Calcium carbonate unit realignment under acidification: A potential compensatory mechanism in an edible estuarine oyster

Highlights

• Impacts of ocean acidification (OA) on edible oyster shells were investigated.

• Microstructure, crystallography and the mechanical properties were quantified.

• OA altered shell microstructure and crystal orientation.

• The mechanical properties, however, were not affected under moderately low pH.

• Altered crystallography appeared to be a potential compensatory mechanism.

Abstract

Ocean acidification (OA) is well-known for impairing marine calcification; however, the end response of several essential species to this perturbation remains unknown. Decreased pH and saturation levels (Ω) of minerals under OA is projected to alter shell crystallography and thus to reduce shell mechanical properties. This study examined this hypothesis using a commercially important estuarine oyster Magallana hongkongensis. Although shell damage occurred on the outmost prismatic layer and the undying myostracum at decreased pH 7.6 and 7.3, the major foliated layer was relatively unharmed. Oysters maintained their shell hardness and stiffness through altered crystal unit orientation under pH 7.6 conditions. However, under the undersaturated conditions (ΩCal ~ 0.8) at pH 7.3, the realigned crystal units in foliated layer ultimately resulted in less stiff shells which indicated although estuarine oysters are mechanically resistant to unfavorable calcification conditions, extremely low pH condition is still a threat to this essential species.

Meng Y., Guo Z., Yao H., Yeung K. W. K. & Thiyagarajan V., 2019. Calcium carbonate unit realignment under acidification: A potential compensatory mechanism in an edible estuarine oyster. Marine Pollution Bulletin 139: 141-149. Article (subscription required).


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