Some Plankton Make Shells of Calcite/aragonite,that Is,CaCO₃

Some plankton make shells of calcite/aragonite,that is,CaCO₃.They do this metabolically by combining calcium (Ca²⁺) ions and bicarbonate (HCO₃-) ions that are both dissolved in water around them.When such plankton dies,their shells sink downward to become sediment on the ocean floor.Under some conditions in the ocean or sediment,the CaCO₃ shells may dissolve,locally enriching the pore waters or deep-ocean waters in HCO₃-.Portions of this total process could be considered belonging to each of the following cycles,EXCEPT for the ____________.

A) carbon cycle
B) biogeochemical cycle
C) methane cycle
D) calcium cycle