Role of ARC processes in ecosystem recovery

We confirmed that biotic degradation is mainly driven by species’ tolerances, while recovery is mainly driven by dispersal (particularly in the initial phase) and biotic interactions. In general,  

• The ExStream experiment revealed flow velocity as a key driver for stream microbiomes, outcompeting the effects of other stressors and resulting in substantially restructured microbiomes. The stability of metagenome-encoded functions contrasted highly active keystone species and short-term stressor adaptations in gene expression, e.g., upregulation of chaperones. After recovery, however, the dominant tolerant taxa did not decline as expected, but increased in density at the expense of other species. In other words, stress tolerant taxa enhance their dominant position even more during the recovery phase - an obvious case of monopolisation (Stach et al., submitted).
• Gillmann et al. (2024) analysed time series from the Boye, one of the project’s study catchments, which was formerly severely degraded by wastewater discharge. Once the wastewater was removed, the community recovered, and the species traits responded as predicted by the ARC: With time since restoration, the dispersal capacity of the community declined, while the competition between species increased. The community’s tolerances against stressors, however, developed differently, with a decreasing tolerance towards organic pollution (indicating continuously increasing water quality) and a constant level of tolerance against salinity.