Benthic organisms of the Southern Ocean are particularly vulnerable to ocean acidification (OA), as they inhabit cold waters where calcite-aragonite saturation states are naturally low. OA most strongly affects animals with calcium carbonate skeletons or shells, such as corals and mollusks. We exposed the abundant cold-water coral Malacobelemnon daytoni from an Antarctic fjord to low pH seawater (LpH) (7.68 ± 0.17) to test its physiological responses to OA, at the level of gene expression (RT-PCR) and enzyme activity. Corals were exposed in short- (3 days) and long-term (54 days) experiments to two pCO₂ conditions (ambient and elevated pCO₂ equaling RCP 8.5, IPCC 2019, approximately 372.53 and 956.78 μatm, respectively).

Of the eleven genes studied through RT-PCR, six were significantly upregulated compared with control in the short-term in the LpH condition, including the antioxidant enzyme superoxide dismutase (SOD), Heat Shock Protein 70 (HSP70), Toll-like receptor (TLR), galaxin and ferritin. After long-term exposure to low pH conditions, RT-PCR analysis showed seven genes were upregulated. These include the mannose-binding C-Lectin and HSP90. Also, the expression of TLR and galaxin, among others, continued to be upregulated after long-term exposure to LpH. Expression of carbonic anhydrase (CA), a key enzyme involved in calcification, was also significantly upregulated after long-term exposure. Our results indicated that, after two months, M. daytoni is not acclimatized to this experimental LpH condition. Gene expression profiles revealed molecular impacts that were not evident at the enzyme activity level. Consequently, understanding the molecular mechanisms behind the physiological processes in the response of a coral to LpH is critical to understanding the ability of polar species to cope with future environmental changes. Approaches integrating molecular tools into Antarctic ecological and/or conservation research make an essential contribution given the current ongoing OA processes.

南大洋底栖生物特别容易受到海洋酸化 (OA) 的影响，因为它们栖息在方解石-文石饱和度自然较低的冷水中。OA 最强烈地影响具有碳酸钙骨骼或贝壳的动物，例如珊瑚和软体动物。我们将南极峡湾中丰富的冷水珊瑚Malacobelemnon daytoni暴露于低 pH 值海水 (LpH) (7.68 ± 0.17)，以在基因表达 (RT-PCR) 和酶活性水平测试其对 OA 的生理反应。珊瑚在短期（3 天）和长期（54 天）实验中暴露于两种 pCO ₂条件（环境和升高的 pCO ₂等于 RCP 8.5，IPCC 2019，分别约为 372.53 和 956.78 μatm）。

在通过 RT-PCR 研究的 11 个基因中，在 LpH 条件下短期内与对照相比有 6 个基因显着上调，包括抗氧化酶超氧化物歧化酶 (SOD)、热休克蛋白 70 (HSP70)、Toll 样受体 ( TLR)、galaxin 和铁蛋白。长期暴露于低 pH 条件后，RT-PCR 分析显示七个基因上调。这些包括甘露糖结合 C-凝集素和 HSP90。此外，在长期暴露于 LpH 后，TLR 和 galaxin 等的表达继续上调。碳酸酐酶 (CA) 是参与钙化的关键酶，在长期暴露后也显着上调。我们的结果表明，两个月后，M. daytoni不适应这种实验性 LpH 条件。基因表达谱揭示了在酶活性水平上不明显的分子影响。因此，了解珊瑚对 LpH 反应的生理过程背后的分子机制对于了解极地物种应对未来环境变化的能力至关重要。鉴于当前正在进行的 OA 过程，将分子工具整合到南极生态和/或保护研究中的方法做出了重要贡献。