Land Cover and hydrology - assessing controls on Si cycling in a changing Arctic

乔安娜·C·凯里博士获得了NSF EAR博士后奖学金，将在马萨诸塞州伍兹霍尔的海洋生物实验室开展一项研究和教育计划。她的研究将考察变化的土地覆盖和永久冻土融化如何改变北极地区的硅(Si)生物地球化学。通过研究阿拉斯加的十大河流系统，该项目将量化陆地景观变暖如何改变下游接收水中硅的有效性。由于硅在海洋系统中的有效性对硅藻的生存至关重要，硅藻是海洋水域中最丰富的浮游植物类型，因此这项研究的结果将对海洋碳动力学产生直接影响。土地覆盖和水文是控制硅向海洋系统出口的两个重要因素，但迄今为止，这些因素尚未在北极生态系统中一并进行审查。除了缺乏关于北极硅循环的基线信息外，极地地区快速变暖的速度使这项工作变得及时。该奖学金的教育分支将包括通过与育空河部落间分水岭委员会合作，与阿拉斯加当地社区接触，并与国际利桑那州普罗维登斯的公立高中地球科学课程进行外联，向学生传授气候变化和北极生态系统。此外，凯里还将与政策制定者分享她的研究成果。尽管地球化学因素对河流Si通量有很大的控制作用，但近年来，流域土地覆盖(即陆地植被)也被认为是温带和热带系统河流Si通量的另一个重要控制因素。然而，陆地生物过程在北极的作用还有待研究。水文径流，包括水的停留时间，是河流硅通量的另一个关键驱动因素。由于最近的变暖，这两个因素在北极生态系统中都在迅速变化，可能会影响到向沿海接收水域出口硅的数量和时间，并改变浮游植物物种的组成。锗(Ge)/硅示踪剂的新颖使用将使凯里博士能够破译硅在植被和永久冻土覆盖梯度上的流动的地球化学和生物驱动因素之间的关系。利用空间换时间的方法，这项工作将创建第一个关于未来变暖将如何改变海洋水域中硅的有效性的预测框架。

Dr. Joanna C. Carey has been awarded an NSF EAR Postdoctoral fellowship to carry out a research and education plan at the Marine Biological Laboratory in Woods Hole, MA. Her research will examine how shifting land cover and permafrost thaw is altering silicon (Si) biogeochemistry in the Arctic. By examining ten large river systems in Alaska, this project will quantify how warming of the terrestrial landscape is altering Si availability in downstream receiving waters. Because Si availability in marine systems is critical for the survival of diatoms, the most abundant type of phytoplankton in marine waters, the results of this research will have direct implications for marine carbon dynamics. Land cover and hydrology are two important controls over Si export to marine systems, but to date these factors have yet to be examined in conjunction in Arctic ecosystems. In addition to a lack of baseline information on Arctic Si cycling, the rapid pace of warming in polar latitudes makes this work timely. The education arm of this fellowship will consist of engagement with local Alaskan communities through working with the Yukon River Inter-tribal Watershed Council and outreach with public high school Earth Science courses in Providence, RI to teach students about climate change and Arctic ecosystems. In addition, Dr. Carey will share the results of her research results with policy makers. Although geochemical factors exert large controls over riverine Si fluxes, watershed land cover (i.e. terrestrial vegetation) has also recently been identified as another important control over riverine Si fluxes in temperate and tropical systems. However, the role of terrestrial biological processes has yet to be examined in the Arctic. Hydrologic flowpaths, including water residence time, is another critical driver of riverine Si fluxes. Both of these factors are rapidly changing in Arctic ecosystems due to recent warming, potentially impacting the magnitudes and timing of Si exports to coastal receiving waters and shifting phytoplankton species compositions. The novel use of germanium (Ge)/Si tracers will allow Dr. Carey to decipher between geochemical vs. biological drivers of Si fluxes across a gradient of vegetation and permafrost cover. Using a space-for-time substitution, this work will create the first predictive framework of how future warming will alter Si availability in marine waters.