ENTROPIE, IRD, Université de la Réunion, CNRS, IFREMER, Université de Nouvelle-Calédonie, Nouméa, New Caledonia.
Laboratoire d'Excellence CORAIL, ENTROPIE (UMR9220), IRD, Nouméa, New Caledonia.
PLoS One. 2024 Feb 28;19(2):e0296902. doi: 10.1371/journal.pone.0296902. eCollection 2024.
Widespread coral bleaching has generally been linked to high water temperatures at larger geographic scales. However, the bleaching response can be highly variable among individual of the same species, between different species, and across localities; what causes this variability remains unresolved. Here, we tracked bleached and non-bleached colonies of Acropora muricata to see if they recovered or died following a stress event inside the semi-enclosed lagoon of Bouraké (New Caledonia), where corals are long-term acclimatized to extreme conditions of temperature, pH and dissolved oxygen, and at a nearby control reef where conditions are more benign. We describe Symbiodiniaceae community changes based on next-generation sequencing of the ITS2 marker, metabolic responses, and energetic reserve measures (12 physiological traits evaluated) during the La Niña warm and rainy summer in 2021. Widespread coral bleaching (score 1 and 2 on the coral colour health chart) was observed only in Bouraké, likely due to the combination of the high temperatures (up to 32°C) and heavy rain. All colonies (i.e., Bouraké and reference site) associated predominantly with Symbiodinaceae from the genera Cladocopium. Unbleached colonies in Bouraké had a specific ITS2-type profile (proxies for Symbiodiniaceae genotypes), while the bleached colonies in Bouraké had the same ITS2-type profile of the reef control colonies during the stress event. After four months, the few bleached colonies that survived in Bouraké (B2) acquired the same ITS2 type profiles of the unbleached colonies in Bouraké. In terms of physiological performances, all bleached corals showed metabolic depression (e.g., Pgross and Rdark). In contrast, unbleached colonies in Bouraké maintained higher metabolic rates and energetic reserves compared to control corals. Our study suggests that Acropora muricata enhanced their resistance to bleaching thanks to specific Symbiodiniaceae associations, while energetic reserves may increase their resilience after stress.
广泛的珊瑚白化通常与较大地理尺度上的高水温有关。然而，同一物种的个体之间、不同物种之间以及不同地点之间的白化反应可能存在很大差异；造成这种差异的原因仍未解决。在这里，我们跟踪了 Bouraké（新喀里多尼亚）半封闭泻湖内白化和非白化的 Acropora muricata 群体，以观察它们在经历应激事件后是恢复还是死亡，在这个泻湖内，珊瑚长期适应极端的温度、pH 值和溶解氧条件，而在附近的对照珊瑚礁内，条件则更为温和。我们描述了基于 ITS2 标记的下一代测序、代谢反应和能量储备措施（评估了 12 种生理特征）的 Symbiodiniaceae 群落变化，这些变化发生在 2021 年拉尼娜暖湿夏季。只有在 Bouraké 观察到广泛的珊瑚白化（珊瑚颜色健康图表上的评分 1 和 2），这可能是由于高温（高达 32°C）和大雨的共同作用。所有的群体（即 Bouraké 和参考地点）主要与 Cladocopium 属的 Symbiodinaceae 共生。Bouraké 中未白化的群体具有特定的 ITS2 型谱（Symbiodiniaceae 基因型的代表），而 Bouraké 中白化的群体在应激事件期间具有与对照珊瑚礁相同的 ITS2 型谱。四个月后，在 Bouraké 中幸存下来的少数白化群体获得了与 Bouraké 中未白化群体相同的 ITS2 型谱。就生理表现而言，所有白化珊瑚都表现出代谢抑制（例如，Pgross 和 Rdark）。相比之下，Bouraké 中未白化的群体与对照珊瑚相比，保持了更高的代谢率和能量储备。我们的研究表明，Acropora muricata 通过特定的 Symbiodiniaceae 共生关系增强了对白化的抵抗力，而能量储备可能会增加它们在应激后的恢复力。
