Seawater carbonate chemistry and the intrinsic and extrinsic phenotypic characteristics and the survival of important calcifiers, the edib oysters Crassostrea angulata and C. hongkongensis

Ocean acidification (OA) has important effects on the intrinsic phenotypic characteristics of many marine organisms. Concomitantly, OA can alter the extended phenotypes of these organisms by perturbing the structure and function of their associated microbiomes. It is unclear, however, the extent to which interactions between these levels of phenotypic change can modulate the capacity for resilience to OA. Here, we explored this theoretical framework assessing the influence of OA on intrinsic (immunological responses and energy reserve) and extrinsic (gut microbiome) phenotypic characteristics and the survival of important calcifiers, the edible oysters Crassostrea angulata and C. hongkongensis. After one-month exposure to experimental OA (pH 7.4) and control (pH 8.0) conditions, we found species-specific responses characterised by elevated stress (hemocyte apoptosis) and decreased survival in the coastal species (C. angulata) compared with the estuarine species (C. hongkongensis). Phagocytosis of hemocytes was not affected by OA but in vitro bacterial clearance capability decreased in both species. Gut microbial diversity decreased in C. angulata but not in C. hongkongensis. Overall, C. hongkongensis was capable of maintaining the homeostasis of the immune system and energy supply under OA. In contrast, C. angulata's immune function was suppressed, and the energy reserve was imbalanced, which might be attributed to the declined microbial diversity and the functional loss of essential bacteria in the guts. This study highlights a species-specific response to OA determined by genetic background and local adaptation, shedding light on the understanding of host-microbiota-environment interactions in future coastal acidification.海洋酸化（Ocean Acidification, OA）对诸多海洋生物的固有表型特征具有重要影响。与此同时，海洋酸化可通过扰动宿主共生微生物组的结构与功能，改变这些生物的扩展表型。然而，尚不清楚这两类表型变化之间的相互作用，能够在多大程度上调节生物对海洋酸化的耐受能力。本研究围绕该理论框架展开探索，评估了海洋酸化对固有表型（免疫应答与能量储备）及外在表型（肠道微生物组）的影响，同时探究了其对两类重要钙化食用牡蛎——Crassostrea angulata与C. hongkongensis存活率的作用。 在为期1个月的实验性海洋酸化（pH 7.4）与对照（pH 8.0）条件暴露后，我们发现：与河口物种香港牡蛎（C. hongkongensis）相比，近岸物种葡萄牙牡蛎（C. angulata）表现出以应激水平升高（血细胞凋亡）及存活率下降为特征的物种特异性响应。血细胞的吞噬作用未受海洋酸化影响，但两种牡蛎的体外细菌清除能力均出现下降。葡萄牙牡蛎（C. angulata）的肠道微生物多样性出现下降，而香港牡蛎（C. hongkongensis）则无此变化。 整体而言，香港牡蛎（C. hongkongensis）在海洋酸化条件下能够维持免疫系统与能量供给的稳态。与之相反，葡萄牙牡蛎（C. angulata）的免疫功能受到抑制，能量储备失衡，这或许可归因于其肠道微生物多样性下降以及核心细菌的功能丧失。本研究揭示了由遗传背景与本地适应决定的物种特异性海洋酸化响应，为未来近岸酸化背景下宿主-微生物组-环境互作的研究提供了新的见解。