Coral skeletal cores as windows into past Symbiodiniaceae community dynamics

Abstract taken from Grillo et al. 2025 https://doi.org/10.1101/2025.03.21.644536The symbiosis between the dinoflagellate Symbiodiniaceae family and reef-building corals underpins the productivity of coral reefs. This relationship facilitates the deposition of calcium-carbonate skeletons that build the reef structure thanks to the energy derived from photosynthesis. The loss of Symbiodiniaceae from coral tissues - resulting in coral bleaching - impedes coral growth and can lead to mass mortality if the symbiosis fails to recover. Given that Symbiodiniaceae communities are dynamic and can shift in response to environmental stressors in the decades- to centuries-long lifespan of coral colonies, understanding these changes is crucial. Although the reconstruction of Symbiodiniaceae communities from coral skeleton records has recently been demonstrated as feasible, no studies have yet assessed reconstructions across different species and locations. Here, we present an approach to use coral skeletons for reconstructing the Symbiodiniaceae community on decadal and centennial scales and resolving dynamics related with coral species and environmental history of sampling locations. For this, we used dated coral skeleton cores from Porites Iobata and Diploastrea heliopora, species commonly used as climate archives, sampled in Palau and Papua New Guinea. We also examined the effect of various DNA extraction protocols on community reconstruction. Here we show that the reconstructed Symbiodiniaceae communities significantly varied across all cores and DNA extraction methods, with decalcification-based protocols enhancing the retrieval of skeletal-bound DNA. Moreover, we observed distinct community dynamics related to the specific coral host and sampling location. Notably, associations of Symbiodiniaceae dynamics with past heat stress events were apparent in cores of both species from Palau. Our findings enable a deeper understanding of the temporal and spatial variability in Symbiodiniaceae communities, offering insights that may refine the use of paleobiological proxies in climate studies and reveal broader ecological trends and microbially-aided adaptation pathways in corals.

本摘要引自Grillo等人2025年发表的研究，DOI：10.1101/2025.03.21.644536。植虫藻科（Symbiodiniaceae）甲藻与造礁珊瑚之间的共生关系，是珊瑚礁生态系统生产力的核心支撑。该共生关系借助光合作用产生的能量，助力珊瑚合成碳酸钙骨骼，进而构建出珊瑚礁的主体结构。当珊瑚组织内的植虫藻科物种流失时，便会引发珊瑚白化现象；若共生关系无法恢复，则会阻碍珊瑚生长，甚至引发大规模死亡。鉴于珊瑚群落的寿命可达数十年至数百年，而植虫藻科群落具有动态性，可随环境胁迫发生改变，因此解析这类群落变化至关重要。尽管近期已有研究证实，可通过珊瑚骨骼记录重建植虫藻科群落，但目前尚无研究针对不同珊瑚物种与采样地点开展相关重建效果评估。本研究提出一种利用珊瑚骨骼，在年代际至百年尺度上重建植虫藻科群落的方法，以解析与珊瑚宿主物种及采样地点环境历史相关的群落动态。为此，我们选取了采自帕劳与巴布亚新几内亚的两处定年珊瑚岩芯样本，宿主物种分别为团块滨珊瑚（Porites lobata）与重盘珊瑚（Diploastrea heliopora），二者均为常用的气候代用档案载体。同时，我们还评估了多种DNA提取方案对群落重建结果的影响。研究结果表明，不同岩芯与不同DNA提取方法得到的植虫藻科重建群落均存在显著差异；其中基于脱钙处理的提取方案，可更高效地获取结合于骨骼的DNA。此外，我们还观察到，植虫藻科群落动态与特定珊瑚宿主及采样地点存在显著关联。值得注意的是，在帕劳采集的两种珊瑚岩芯中，均可观察到植虫藻科群落动态与过往热应激事件的明确关联。本研究结果有助于更深入地理解植虫藻科群落的时空分布变化，可为优化古生物代用指标在气候研究中的应用提供参考，并揭示珊瑚更广泛的生态趋势与微生物介导的适应性演化路径。