Gillies Lauren E, Thrash J Cameron, deRada Sergio, Rabalais Nancy N, Mason Olivia U
Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, 32306, USA.
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
Environ Microbiol. 2015 Oct;17(10):3847-56. doi: 10.1111/1462-2920.12853. Epub 2015 Apr 27.
Areas of low oxygen have spread exponentially over the past 40 years, and are cited as a key stressor on coastal ecosystems. The world's second largest coastal hypoxic (≤ 2 mg of O2 l(-1)) zone occurs annually in the northern Gulf of Mexico. The net effect of hypoxia is the diversion of energy flow away from higher trophic levels to microorganisms. This energy shunt is consequential to the overall productivity of hypoxic water masses and the ecosystem as a whole. In this study, water column samples were collected at 39 sites in the nGOM, 21 of which were hypoxic. Analysis of the microbial community along a hypoxic to oxic dissolved oxygen gradient revealed that the relative abundance (iTag) of Thaumarchaeota species 16S rRNA genes (> 40% of the microbial community in some hypoxic samples), the absolute abundance (quantitative polymerase chain reaction; qPCR) of Thaumarchaeota 16S rRNA genes and archaeal ammonia-monooxygenase gene copy number (qPCR) were significantly higher in hypoxic samples. Spatial interpolation of the microbial and chemical data revealed a continuous, shelfwide band of low dissolved oxygen waters that were dominated by Thaumarchaeota (and Euryarchaeota), amoA genes and high concentrations of phosphate in the nGOM, thus implicating physicochemical forcing on microbial abundance.
在过去40年里，低氧区域呈指数级扩散，并被视为沿海生态系统的一个关键压力源。全球第二大沿海低氧（≤2毫克O2/升）区域每年出现在墨西哥湾北部。低氧的净效应是能量流从较高营养级转向微生物。这种能量分流对低氧水体和整个生态系统的总体生产力产生影响。在本研究中，在墨西哥湾北部的39个地点采集了水柱样本，其中21个地点为低氧区域。对沿低氧到有氧溶解氧梯度的微生物群落分析表明，奇古菌门物种16S rRNA基因的相对丰度（iTag）（在一些低氧样本中占微生物群落的40%以上）、奇古菌门16S rRNA基因的绝对丰度（定量聚合酶链反应；qPCR）和古菌氨单加氧酶基因拷贝数（qPCR）在低氧样本中显著更高。对微生物和化学数据的空间插值显示，在墨西哥湾北部存在一条连续的、覆盖整个陆架的低溶解氧水域带，该水域带以奇古菌门（和广古菌门）、amoA基因和高浓度磷酸盐为主，因此表明物理化学因素对微生物丰度有影响。
