been conducted to determine whether "algal sheens" observed on the dolphins are pathogenic, opportunistic or are indicators of poor health or water quality. The aim of this study was to investigate the etiology of "algal sheens" and orofacial lesions, to assess the pathogenic potential. In this study, 13 skin and "algal sheen" swabs from 11 dolphins were sequenced using metabarcoding techniques. Genus-level identification was achieved and compared. Results from both "algal sheen" and orofacial lesion samples demonstrated higher bacterial diversity than reported in normal bottlenose dolphin skin microbiomes. Previously unreported bacterial genera were identified, genera containing pathogenic species found in both sample types. Species responsible for "algal sheens" were not definitively identified. Numerous cyanobacterial genera typically found in eutrophic conditions were identified.