Do the relationships between testate amoebae and fungi reflect the variability of past water table fluctuations in the ombrotrophic peatlands of Central Europe?

In this article, we examined the indicative value of a relationship between two non-pollen palynomorphs (NPPs), fungal HdV-10, related to the presence of Calluna vulgaris, and HdV-31A, which is testate amoeba – Archerella flavum. Both are frequently present on slides designated for pollen analysis, prepared from Sphagnum peat. We analysed three profiles from three extensive ombrotrophic peatlands in northern Poland, in which the content of testate amoebae (TA) was examined and TA-inferred depth to the water table (DWT) was reconstructed. The new analysis of palynological samples regarding NPPs revealed that strong increases in HdV-10 content were mostly simultaneous to HdV-31A declines. However, the relations between both types were not statistically significant. The rapid increases in HdV-10, despite the fact that this type of conidiospores is related to drier habitats on peatlands, were tentatively interpreted as an indicator of rapid rises in the water table level which, in consequence, might have stimulated the production of these spores by fungi. In addition, a negative correlation between HdV-31A and Arcella discoides and positive one, but weaker, in case of HdV-10 (attributed by some authors to species Trichocladium opacum (Corda) S Hughes) and A. discoides show a link between mutual fluctuations of both NPPs and hydrological instabilities on peatland. The Bagno Kusowo bog, the westernmost peatland subjected to the study, displayed an intriguing agreement between the presence of peat sections with strong increases in HdV-10 and cold climate events affecting Europe. Our study reveals that counting even a limited number of NPP types during the standard pollen analysis of Sphagnum peat may support the interpretation of results, especially, in cases when the investigation lacks testate amoeba analysis. When the reconstruction of TA-inferred DWT is provided, it may introduce additional information about the patterns of hydrological dynamics.