Global warming is considered to be the most severe threat to coral reefs globally, which makes it important for scientists to develop novel strategies that mitigate the impact of warming on corals and associated habitats. Artificial upwelling of cooler deep water to the surface layer may be a possible mitigation/management tool. In this study, we investigated the effect of simulated artificial upwelling with deep water off Bermuda collected at 50 m (24°C) and 100 m (20°C) on coral symbiont biology of 3 coral species (Montastrea cavernosa, Porites astreoides, and Pseudodiploria strigosa) in a temperature stress experiment. The following treatments were applied over a period of 3 weeks: (i) control at 28°C (ii) heat at 31°C, (iii) heat at 31°C+ deep water from 50 m depth, and (iv) heat at 31°C+ deep water from 100 m depth. Artificial upwelling was simulated over a period of 25 min on a daily basis resulting in a reduction of temperature for 2 h per day and the following degree-heating-weeks: 5.7°C-weeks for ii, 4.6°C-weeks for iii and 4.2°C-weeks for iv. Comparative analysis of photosynthetic rate, chlorophyll-a concentration and zooxanthellae density revealed a reduction of heat stress responses in artificial upwelling treatments in 2 of the 3 investigated species, and a stronger positive effect of 100-m water than 50-m water. These results indicate that artificial upwelling could be an effective strategy to mitigate coral bleaching during heat stress events allowing corals to adjust to increasing temperatures more gradually. It will still be necessary to further explore the ecological benefits as well as potential ecosystem impacts associated with different artificial upwelling scenarios to carefully implement an effective in situ artificial upwelling strategy in coral reefs.

中文翻译：

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较冷深水的离散脉冲可以在热应力期间减缓珊瑚的漂白：对热应力事件期间人工上涌的影响

全球变暖被认为是全球珊瑚礁面临的最严重威胁，这使得科学家们必须制定新的策略来减轻变暖对珊瑚和相关栖息地的影响。将较冷的深水人工上涌至表层可能是一种可能的缓解/管理工具。在这项研究中，我们研究了在 50 m (24°C) 和 100 m (20°C) 处收集的百慕大深水模拟人工上升流对 3 种珊瑚物种（Montastrea cabernosa、Porites asstreoides 和Pseudodiploria strigosa) 在温度应力实验中。在 3 周的时间内进行了以下处理：(i) 控制在 28°C (ii) 在 31°C 下加热，(iii) 在 31°C + 50 m 深的深水中加热，以及 (iv) 在100 m 深的 31°C+ 深水。在每天 25 分钟的时间内模拟人工上升流，导致每天温度降低 2 小时和以下加热周：ii 5.7°C 周，iii 和 4.6°C 周iv. 4.2°C-周。光合速率、叶绿素-a 浓度和虫黄藻密度的比较分析表明，在 3 个研究物种中的 2 个物种中，人工上升流处理的热应激反应降低，100-m 水的积极作用比 50-m 水更强。这些结果表明，人工上升流可能是缓解热应激事件期间珊瑚白化的有效策略，使珊瑚能够更缓慢地适应温度升高。