Disconnected: integrating spatial complexity in multiple stressor research
Ecology of Land Use
Final Report Abstract
River networks are complex ecosystems characterized by a continuous exchange of material and energy through longitudinal connectivity gradients. These ecosystems are threatened by a growing number of human-induced stressors, which frequently co-occur, interacting in complex and unexpected ways. Moreover, stressors’ effects can propagate to downstream reaches along the river network and trigger cascading effects. The Disconnected project aimed at integrating spatial complexity of river networks into multiple stressors research, investigating local and downstream effects of multiple stressors. For this, a system of 18 flow-through mesocosms was created, mimicking a simplified river network with two upstream tributaries under the influence of different anthropogenic stressors (flow velocity reduction and ALAN) merging in a downstream section. We measured the response of macroinvertebrates, microbial communities and ecosystem function (organic matter decomposition) in the system and monitored the local and downstream effects of stressors on aquatic communities. We built the system in spring 2021 (WP0) and conducted the experiment in summer 2021 (WP1). After 26 days of colonisation, we applied the stressors in the upstream sections of the system and we monitored the drift of the macroinvertebrates and the formation of biofilm. After 3 weeks of manipulation, we sampled the benthic macroinvertebrates in the upstream and downstream sections to assess local and downstream patterns of community assembly. Samples collected during WP1 were processed with a combination of novel and traditional techniques (WP2), including metabarcoding tools and morphological identification. Results show that flow reduction was the strongest determinant of local community assembly patterns and ecosystem function, though responses were taxon-specific. Further, the upstream arrangement of the stressor had a limited effect on ecosystem function but influenced the assembly of microbial communities by increasing the degree of stochasticisty and exerted taxon-specific changes in drift rate and downstream macroinvertebrate communities.
Publications
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Effects of flow reduction and artificial light at night (ALAN) on litter decomposition and invertebrate communities in streams: A flume experiment. Science of The Total Environment, 912, 168836.
Juvigny-Khenafou, Noël P.D.; Burgazzi, Gemma; Steiner, Nikita; Harvey, Eric; Terui, Akira; Piggott, Jeremy; Manfrin, Alessandro; Feckler, Alexander; Leese, Florian & Schäfer, Ralf B.
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Multiple stressors in river networks: local and downstream effects on freshwater macroinvertebrates. Ecography, 2026(1).
Burgazzi, Gemma; Juvigny‐Khenafou, Noël P. D.; Schreiner, Verena C.; Manfrin, Alessandro; Jupke, Jonathan; Piggott, Jeremy; Harvey, Eric; Terui, Akira; Leese, Florian & Schäfer, Ralf B.
