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

虽然我们都知道浮游植物和异养浮游细菌都能在绿化带吸收铵，但对细菌吸收的控制尚不清楚。浮游细菌相对铵吸收量（占总铵吸收量的10- 60%）变化很大，控制其变化的因素知之甚少，而细菌对硝酸盐的吸收量则一无所知。异养细菌对氮的吸收可以极大地影响我们对新产物和再生产物的理解，这已经成为全球碳氮模型的一个重要变量。例如，在亚北极太平洋地区，大约50%的新产量可以用异养细菌对氮的利用变化来解释。为了了解溶解无机氮吸收（DIN）。（包括铵、硝酸盐和亚硝酸盐），该研究项目将研究浮游植物和细菌对生物量、生物量生产和溶解有机物吸收的关系。研究人员将利用改进的方法来检查藻类和细菌溶解无机氮（DIN）的吸收情况，并将与正在俄勒冈沿海水域进行的过程导向研究合作开展该项目，特别是俄勒冈州外的加利福尼亚洋流系统。先前的结果表明，将遇到营养浓度、生物量和产量的广泛范围。由于这种变化，研究人员希望观察并最终了解细菌对DIN吸收的变化，并为如何将细菌和浮游植物的活性纳入到真光区氮循环和碳循环的现实模型中提供见解。

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.