Abstract

Over the past three decades, numerous factors have adversely affected the marine ecosystem, such as marine pollution, oil spills, habitat destruction, indiscriminate fishing, and climate change.¹ Animals exposed to these conditions experience increased stress levels and become susceptible to diseases.² Increased morbidity and unusual strandings in marine mammals are evidence of this phenomenon.³ Microorganisms play an essential role in animal health; thus, the incidence of certain bacterial taxa can be used as an indicator of health and disease. Therefore, it is crucial to continuously monitor these individuals and their environmental factors to understand microbiome dynamics. This research aimed to characterize the respiratory bacterial microbiome of blue whales (Balaenoptera musculus), determine the common core microbiome, identify differences between sex and age, and assess the temporality of bacterial communities.

This study was conducted during the breeding season of 2016 to 2018 in Bahia de Loreto National Park in the Gulf of California, Mexico. We analyzed 47 blow samples and seven technical controls. Phylogenetic analysis showed 17 bacterial classes (Alphaproteobacteria, Deltaproteobacteria, Gammaproteobacteria, Acidimicrobiia, Actinobacteria, Bacilli, Clostridia, Erysipelotrichia, Negativicutes, Bacteroidia, Fusobacteriia, Mollicutes, Melainabacteria, Oxyphotobacteria, Leptospirae, Spirochaetia, Campylobacteria, and Verrucomicrobiae). Alpha diversity measurements indicated an average richness of 710 species, and the Simpson index showed an average diversity of 0.96. Beta diversity analyses between female and male beats did not identify differences in species richness or relative abundance. Network analysis identified two clusters: one in which most of the blows were grouped and one formed by the blows of two adult females. These blows showed a different microbiome composition than the other whale blows (PERMANOVA, p=0.001), with lower species richness and higher relative abundance of Mycoplasma spp. (38.8%) and Prevotella spp. (13.84%) bacteria reported during the common cold in humans,^4,5 and respiratory diseases in terrestrial mammals.⁶ These findings provide a starting point to analyze the etiology of infection and the possible health consequences to this population of blue whales.

To our knowledge, this is the first study to analyze the dynamics of the bacterial microbiome in blue whales as a health indicator. The common central blue whale respiratory microbiome described in this study is proposed as a starting point for long-term studies attempting to link changes in the composition and patterns of co-occurrence of the respiratory microbiome to individual and population disease status. Furthermore, we showed that the structure of the blue whale respiratory microbiome could be used to predict disease progression since the presence of known pathogenic bacteria affects the composition of the common bacterial microbiome.

*Presenting author

Literature Cited

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