EVIDENCE OF TESTATE AMOEBAE IN MIDDLE MISSISSIPPI RIVER FLOODPLAIN SEDIMENTS

Dave Scott was a prolific researcher of near-shore and marginal marine benthic foraminifera, but in addition he co-authored several works on testate amoebae (thecamoebians). The project presented honor his contribution to the study of the testate amoebae.

Testate amoebae have been demonstrated to be useful indicators for changing land-use and climate, as well as pollution. This study examined the potential presence of testate amoebae in the Middle Mississippi River (MMR) floodplain and their application for environmental assessment. Sediment cores and surface sediment samples were collected from two sites in the MMR floodplain, the MMR Wetlands Field Station and Horseshoe Lake. These sites were chosen because they represented contrasting floodplain environmental conditions and differing land use, water management, and flooding histories. Cores were subsampled at 5 cm intervals. The surface and core samples were sieved at 150 µm and 45 µm. The >45 µm to <150 µm size fraction was examined for testate amoebae. Testate amoebae were abundant in the samples and a minimum of 100 tests were identified from each sample. A total of 21 strains representing 15 species were identified. The dominant taxa were Arcella vulgaris, Centropyxis aculeata, Centropyxis constricta, Cucurbitella tricuspis, Difflugia protaeiformis, and Difflugia oblonga. Discrete assemblages were recognized at each site and throughout the cores that suggested varying environmental conditions. The patterns will be presented and compared to the known history of the sites to determine the driving factors. The results of this study will provide a greater understanding of the utility of testate amoebae in assessing changing conditions in floodplain environments of the MMR region.