== Carbonates == 

 So, PL wants to add: 

 : There is some concern that as a result of increased  in the atmosphere the acidity of seawater may increase and adversely affect organisms living in the water. In particular, with increasing acidity, the availability of carbonates for forming shells may decrease. No explanation for the mechanism has been suggested however 

 (the bit in bold is what he wants to add). I don't think that is defensible