Latitudinal distribution of diazotrophs and their nitrogen fixation in the tropical and subtropical western North Pacific
Latitudinal distribution of diazotrophs and their nitrogen fixation in the tropical and subtropical western North Pacific
复制标题
DOI：
10.4319/lo.2009.54.2.0537
复制
发表时间：
2009-03-01
影响因子：
4.5
通讯作者：
Kanda, Jota
中科院分区：
文献类型：
--
作者：
Kitajima, Satoshi;Furuya, Ken;Kanda, Jota
在北太平洋西部冬季（2004年11月至12月）和夏季（2005年5月至6月）沿北纬37度至赤道的经向横断面调查了固氮生物的纬度分布及其固氮（N-2）活性。通过乙炔还原测定全海水和通过10μm过滤器的海水中的N-2固定活性。与夏季相比，整个研究区冬季全水体 N-2 固定量显着升高，这可能是由于冬季混合层加深导致磷酸盐向上供应增加。在这两个时期，在表面全水样本的 N-2 固定中观察到明显的纬度变化；此外，在黑潮延伸带和北赤道海流盐度锋之间观察到的活动高于邻近地区。 N-2 固着率升高主要归因于两个季节中< 10-μm 的固氮菌。夏季进行的流式细胞术显示，纳米浮游蓝藻的分布与< 10 μ m部分的N-2固定活性密切相关，表明纳米浮游蓝藻是该区域的主要固氮菌。相反，微型浮游固氮生物，Trichodesmium spp。细胞内黎氏藻和细胞内黎氏菌表现出与纳米浮游蓝细菌不同的纬度分布，细胞内黎氏菌的最大丰度在北纬8度和30度左右，而Trichodesmium spp的最大丰度在北纬8度和30度左右。位于北纬 26.5 度。冬季很少出现微浮游固氮生物。固氮生物的分布及其 N-2 固定活性可能受磷酸盐供应和风尘沉积的控制。
Latitudinal distribution of diazotrophs and their nitrogen (N-2) fixation activity were investigated in the western North Pacific in winter (Nov to Dec 2004) and summer (May to Jun 2005) along meridional transects from 37 degrees N to the equator. N-2 fixation activity in whole seawater and seawater passed through a 10-mu m filter was assayed by acetylene reduction. The whole-water N-2 fixation was markedly elevated in winter throughout the study area compared to that in summer, probably due to the increased upward supply of phosphate as a result of deeper mixed layer in winter. During both periods a distinct latitudinal variation was observed in N-2 fixation of the whole-water samples at the surface; further, higher activity was observed between the Kuroshio Extension and the salinity front in the North Equatorial Current than in the neighboring areas. The elevated N-2 fixation was primarily ascribed to < 10-mu m diazotrophs during both seasons. Flow cytometry conducted in summer revealed that distribution of nanoplanktonic cyanobacteria was closely correlated with that of N-2 fixation activity in the < 10-mu m fraction, indicating that nanoplanktonic cyanobacteria were the major diazotrophs in that area. In contrast, microplanktonic diazotrophs, Trichodesmium spp. and Richelia intracellularis exhibited different latitudinal distributions from that of nanoplanktonic cyanobacteria, with maximum numerical abundance of R. intracellularis around 8 degrees N and 30 degrees N, and that of Trichodesmium spp. at 26.5 degrees N. Few microplanktonic diazotrophs occurred in the winter. The distribution of the diazotrophs and their N-2 fixation activity may be controlled by the supply of phosphate and aeolian dust deposition.