Microbiota of host sea anemones and their associated anemonefish show contrasting responses to a bleaching event
Résumé
Sea anemones form complex holobiont communities that include not only microorganisms (microbiota) but also metazoans, such as anemonefish. Previous studies have revealed the significant impacts of bleaching events on anemone microbiota and on anemonefish physiology. However, the impacts of bleaching on anemonefish microbiota remain understudied, despite the potential for microbial dysbiosis to favor the emergence of pathogens and opportunistic microbes which could be detrimental for anemonefish. As a consequence, we sampled microbiota in situ from healthy and bleached anemones (Radianthus magnifica) and their associated anemonefish (Amphiprion maohiensis) during the 2019 bleaching event in the lagoon of Mo’orea, French Polynesia. Metabarcoding was used to examine the diversity of Symbiodiniaceae and bacterial communities. Our results revealed significant differences in the assemblages of Symbiodiniaceae and bacteria between healthy and bleached anemones. Specifically, the alpha diversity of these microbial communities was higher in bleached anemones, suggesting microbial dysbiosis and an increase in opportunistic taxa. In contrast, no differences were observed in the bacterial assemblages of anemonefish associated with healthy and bleached anemones. Despite this lack of correlation between anemonefish microbiota and anemone bleaching status, we found that anemonefish living within the same anemone had nevertheless similar bacterial assemblages. As a consequence, we hypothesized that anemone bleaching does not significantly impact the microbiota of anemonefish, and that direct skin-to-skin contact among anemonefish is the primary factor influencing their microbiota composition.