Department of Biological Sciences, University of Rhode Island, 120 Flagg Road, Kingston, RI, 02881, USA.
Climate Change Cluster, University of Technology Sydney, Ultimo, NSW, Australia.
Biol Rev Camb Philos Soc. 2023 Apr;98(2):623-642. doi: 10.1111/brv.12922. Epub 2022 Nov 22.
The juxtaposition of highly productive coral reef ecosystems in oligotrophic waters has spurred substantial interest and progress in our understanding of macronutrient uptake, exchange, and recycling among coral holobiont partners (host coral, dinoflagellate endosymbiont, endolithic algae, fungi, viruses, bacterial communities). By contrast, the contribution of trace metals to the physiological performance of the coral holobiont and, in turn, the functional ecology of reef-building corals remains unclear. The coral holobiont's trace metal economy is a network of supply, demand, and exchanges upheld by cross-kingdom symbiotic partnerships. Each partner has unique trace metal requirements that are central to their biochemical functions and the metabolic stability of the holobiont. Organismal homeostasis and the exchanges among partners determine the ability of the coral holobiont to adjust to fluctuating trace metal supplies in heterogeneous reef environments. This review details the requirements for trace metals in core biological processes and describes how metal exchanges among holobiont partners are key to sustaining complex nutritional symbioses in oligotrophic environments. Specifically, we discuss how trace metals contribute to partner compatibility, ability to cope with stress, and thereby to organismal fitness and distribution. Beyond holobiont trace metal cycling, we outline how the dynamic nature of the availability of environmental trace metal supplies can be influenced by a variability of abiotic factors (e.g. temperature, light, pH, etc.). Climate change will have profound consequences on the availability of trace metals and further intensify the myriad stressors that influence coral survival. Lastly, we suggest future research directions necessary for understanding the impacts of trace metals on the coral holobiont symbioses spanning subcellular to organismal levels, which will inform nutrient cycling in coral ecosystems more broadly. Collectively, this cross-scale elucidation of the role of trace metals for the coral holobiont will allow us to improve forecasts of future coral reef function.
在贫营养水域中，生产力极高的珊瑚礁生态系统并置在一起，这激发了人们对珊瑚共生体伙伴（宿主珊瑚、虫黄藻内共生体、附生藻类、真菌、病毒、细菌群落）之间宏量营养素吸收、交换和再循环的大量兴趣和研究进展。相比之下，痕量金属对珊瑚共生体生理表现的贡献，以及进而对造礁珊瑚功能生态学的贡献仍不清楚。珊瑚共生体的痕量金属经济是一个由跨界共生伙伴关系支撑的供应、需求和交换网络。每个伙伴都有独特的痕量金属需求，这些需求是它们生化功能和共生体代谢稳定性的核心。生物体内平衡和伙伴之间的交换决定了珊瑚共生体适应异质珊瑚礁环境中痕量金属供应波动的能力。本综述详细介绍了核心生物过程中痕量金属的需求，并描述了共生体伙伴之间的金属交换如何是维持贫营养环境中复杂营养共生关系的关键。具体而言，我们讨论了痕量金属如何有助于伙伴兼容性、应对压力的能力，从而有助于生物体的适应性和分布。除了共生体痕量金属循环之外，我们还概述了环境痕量金属供应的可用性如何受到多种非生物因素（例如温度、光照、pH 等）的变化的影响。气候变化将对痕量金属的可利用性产生深远影响，并进一步加剧影响珊瑚生存的无数压力源。最后，我们建议未来研究方向，这些研究方向对于理解痕量金属对跨越亚细胞到生物体水平的珊瑚共生体的影响是必要的，这将更广泛地了解珊瑚生态系统中的养分循环。总的来说，这种跨尺度阐明痕量金属对珊瑚共生体的作用，将使我们能够改进对未来珊瑚礁功能的预测。
