Background nutrient concentration determines phytoplankton bloom response to marine heatwaves
Background nutrient concentration determines phytoplankton bloom response to marine heatwaves
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DOI：
10.1111/gcb.15255
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发表时间：
2020-07-15
影响因子：
11.6
通讯作者：
Strutton, Peter G.
中科院分区：
文献类型：
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作者：
Hayashida, Hakase;Matear, Richard J.;Strutton, Peter G.
由于人类活动造成的全球变暖，海洋热浪等海洋温度极端事件预计在未来几十年将加剧。据报告，海洋热浪造成的生态和经济影响包括珊瑚白化、红树林和海藻林局部灭绝以及无脊椎动物、鱼类、海鸟和海洋哺乳动物死亡率上升。相比之下，人们对海洋热浪对调节海洋生物地球化学过程的微生物的影响知之甚少。在这里，我们分析了近全球海洋物理-地球化学模型模拟的每日输出，以描述1992年至2014年期间海洋热浪对23个热带和温带海洋区域浮游植物水华的影响。结果表明，在海洋热浪期间，较浅的表面混合层和较低的表面硝酸盐浓度的区域相干异常。这些异常通过光和营养盐限制对浮游植物生长产生抵消作用。因此，浮游植物水华的反应是混合的，但可以与研究区域的背景营养条件。在海洋热浪期间，营养物贫乏的沃茨中的水华较弱，而在营养物丰富的沃茨中，热浪水华较强。基于卫星观测和现场气候学的海表温度、叶绿素a和硝酸盐的相应分析支持浮游植物水华异常与背景硝酸盐浓度之间的这种关系。鉴于营养贫乏的沃茨预计将在21世纪在全球范围内扩大，这项研究表明，在未来几十年的海洋热浪期间，较弱的水华的发生率将增加，这将对更高的营养水平和关键元素的生物地球化学循环产生影响。
Ocean temperature extreme events such as marine heatwaves are expected to intensify in coming decades due to anthropogenic global warming. Reported ecological and economic impacts of marine heatwaves include coral bleaching, local extinction of mangrove and kelp forests and elevated mortalities of invertebrates, fishes, seabirds and marine mammals. In contrast, little is known about the impacts of marine heatwaves on microbes that regulate biogeochemical processes in the ocean. Here we analyse the daily output of a near-global ocean physical-biogeochemical model simulation to characterize the impacts of marine heatwaves on phytoplankton blooms in 23 tropical and temperate oceanographic regions from 1992 to 2014. The results reveal regionally coherent anomalies of shallower surface mixing layers and lower surface nitrate concentrations during marine heatwaves. These anomalies exert counteracting effects on phytoplankton growth through light and nutrient limitation. Consequently, the responses of phytoplankton blooms are mixed, but can be related to the background nutrient conditions of the study regions. The blooms are weaker during marine heatwaves in nutrient-poor waters, whereas in nutrient-rich waters, the heatwave blooms are stronger. The corresponding analyses of sea-surface temperature, chlorophyllaand nitrate based on satellite observations and in situ climatology support this relationship between phytoplankton bloom anomalies and background nitrate concentration. Given that nutrient-poor waters are projected to expand globally in the 21st century, this study suggests increased occurrence of weaker blooms during marine heatwaves in coming decades, with implications for higher trophic levels and biogeochemical cycling of key elements.