The role of the microbiome in coral bleaching - Friends or Foes?

Shallow-water coral reef ecosystems are on decline globally, with heat stress and
deteriorating water quality identified as major causes of coral bleaching and subsequent
mass mortality (1,2). The main habitat-founding species, scleractinian corals, are described
as a holobiont formed by the coral host animal, its endosymbiotic dinoflagellates and the
'coral microbiome' - constituted by highly diverse and abundant communities of microbes
living on and within the coral. While intense research efforts have focused on how the animal
hosts and dinoflagellate symbionts respond to environmental stress, recent evidence
suggests that the coral microbiome changes along environmental gradients and that this
process may influence coral resilience to stress (3). Although marine microbes are known
to be key drivers of global biogeochemical cycles; their exact functional roles in the coral
holobiont remain unknown. It is unclear how specific environmental parameters shape the
structure of coral microbiome, and which specific mechanisms and microbes drive the
healthy functioning of the holobiont. This project aims to study how environmental multistressors,
especially heat and nutrient stress, influence the composition of the microbiome
and their interactions with their hosts in different coral species; thus affecting the resilience
of corals and their capacity to recover from bleaching events.