Holocene changes on a peatland in northwestern Ontario interpreted from testate amoebae (Protozoa) analysis

Radiocarbon‐dating and analyses of fossil testate amoebae (Protozoa) have established changes in soil moisture conditions on the developing surface of a Sphagnum ‐dominated peatland near Emo in northwestern Ontario. The distribution and composition of modern testate amoebae communities were studied from peatlands in the region of Ontario and Minnesota as a guide to interpreting fossil assemblages. Although the core spans all of the Holocene, fossil testate amoebae were recovered only from the part post‐dating 6500 BP. Earliest testate amoebae assemblages associated with bryophytic and cyperaceous‐rich fen peat are dominated by species in the genera Cyclopyxis and Centropyxis. By 5000 BP, Amphitrema Jraaum, Assulina muscorum, Heleopera sphugni and Hyalosphenia subjaoa become important species as Sphagnum‐rich peat accumulated at the site. Present‐day microtopographic differentiation probably developed during historic time when the site became progressively drier, as indicated by a change of Nebela griseola, N. militaris and Trigonopyxis arcula. Although it is possible to derive quantitative estimates of changing soil moisture conditions from testate amoebae, care should be taken in interpreting results, particularly from non‐Sphagnum‐rich peats, until more is learned about the distribution and ecology of modern faunas.