UPDATE ON THE POTENTIAL EFFECTS OF OCEAN ACIDIFICATION ON ANTARCTIC MARINE BIVALVES
All Antarctic bivalves examined have shells formed of either a composite of calcite/aragonite or aragonite. Of the 41 families in the study, 34 families (83%) have hard parts constructed of aragonite, which is reported to be approximately 35% more soluble than its calcite counterpart. Microstructures were classified and ranked based on resistance to dissolution. Bivalves with more resistant shell microstructures (complex cross-lamellar) will likely have higher survival rates in undersaturated waters than those with weaker microstructures (e.g., prismatic). However, the two microstructures that are least resistant to dissolution, simple prismatic and composite prismatic, account for 39% of family diversity, while the most resistant microstructure, complex cross-lamellar, accounts for only 2.4% of family diversity. Deep-water bathymetric distributions may provide a refuge for some bivalve species, although carbonate saturation states are inherently lower in deeper waters. The paucity of Antarctic bivalves with hard parts constructed from dissolution-resistant microstructures and mineralogy does not bode well for their survival under global warming/ocean acidification scenarios.