What is the primary role of calcium in marine environments?

The primary role of calcium in marine environments is indeed the production of coral and shells. Calcium is a critical element in the formation of calcium carbonate (CaCO3), which is the main component of coral skeletons and the shells of many marine organisms, including mollusks and some plankton. Through a process known as biomineralization, marine organisms extract calcium (and carbonate ions) from seawater to build their skeletal structures. This process not only plays a crucial role in the growth and health of corals, which are foundational species in many marine ecosystems, but also contributes to the overall structure and function of marine habitats like reefs. The presence of calcium in the marine ecosystem is vital for maintaining biodiversity, as coral reefs serve as critical habitats for many marine species.