Exploring testate amoebae as bioindicators in UK upland peatlands: habitat status, vegetation management, peatland restoration and ecosystem functioning

Many UK blanket bogs are modified and often classified as being in a degraded state due to various management regimes including drainage and potentially also heather burning. While many restoration efforts (e.g., ditch-blocking, alternative heather cutting) are tried to restore these peatlands, we still lack monitoring tools to assess if, when and over what time such interventions achieve restoration goals towards improved ecology of the bog and associated functions. Testate amoebae (TA), as known bioindicators, could provide such a monitoring tool. TA communities were investigated at a series of modified blanket bog peatland sites under different heather management regimes, across blanket bog restoration sites and compared to near intact peatland communities to 1) investigate the optimal sampling strategies of TA for indicating site/habitat wetness condition, 2) assess the potential of TA as hydrological bioindicators to monitor the restoration trajectory and success, 3) explore their possible functional contribution to ecosystem processes. TA communities from Sphagnum mosses were shown to best reflect the wetness gradient among sites. TA species richness and density reached their highest value in either late autumn or early winter. Clear vertical separation of TA communities (e.g., living status, specific species) was observed along Sphagnum moss sections. TA communities showed species-specific sensitivity to hydrological changes, with species indicative of dry habitat (e.g., Hyalosphenia subflava, Corythion dubium) being particularly abundant in the degraded and uncut peatland areas, while those representing wet habitat (e.g., Amphitrema flavum, A. wrightianum) being more common in the near intact sites. TA key functional traits (e.g., body and aperture size) showed significant responses to management interventions. The distinctive change in TA community between living Sphagnum and peat may suggest different functional roles they play, with mixotrophic TA in Sphagnum being more important in carbon fixation in very wet habitats, while heterotrophic TA communities in peat are crucial in decomposition in drier habitats. Overall, this study highlights the potential of TA as hydrological bioindicators to monitor peatland recovery, and also clearly demonstrates the link between biodiversity, management, and likely inferred ecosystem functioning of peatland ecosystems.