Spatially cascading effect of perturbations in experimental meta-ecosystems

Ecosystemsare linked to neighbouring ecosystemsnot only by dispersal, but also by the movement of subsidy. Such subsidycouplings between ecosystemshave important landscape-scale implications because perturbations in one ecosystemmay affect community structure and functioning in neighbouring ecosystemsvia increased/decreased subsidies. Here, we combine a general theoretical approach based on harvesting theory and a two-patch protistmeta- ecosystemexperiment to test the effect of regional perturbations on local communitydynamics. We first characterized the relationship between the perturbation regime and local population demography on detritusproduction using a mathematical model. We then experimentally simulated a perturbation gradient affecting connected ecosystemssimultaneously, thus altering cross- ecosystem subsidyexchanges. We demonstrate that the perturbation regime can interact with local population dynamicsto trigger unexpected temporal variations in subsidypulses from one ecosystemto another. High perturbation intensity initially led to the highest level of subsidyflows; however, the level of perturbation interacted with population dynamicsto generate a crash in subsidyexchange over time. Both theoretical and experimental results show that a perturbation regime interacting with local communitydynamics can induce a collapse in population levels for recipient ecosystems. These results call for integrative management of human-altered landscapes that takes into account regional dynamics of both species and resource flows.