METAPONDS – Impact of multiple stressors on fishpond metacommunities

Small, species-rich ponds (e.g. fishponds) are intensively affected by human activities within landscapes and relatively underexplored in ecological theories. Environmental filtering, competition, and dispersal shape plankton diversity, ecosystem function, and stability of metacommunities. Yet, those processes are poorly understood for fishpond networks, limiting evidence-based conservation and management. We will examine the effects of different stressors, namely land use alteration, eutrophication, warming, and invasion of non-native species, on the diversity, stability, and ecosystem function of plankton metacommunities in Austrian fishpond networks. METAPONDS combines large-scale field surveys and experimental mesocosm manipulations to understand the isolated and combined effects of nutrient pollution, agricultural land use, warming, and invasions on plankton communities. Over 60 Waldviertel fishponds (Lower Austria), from various land use types, will be sampled for physicochemical, biological, and landscape parameters (space-for-time approach). Amplicon (eDNA) analysis will provide deep taxonomic resolution and reveal cryptic diversity, uncovering metacommunity structure, assembly, and functional patterns across pondscapes. Mesocosm experiments will simulate eutrophication, warming, and invasions, tracking responses of plankton diversity, functioning, and stability indices. By integrating eDNA metabarcoding with functional trait analysis and metacommunity theory, the project will rigorously test assembly rules and develop predictive models for biodiversity conservation under multiple stressors. The findings will directly support Austria's Biodiversity Strategy 2030+ by providing insights into monitoring, management, and hotspot habitat prioritisation, thereby enabling policy and outreach efforts. METAPONDS aims to advance freshwater conservation theory and practice, from local restoration efforts to global change adaptation, positioning fishpond pondscapes as natural laboratories for testing biodiversity and ecosystem responses to modern challenges for the first time.