Short answers, pulled from the story.
The skeletal structures of marine calcifiers are predominantly composed of calcium carbonate minerals, specifically aragonite and calcite. Some species like corals can incorporate both calcite and aragonite polymorphs into their skeletons.
Mollusks use the extracellular strategy in which ion exchange pumps actively pump ions out of a cell into the extracellular space where environmental conditions such as pH can be tightly controlled. Specialized cells follow genetic instructions to synthesize minerals under non-equilibrium conditions within a confined space.
Skeletal diversity increased during the Cambrian Period with a gradual increase in abundance and diversity over 25 million years. The appearance of mineralized skeletons in various groups marked a significant watershed in skeletal evolution driven by predation pressure favoring protective armor.
Ocean acidification presents a formidable threat to global shellfish production by reducing calcification rates due to lower saturation states of seawater. Projections indicate that by the end of the century mussel and oyster calcification could witness substantial reductions of 25% and 10% respectively under the IPCC IS92a scenario.
The Philippine economy receives at least US$1.06 billion each year from coral reefs. This figure represents specific regional economic significance alongside the worldwide combined economic value of coral reefs which is an estimated average of US$490 per hectare annually.