Gut bacterial communities in Atlantic bottlenose dolphins (Tursiops truncatus) throughout a disease-driven (Morbillivirus) unusual mortality event

Gut microbiomes are important determinants of animal health. In sentinel marine mammals where animal and ocean health are connected, microbiome impacts can scale to ecosystem-level importance. Mass mortality events affect cetacean populations worldwide, yet little is known about the contributory role of their gut bacterial communities to disease susceptibility and progression. Here, we characterized bacterial communities from fecal samples of common bottlenose dolphins, Tursiops truncatus, across an unusual mortality event (UME) caused by dolphin Morbillivirus (DMV). 16S rRNA gene sequence analysis revealed similar diversity and structure of bacterial communities in individuals stranding before, during, and after the 2013-2015 Mid-Atlantic Bottlenose Dolphin UME and these trends held in a subset of dolphins tested by PCR for DMV infection. Fine-scale shifts related to the UME were not common (10 of 968 bacterial taxa) though potential biomarkers for health monitoring were identified within the complex bacterial communities. Accordingly, acute DMV infection was not associated with a distinct gut bacterial community signature in T. truncatus. However, temporal stratification of DMV-positive dolphins did reveal changes in bacterial community composition between early and late outbreak periods, suggesting that gut community disruptions may be amplified by the indirect effects of accumulating health burdens associated with chronic morbidity.

Automated summary

The gut microbiomes play a crucial role in animal health, even extending to ecosystem-level importance in marine mammals. However, little is known about the impact of gut bacterial communities on disease susceptibility and progression in cetacean populations. In this study, the bacterial communities in fecal samples of common bottlenose dolphins during a mortality event caused by dolphin Morbillivirus were characterized. The results showed that while acute DMV infection did not have a distinct effect on the gut bacterial community of T. truncatus, changes in community composition were observed between the early and late outbreak periods, suggesting the potential amplification of gut community disruptions by accumulating health burdens associated with chronic morbidity.