Global warming is profoundly altering aquatic ecosystems, with climate models predicting a significant increase in the frequency, duration, and intensity of heatwaves. These prolonged periods of unusually high temperatures are becoming more common globally, and especially in the Mediterranean, recognized as one of the most vulnerable areas. Artificial lakes, crucial for essential ecosystem services, are particularly sensitive to these changes.

This scientific proposal investigates the impact of a simulated summer heatwave on a natural plankton community collected from Bidighinzu Lake, an artificial lake located in Sardinia (Western Mediterranean). In July 2024, we incubated a multi-trophic level plankton community (including picoplankton, nanoplankton, microplankton and mesoplankton) in laboratory for 15 days, applying two combined treatments in triplicates: a + 5°C water temperature increase and the presence/absence of mesozooplankton as apical predator. Temperature, dissolved oxygen, conductivity and pH were monitored daily, while water samples for analyses of algal nutrients, chlorophyll a, and the different biological planktonic components were collected every 3-4 days.

Preliminary results suggest significant taxonomical shifts in several planktonic trophic levels under warming, changing the predator-prey relationships in the community. In addition, the affirmation of potentially harmful cyanobacteria throughout the laboratory manipulation deserves particular attention in relation to the Bidighinzu Lake’s use for producing potable water, such as a lot of other Mediterranean artificial lakes.

This study provides new scientific insights on the heatwave effects on Mediterranean planktonic communities considering the entire planktonic trophic web, that are still very limited for freshwater environments.