Thecamoebians as an environmental proxy for the Middle Mississippi River floodplain

Author

Stephanie Jarvis, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2014

Degree Name

Master of Science

Department

Geology

First Advisor

Ishman, Scott

Abstract

Thecamoebian tests from recent lacustrine sediments have been shown to be a useful proxy to study environmental changes such as land-use changes, pollution, and climate shifts. In this study, the usefulness of thecamoebians as an environmental proxy for the Middle Mississippi River (MMR) floodplain is explored. Sediment cores and surface samples were collected from two sites in Alexander County, IL: Southern Illinois University's (SIU) MMR Wetland Field Station near East Cape Girardeau, IL and Horseshoe Lake, a dammed oxbow managed by the IL Department of Natural Resources (DNR), near Olive Branch, IL. These sites represent different floodplain environments, management histories, and flooding patterns. The thecamoebian populations were expected to reflect these differences while also responding to regional signals associated with development, agriculture, and climate. Cores were subsampled at a 5cm interval and all samples were sieved with 150μm and 45μm screens to retain thecamoebian tests. Sieved sediment was examined under a microscope and at least 100 tests were identified in each sample. Pre- and post-land clearing assemblages are recognized at each site, primarily by the increased abundance of the eutrophic-indicating species Cucurbitella tricuspis. Additionally, grab samples collected from the wetlands site during the spring indicate that the site may be influenced by road salt runoff in addition to agricultural activity. These results suggest that thecamoebians are a useful land-use change proxy and more research is needed to better understand the environmental conditions influencing assemblages.