Limpets counteract ocean acidification induced shell corrosion by thickening of aragonitic shell layers
Specimens of the patellogastropod limpet Patella caerulea were collected within (pH low-shells) and outside (pH n-shells) a CO 2 vent site at Ischia, Italy. Four pH low-shells and four pH n-shells were sectioned transversally and scanned for polymorph distribution by means of confocal Raman microscopy. The pH low-shells displayed a twofold increase in aragonite area fraction and size-normalised aragonite area. Size-normalised calcite area was halved in pH low-shells. Taken together with the increased apical and the decreased flank size-normalised thickness of the pH low-shells, these data led us to conclude that low-pH-exposed P. caerulea specimens counteract shell dissolution by enhanced shell production. This is different from normal elongation growth and proceeds through addition of aragonitic parts only, while the production of calcitic parts is confined to elongation growth. Therefore, aragonite cannot be regarded as a disadvantageous polymorph per se under ocean acidification conditions.