Potential implications of differential preservatio

Authors: Edward A D Mitchell Richard J Payne Mariusz Lamentowicz

Publish Date: 2007/12/22

Volume: 40, Issue: 2, Pages: 603-618

PDF Link

Abstract

Testate amoebae are now commonly used in paleoenvironmental studies but little is known of their taphonomy There is some experimental evidence for differential preservation of some testate amoeba shell types over others but it is unclear what if any impact this has on palaeoenvironmental reconstruction To investigate this issue we looked at palaeoecological evidence for the preservation of different shell types We then investigated the possible impact of selective preservation on quantitative palaeoenvironmental inference We first used existing palaeoecological data sets to assess the vertical patterns of relative abundance in four testate amoeba shell types 1 shells made of secreted biosilica plates idiosomes eg Euglypha 2 idiosomes with thick organic coating Assulina 3 proteinaceous shells eg Hyalosphenia 4 shells built from recycled organic or mineral particles xenosomes eg Difflugia Centropyxis In three diagrams a clear pattern of decay was only observed for the idiosome type In order to assess the implications of differential preservation of testate amoeba taxa for paleoenvironmental reconstruction we then carried out simulations using three existing transfer functions and a wide range of scenarios downweighting different test categories to represent the impact of selective test decomposition Simulation results showed that downweighting generally reduced overall model performance However downweighting a shell type only produced a consistent directional bias in inferred water table depth where that shell type is both dominant and shows a clear preference along the ecological gradient Applying a scenario derived from previous experimental work did not lead to significant difference in inferred water table Our results show that differential shell preservation has little impact on paleohydrological reconstruction from Sphagnumdominated peatlands By contrast for the minerotrophic peatlands dataset loss of idiosome tests leads to consistent underestimation of water table depth However there are few studies from fens and it is possible that idiosome tests are not always dominant and/or that differential decomposition is less marked than in Sphagnum peatlands Further work is clearly needed to assess the potential of testate amoebae for paleoecological studies of minerotrophic peatlandsFinancial support is gratefully acknowledged from the Swiss National Science Foundation Project no 205321–109709/1 to EM the University of Alaska Anchorage Faculty Development Grant to EM a Queen Mary University of London Westfield studentship to RJP a British School at Athens MacMillanRodewald fellowship to RJP a University of Manchester Humanities Research Fellowship to RJP the State Forests of Poland project “Functions of natural and seminatural peatlands in nature and management structure of Tuchola Pinewoods” Principal Investigator Kazimierz Tobolski and the Polish Ministry of Scientific Research and Information Technology project “Development and origin of mires situated in Stążka Valley in Tuchola Landscape Park” No 3P04G04323 Principal Investigator M Lamentowicz We thank two anonymous reviewers for their comments

Keywords: