Analysis of fossil testate amoebae in Selisoo Bog, Estonia: local variability and implications for palaeoecological reconstructions in peatlands

Local variability in decadal water-table changes on an ombrotrophic peatland was explored using testate amoebae analysis of near-surface peats in an Estonian raised bog. The distribution of testate amoebae assemblages was studied along the gradient from hummock to hollow in the upper 30-cm layer of peat. As expected, testate amoebae assemblages in different micro-ecotypes from hummock to hollow, even as close as 10 m apart, are distinctly different. Past water-table change was reconstructed by applying a transfer function based on modern samples from throughout Europe. Results show a decline in water level from the mid-late 20th century on Selisoo bog in all profiles from the different micro-ecotypes. However, the absolute water-table depths and amplitudes of fluctuations vary between reconstructions from different sampling micro-ecotypes. Cores were correlated using changes in non-mire pollen concentrations down-core, but it was not possible to correlate minor changes in water-table owing to non-contiguous sampling and variable accumulation rates. We conclude that different microtopes show the same decadal trends in relative water-table change but that the absolute magnitude of change may be more variable locally. It is important that reconstructed palaeohydrological changes in bogs consider changes in bog micro-ecotypes, and their variation over time, as this may alter the sensitivity of an individual record to drivers such as climate change. Comparison and compilation of data from parallel cores from different micro-ecotypes and/or different sites are likely to provide more robust reconstructions.