From Marine Biodiversity Wiki
(Ca) metallic element that occurs in many rocks and in seawater and is an essential macronutrient. As Ca+ it is an important regulatory ion in living cells, involved e.g. in regulation of enzyme activity, stimulation of muscle contraction, and control of secretion. As calcium salts (e.g. calcium phosphates), it is a major constituent of bone..
- Lawrence, E. (2005). Henderson’s dictionary of biology. Pearson Education Limited, 13th ed., Harlow. 748 p.