Think of a hot summer day. Imagine getting a glass of cold water, but no water is coming, or it is brownish with a foul odor. Imagine being a farmer, and your cattle need water but there is only smelly (blue-)green water. Imagine going for a cooling swim, but the lake is closed for recreation. For millions of people, this is not imagination, but a recurring reality caused by toxic cyanobacterial blooms. Scarcity of clean and healthy water is among the biggest societal challenges for the 21st century, listed as one of the United Nations Sustainable Development Goals (SDG2), and among the main concerns of the European Union. The quantity and quality of surface waters are declining at a high rate by increased societal demands and global environmental change. Notably, eutrophication may lead to harmful cyanobacterial blooms, which are expected to be further promoted by elevated pCO2 and warming. Although studies focusing on individual global change factors are relatively common, studies on combined stressors on harmful cyanobacterial blooms are remarkably rare. Importantly, harmful cyanobacteria produce toxins, which are the major cause of their threat to human health. Overall bloom toxicity is thus not only driven by the biomass of cyanobacteria, but also depends on the amounts and types of toxins produced by the dominant species and genotypes. The aim of this project is to mechanistically understand the processes underlying bloom toxicity, and their response to the complex interplay of multiple global change factors. It follows a unique approach crossing all scales that determine bloom toxicity, from cellular processes to ecosystem dynamics. The project will technologically scale from cell the ecosystem using a novel high-throughput flow-cytometry based multi-trait pipeline. It will experimentally scale from traits to population and community interactions using a novel lab-on-a-chip experimental platform for massive parallel screening of key traits, and state-of-the-art flat panel chemostat experiments. These experiments will provide the mechanisms underlying natural community dynamics that will be tested in microcosms, large-scale indoor mesocosms, and the field. Overall, being able to mechanistically scale from cells to the ecosystem will advance the ecological field, and by revealing key indicators that determine the toxicity of cyanobacterial blooms may support water management actions.
