The meta-organism response of the environmental generalist Pocillopora damicornis exposed to differential accumulation of heat stress

Bleaching events in the marine
environment are now occurring globally, and the frequency and severity of these
events are increasing. Critically, these events can cause the symbiosis between Symbiodiniaceae and their
coral hosts to break down, however what is still equivocal is how the microbial
community within the coral responds to bleaching. Here we investigate
the impact of thermal stress exposure on the meta-organism responses of the generalist
scleractinian coral species Pocillopora damicornis. Using mesocosms to
recreate warming scenarios previously observed at Heron Island, we show that P.
damicornis symbiont densities and photophysiological parameters decline at
a similar rate under thermal stress regardless of length of pre-stress period. However,
we find that the P. damicornis microbiome remains stable over time
regardless of the degree of thermal stress and the accumulation of
pre-bleaching thermal stress. Our study therefore suggests that while P.
damicornis is physiologically impacted by bleaching temperatures, the
microbial community remains unchanged at the taxonomic level identifiable here,
throughout bleaching. Given that P. damicornis
is an environmental generalist coral species common throughout the
Indo-Pacific, understanding the capacity of this coral to withstand bleaching
events is imperative. Furthermore, the widespread distribution of environmental
generalist coral species as a whole suggests their potential contribution to
coral reef structure under future climate conditions and as such the biology,
physiology and bleaching responses of these corals needs to be determined.