Coral Calcification at the Cellular Scale: Insight Through the ‘Window’ of the Growing Edge

Corals form the structural basis of coral reefs, the world’s largest bioconstructions, which cover an area of about 284,300 km² globally (Spalding et al., 2001). Although this represents a relatively small portion of the ocean’s surface area, coral reefs rank among the world’s most valuable ecosystems in ecological and socio-economic terms. About a third of all marine species associate with coral reef habitats (Reaka-Kudla, 2005) and an estimated 500 million people depend on coral reef ecosystem goods and services (Hoegh-Guldberg et al., 2019; Wilkinson, 2008). Despite such profound importance to both marine biodiversity and humanity, much remains to be learned about the fundamental processes underlying the production of the building blocks that form coral reef architecture: coral skeletons.