Questioning High Nitrogen Fixation Rate Measurements in the Southern Ocean
Questioning High Nitrogen Fixation Rate Measurements in the Southern Ocean
复制标题
对南大洋高固氮率测量的质疑
作者：
Angelicque E. White;J. Granger;K. Turk
N 2 fixation in the global ocean is a microbially-mediated process performed by a special class of organisms able to enzymatically reduce dinitrogen gas (N 2 ) to ammonia in order to fuel cellular nitrogen (N) demands. The collective activity of N 2 fixing organisms comprises the largest source of N to the global ocean ecosystem, where it is ultimately used to support organic matter production and particle export 1,2 . Historically, N 2 fixation was thought to be confined to the warm, well-stratified surface waters of the subtropics and tropics and driven by the activity of large cell-sized organisms including the colony-forming genus Trichodesmium and symbioses between diatoms and the cyanobacteria Richelia 3 . In recent years, the known diversity of N 2 fixing organisms as well as their biogeography has been refined as new classes of organisms have been discovered, including broadly dispersed unicellular cyanobacteria (UCYN-A)-haptophyte symbioses 4,5 . There now seem to be few ocean habitats wholly unfavorable to at least a subset of N 2 fixing organisms; Oceanic N 2 fixation has been reported in polar waters, along the continental margins, and within the aphotic mesopelagic 6-8 – thus widely expanding the known biogeography and further intimating that the global input of N to the ocean via this process is larger than previously estimated. In this context of new players in new places, Shiozaki et al. 5 report “substantial nitrogen fixation” in one of the coldest and most isolated regions of our planet: the coastal waters near the ice-edge of Antarctica, wherein the authors speculate that iron additions from melting sea-ice fuel the activity of the UCYN-A/haptophyte symbiosis.
影响因子：
11.4
作者：
Luo, Y. -W.;Doney, S. C.;Zehr, J. P.
通讯作者：
Zehr, J. P.