BLOOMTOX · Global change impacts on cyanobacterial bloom toxicity

Harmful cyanobacterial blooms produce toxins that are a major threat to water quality and human health. Blooms increase with eutrophication and are expected to be amplified by climate change. Yet, we lack a mechanistic understanding on the toxicity of blooms, and their response to the complex interplay of multiple global change factors. Bloom toxicity is determined by a combination of mechanisms acting at different ecological scales, ranging from cyanobacterial biomass accumulation in the ecosystem, to the dominance of toxic species in the community, contribution of toxic genotypes in the population, and the amounts of toxins in cells. I will develop a fundamental understanding of bloom toxicity by revealing the combined effects of nutrients, elevated pCO2 and warming at each scale, and integrate these responses using a unique combination of ecological theory, technological advances, and methodological innovations. Specifically, I will use first principles to scale from cellular traits, like carbon and nutrient acquisition, cellular toxin synthesis and growth rates, to population and community dynamics. To enable rapid assessment of numerous cyanobacterial traits, I will set-up a high-throughput flow-cytometry pipeline. Also, I will develop a novel lab-on-a-chip experimental platform to allow massive parallel screening of key competitive traits in various phytoplankton species and cyanobacterial genotypes. To scale from these cellular traits to population and community interactions, I will study genotype selection and interspecific resource competition in state-of-the-art chemostats. I will further scale-up to natural communities in the field and in large-scale indoor mesocosms to assess global change impacts on the mechanisms underlying toxicity of (near) real-life blooms. With this unique combination of scaling approaches, I will provide a breakthrough in our mechanistic understanding on the toxicity of cyanobacterial blooms, and their response to global change.