Guangxi Key Lab of Mangrove Conservation and Utilization, Guangxi Mangrove Research Center of Guangxi Sciences Academy, Beihai, 536000, China.
Key Laboratory of Environment Change and Resources Use in Beibu Gulf (Nanning Normal University), Ministry of Education, China, Guangxi Key Laboratory of Earth Surface Processes and Intelligent Simulation, Nanning Normal University, Nanning, 530001, China.
Environ Sci Pollut Res Int. 2024 Jan;31(1):1576-1588. doi: 10.1007/s11356-023-31173-5. Epub 2023 Dec 4.
Extensive coral bleaching events can result in catastrophic degradation of coral reefs and reorganization of coral communities. In the present study, we analyzed the spatial differences in coral bleaching and possible reasons of large-scale coral bleaching, based on the results of a survey carried out in the northern South China Sea in 2020. In addition, we have continuously monitored the sea surface temperature (SST) of the northernmost Weizhou Island for more than six years. The living coral cover at Weizhou Island (W), Xuwen Nature Reserve (X), and Haihua Island (H) was relatively high at 24.6% ± 4.8%, 12.1% ± 3.8%, and 8.1% ± 2.6%, respectively, whereas their bleaching rates were 9.7% ± 2.6%, 9.7% ± 3.3%, and 6.9% ± 2.1%, respectively. Among them, the living coral cover of W was significantly different from those of X and H, whereas the bleaching rate was not significantly different among the three areas. In all three areas, the massive and encrusting corals predominate and exhibit relatively high bleaching rates, with Porites lutea and Bernardpora stutchburyi being the dominant species. In addition, the temperature monitoring results of Weizhou Island for six consecutive years showed that the critical SST of coral bleaching was 31.5 ℃. The monitoring results also showed that the average SST of Weizhou Island was 32.1 ℃, exceeding 32 ℃ in July 2020 for up to 533 h. The longest continuous time when the SST exceeded 32 ℃ was 97 h. These findings indicated that the coral bleaching event that occurred in the Beibu Gulf during 2020 was a large-scale and high-temperature transient event that presented a relatively homogeneous threat to the coral communities. We inferred that this sudden heat stress event was caused by the enclosed tidal current in the Beibu Gulf, which prevented the southern upwelling from reaching the north, as well as by the inability of the SST to decrease without rainfall caused by typhoon cyclones. Our findings suggested that abnormal heat waves can result in coral bleaching at high latitudes and even coral reef degradation. Furthermore, our study provides a new perspective for investigating the self-recovery and reorganization of coral communities following accumulated coral bleaching.
大规模珊瑚白化事件会导致珊瑚礁灾难性退化和珊瑚群落重组。本研究基于 2020 年南海北部的调查结果，分析了珊瑚白化的空间差异和大规模珊瑚白化的可能原因。此外，我们已经连续六年多监测了涠洲岛最北部的海面温度 (SST)。涠洲岛 (W)、徐闻自然保护区 (X) 和海花岛 (H) 的活珊瑚覆盖率分别为 24.6%±4.8%、12.1%±3.8%和 8.1%±2.6%，但其白化率分别为 9.7%±2.6%、9.7%±3.3%和 6.9%±2.1%。其中，W 的活珊瑚覆盖率与 X 和 H 有显著差异，而三个区域的白化率无显著差异。在这三个区域，块状和丛生珊瑚占优势，白化率相对较高，主要种类有滨珊瑚和石珊瑚。此外，涠洲岛连续六年的温度监测结果表明，珊瑚白化的临界 SST 为 31.5℃。监测结果还显示，涠洲岛的平均 SST 为 32.1℃，2020 年 7 月有长达 533 小时的时间 SST 超过 32℃，SST 超过 32℃的最长连续时间为 97 小时。这些发现表明，2020 年北部湾发生的珊瑚白化事件是一次大规模、高温的暂态事件，对珊瑚群落构成了相对均匀的威胁。我们推断，这种突发性热应激事件是由北部湾的封闭潮流导致南部上升流无法到达北部，以及没有热带气旋降雨导致 SST 无法降低所致。我们的研究结果表明，异常热浪会导致高纬度珊瑚白化甚至珊瑚礁退化。此外，我们的研究为调查珊瑚白化积累后珊瑚群落的自我恢复和重组提供了新的视角。
