Doctoral Dissertation Research: A Paleolimnological Investigation of Climate and Nitrogen Impacts on Primary Producers in Greenland Lakes and Community Water Supplies

这个博士论文研究改进项目将使用古代湖泊沉积物记录重建5,000年的北极湖泊生态系统变化的历史，这些湖泊与北方社区特别相关。尽管许多偏远的北极村庄依靠湖泊提供饮用水储备和农业灌溉等关键的生态系统服务，但这些小型供水缺乏足够的监测，而且对气候变化和土地使用的敏感性也很少进行调查。这项研究将研究哪些因素，包括温度和营养物质的投入，最影响北极湖泊的光合生物的生物生产力和多样性在几十年和几千年的时间尺度。这项研究的第二个目标是为博士生提供正式培训，以建立美国科学家和北极土著社区之间的国际合作。博士生将促进美国和格陵兰岛之间的关系，作为合作研究的职业生涯的基础，结合当地和土著知识，为北方社区的利益。北极地区的变暖速度比全球趋势快四倍，为了应对这一趋势，北极景观正在“绿化”，生态系统，包括湖泊内的生态系统，正在变得更加富有成效。这项工作探讨了温度变化和氮循环变化在湖泊藻类和蓝藻群落变化中的作用。该项目采用了一种新的方法，通过量化大量的沉积色素来评估生产力。色素作为替代物具有许多优势，包括它们的生物体类别或分类特异性以及它们反映不产生硬宏化石的生物体的能力，这是旨在了解蓝藻群落趋势的工作的特殊资产。量化不同生物的沉积色素既可以提供关于是什么驱动了大宗初级生产力的洞察力，也可以描述初级生产者的个体群体可能如何应对。这项研究将促进这种未充分利用的方法的使用，这是潜在的适用于许多地区，不断变化的湖泊藻类或蓝藻群落和/或富营养化是一个社会问题。这一奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

This doctoral dissertation research improvement project will use ancient lake sediment records to reconstruct 5,000-year histories of ecosystem changes in Arctic lakes that are of particular relevance to Northern communities. Though many remote Arctic villages rely on lakes for critical ecosystem services like drinking water reserves and agricultural irrigation, these small water supplies are insufficiently monitored and their susceptibility to changing climate and land use have been minimally investigated. This study will examine what factors, including temperature and nutrient inputs, have most influenced the biological productivity and diversity of photosynthetic organisms in Arctic lakes over multi-decadal and multi-millennial timescales. A second goal of this study is to provide formal training to the doctoral student in building international collaborations between U.S. scientists and Arctic Indigenous communities. The doctoral student will foster relationships between the United States and Greenland as a foundation for a career in collaborative research that incorporates local and Indigenous knowledge for the benefit of Northern communities. In response to warming in Arctic regions that outpaces global trends by four-fold, Arctic landscapes are “greening” and ecosystems, including those within lakes, are becoming more productive. This work examines the roles of temperature shifts and changing nitrogen cycling in driving changes in algal and cyanobacterial communities in lakes. This project employs a novel methodology to assess productivity through quantifying numerous sedimentary pigments. Pigments have many strengths as proxies, including their organism class or taxonomic specificity and their ability to reflect organisms that do not produce hard macrofossils, which are particular assets for work that aims to understand trends in cyanobacterial communities. Quantifying sedimentary pigments of different organisms can both provide insight on what drives bulk primary productivity and characterize how individual groups of primary producers might respond. This research will advance the use of this underutilized methodology, which is potentially applicable in many regions where changing lacustrine algal or cyanobacterial communities and/or eutrophication are a societal concern.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.