Microbial shifts associated to ENSO-derived thermal anomalies reveal coral resilience acclimatation at the holobiont level

The coral microbiome is vital to maintain holobiont homeostasis, conferring important benefits such as nutrient acquisition and disease resistance. Since the microbiome is substantially sensible to the surrounding environment, it conforms a proxy to study effects of changing environmental conditions. However, scarce information exists regarding the microbiome responses to environmental changes. We assessed thermal associated shifts in the bacterial microbiome of Pacifigorgia cairnsi, a sea fan from the remote island of Malpelo in the Tropical Eastern Pacific with absence of direct anthropogenic impacts and considered a hot spot of biodiversity. Analyzing 16S rRNA gene amplicons during 2015, 2017 and 2018, we evaluated the community composition and functional profiles of the bacterial microbiome through different phases of El Nino Southern Oscillation (ENSO) cycle (i.e. El Nino-warming phase, La Nina-cooling phase and the Neutral phase). Our major findings revealed different bacterial community diversity and composition between the warming and cooling phase on the one side, and the neutral phase on the other side.