Effects of elevated pCO2 on the physiological energetics of Pacific oyster, Crassostrea gigas

Abstract

Abstract Ocean acidification is predicted to have significant implications for marine calcifying organisms. However, little is known about the physiological responses of Pacific oyster, Crassostrea gigas, to elevated partial pressure of atmospheric carbon dioxide (pCO2) under natural fluctuations associated with a farm environment. The present study evaluated the effect of two pCO2 levels (i.e. ambient ∼625 μatm and elevated ∼1432 μatm) on the physiological processes and growth of C. gigas in in situ mesocosms that simulated the farm environment. Oysters were exposed for 30 days over a sensitive period during their production cycle when they are first exposed to natural coastal conditions. Despite this being a well-known “bottleneck” in production, it remains understudied with respect to climate change. Results showed that elevated pCO2 levels decreased clearance rate, ingestion rate, absorption efficiency, and oxygen to nitrogen ratio, while increasing oxygen consumption and ammonia-N excretion rates. These physiological responses of oysters resulted in a reduction in energy available for growth (scope for growth). No mortality was observed in the control or elevated pCO2 treatments, indicating that although oyster may survive future coastal acidification, the allocation of energy towards production within aquaculture systems will decrease in the future, affecting the culture of these economically important marine bivalves.