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

本研究计划是利用重氮营养蓝藻对开放海洋上层固氮作用的系统重新评估。开放海洋中的固氮可能是海水中氮的主要来源，也是大气中氮转移到海洋的少数几种方式之一。将对氮酶活性的乙炔还原试验进行程序重新设计，以便将未浓缩的海水样品用于研究。这项新技术必须先在实验室里加以完善、测试和校准。其次，该技术将在伍兹霍尔附近的当地水域进行现场测试，并在马尾藻海进行为期两周的实地研究。海洋生物在开阔海洋中对氮的固定是大气中氮转移到海洋的少数途径之一。由于氮是海洋中最经常短缺的施肥元素，它的浓度往往决定了在开阔的海洋中可以进行的初级生产的数量。在氮特别稀缺的海洋区域，已经发现微生物可以将大气中的氮转化为自己的组织。测定固氮的方法陈旧且存在问题。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.