HR: 0800h
AN: PP11A-1435    [Abstracts]
TI: Paleoclimate Records From Testate Amoebae: Calibration and Application in Eastern North America
AU: * Booth, R K
EM: rkbooth@wisc.edu
AF: University of Wisconsin, 1225 W. Dayton Street, Madison, WI 53706 United States
AU: Jackson, S T
EM: jackson@uwyo.edu
AF: University of Wyoming, 1000 E. University Avenue, Laramie, WY 82071 United States
AB: Testate amoebae (Protozoa: Rhizopoda) are amoeboid protozoans that produce decay-resistant and morphologically distinct shells, or tests. Peatland-inhabiting testate amoebae occupy discrete ecological niches related to surface- moisture conditions, making them good indicators of past hydrological changes, particularly changes in water-table depth. However, most calibration datasets have measured water-table depths only at the time of sampling, and thus reconstructions have been limited to relative or ordinal moisture gradients. Most calibration datasets have also been limited geographically, and more spatially extensive datasets are needed to support widespread application. Efforts are underway to refine and improve the precision of testate amoeba-based paleoclimate reconstructions. These studies are aimed at 1) developing and validating transfer functions for continental North America using estimates of mean water-table depth integrated over the entire growing season, 2) comparing the stability of species-environment relationships between different regions, and 3) confirming that climate variability is the dominant control on testate amoeba-based paleohydrological reconstructions at decadal to multi-centennial timescales. Testate amoeba communities and environmental data were collected at over 400 locations within 32 peatlands extending from Minnesota to Maine. Mean water-table depth at each of these locations was estimated using the PVC-tape (polyvinyl chloride) discoloration method. Transfer functions indicate that mean water-table depth during the growing season can be reconstructed from testate amoeba assemblages with a mean error of 5.0 cm (r²=0.87). Water-table depth optima are constant within species among different regions (Rocky Mountains, Great Lakes, and eastern North America), suggesting that the ecological niches of testate amoebae with respect to moisture are conserved in different geographic regions, even when community composition is relatively different. Comparison of testate amoeba-based paleohydrological reconstructions between raised bogs in Michigan and Minnesota indicate a strong correspondence between the two regions (r=0.53), particularly during time periods dominated by high-magnitude moisture fluctuations. Strong correlations also exist between instrumental climate records and testate amoeba-based reconstructions from ²¹⁰Pb dated peat profiles. A network of peatland-based paleoclimate reconstructions is currently being developed using testate amoebae and other proxies (humification, stable isotopes) from an array of sites extending from Minnesota to Maine.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1833 Hydroclimatology
DE: 1890 Wetlands (0497)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 9350 North America
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005