Effect of High pCO2 Seawater Exposure on Hatching Success and Subsequent Larval Development of the Pacific Oyster, Crassostrea gigas

This study demonstrated the effects of high pCO₂ levels on larvae of the economically and ecologically important Pacific oyster (Crassostrea gigas).  During the spring and summer, these animals are exposed to seasonal upwelling, where the Aleutian low-pressure system moves to the northwest and northwesterly winds drive surface-water Ekman transport offshore.  The result is upwelling of water rich in CO₂ and low in pH onto the continental shelf.  The objective of this study was to determine if exposure of the oyster's eggs to high levels of pCO₂ had a detrimental effect on subsequent larval development.  It was observed that high levels of pCO₂ and low pH exposure during egg development resulted in lower hatching success to normal D-larvae.  A regression showed that as pH decreased, the percent hatch to normal D-larvae also decreased (P < 0.001, R² = 92.8%).  This research further aims to analyze the egg development process to determine at what phase the egg is most sensitive to environmental stress.  This discovery may lend insight into the physiological processes during egg development that are most vulnerable to upwelling.  Finally, water conditions of upwelling are characteristic of ocean acidification, where atmospheric CO₂ absorbed into the ocean lowers ambient pH conditions.  By understanding the physiological responses of C. gigas to seasonal periods of upwelling, we may have the ability to predict its performance in acidified ocean conditions as is predicted for the near future.