A mechanistic model of coral bleaching due to temperature-mediated light-driven reactive oxygen build-up in zooxanthellae
A mechanistic model of coral bleaching due to temperature-mediated light-driven reactive oxygen build-up in zooxanthellae
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DOI：
10.1016/j.ecolmodel.2018.07.013
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发表时间：
2018-10-24
影响因子：
3.1
通讯作者：
Skerratt, Jennifer
中科院分区：
文献类型：
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作者：
Baird, Mark E.;Mongin, Mathieu;Skerratt, Jennifer
大规模的珊瑚白化已经成为21世纪世纪对世界珊瑚礁健康的最大威胁。通过实验室和实地研究，现在已经对珊瑚虫规模的漂白过程有了一个复杂的了解，但这方面的知识还有待于应用于陆架规模珊瑚礁系统的机械模型。在这项研究中，我们开发了一个机械模型的珊瑚共生体的关系，认为温度介导的积累的活性氧，由于过量的光，导致zooxanthropium驱逐。该模型明确表示珊瑚宿主生物量，以及虫黄藻生物量，细胞内色素浓度，营养状态，反应中心和叶黄素循环的状态。光生理过程包括光适应，叶黄素循环动力学，反应中心状态转换。珊瑚共生关系的机制模型被纳入一个类似的1公里分辨率耦合水动力-地球化学模型，包括整个类似2000公里长的大堡礁。对2016年漂白事件的模拟显示，该模型能够捕捉到所观察到的漂白的大尺度特征，但由于模型的网格无法解决被深水包围的浅平台的水深测量，因此未能捕捉到近海珊瑚礁的漂白。为了进一步分析模式的行为，戴维斯礁（18度49' S，147'38' E）进行了类似的200米分辨率嵌套模拟。我们使用这个嵌套模型来演示虫黄藻对热胁迫的深度梯度响应。最后，我们讨论了漂白模型中的不确定性，主要在于量化活性氧积累和驱逐过程之间的联系。通过机械表示的环境强迫，这种模式的珊瑚漂白应用在现实的环境条件下，有可能产生更详细的预测比目前可用的基于卫星的珊瑚漂白指标，并可用于评估拟议的管理策略。
Mass coral bleaching has emerged in the 21st century as the greatest threat to the health of the world's reefs. A sophisticated process understanding of bleaching at the polyp scale has now been achieved through laboratory and field studies, but this knowledge is yet to be applied in mechanistic models of shelf-scale reef systems. In this study we develop a mechanistic model of the coral-symbiont relationship that considers temperature-mediated build-up of reactive oxygen species due to excess light, leading to zooxanthellae expulsion. The model explicitly represents the coral host biomass, as well as zooxanthellae biomass, intracellular pigment concentration, nutrient status, and the state of reaction centres and the xanthophyll cycle. Photophysiological processes represented include photoadaptation, xanthophyll cycle dynamics, and reaction centre state transitions. The mechanistic model of the coral-symbiont relationship is incorporated into a similar to 1 km resolution coupled hydrodynamic - biogeochemical model that encompasses the entire similar to 2000 km length of the Great Barrier Reef. A simulation of the 2016 bleaching event shows the model is able to capture the broadscale features of the observed bleaching, but fails to capture bleaching on offshore reefs due to the model's grid being unable to resolve the bathymetry of shallow platforms surrounded by deep water. To further analyse the model behaviour, a similar to 200 m resolution nested simulation of Davies Reef (18 degrees 49' S, 147'38' E) is undertaken. We use this nested model to demonstrate the depth gradient in zooxanthellae response to thermal stress. Finally, we discuss the uncertainties in the bleaching model, which lie primarily in quantifying the link between reactive oxygen buildup and the expulsion process. Through the mechanistic representation of environmental forcing, this model of coral bleaching applied in realistic environmental conditions has the potential to generate more detailed predictions than the presently-available satellite-based coral bleaching metrics, and can be used to evaluate proposed management strategies.