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。通过关注自养生物和异养生物对氮(N)的竞争，研究微生物对北极沿海生态系统生产力的控制。在阿拉斯加巴罗附近的冬季和夏季水域，辅以互补的国际研究机会，PIs建议测量关键微生物和生物地球化学成分的原位浓度，相关的吸收活动和关键N循环基因的表达，以解决两个假设：H1：北极自养和异养的平衡是由硝酸盐（NO3ˉ）和光在时间和空间上调节的。浮游植物与异养细菌竞争no3；在光照充足的春夏季节。异养细菌吸收NO3&amp；#713；在黑暗的冬季和海冰下，会比在开阔的水域或光照充足的夏季条件下（细菌中充满了浮游植物衍生的DON）更大。NO3 -与来自河流和地下水的陆源DOC结合，可能在黑暗的冬季为细菌生长和呼吸提供了手段。H2：微生物群落结构会根据季节性光照周期和有效氮的来源而变化。观察到细菌对浮游植物生长的反应滞后是由于群落的变化。细菌群落组成在冬季和夏季之间有显著差异。细菌群落的组成和动态将与n ？关键氮循环基因的表达、氮的吸收和再生以及DON的吸收动力学会随着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).Frischer 0909647Skidaway Institute of OceanographyUnds 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.