Robustness and precision of Holocene palaeoclimatic records from peatlands using testate amoebae

This thesis represents the first attempt to use quantitative testate amoebae (Protozoa: Rhizopoda) analysis to measure hydrological fluctuations in British peatbogs over the Holocene. Changes in the fossil species assemblage are used to reconstruct the mean annual water table records at different locations on mire surfaces using a transfer function designed for application on oligotrophic peatlands. The transfer function was found to provide more precise reconstructions for depth to water table than percentage soil moisture. Multiple cores were extracted from three of the Border Mires; Coom Rigg Moss and Butterburn Flow (both intermediate ombrotrophic bogs) and The Wou (a minerogenic valley mire). Testate amoebae analysis of these cores was used to assess the variability of hydrological change at three spatial scales, in an attempt to separate autogenic and allogenic influences on site hydrology. The morphology of each mire ensured a strong link between water and prevailing climate (precipitation-evaporation balance). At the micro-scale (1-10m), within the centre of a mire, microtopography explains differences between the hydrological record for two cores. This is inferred because one of the cores appears to have been the location of an insensitive hummock over much of the period of accumulation. At the meso-scale (100-1000m), between the central mire expanse and the mire margins, synchronous changes can be identified, but the edges generally have lower water tables than the central portions of the mires. However, this may be attributable to autogenic factors acting over the whole site, as well as to climate. Between sites, at the macro-scale (1-10Iun), climatic influences can be clearly identified. The climatic signal is strongest in the centre of the mire and is more consistent between locations in the upper peats. If a hydrological shift is replicated in at least three cores from at least two sites, a climatic signal can be inferred. The testate amoebae preparation technique was also modified as part of this research to provide cleaner slides for more efficient counting. Testate amoebae analysis provides a new quantitative technique for reconstructing the palaeohydrology and from this, inferred palaeoclimatic conditions of ombrotrophic peatlands

Distribution of testate amoebae in salt marshes along the North American East Coast

Reproduced with permission of the publisher. © 2006 Cushman Foundation for Foraminiferal ResearchThis study describes the distribution of testate amoebae in three North American East Coast salt marshes (Leipsic River marsh, Delaware, USA; Little River marsh, Maine, USA; and Little Dipper Harbour marsh, New Brunswick, Canada). Five zones are recognized in the high salt marsh. With increasing marine influence, these zones are characterized by the following succession of dominant taxa: Valkanovia elegans, Tracheleuglypha dentata, Centropyxis cassis type, C. platystoma type and Difflugia pristis type. Most species occur in all three marshes, and their general vertical distribution is comparable. The results are also comparable with those obtained from British salt marshes, suggesting that salt-marsh testate amoebae have similar distributions on both sides of the Atlantic Ocean. The precision of the sea-level indicative value of testate amoebae in fossil salt-marsh sediments is a function of the local mean tidal range (MTR). Results of this study show that testate amoebae can indicate former sea levels with a precision of ±0.04 m in the Leipsic River marsh (MTR = 1.75 m), ±0.09 m in the Little River marsh (MTR = 2.6 m), and ±0.18 m in the Little Dipper marsh (MTR = 5.8 m)