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| Abstract Title:
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| A Diatom-Inferred Record of Regime Shift in an Oxbow Lake, Alabama, USA: Perspectives for Current Climate Change
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| Graduate Student Presenter:
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Jay Y.S. Hodgson
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| Name of the Author(s) and Affiliation(s):
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Jay Y.S. Hodgson, The University of Alabama; Amelia K. Ward, The University of Alabama
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Diatoms preserved in sediments serve as robust indicators of historical water chemistry, hydrology, and temperature. As part of a climate change study, we cored the sediments of a floodplain oxbow lake in Alabama, USA. Our hypothesis for this lake was that it would show minimal effects from hydrological and climate changes over its life span. However, our analyses of diatom composition suggest that the lake has gone through a series of hydrological and temperature changes. Prior to ~3000 BCE, sedimentation was low and diatom communities were characteristic of lotic conditions. After ~3000 BCE, sedimentation increased and the diatom community became dominated by more pelagic species and species tolerant of turbid waters. These data suggest that the oxbow was actively connected to the river channel prior to ~3000 BCE but then became isolated. Additionally, between 900 to 1300 AD, the diatom community shifted from aerophilic, cold water species to planktonic, warm water species, coinciding with the Medieval Climate Optimum. In contrast, the opposite occurred between 1650 and 1850 AD, coinciding with the Medieval Climate Minimum. Moreover, because the diatom communities shifted in response to past climate changes, it is possible to use modeled trends to assess any recent, post-industrialization climate warming anomalies compared to long-term trends.
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