Bacterial community dynamics are linked to patterns of coral heat tolerance

TLDR

Ocean warming threatens coral reefs, yet corals inherit heat tolerance and their diverse microbiomes can rapidly shift, potentially aiding adaptation or reflecting parallel responses to high temperatures. We found that reef coral microbiomes vary by habitat, shift with reciprocal transplantation, respond to bleaching in heat‑sensitive but not heat‑tolerant corals, and that specific bacterial taxa predict short‑term heat stress responses.

Abstract

Abstract Ocean warming threatens corals and the coral reef ecosystem. Nevertheless, corals can be adapted to their thermal environment and inherit heat tolerance across generations. In addition, the diverse microbes that associate with corals have the capacity for more rapid change, potentially aiding the adaptation of long-lived corals. Here, we show that the microbiome of reef corals is different across thermally variable habitats and changes over time when corals are reciprocally transplanted. Exposing these corals to thermal bleaching conditions changes the microbiome for heat-sensitive corals, but not for heat-tolerant corals growing in habitats with natural high heat extremes. Importantly, particular bacterial taxa predict the coral host response in a short-term heat stress experiment. Such associations could result from parallel responses of the coral and the microbial community to living at high natural temperatures. A competing hypothesis is that the microbial community and coral heat tolerance are causally linked.