Hidden biosphere in an oxygen-deficient Atlantic open-ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic
Hidden biosphere in an oxygen-deficient Atlantic open-ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic
复制标题
DOI：
10.5194/bg-12-7467-2015
复制
发表时间：
2015-12
期刊：
影响因子：
4.9
通讯作者：
C. Löscher;Martin Fischer;S. Neulinger;B. Fiedler;M. Philippi;F. Schütte;Ashutosh Kumar Singh;Ashutosh Kumar Singh;H. Hauss;J. Karstensen;A. Körtzinger;S. Künzel;R. Schmitz
中科院分区：
文献类型：
--
作者：
C. Löscher;Martin Fischer;S. Neulinger;B. Fiedler;M. Philippi;F. Schütte;Ashutosh Kumar Singh;Ashutosh Kumar Singh;H. Hauss;J. Karstensen;A. Körtzinger;S. Künzel;R. Schmitz
摘要。热带北大西洋东部（ETNA）具有高产的沿海上升流系统和中等氧最小带的特征，其中远洋氧（O2）浓度最低，约为40 μmol kg−1。最近发现了接近缺氧O2浓度的中尺度漩涡(在这里，我们首次从埃特纳火山开放水域的脱氧反气旋模式水漩涡中研究微生物群落。在涡流中，我们观察到与周围水域相比，细菌多样性明显降低，并且群落发生了重大变化。我们检测到涡旋表层的初级生产力增强，这表明叶绿素浓度升高，碳吸收率高达周围水域的三倍。绿光带以下的碳吸收率与原绿球藻特定高光生态型的存在相关，这在ETNA中通常未被充分代表。我们的数据表明，涡流中较高的初级产量为出口产量提供了燃料，并支持在混合层底部以下的浅深度特定微生物群落中增强的呼吸作用。树状化关键功能标记基因nirS的转录进一步表明，在涡旋缺氧的核心水域中可能存在氮损失过程。开阔的埃特纳火山水域通常不存在齿化作用。根据未来预测的海洋脱氧，我们的研究结果表明，即使是不同的缺氧事件也有可能改变微生物群落结构，对海洋水体的初级生产力和生物地球化学过程产生关键影响。
Abstract. The eastern tropical North Atlantic (ETNA) is characterized by a highly productive coastal upwelling system and a moderate oxygen minimum zone with lowest open-ocean oxygen (O2) concentrations of approximately 40 μmol kg−1. The recent discovery of re-occurring mesoscale eddies with close to anoxic O2 concentrations ( Here, we present the first microbial community study from a deoxygenated anticyclonic modewater eddy in the open waters of the ETNA. In the eddy, we observed significantly lower bacterial diversity compared to surrounding waters, along with a significant community shift. We detected enhanced primary productivity in the surface layer of the eddy indicated by elevated chlorophyll concentrations and carbon uptake rates of up to three times as high as in surrounding waters. Carbon uptake rates below the euphotic zone correlated to the presence of a specific high-light ecotype of Prochlorococcus, which is usually underrepresented in the ETNA. Our data indicate that high primary production in the eddy fuels export production and supports enhanced respiration in a specific microbial community at shallow depths, below the mixed-layer base. The transcription of the key functional marker gene for dentrification, nirS, further indicated a potential for nitrogen loss processes in O2-depleted core waters of the eddy. Dentrification is usually absent from the open ETNA waters. In light of future projected ocean deoxygenation, our results show that even distinct events of anoxia have the potential to alter microbial community structure with critical impacts on primary productivity and biogeochemical processes of oceanic water bodies.