CLIMATE RECONSTRUCTION BASED ON DIATOM ASSEMBLAGES WITHIN PRETTY LAKE, INDIANA

Pretty Lake, located in northeastern Indiana, is of glacial origin, is endorheic in nature, and, because it never completely mixes, holds several clues to past climate fluctuations within the Midwestern United States. One of the most important biological indicators found within Pretty Lake are diatoms, significant because these organisms are incredibly sensitive to the aquatic conditions in which they live. When the overarching climate of a region shifts, regional lakes tend to experience a comparable ecological shift. For instance, when the predominant diatom in a lake setting shifts, one can assume that it is because of a corresponding shift in the surrounding climate and due to resultant changes within the lake environment. Ecological changes occur as a result of climatological shifts in precipitation, evaporation, temperature, and pH, as well as other variables. This study aims to examine diatom assemblages within the lake record over the past 2000 or so years to analyze variations in atmospheric circulation over the Midwest and to determine how Midwest climate responded to well-known climate events as opposed to other regions within the contiguous United States. It is important to study this lake due to the low resolution of climate data from this region, generally created using pollen records. Diatoms, particularly planktic diatoms, are more helpful in this particular study because of their variation over time within the record and because they have well established ecologies. Limnological records within Pretty Lake have the potential to produce a higher resolution and a more distinctive record of past climate change within the Midwestern United States.