Influence of the Amazon River plume on distributions of free-living and symbiotic cyanobacteria in the western tropical north Atlantic Ocean
Influence of the Amazon River plume on distributions of free-living and symbiotic cyanobacteria in the western tropical north Atlantic Ocean
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DOI：
10.4319/lo.2007.52.2.0517
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发表时间：
2007-03-01
影响因子：
4.5
通讯作者：
Zehr, J. P.
中科院分区：
文献类型：
--
作者：
Foster, R. A.;Subramaniam, A.;Zehr, J. P.
使用 nifH DNA 定量聚合酶链反应 (QPCR) 方法检查了热带北大西洋西部 (WTNA) 海洋中七个固氮种群的垂直和水平分布。 nifH 系统发育型丰度在地表附近最高，并随着深度的增加而降低，但蓝藻共生体 Calothrix 除外，它在任何站点均未检测到。与硅藻Rhizosolenia clevei 和Hemiaulus hauckii 相关的Richelia 分布在亚马逊羽流的淡水透镜体中。在 10 个垂直剖面中的 6 个和 20 个表面样本中的 10 个中，H. hauckii-Richelia nifH 基因的丰度主导了所有深度。此外，与 H. hauckii 相关的 Richelia 估计值从河口向西北方向（北纬 8-12 度，西经 56-54 度）增加，其中在中盐水域 (31-34.9) 中发现了显着 (p < 0.001) 较高的丰度 (> 10(5) 个拷贝 L-1)。 H. hauckii-Richelia 共生体表面种群的 nifH 拷贝丰度与盐度呈正相关 (r(2) = 0.59)。三个单细胞蓝藻群和木藻具有相似的水平分布，其中最高的 nifH 拷贝估计位于盐度 >= 35 的站点和淡水透镜体的东北部（6-10 度 N 50 度 W）。 Trichodesmium spp 的丰度。和单细胞 B 组 nifH 基因拷贝共变 (r(2) = 0.60)。 QPCR 研究表明 H. hauckii-Richelia 共生体在亚马逊羽流水域中占主导地位，这意味着这些共生体比其他固氮生物具有生态优势。在羽状营养物之外，检测不到，自由生活的单细胞蓝细菌系统型的丰度，包括指定为 C 组的新组，非常丰富（> 10(5) 拷贝 L-1），并且与 Trichodesmium spp 的丰度相当。因此，WTNA 中沿着盐度和营养物的梯度似乎存在级联的固氮菌群落。
The vertical and horizontal distributions of seven diazotrophic populations in the western tropical north Atlantic (WTNA) Ocean were examined using a nifH DNA quantitative polymerase chain reaction (QPCR) approach. The nifH phylotype abundances were highest near the surface and decreased with depth, with the exception of the cyanobacterial symbiont Calothrix, which was not detected at any station. Richelia associated with the diatoms Rhizosolenia clevei and Hemiaulus hauckii were distributed within the freshwater lens of the Amazon plume. Abundances of H. hauckii-Richelia nifH genes dominated all depths in 6 of 10 vertical profiles and 10 of 20 surface samples. In addition, estimates of Richelia associated with H. hauckii increased northwest (8-12 degrees N, 56-54 degrees W) from the river mouth, where significantly (p < 0.001) higher abundances (> 10(5) copies L-1) were found in mesohaline waters (31-34.9). nifH copy abundance for surface populations of the H. hauckii-Richelia symbioses were positively correlated (r(2) = 0.59) with salinity. Three unicellular cyanobacterial groups and Trichodesmium had similar horizontal distributions, where the highest nifH copy estimates were at stations with salinity >= 35 and northeast (6-10 degrees N 50 degrees W) of the freshwater lens. The abundance of Trichodesmium spp. and unicellular Group B nifH gene copies co-varied (r(2) = 0.60). The QPCR study showed the dominance of H. hauckii-Richelia symbioses in the Amazon plume waters, implying that these associations had an ecological advantage over the other diazotrophs. Outside of the plume nutrients were below detection, abundances of free-living unicellular cyanobacterial phylotypes, including a novel group designated Group C, were abundant (> 10(5) copies L-1) and comparable to the abundances of Trichodesmium spp. Thus, there appeared to be a cascade of diazotrophic communities along gradients of salinity and nutrients in the WTNA.