Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
Science. 2010 Mar 19;327(5972):1512-4. doi: 10.1126/science.1185468. Epub 2010 Feb 25.
Nitrogen (N2)-fixing microorganisms (diazotrophs) are an important source of biologically available fixed N in terrestrial and aquatic ecosystems and control the productivity of oligotrophic ocean ecosystems. We found that two major groups of unicellular N2-fixing cyanobacteria (UCYN) have distinct spatial distributions that differ from those of Trichodesmium, the N2-fixing cyanobacterium previously considered to be the most important contributor to open-ocean N2 fixation. The distributions and activity of the two UCYN groups were separated as a function of depth, temperature, and water column density structure along an 8000-kilometer transect in the South Pacific Ocean. UCYN group A can be found at high abundances at substantially higher latitudes and deeper in subsurface ocean waters than Trichodesmium. These findings have implications for the geographic extent and magnitude of basin-scale oceanic N2 fixation rates.
固氮微生物（固氮菌）是陆地和水生生态系统中生物可利用固定氮的重要来源，它们控制着贫营养海洋生态系统的生产力。我们发现，两种主要的单细胞固氮蓝藻（UCYN）具有不同的空间分布，与之前被认为是海洋中最重要的固氮贡献者的固氮蓝藻 Trichodesmium 不同。这两种 UCYN 群体的分布和活性随着南太平洋 8000 公里横剖面的深度、温度和水柱密度结构而变化。UCYN 组 A 的丰度在高纬度和深海的次表层海水比 Trichodesmium 高得多。这些发现对海域尺度海洋固氮速率的地理范围和幅度有重要影响。
