Highly conserved thermal performance strategies may limit adaptive potential in corals

Increasing seawater temperatures are expected to have profound
consequences for reef-building corals’ physiology. Understanding how
demography changes in response to chronic exposure to warming will help
forecast how coral communities will respond to climate change. Here, we
measure growth rates of coral fragments of four common species, while
exposing them to temperatures ranging from 19 to 31˚C for one month to
calibrate their thermal-performance curves (TPCs). Our results show that,
while there are contrasting differences between species, the shape of the
TPCs was remarkably consistent among individuals of the same species. The
low variation in thermal sensitivity within species may imply a reduced
capacity for rapid adaptive responses to future changes in thermal
regimes. Additionally, interspecific differences in thermal responses show
a negative relationship between maximum growth and thermal optima,
contradicting expectations derived from the classic “warmer-is-better”
hypothesis. Among species, there was a trade-off between current and
future growth, whereby most species perform well under current thermal
regimes but are susceptible to future increases in temperature. Increases
in water temperature with climate change are likely to reduce growth
rates, further hampering future coral reef recovery rates and potentially
altering community composition.