Diazotrophic Cyanobacteria: An Underestimated Source of NewNitrogen in the Oligotrophic Oceans

这项研究计划系统地重新评估了利用重氮营养的蓝藻在开放海洋上层固定氮的作用。开放海洋中的固氮可能是海水中氮的主要来源，也是大气氮转移到海洋的为数不多的方式之一。将对用于固氮酶活性的丙烯还原试验进行程序性重新设计，以便可以使用未浓缩的海水样本进行研究。这项新技术必须首先在实验室进行完善、测试和校准。其次，这项技术将在伍兹霍尔附近的当地水域进行实地测试，并在马尾藻海进行为期两周的实地研究。开放海洋中海洋生物对氮的固定是大气中氮向海洋转移的为数不多的途径之一。由于氮是海洋中最常见的供不应求的肥料元素，其浓度往往决定着开阔海洋可以产生的初级生产量。在氮特别稀缺的海洋地区，已经发现了将大气中的氮转化为自身组织的微生物。用来测量固氮率的方法很陈旧，而且存在问题。将尝试开发和测试比以前的方法更敏感、侵入性更小的新方法。

This research program is a systematic reassessment of the role of dinitrogen fixation in the upper layers of the open ocean using diazotrophic cyanobacteria. Nitrogen fixation in the open ocean is potentially a major source of nitrogen in seawater, and one of the few ways in which atmospheric nitrogen is transferred to the sea. A procedural redesign of the actylene reduction assay for nitrogenase activity will be undertaken so that unconcentrated seawater samples can be used for study. The new technique has to be perfected, tested and calibrated in the laboratory first. Second the technique will be field tested in local waters near Woods Hole and in a two week field study in the Sargasso Sea. %%% The fixation of nitrogen by marine organisms in the open ocean is one of the few pathways by which nitrogen in the atmosphere is transferred to the sea. Because nitrogen is the fertilizing element most often in short supply in the sea, its concentration often determines the amount of primary production that can take place in the open ocean. In areas of the ocean where nitrogen is especially scarce, microorganisms have been found that convert atmospheric nitrogen to their own tissues. The methods used for measuring nitrogen fixation are old and have problems. An attempt will be made to develop and test new methods that are more sensitive and less invasive than previous approaches.