Microbial dinitrogen fixation in coral holobionts exposed to thermal stress and bleaching
Microbial dinitrogen fixation in coral holobionts exposed to thermal stress and bleaching
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DOI：
10.1111/1462-2920.13385
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发表时间：
2016-08-01
影响因子：
5.1
通讯作者：
Wild, Christian
中科院分区：
文献类型：
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作者：
Cardini, Ulisse;van Hoytema, Nanne;Wild, Christian
珊瑚全息生物（即珊瑚-藻类-原核生物共生）表现出不同的热敏感性，这可能决定了哪种珊瑚物种将适应全球变暖。尽管如此，同时调查变暖对所有全息生物成员影响的研究仍然缺乏。本研究表明，温度升高会影响柱头孢和麻孔孢在热胁迫期间和之后的所有成员（包括动物宿主、虫黄藻和重氮营养体）的关键生理性状。雌蕊花在实验结束时经历了严重的虫黄藻损失（即漂白），没有净光合作用。相反地，麻纹伊蚊对热应激的适应能力更强。暴露于升高的温度（+ 6℃）导致日光二氮（N-2）固定急剧增加，特别是在麻孔伊蚊中（与对照相比增加了三倍）。当温度再次降低到原位水平后，重氮营养体表现出相反的活动模式，仅在黑暗中记录到氮-2固定率的增加，特别是在漂白的雌蕊花中（与对照相比是两倍）。同时，这两种动物寄主，特别是漂白的雌柱头藻，都减少了有机物释放和对浮游生物的异养摄食。我们的研究结果表明，珊瑚相关重氮营养体的生理可塑性可能在决定珊瑚全息生物对海洋变暖的响应中起重要作用。
Coral holobionts (i.e., coral-algal-prokaryote symbioses) exhibit dissimilar thermal sensitivities that may determine which coral species will adapt to global warming. Nonetheless, studies simultaneously investigating the effects of warming on all holobiont members are lacking. Here we show that exposure to increased temperature affects key physiological traits of all members (herein: animal host, zooxanthellae and diazotrophs) of both Stylophora pistillata and Acropora hemprichii during and after thermal stress. S. pistillata experienced severe loss of zooxanthellae (i.e., bleaching) with no net photosynthesis at the end of the experiment. Conversely, A. hemprichii was more resilient to thermal stress. Exposure to increased temperature (+ 6 degrees C) resulted in a drastic increase in daylight dinitrogen (N-2) fixation, particularly in A. hemprichii (threefold compared with controls). After the temperature was reduced again to in situ levels, diazotrophs exhibited a reversed diel pattern of activity, with increased N-2 fixation rates recorded only in the dark, particularly in bleached S. pistillata (twofold compared to controls). Concurrently, both animal hosts, but particularly bleached S. pistillata, reduced both organic matter release and heterotrophic feeding on picoplankton. Our findings indicate that physiological plasticity by coral-associated diazotrophs may play an important role in determining the response of coral holobionts to ocean warming.