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。美国佐治亚大学提供该奖项是为了调查微生物对北极沿海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水域，辅以互补的国际研究机会，PI建议原位测量关键微生物和生物地球化学成分的浓度、相关吸收活动和关键N循环基因的表达，以解决两个假设：H1：北极的自养和异养平衡在时间和空间上都受到硝酸盐(NO3)和光的调节。在光照充足的春夏季节，浮游植物胜过异养细菌。在黑暗的冬季和海冰下，当细菌中充满浮游植物来源的DON时，异养细菌对N3的吸收将比在开阔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相结合，可能为细菌在黑暗冬季的生长和呼吸提供手段。H2：微生物群落结构将根据季节光周期和有效氮的来源而变化。观察到的细菌对浮游植物生长的反应滞后是由于群落的转移。细菌群落组成在冬季和夏季之间会有很大的差异。细菌群落的组成和动态与氮的浓度和来源相对应。关键N循环基因的表达、N吸收和再生以及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.