Collaborative Research: Cobalamin and Iron Co-Limitation Of Phytoplankton Species in Terra Nova Bay

南极罗斯海沿岸沃茨的浮游植物水华通常由硅藻或南极棕囊藻（一种鞭毛藻类，通常可以在凝胶状基质中形成大型菌落）主导。该项目旨在确定细菌种群与南极棕囊藻菌落的关联是否可以直接为棕囊藻提供维生素B12，维生素B12可能是罗斯海重要的共同限制性微量营养素。一种必需维生素的供应加上在较低铁浓度下生长的能力可能使棕囊藻比硅藻具有竞争优势。由于棕囊藻细胞可以比硅藻固定更多的碳，而且棕囊藻不像硅藻那样有效地被放牧，因此该项目将有助于加深对该地区碳动力学以及食物网基础的理解。这种理解也有可能帮助完善该地区的预测生态模型。该项目将开展公共宣传活动，并将促进本科生和研究生的研究。参与人数不足的学生将发生在暑期学生实习。与自1980年代以来一直在研究特拉诺瓦湾生态系统的意大利南极研究人员合作，旨在加强该项目并促进国际科学合作。该研究将测试附着的细菌和棕囊藻之间的互惠共生是否为菌落细胞提供了一种缓解慢性维生素B12共同限制效应的机制，从而赋予它们相对于硅藻群落的竞争优势。 在时间序列研究中使用漂流物将提供机会，在空间和时间上跟踪Terra Nova湾正在发展的藻华，并确定微生物种群的群落结构和生理营养状况。 流式细胞术，蛋白质组学，元转录组学，放射性同位素和稳定同位素标记实验的组合将确定碳和营养素的吸收率以及细菌在减轻潜在的维生素B12和铁限制中的作用。 膜入口和质子转移反应质谱法还将用于估计群落净产量和具有气候活性的挥发性有机碳化合物的释放。了解环境参数如何影响南极沿海沃茨的微生物群落动态，将有助于了解海洋分层和化学变化如何影响南大洋生态系统的海洋地球化学和食物网动态。

Phytoplankton blooms in the coastal waters of the Ross Sea, Antarctica are typically dominated by either diatoms or Phaeocystis Antarctica (a flagellated algae that often can form large colonies in a gelatinous matrix). The project seeks to determine if an association of bacterial populations with Phaeocystis antarctica colonies can directly supply Phaeocystis with Vitamin B12, which can be an important co-limiting micronutrient in the Ross Sea. The supply of an essential vitamin coupled with the ability to grow at lower iron concentrations may put Phaeocystis at a competitive advantage over diatoms. Because Phaeocystis cells can fix more carbon than diatoms and Phaeocystis are not grazed as efficiently as diatoms, the project will help in refining understanding of carbon dynamics in the region as well as the basis of the food web webs. Such understanding also has the potential to help refine predictive ecological models for the region. The project will conduct public outreach activities and will contribute to undergraduate and graduate research. Engagement of underrepresented students will occur during summer student internships. A collaboration with Italian Antarctic researchers, who have been studying the Terra Nova Bay ecosystem since the 1980s, aims to enhance the project and promote international scientific collaborations. The study will test whether a mutualistic symbioses between attached bacteria and Phaeocystis provides colonial cells a mechanism for alleviating chronic Vitamin B12 co-limitation effects thereby conferring them with a competitive advantage over diatom communities. The use of drifters in a time series study will provide the opportunity to track in both space and time a developing algal bloom in Terra Nova Bay and to determine community structure and the physiological nutrient status of microbial populations. A combination of flow cytometry, proteomics, metatranscriptomics, radioisotopic and stable isotopic labeling experiments will determine carbon and nutrient uptake rates and the role of bacteria in mitigating potential vitamin B12 and iron limitation. Membrane inlet and proton transfer reaction mass spectrometry will also be used to estimate net community production and release of volatile organic carbon compounds that are climatically active. Understanding how environmental parameters can influence microbial community dynamics in Antarctic coastal waters will advance an understanding of how changes in ocean stratification and chemistry could impact the biogeochemistry and food web dynamics of Southern Ocean ecosystems.