Data from: Depth moderates loss of marine foundation species after an extreme marine heatwave: could deep temperate reefs act as a refuge?

Marine heatwaves have been documented around the world, causing widespread mortality of numerous benthic species on shallow reefs (< 15 m depth). Deeper habitats are hypothesized to be a potential refuge from environmental extremes, though we have little understanding of the response of deeper benthic communities to marine heatwaves. Here, we show how increasing depth moderates the response of seaweed- and coral-dominated benthic communities to an extreme marine heatwave across a subtropical-temperate biogeographical transition zone. Benthic community composition and key habitat-building species were characterised across three depths (15, 25 and 40 m) before and several times after the 2011 Western Australian marine heatwave to assess resistance during and recovery after the heatwave. We found high natural variability in benthic community composition along the biogeographic transition zone and across depths with a clear shift in the composition after the marine heatwave in shallow (15 m) sites but a lot less in deeper communities (40 m). Most importantly, key habitat-building seaweeds such as Ecklonia radiata, and Syctothalia dorycarpa, which had catastrophic losses on shallow reefs, remained and were less affected in deeper communities. Evidently, deep reefs have the potential to act as a refuge during marine heatwaves for the foundation species of shallow reefs in this region.

全球范围内已有海洋热浪（marine heatwaves）的相关记录，其会造成水深<15米的浅礁（shallow reefs）区域内大量底栖物种（benthic species）大规模死亡。尽管学界对较深底栖群落对海洋热浪的响应机制仍缺乏深入认知，但此前已有假说提出，较深生境可作为抵御极端环境胁迫的潜在避难所。本研究聚焦亚热带-温带生物地理过渡带内以海藻和珊瑚为主的底栖群落，阐明了水深梯度如何调控其对极端海洋热浪的响应过程。我们于2011年西澳大利亚州（Western Australian）海洋热浪发生前后，在15米、25米及40米三个水深梯度下，对底栖群落组成与关键造境物种（habitat-building species）开展了多次调查，以评估群落于热浪期间的抗逆性及灾后恢复能力。研究结果显示，沿该生物地理过渡带及不同水深梯度，底栖群落组成存在显著自然变异性；海洋热浪发生后，15米浅礁区域的群落组成发生了清晰偏移，而40米较深群落的组成变化则相对微弱。尤为关键的是，在浅礁区域出现灾难性消亡的关键造境海藻——如辐射马尾藻（Ecklonia radiata）与多果隐丝藻（Syctothalia dorycarpa）——在较深生境中仍得以留存，且受影响程度更低。显然，该区域内的深礁可为浅礁建群种（foundation species）提供海洋热浪期间的避难场所。