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

在南极洲罗斯海的沿海水域，浮游植物大量繁殖，通常以硅藻或南极褐囊藻（一种鞭毛藻类，通常可以在凝胶基质中形成大菌落）为主。该项目旨在确定与南极Phaeocystis菌落相关的细菌种群是否可以直接为Phaeocystis提供维生素B12，维生素B12可能是罗斯海中重要的共同限制微量营养素。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褐囊藻比硅藻具有竞争优势。由于褐囊藻细胞比硅藻能固定更多的碳，而且褐囊藻的放牧效率不如硅藻高，因此该项目将有助于完善对该地区碳动态的理解，以及对食物网的基础。这种理解也有可能有助于完善该地区的预测生态模型。该项目将开展公众宣传活动，并将为本科生和研究生的研究做出贡献。未被充分代表的学生将在暑期学生实习期间参与。意大利南极研究人员自20世纪80年代以来一直在研究特拉诺瓦湾生态系统，他们与他们的合作旨在加强该项目并促进国际科学合作。该研究将测试附着细菌和Phaeocystis之间的互惠共生是否为殖民地细胞提供了一种减轻慢性维生素B12共限制效应的机制，从而使它们比硅藻群落具有竞争优势。在时间序列研究中使用漂流者将提供机会在空间和时间上跟踪特拉诺瓦湾正在形成的藻华，并确定群落结构和微生物种群的生理营养状况。流式细胞术、蛋白质组学、超转录组学、放射性同位素和稳定同位素标记实验的结合将确定碳和营养吸收速率以及细菌在缓解潜在的维生素B12和铁限制中的作用。膜入口和质子转移反应质谱法也将用于估计具有气候活性的挥发性有机碳化合物的净群落生产和释放。了解环境参数如何影响南极沿海水域微生物群落动态，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生物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.