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.
