Collaborative Research: The Effect of Iron Bioavailability on Synechococcus Diversity from a HNLC Regime to the Costa Rica Upwelling Dome

在地球上，来自海洋的光合作用固定的二氧化碳约占全球初级生产量的一半。在中央海洋环流中，数量最多的光合作用生物是微浮游生物、聚球藻和原氯球菌属。最近的研究表明，这些种群由许多密切相关但遗传上截然不同的生态型组成。到目前为止，在已鉴定的十多个聚球菌分支中，只有几个与表型有关，而区分其余分支的因素尚不清楚。这些研究人员推测，微量金属铁(Fe)的生物可利用性是推动该属分化的重要因素。了解铁是否以及何时限制聚球藻的生产力，以及这种限制如何调节聚球藻的群落结构，将有助于我们理解这种重要的微量元素如何影响海洋生物地球化学循环，以及参与其中一些循环的生物的多样性。该项目：1)正在开发海洋聚球藻的全细胞标记铁胁迫分析，2)正在使用全细胞标记结合流式细胞术来探索聚球藻群落的铁胁迫，以通过少营养和高营养的低叶绿素(HNLC)制度从东太平洋横断面上的完整细胞到哥斯达黎加上升流穹顶分离应激细胞，3)使用群落指纹方法检测该样带上聚球藻的遗传多样性，并确定铁胁迫或富铁细胞的遗传支；4)从寡营养、HNLC和哥斯达黎加上升流制度中分离出新的海洋聚球菌株，并研究它们的系统发育和铁的生理特征。该项目正在利用哥斯达黎加上升流穹顶(CRD)现有的邮轮机会，据报道，那里聚球藻的浓度非常高(106/毫升)。现有的关于痕量金属浓度和形态的辅助数据为研究多种痕量金属(Fe、Co、铜、锌、镉)的相互作用如何有助于维持这些微浮游动物的遗传多样性提供了一个前所未有的机会。该项目正在培养两名研究生和几名本科生研究员。基金允许这些学生中的一些人参加全国会议。在小型大学中，来自代表人数不足的群体的学生将得到优先考虑。

On Earth, photosynthetic fixation of CO2 from the oceans accounts for approximately half of total global primary production. In the central oceanic gyres the most numerous photosynthetic organisms are the picoplankton, Synechococcus and Prochlorococcus. Recently it has been shown that these populations consist of numerous closely related but genetically distinct ecotypes. Of the more than ten clades of Synechococcus identified to date, only a few have been associated with a phenotype, while the factors differentiating the remaining clades are not yet understood. These investigators hypothesize that the bioavailability of the trace metal iron (Fe) is an important factor driving the differentiation in this genus. Understanding if and when Fe is limiting Synechococcus productivity and how this limitation modulates Synechococcus community structure will increase our understanding of how this important trace element impacts oceanic biogeochemical cycles and the diversity of the organisms mediating some of these cycles. This project: 1) is developing a whole cell labeling Fe stress assay for marine Synechococcus,, 2) is probing the Synechococcus community for Fe stress using whole cell labeling coupled with flow cytometry to sort the stressed cells from the replete cells on a transect in the Eastern Pacific through oligotrophic and high nutrient low chlorophyll (HNLC) regimes to the Costa Rica upwelling dome, 3) is examining the genetic diversity of Synechococcus along the transect using community fingerprinting methods and determining the genetic clade of the cells that are Fe-stressed or Fe replete and 4) isolating new strains of marine Synechococcus from oligotrophic, HNLC, and Costa Rica upwelling regimes and characterize their phylogeny and Fe physiology. This project is taking advantage of existing cruise opportunities to the Costa Rica upwelling dome (CRD), where remarkably high concentrations (106/ml) of Synechococcus have been reported. Available ancillary data on both trace metal concentrations and speciation is providing an unprecedented opportunity to examine how the interplay of multiple trace metals (Fe, Co, Cu, Zn, Cd) is contributing to maintaining genetic diversity in these picoplankters. This project is training two graduate students and several undergraduate research fellows. Funds are allowing some of these students to attend national meetings. Priority is being given to students from under-represented groups at small colleges.