Impact of two hot and dry summers on the community structure and functional diversity of testate amoebae in an artificial bog, illustrating their use as bioindicators of peatland health

Ongoing climate warming threatens the survival of bogs at the warm/dry limit of their distribution (<i>e.g.</i> in central Europe), and jeopardises the restoration of damaged bogs even more. Because vegetation changes can be slow, early indicators of hydrological change such as testate amoebae are useful. We used testate amoeba community structure and community weighted mean of functional traits to monitor the impact of two very hot and dry summers on a small (around 100 m²) artificial peatland constructed in the botanic garden of Neuchâtel, Switzerland. We collected analogous samples in a naturally regenerating cutover peatland at 1000 m a.s.l. in the Jura Mountains as a reference. The comparison of living and dead assemblages in the botanic garden showed an increased representation of smaller testate amoeba taxa (<i>Corythion dubium</i>, small <i>Euglypha</i> sp.) with a small pseudostome (indicative of dry conditions) and a loss of mixotrophy in 2015, followed by a weaker further shift in 2016. Nevertheless, the testate amoeba community structure in 2016 still indicated a dry <i>Sphagnum</i> bog. Testate amoeba analysis allows rapid assessment of peatland health and/or restoration success. The comparison of living and dead assemblages makes it possible to observe changes within a season in a single sampling campaign.