Coral growth persistence amidst bleaching events

As mass bleaching events decimate stony coral populations, production of calcium carbonate is diminished on reefs, dampening their capacity to keep pace with rising sea levels. However, perturbations to the calcification process of surviving wild corals during bleaching are poorly constrained, owing to the lack of suitable techniques to retroactively extract this information from coral skeletons at sufficient resolution. Here, we use novel Raman spectrometry techniques to test the biogeochemical response of long-lived corals before, during, and after bleaching. Maintenance of high aragonite saturation state (O-Ar) in the coral calcifying fluid is key to driving rapid skeletal growth but would be expected to decrease when corals become energetically depleted without their symbionts. Contrary to this expectation, our results demonstrate that corals upregulate calcifying fluid O-Ar during bleaching and for at least 2 yr after recovery. This indicates that the calcification process of coral-bleaching survivors is unexpectedly resilient.

Automated summary

Mass bleaching events lead to reduction in coral populations and calcium carbonate production, which weakens the ability of reefs to counter rising sea levels. This study used Raman spectrometry techniques to examine the biogeochemical response of long-lived corals before, during, and after bleaching. The findings indicate that the calcification process of coral-bleaching survivors is unexpectedly resilient.