Core respiratory microbiome of the blue whale, Balaenoptera musculus

The number of strandings and unusual mortality events that involve marine mammals may have increased, and potential pathogens of the respiratory tract have been found during examination of individuals in many of these events. Given that the core microbiome is key to understand host-bacteria relationships and to identify their relevance for host health, we characterized the core respiratory microbiome of the Eastern North Pacific blue whale, Balaenoptera musculus, using blow samples collected by a small quadracopter drone. 16S rRNA gene high-throughput sequencing revealed 2,732 amplicon sequence variants (ASVs) of which 18 were shared by more than 50% of all blue whales and were considered as the core respiratory microbiome. Sixteen bacterial classes with a relative abundance higher than 0.02% were identified in the blow samples, and eight of these were also found in the seawater samples. Nonetheless, blow samples harboured classes not commonly found in seawater, such as Acidiomicrobia, Actinobacteria, Campylobacteria, Erysipelotrichia, Leptospirae, Mollicutes, and Oxyphotobacteria. Only one whale presented a potential pathogen, Mycoplasma, associated with pulmonary pathology in mammals. Ours is the first study to characterize the respiratory microbiome of apparently healthy blue whales. The core microbiome identified here could be used as a baseline for future long-term studies on blue whale health.