Macrobiodiversity Lab, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, UK.
Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, UK.
BMC Ecol Evol. 2022 May 4;22(1):58. doi: 10.1186/s12862-022-02011-y.
The rising temperature of the oceans has been identified as the primary driver of mass coral reef declines via coral bleaching (expulsion of photosynthetic endosymbionts). Marine protected areas (MPAs) have been implemented throughout the oceans with the aim of mitigating the impact of local stressors, enhancing fish biomass, and sustaining biodiversity overall. In coral reef regions specifically, protection from local stressors and the enhanced ecosystem function contributed by MPAs are expected to increase coral resistance to global-scale stressors such as marine heatwaves. However, MPAs still suffer from limitations in design, or fail to be adequately enforced, potentially reducing their intended efficacy. Here, we address the hypothesis that the local-scale benefits resulting from MPAs moderate coral bleaching under global warming related stress.
Bayesian analyses reveal that bleaching is expected to occur in both larger and older MPAs when corals are under thermal stress from marine heatwaves (quantified as Degree Heating Weeks, DHW), but this is partially moderated in comparison to the effects of DHW alone. Further analyses failed to identify differences in bleaching prevalence in MPAs relative to non-MPAs for coral reefs experiencing different levels of thermal stress. Finally, no difference in temperatures where bleaching occurs between MPA and non-MPA sites was found.
Our findings suggest that bleaching is likely to occur under global warming regardless of protected status. Thus, while protected areas have key roles for maintaining ecosystem function and local livelihoods, combatting the source of global warming remains the best way to prevent the decline of coral reefs via coral bleaching.
海洋温度升高已被确定为大规模珊瑚礁衰退的主要驱动因素，即珊瑚白化（驱逐光合共生体）。海洋保护区（MPAs）已在全球范围内实施，旨在减轻局部胁迫的影响、增加鱼类生物量，并维持整体生物多样性。在珊瑚礁地区，特别是从局部胁迫中得到保护，以及 MPA 所带来的增强的生态系统功能，预计将提高珊瑚对全球规模胁迫（如海洋热浪）的抵抗力。然而，MPAs 仍然存在设计上的限制，或者无法得到充分执行，这可能会降低其预期效果。在这里，我们提出了一个假设，即 MPA 带来的局部效益可以减轻与全球变暖相关的胁迫下的珊瑚白化。
贝叶斯分析表明，当珊瑚受到海洋热浪（以加热周数衡量）的热胁迫时，较大和较老的 MPA 中预计会发生白化，但与单独的 DHW 相比，这种情况会部分缓解。进一步的分析未能确定在经历不同热胁迫水平的珊瑚礁中，MPA 与非 MPA 之间的白化患病率存在差异。最后，在 MPA 和非 MPA 地点发生白化的温度没有差异。
我们的研究结果表明，无论保护区的保护状况如何，白化都可能在全球变暖的情况下发生。因此，虽然保护区在维持生态系统功能和当地生计方面发挥着关键作用，但应对全球变暖的根源仍然是防止珊瑚白化导致珊瑚礁衰退的最佳途径。
