Methodological design to study the effects of heatwaves on natural plankton communities from Mediterranean vulnerable ecosystems

The Mediterranean Region is considered one of the areas most exposed to climate warming, with artificial lakes and coastal lagoons representing particularly vulnerable ecosystems, that provide essential goods and services. Amongst the extreme events linked to warming, heatwaves are of growing concern, yet their ecological effects on the functioning of Mediterranean aquatic systems remain poorly investigated. We present a methodological framework designed by the Project “ a warmer Future world: effects on plankton commUnities and paThogens in Mediterranean vUlneRable Ecosystems (FUTURE) “ to study how natural plankton communities respond to abrupt and sustained thermal stress. The approach targets on entire plankton communities, from bacteria to zooplankton, integrates laboratory experiments and field monitoring activities and combines classical techniques with molecular tools to capture changes in biodiversity, food web size-structure and the occurrence of potentially pathogenic and antibiotic-resistant bacteria. We selected two diverse aquatic ecosystems in the western Mediterranean as case studies: an artificial lake, an important source for drinking water and a coastal lagoon vital for fishery, both of high ecological and economic importance. By applying controlled experimental simulations with ecological relevance, the framework provides a replicable approach to investigate plankton community-level responses to heatwaves. This methodological contribution provides a comparative framework for vulnerable Mediterranean ecosystems and promotes standardised approaches to assess the impacts of extreme climate-driven events. The scalable and reproducible protocol presented here fills a critical regional knowledge gap and will support the effective management of climate-sensitive aquatic ecosystems.