Biocalcification through time: environmental challenge and cellular response

A concept explaining biocalcification as a form of calcium detoxification is advanced using geochemical and paleontological criteria. The first appearence of calcareous skeletons at the turn of the Precambrian/Cambrian is interpreted as a biotic response to a gradual rise of Ca2+ in world ocean resulting in Ca2+ stress environments in shelf areas. Periodic appearance in the Phanerozoic record of heavily calcified marine biota, absent or relic in modern seas, suggests considerable temporal fluctuations of calcium concentrations in the ancient ocean. Temporal changes in Ca2+ and mineral nutrient contents in the environment can thus be seen as overriding factors in the evolution of organisms