Sensitivity to ocean acidification differs between populations of the Sydney rock oyster: role of filtration and ion-regulatory capacities

Highlights

• We investigated the underlying physiology of higher OA resilience of oysters selected for higher growth.
• OA exposure affected hemolymph pH and PCO2 in wild but not in selected oysters.
• Selected oysters have a higher systemic capacity to release metabolic CO2 under OA.
• High capacity for CO2 release correlates with lower gill MO2 and high filtration rates.
• High and energy efficient filtration rates may promote OA resilience in oysters.

Abstract

Understanding mechanisms of intraspecific variation in resilience to environmental drivers is key to predict species’ adaptive potential. Recent studies show a higher CO2 resilience of Sydney rock oysters selectively bred for increased growth and disease resistance (‘selected oysters’) compared to the wild population. We tested whether the higher resilience of selected oysters correlates with an increased ability to compensate for CO2-induced acid-base disturbances. After 7 weeks of exposure to elevated seawater PCO2 (1100 μatm), wild oysters had a lower extracellular pH (pHe = 7.54 ± 0.02 (control) vs. 7.40 ± 0.03 (elevated PCO2)) and increased hemolymph PCO2 whereas extracellular acid-base status of selected oysters remained unaffected. However, differing pHe values between oyster types were not linked to altered metabolic costs of major ion regulators (Na+/K+-ATPase, H+-ATPase and Na+/H+-exchanger) in gill and mantle tissues. Our findings suggest that selected oysters possess an increased systemic capacity to eliminate metabolic CO2, possibly through higher and energetically more efficient filtration rates and associated gas exchange. Thus, effective filtration and CO2 resilience might be positively correlated traits in oysters.

Stapp L. S., Parker L. M., O’Connor W. A., Bock C., Ross P. M., Pörtner H. O., & Lannig G., in press. Sensitivity to ocean acidification differs between populations of the Sydney rock oyster: role of filtration and ion-regulatory capacities. Marine Environmental Research. Article (subscription required).

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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book