Why Do Bio-Carbonates Exist?

Calcium carbonate precipitation associated with biotic activity is first recorded in Archaean rocks. The oldest putative fossils related to hydrothermal vents have been dated at similar to 3.77 Ga (possibly 4.29 Ga). Stromatolites, the oldest dated at 3.70 Ga, have since occurred through Earth history, despite dramatic changes in physical and chemical conditions in aquatic environments. A key question is: what advantages do photosynthesizing aquatic prokaryotes and algae gain by precipitating carbonates? We propose the Phosphate Extraction Mechanism (PEM) to explain the benefits of biomineralization in warm, oligotrophic, alkaline, euphotic environments. Carbonate precipitation enhances access to otherwise limited carbon dioxide and phosphate in such environments. This mechanism also provides an explanation for prolific production of carbonates during times of elevated atmospheric carbon dioxide at intervals in the Phanerozoic.

Automated summary

Calcium carbonate precipitation associated with biotic activity in Archaean rocks is studied, and the advantages of carbonates precipitation for photosynthesizing aquatic prokaryotes and algae are explained. The study proposes the Phosphate Extraction Mechanism (PEM) to explain the benefits of biomineralization and the prolific production of carbonates during times of elevated atmospheric carbon dioxide.