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

Mar Pollut Bull. 2019 Feb:139:141-149. doi: 10.1016/j.marpolbul.2018.12.030. Epub 2019 Jan 4.

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.

Keywords: Calcification; Compensatory mechanism; Crystallography; Mechanical property; Ocean acidification; Oyster shells.

MeSH terms

  • Animal Shells / chemistry*
  • Animal Shells / ultrastructure
  • Animals
  • Biomechanical Phenomena
  • Calcification, Physiologic
  • Calcium Carbonate / chemistry*
  • Carbon Dioxide / analysis*
  • Crystallography
  • Hydrogen-Ion Concentration
  • Microscopy, Electrochemical, Scanning
  • Ostrea / chemistry*
  • Ostrea / growth & development
  • Ostrea / ultrastructure
  • Seawater / chemistry*

Substances

  • Carbon Dioxide
  • Calcium Carbonate