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

南极洲罗斯海沿岸水域的浮游植物水华通常由硅藻或南极洲棕囊藻(一种鞭毛藻，通常可以形成胶状基质中的大菌落)主导。该项目旨在确定南极洲棕囊藻菌落的细菌种群是否可以直接向棕囊藻供应维生素B12，维生素B12可能是罗斯海的一种重要的共同限制微量营养素。提供一种必需的维生素，再加上在较低铁浓度下生长的能力，可能会使棕囊藻相对于硅藻具有竞争优势。由于棕囊藻细胞比硅藻能够固定更多的碳，而且棕囊藻的捕食效率不如硅藻，该项目将有助于完善对该地区碳动态的理解以及食物网的基础。这样的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，并将对本科生和研究生研究作出贡献。代表人数不足的学生将在暑期学生实习期间参与进来。与意大利南极研究人员的合作旨在加强该项目并促进国际科学合作。自20世纪80年代以来，意大利研究人员一直在研究Terra Nova Bay生态系统。这项研究将测试附着细菌和棕囊藻之间的互惠共生是否为克隆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移物将提供机会，在空间和时间上跟踪Terra Nova Bay正在发展的藻类水华，并确定微生物种群的群落结构和生理营养状况。结合流式细胞术、蛋白质组学、转录组学、放射性同位素和稳定同位素标记实验，将确定碳和养分的摄取率以及细菌在缓解潜在的维生素B12和铁限制方面的作用。膜进口和质子转移反应质谱学也将被用来估计具有气候活跃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的微生物群落动态，将促进对海洋层结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的理解。

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.