biodiversity is sheltered by the 3D structure of coral skeletons. My group and I revealed that corals form
their skeletons by attachment of amorphous calcium carbonate (ACC) nanoparticles, then fill
interstitial spaces by ion attachment. Subsequent crystallization starts as aragonite (CaCO3)
nanocrystals, randomly oriented and termed sprinkles, which coarsen and become radially oriented
acicular crystals termed spherulites. This is Nature’s 3D printing! The resulting space-filling, solid,
isotropic structure grows slowly (0.5-5.0 cm/year) to form m-km coral reefs visible from outer space.
Corals are threatened by climate change, including ocean warming and acidification. With acidification,
the solubility of CaCO3 increases, thus, making it increasingly difficult for corals to build their skeletons,
especially because the ACC transient precursor phase is more soluble than aragonite. Different coral
species are differently sensitive to ocean acidification, indicating that mechanistic biological factors link
ocean chemistry and CaCO3 mineral growth, which we are studying. My group’s research suggests two
science-based interventions to help coral reefs. First, species selection based on resilience to acidification may allow repopulation of damaged reef ecosystems. Second, we are building electrified grids on
which corals are expected to grow faster, resist bleaching and acidification.