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

本博士论文研究改进项目将利用古湖泊沉积物记录重建北极湖泊5000年生态系统变化历史，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关键的生态系统服务，如饮用水储备和农业灌溉，但对这些小水源的监测不足，对它们对气候变化和土地利用的易感性的调查也很少。本研究将研究在几十年和几千年的时间尺度上，包括温度和养分输入在内的哪些因素对北极湖泊光合生物的生物生产力和多样性影响最大。这项研究的第二个目标是为博士生提供正式的培训，以建立美国科学家与北极土著社区之间的国际合作。该博士生将促进美国和格陵兰之间的关系，作为合作研究事业的基础，为北方社区的利益融合当地和土著知识。北极地区的变暖速度是全球趋势的四倍，为了应对这种趋势，北极地区的景观正在“绿化”，生态系统，包括湖泊内的生态系统，正在变得更有生产力。这项工作考察了温度变化和氮循环变化在驱动湖泊藻类和蓝藻群落变化中的作用。该项目采用了一种新颖的方法，通过量化众多沉积色素来评估生产力。色素作为替代品有很多优势，包括它们的生物类别或分类特异性，以及它们反映不产生硬大化石的生物的能力，这对于旨在了解蓝藻群落趋势的工作来说是特别的资产。对不同生物的沉积色素进行定量分析，既可以深入了解是什么驱动了大量初级生产力，也可以表征单个初级生产者群体的反应。这项研究将推进使用这种未充分利用的方法，这是潜在的适用于许多地区，其中变化的湖泊藻类或蓝藻群落和/或富营养化是一个社会关注。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.