Collaborative Research: Does competition for nitrogen between autotrophs and heterotrophs control carbon fluxes in the western coastal Arctic?

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。Yager 0910252乔治亚大学的Unds被提供来调查微生物对沿海北极生态系统生产力的控制，重点是自养和异养之间对氮（N）的竞争。在阿拉斯加州巴罗附近的冬季和夏季沃茨，辅以互补的国际研究机会，PI建议测量关键微生物和生物地球化学成分的原位浓度，相关的吸收活动，以及关键氮循环基因的表达，以解决两个假设：H1：在北极的自养和异养的平衡在时间和空间上都受到硝酸盐（NO3 #713;）和光的调节。在光照充足的春季和夏季条件下，浮游植物与异养细菌竞争NO3#713;。NO3的异养细菌摄取ˉ在黑暗的冬季和海冰下，当细菌充满了植物毒素衍生的DON时，比在开放的水域或光线充足的夏季条件下更大。NO3 -与来自河流和地下水流的陆地DOC结合，可能为细菌的生长和呼吸提供了途径。H2：微生物群落结构将根据季节性光周期和有效N的来源而变化。观察到的细菌对浮游植物生长反应的滞后是由于群落的变化。冬季和夏季的细菌群落组成会有很大的不同。细菌群落的组成和动态将对应于N的浓度和来源。关键的N-循环基因的表达，N-吸收和再生，DON吸收动力学将随季节和群落组成而变化。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Yager 0910252University of GeorgiaUnds are provided to investigate the microbial controls on the productivity of a coastal Arctic ecosystem by focusing on the competition between autotrophs and heterotrophs for nitrogen (N). In the winter and summer waters near Barrow, Alaska, supplemented with complementary international research opportunities, the PIs propose to measure in situ concentrations of key microbial and biogeochemical constituents, relevant uptake activities, and expression of key N cycling genes to address two hypotheses:H1: The balance of autotrophy and heterotrophy in the Arctic is regulated both temporally and spatially by nitrate (NO3ˉ) and light.? Phytoplankton out-compete heterotrophic bacteria for NO3ˉ during the well-lit spring and summer conditions.? Heterotrophic bacterial uptake of NO3ˉ will be greater during the dark winter and under sea ice than in open water or well-lit summer conditions when bacteria are replete with phytoplankton-derived DON.? NO3 -, combined with terrestrial DOC derived from riverine and groundwater flow, may provide the means for bacterial growth and respiration during the dark winter.H2: Microbial community structure will vary according to the seasonal light cycle and the sources of available N. The observed lag in bacterial response to phytoplankton growth is due to a community shift.? Bacterial community composition will vary significantly between winter and summer.? The composition and dynamics of bacterial communities will correspond to concentrations and sources of N.? The expression of key N-cycling genes, N-uptake and regeneration, and DON uptake kinetics will vary with season and community composition.