Abstract
The composition of mammalian microbiota has been related with the host health status. In this study, we assessed the oral microbiome of 3 cetacean species most commonly found stranded in Iberian Atlantic waters (Delphinus delphis, Stenella coeruleoalba and Phocoena phocoena), using 16S rDNA-amplicon metabarcoding. All oral microbiomes were dominated by Proteobacteria, Firmicutes, Bacteroidetes and Fusobacteria bacteria, which were also predominant in the oral cavity of Tursiops truncatus. A Constrained Canonical Analysis (CCA) showed that the major factors shaping the composition of 38 oral microbiomes (p-value < 0.05) were: (i) animal species and (ii) age class, segregating adults and juveniles. The correlation analysis also grouped the microbiomes by animal stranding location and health status. Similar discriminatory patterns were detected using the data from a previous study on Tursiops truncatus, indicating that this correlation approach may facilitate data comparisons between different studies on several cetacean species. This study identified a total of 15 bacterial genera and 27 OTUs discriminating between the observed CCA groups, which can be further explored as microbiota fingerprints to develop (i) specific diagnostic assays for cetacean population conservation and (ii) bio-monitoring approaches to assess the health of marine ecosystems from the Iberian Atlantic basin, using cetaceans as bioindicators.
Highlights
The ecological sustainability of aquatic environments is being dramatically threatened by climate change, habitat deterioration and a vast array of human-driven activities
All oral microbial communities were dominated by members belonging to the Proteobacteria, Firmicutes, Bacteroidetes and Fusobacteria phyla (Supplementary Fig. S1), which were predominantly detected in the oral cavity of bottlenose dolphins (Tursiops truncatus), described by Bik et al.[17]
Due to the high heterogeneity of the samples from the 38 Odontoceti used in the present study, clustering patterns of their oral microbiomes were not clearly observed with ordinations based on Bray-Curtis, as reported by Bik et al.[17]
Summary
The ecological sustainability of aquatic environments is being dramatically threatened by climate change, habitat deterioration and a vast array of human-driven activities. The common dolphin (Delphinus delphis) is one of the most abundant cetacean species in Atlantic Iberian waters[8], sharing the habitat with other members of the family Delphinidae, such as the bottlenose dolphin (Tursiops truncatus) and the striped dolphin (Stenella coeruleoalba). The highest abundances of striped dolphins in Portugal are markedly found offshore, whereas harbor porpoises are mostly concentrated near the coast. The more near-coastal animals may be exposed to a wide variety of anthropogenic www.nature.com/scientificreports/. Systematic studies on marine mammal health and disease are crucial to support conservation and management measures, considering species such as the harbour porpoise. In Continental Portugal, since the year 2000 when regional dedicated marine animals stranding networks started operating until 2016, a relatively high cetacean stranding rate was registered. In many cases (about 36%), the observed cetacean mortality causes remained undetermined, due to the number of stranded animals found in advanced decomposition stages
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