Biogeochemistry of Victoria Land Coastal Ponds: Role in Terrestrial Ecosystem Organic Carbon Dynamics and Structure

自1993年以来，南极陆地生态系统的结构、过程和功能联系一直是麦克默多长期生态研究站（LTER）的研究重点。这个生态系统有一个现代的组成部分，连接了土壤、冰川、溪流和冰雪覆盖的湖泊之间的有机碳动态，加上古冰川事件的遗产，在该地区沉积了古有机碳。土壤储存库包含了泰勒山谷内72%的季节性解冻和生物可利用的有机碳，其中很大一部分碳可能是来自古代气候事件的顽固性碳。虽然LTER的中心主题之一是了解生态系统要素之间在有机碳运输和影响初级生产过程方面的联系，但尚未调查的不稳定有机碳的一个潜在大来源，即生物可利用的有机碳，是在麦克默多干谷的大多数地区，特别是在海岸附近发现的丰富的小池塘。这些池塘的表面积相对较大，当它们在景观上移动位置时，似乎会产生大量的搁浅微生物垫。这些池塘的短暂性使得有机物质容易被运输，并且可能是麦克默多干谷生态系统中其他组成部分的现代、不稳定碳的重要来源。虽然它们的确切范围尚不清楚，但初步估计表明，沿海池塘水库可能至少占干谷土壤水库碳的11%。因此，这些池塘可能会显著影响干谷生态系统的碳循环，如果要为这片极地沙漠开发一个完整的碳预算，就必须考虑它们。本项目将(1)确定沿海池塘水库的范围，(2)评估水库的整体生产力，(3)确定沿海池塘水库是干河谷地区陆地生态系统有机碳动态和整体结构的来源还是汇。这项工作的大部分将集中在了解这些池塘的生物地球化学因素，影响有机碳生产和养分循环。这项研究的结果将为现代生态系统组成部分之间的联系提供更详细的了解，为极地沙漠生态系统内的生物地球化学循环提供见解，并可能确定有助于在极端环境中维持生命的机制。这项研究还将涉及诺克斯维尔市的学生，他们主要来自非洲裔美国人社区。K-5年级的学生将参与互联网上的问答环节，高年级学生将设计生态实验，并向他们介绍科学方法。数据分析将用于科学和数学课程，以帮助培养学生的分析技能，并将这些技能置于相关的背景中。

Ecosystem structure, processes, and functional linkages in the Antarctic terrestrial ecosystem have been the focus of the McMurdo Long-Term Ecological Research (LTER) site in the McMurdo Dry Valleys since 1993. This ecosystem has a modern component linking the organic carbon dynamics between the soils, glaciers, streams and ice-covered lakes plus a legacy to ancient glacial events that deposited paleo-organic carbon within the region. The soil reservoir contains 72% of the seasonally unfrozen and biologically available organic carbon within Taylor Valley and a substantial fraction of this carbon may be recalcitrant carbon derived from ancient climatic events. While one of the central themes of the LTER is to understand the linkages between ecosystem elements in terms of the transport of organic carbon and processes affecting primary production, one potentially large source of labile, and hence bioavailable, organic carbon that has not been investigated is the abundant small ponds found in most areas of the McMurdo Dry Valleys, especially near the coast. These ponds have a relatively large surface area, and they seem to generate a large amount of stranded microbial mat as they shift position on the landscape. The transient nature of these ponds renders the organic matter vulnerable to transport and possibly represents a significant source of modern, labile carbon to the other components in the McMurdo Dry Valleys ecosystem. While their exact extent is unknown, a preliminary estimate suggests that the coastal pond reservoir may constitute at least 11% of the carbon to the Dry Valleys soil reservoir. Therefore, these ponds may significantly impact the carbon cycle of the Dry Valleys ecosystem and they must be considered if a complete carbon budget is to be developed for this polar desert. This project will (1) determine the extent of the coastal pond reservoir, (2) assess how productive the reservoir is as a whole and (3) to determine if coastal pond reservoir is a source or sink within the organic carbon dynamics and overall structure of the terrestrial ecosystem in the dry valleys region. Much of this work will focus on understanding the biogeochemistry of these ponds in terms of the factors affecting organic carbon production and nutrient cycling. The results of this study will provide a more detailed understanding of the linkages between modern ecosystem components, provide insights into the biogeochemical cycling within polar desert ecosystems and possibly identify mechanisms that help sustain life in extreme environments. This study will also involve Knoxville city school students from predominantly African-American neighborhoods. The K-5 students will be involved in question and answer sessions over the Internet and the older students will design ecological experiments and become introduced to the scientific method. Data analysis will be used in science and math classes to help develop analytical skills and to place the skills in a relevant context for the students.