What happens to the global mean carbonate ion concentration, CO3 2-, if the ocean gains a large amount of CO2 from the atmosphere? How do you know?

What happens to the global mean carbonate ion concentration, CO3 2-, if the ocean gains a large amount of CO2 from the atmosphere? How do you know?

How would this change affect the depth of the calcium carbonate saturation horizon and the rate of CO3 2- sediment dissolution?