RUI: Using a Paleolimnological Approach to Assess the Interactive Effects of Acidic Deposition and Eutrophication on Softwater Lakes

酸沉积富营养化仍然是当今影响水生资源健康的两个最不利的过程。尽管在过去的二十年里对酸沉积和富营养化进行了大量的研究，科学家们才刚刚开始认识到这两个过程对地表水状况的相互作用的重要性。在过去的二十年中，大部分关于酸沉积的研究都集中在流域中产生碱度的陆地过程上，最近则集中在硫生物地球化学对湖内碱度产生的作用上。然而，这种对碱度产生的过分强调有时掩盖了其他因素和过程在确定酸性沉积的长期影响方面的作用和相互作用。同样，我们了解熵化的许多后果，但现在才意识到这一过程也改变了硫循环和沉积硫储存记录。虽然还没有完全理解，但很明显，酸沉积和富营养化在控制地表水条件和随后的降解方面的作用是通过硫、铁和碳的生物地球化学循环以及沉积物中磷的内部负荷耦合的。理解这些联系的关键在于保存在湖泊沉积物中的化学和生物信号。为了了解湖泊硫循环中酸沉积和富营养化之间的相互作用，以及我们在沉积物中测量的化学信号，我们需要检查沉积物中的生物标志物，它们对富营养化或酸化有独特的反应。现在，使用微观藻类遗骸形成推理模型来重建单个湖泊化学结构的历史变化是相对普遍的。这种古湖泊学方法已成功地用于重建pH和营养状况。独立追踪历史pH值和营养状况的变化与硫埋藏的变化有关，将有助于阐明富营养化在解释为什么东北一些低碱度湖泊由于酸沉积而酸化，而其他湖泊没有酸化方面所起的作用。该项目的主要重点将是利用古湖泊学方法来阐明酸化和富营养化对新英格兰南部湖泊硫生物地球化学循环的相互作用。我们建议利用尺度化的绿藻残骸来建立推理模型，用于重建湖泊pH和营养状况的历史变化，同时分析来自同一水体的硫、铁和碳的储存变化。这项研究将集中在过去大约150年的变化上，比较排水（康涅狄格湖）和渗水（科德角湖）湖泊，并包括跨越相对较宽的当代营养和pH梯度的水体。该项目将有效利用并继续增加来自两个地理区域的大型古湖泊数据集。

ABSTRACT SIVER (96-15062) Acid deposition eutrophication remains two of the most adverse processes effecting the health of aquatic resources today. Even though much research on acid deposition and eutrophication has occurred over the last two decades, scientists are just beginning to realize the importance of the interactive effects of both processes on the condition of surface waters. Much of the research on acid deposition over the last twenty years has focused on terrestrial processes generating alkalinity in the watershed and, more recently, on the role of sulfur biogeochemistry on within-lake alkalinity generation. However, this heavy emphasis on alkalinity generation has sometimes obscured the roles and interactions of other elements and processes in determining the long term effects of acidic deposition. Likewise we understand many of the consequences of entrophication, but are just now realizing that this process also alters the sulfur cycle and changes the sedimentary sulfur storage record. Although not completely understood, it is clear that the effects of acid deposition and eutrophication in controlling the condition and subsequent degradation of surface waters are coupled through the biogeochemical cycling of sulfur, iron, and carbon, and the internal loading of phosphorus from the sediments. A key to understanding these linkages resides in the chemical and biotic signals that are archived in lake sediments. To understand the interaction between acid deposition and eutrophication on the sulfur cycle of lakes, and on the chemical signals we measure in sediments, we need to examine biogenic markers in the sediment, which respond uniquely to either eutrophication or acidification. It is now relatively common to use microscopic algal remains to form inference models that are used to reconstruct historical changes in the chemical structure of individual lakes. Such a paleolimnological method has been successfully utilized to reconstruct pH and trophic status. An independent tracking of changes in historical pH and trophic status relative to alterations in the burial of sulfur will help elucidate the role that eutrophication plays in explaining why some low alkalinity lakes in the northeast have acidified as a result of acid deposition, while others have not. The primary focus of this project will be to utilize a paleolimnological method in order to elucidate the interaction of acidification and eutrophication on sulfur biogeochemical cycling in southern New England lakes. We propose to utilize scaled chrysophyte remains in order to form inference models that will be used to reconstruct historical changes in the pH and trophic status of lakes, and simultaneously analyze changes in the storage of sulfur, iron and carbon, from the same waterbodies. The study will focus on changes over the last ca. 150 years, compare drainage (Connecticut lakes) and seepage (Cape Cod lakes) lakes, and include waterbodies that span relatively wide contemporary trophic and pH gradients. The project will effectively utilize and continue to add to large paleolimnological data sets from both geographic regions.