To understand further the effects of biological activity on the formation of apatite and carbonate minerals in marine sediments, an experiment that added soil extract (i.e., soil microbial liquid) to simulated seawater in a laboratory was conducted. By setting the plastic drums containing the fluid under lighting and weaker light (dark) conditions, the pH, conductivity, dissolved oxygen concentration, microbial data, and main mineral types in the sediment of these simulated seawater samples, were analysed. Results showed that the pH and microbial quantities in lit conditions were greater than those in darkroom conditions; the growth of microorganisms could affect pH, conductivity, and the dissolved oxygen concentration. Furthermore, SEM observation showed that calcium phosphate and calcium carbonate crystals were both found in sediment in the bottom of the simulated seawater in lit, and darkroom, conditions; however the crystals found in lit conditions were more abundant and complicated in form than those formed in the dark. This proved that photosynthetic microorganisms could influence the formation and morphology of phosphate and carbonate crystals in simulated seawater. This provided a new research idea for analysing the formation mechanism of phosphate minerals, and the correlation between the abundant apatite resources and the paleontological communities in the Guizhou area.

View here for the details