OA sensitivity differs between populations of the Sydney Rock oyster

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.解析物种面对环境胁迫因子时的种内抗逆性变异机制，是预测物种适应潜力的核心所在。已有研究表明，相较于野生种群，经选育以提升生长性能与抗病能力的悉尼岩牡蛎（Sydney rock oysters，下称“选育牡蛎”）具备更强的CO₂抗逆性。本研究旨在验证选育牡蛎的高CO₂抗逆性，是否与其补偿CO₂诱导的酸碱平衡紊乱的能力提升存在关联。将牡蛎暴露于升高的海水二氧化碳分压（PCO₂，1100 µatm）环境中7周后，野生牡蛎的细胞外pH（pHe）显著降低（对照组为7.54±0.02，高PCO₂组为7.40±0.03），血淋巴PCO₂则升高；而选育牡蛎的细胞外酸碱平衡状态未受显著影响。不过，不同牡蛎类型间的pHe差异，与其鳃与外套膜组织中主要离子调节蛋白（Na⁺/K⁺-ATP酶、H⁺-ATP酶及Na⁺/H⁺交换蛋白）的代谢消耗变化并无关联。本研究结果表明，选育牡蛎具备更强的全身代谢CO₂清除能力，这可能源于其更高且能量利用效率更优的滤食速率，以及与之相关的气体交换过程。因此，在牡蛎中，高效滤食与CO₂抗逆性或许是呈正相关的性状。