Linking Archaeal Membrane Lipids and Ecology in Great Lakes: Understanding the TEX86 Paleotemperature Proxy

在大湖系统中，古温度很难测量。新近建立的古湖膜脂(GDGT)与年平均湖面温度之间的关系为湖温重建提供了一个强有力的、急需的工具。不幸的是，人们对这些GDGT化合物的起源所在的克伦考古群的生态知之甚少。在我们能够理解为什么来自珊瑚的膜脂似乎反映了海洋或湖泊表面的温度之前，仍然有许多问题。目前，这些古生菌的膜脂用于古温度重建的潜力仅基于一套不同的海洋和大型湖泊环境的核心-顶部校准。在这个项目中，明尼苏达大学德卢斯分校的研究人员将试图将苏必利尔湖水柱中GDGT的产生与克伦考古塔生态的特定方面联系起来，以提高我们对克伦考古群本身的了解，并确定在沉积物中发现的GDGT分布是否反映了湖面温度，以及其他因素是否正在影响这些考古界膜脂保存的表观温度信号。研究小组将研究苏必利尔湖(北美)和马拉维湖(东非)水柱和沉积物中克伦考古塔的GDGT膜脂和核酸。在苏必利尔湖，他们将确定一年中这些化合物在一年中最丰富的时间，通过沉积物捕集器将颗粒有机物和它们的通量输送到沉积物中。他们还打算通过分析水柱中不同深度的悬浮颗粒物(SPM)中的这些考古化合物，来确定这些考古化合物占主导地位的特定深度。最后，GDGT膜脂的多样性将与苏必利尔湖和马拉维的SPM和沉积物中古生菌群落的多样性进行比较，以检查古生菌多样性的变化是否反映在GDGT的分布中。该提案中概述的项目有望为理解TEX86古温度指数和大湖水温之间的机制联系奠定基础。最终，这项研究的结果应该会导致其他科学家自信地应用TEX86指数来解决世界范围内湖泊系统中的大陆古气候问题。广泛影响：该项目的更广泛影响包括对研究生和本科生进行实地方法和最先进的分析方法方面的培训，以及加强国家和国际科学合作。这项研究还将极大地提高我们对TEX86古温度指标与大湖古生物群落之间的机制联系的理解，为我们提供一个有用的工具来帮助我们理解过去、现在和未来的全球气候和环境变化。

ABSTRACTOCE-0452927Paleotemperature is difficult to measure in great lakes systems. The recent establishment of the relationship between crenarchaeotal membrane lipids (GDGTs) and mean annual lake surface temperature provides a powerful and much needed lake temperature reconstruction tool. Unfortunately, very little is known about the ecology of the Crenarchaeota from which these GDGT compounds are derived. Many questions remain before we can understand why the membrane lipids derived from the Crenarchaeota seem to reflect sea or lake surface temperatures. Presently, the potential for the membrane lipids from these archaea to be used for paleotemperature reconstruction is based solely on core-top calibrations from a diverse suite of marine and large lake environments.In this project, researchers at the University of Minnesota at Duluth will attempt to link the production of GDGTs in the water column of Lake Superior with specific aspects of the ecology of the Crenarchaeota in order to improve our understanding of the Crenarchaeota themselves as well as to determine whether the GDGT distribution identified in sediments reflects lake surface temperature and whether other factors are influencing the apparent temperature signal preserved by these crenarchaeotal membrane lipids.The research team will study the GDGT membrane lipids and nucleic acids of Crenarchaeota in the water columns and sediments of Lake Superior (North America) and Lake Malawi (East Africa). In Lake Superior, they will identify the time of the year when these compounds are most abundance in settling particulate organic matter and their fluxes to the sediment using sediment traps. They will also intend to identify specific depths where these crenarchaeotal compounds are dominant by analyzing them in suspended particulate matter (SPM) at various depths in the water column. Finally, the diversity of GDGT membrane lipids will be compared with the diversity of archaeal communities in both SPM and sediments from Lakes Superior and Malawi to examine whether variations in archaeal diversity are reflected in GDGT distributions. The project outlined in this proposal is expected to lay the groundwork for understanding the mechanistic link between the TEX86 paleotemperature index and water temperature in great lakes. Ultimately, results from this study should lead to the confident application of the TEX86 index by other scientists to address continental paleoclimate questions in lake systems worldwide.Broader Impacts: The broader impacts of this project include training of graduate and undergraduate students, both in field methods as well as state-of-the-art analytical methods and enhancement of national and international scientific collaborations. This study will also greatly increase our understanding of the mechanistic links between the TEX86 paleotemperature proxy and archaeal communities in great lakes, giving us a useful tool to help understand past, present, and future global climate and environmental change.