Restored tufa-depositing streams: a dynamic interface between terrestrial and aquatic ecosystems

Stream periphyton has implications for ecosystem processes, yet little is known about its function in response to restoration efforts. In this study, we compared the taxonomic and functional composition of periphytic ciliates between restored and unrestored (control) streams for two different immersion periods to identify species with indicator potential, identify ciliate functional traits that differ between the two stream types, and examine the effects of environmental parameters on species and functional trait composition. Our study showed that restored streams differed from control streams in terms of species and functional trait composition. In restored streams, better competitors, i.e., omnivorous and bacterivorous free-swimming ciliates predominated, utilizing a wider range of different niches created by the greater microhabitat complexity due to retention of allochthonous organic matter particles and precipitation of calcite crystals, i.e., tufa. One of these species was Platyophrya vorax, which was identified as a species with indicator potential for restored tufa-depositing streams. The relationship between habitat heterogeneity, ciliate functional traits, and organic matter dynamics suggests that restoration of tufa-depositing streams affects ecosystem functioning by influencing its functional components, highlighting the need to investigate such ecosystems through the prism of connected lotic and terrestrial ecosystems rather than isolated ecosystems.