Characteristics of The Bleached Microbiome of The Generalist Coral Pocillopora damicornis from Two Distinct Reef Habitats

Generalist coral species may play an important role in predicting, managing, and responding to the growing coral reef crisis as sea surface temperatures are rising and reef wide bleaching events are becoming more common. Pocilloporids are amongst the most widely distributed and studied of generalist corals, characterized by a broad geographic distribution, phenotypic plasticity, and tolerance of sub-optimal conditions for coral recruitment and survival. Emerging research indicates that microbial communities associated with Pocilloporid corals may be contributing to their persistence on coral reefs impacted by thermal stress; however, we lack detailed information on shifts in the coral–bacterial symbiosis during bleaching events across many of the reef habitats these corals are found. Here, we characterized the bacterial communities of healthy and bleached Pocillopora damicornis corals during the bleaching events that occurred during the austral summer of 2020 on Heron Island, on the southern Great Barrier Reef, and the austral summer of 2019 on Lord Howe Island, the most southerly coral reef in Australia. Regardless of reef location, significant differences in α and β diversities, core bacterial community, and inferred functional profile of the bleached microbiome of P. damicornis were not detected. Consistent with previous reports, patterns in the Pocilloporid coral microbiome, including no increase in pathogenic taxa or evidence of dysbiosis, are conserved during bleaching responses. We hypothesize that the resilience of holobiont interactions may aid the Pocilloporids to survive Symbiodiniaceae loss and contribute to the success of Pocilloporids.