What Regulates Assimilation of Inorganic Nitrogen by Heterotrophic Bacteria vs. Phytoplankton in the Euphotic Zone

虽然众所周知，浮游植物和异养浮游细菌都吸收真光层中的铵，但对细菌吸收的控制尚不清楚。关于控制浮游细菌对氨氮吸收的巨大差异的因素(占总吸收铵的10-60%)，人们知之甚少，对细菌吸收硝酸盐的影响更是知之甚少。异养细菌的氮素吸收可以极大地影响我们对新的和再生的生产的理解，而再生生产已经成为全球碳和氮模型中的一个重要变量。例如，在亚北极太平洋，大约50%的新产量可以用异养菌利用氮素的变化来解释。为了了解溶解无机氮吸收(DIN.包括铵、硝酸盐和亚硝酸盐)，这项研究项目将研究浮游植物和细菌的吸收与生物量、生物量生产和溶解有机物吸收的关系。将利用改进的方法来检查藻类和细菌对溶解无机氮(DIN)的吸收，研究人员将与俄勒冈州沿海水域正在进行的以过程为导向的研究合作开展该项目，特别是俄勒冈州附近的加州海流系统。以前的结果表明，将会遇到营养浓度、生物量和产量的广泛范围。作为这种变化的结果，研究人员希望观察并最终了解细菌吸收DIN的变化，并为如何将细菌和浮游植物的活动纳入真光区氮循环和碳循环的现实模型提供洞察力。

Although it is well known that both phytoplankton and heterotrophic bacterioplankton assimilate ammonium in the euphotic zone, the controls on bacterial uptake are unclear. Little is known about factors controlling the great variation in relative ammonium uptake by bacterioplankton (10- 60% of total ammonium uptake) and nothing about nitrate uptake by bacteria. Nitrogen uptake by heterotrophic bacteria can greatly impact our understanding of new versus regenerated production, which has emerged as an important variable in global carbon and nitrogen models. In the subarctic Pacific, for example, about 50% of the new production can be explained by changes in nitrogen use by heterotrophic bacteria. In order to understand dissolved inorganic nitrogen uptake (DIN . which includes ammonium, nitrate, and nitrite), this research project will examine uptake by both phytoplankton and bacteria in relationship to biomass, biomass production, and dissolved organic matter uptake. Improved methodologies will be utilized to examine algal and bacterial dissolved inorganic nitrogen (DIN) uptake and the researchers will carry out the project in collaboration with ongoing process oriented studies in Oregon coastal waters, particularly the California Current system off Oregon. Previous results indicate that an extensive range in nutrient concentrations, biomass, and production will be encountered. As a result of this variation, the researchers expect to observe and eventually understand changes in DIN uptake by bacteria and to provide insight into how the activity of both bacteria and phytoplankton should be incorporated into realistic models of nitrogen cycling and carbon cycling in the euphotic zone.