Why do toxic cyanobacteria bloom? A gene to ecosystem approach

This project aims to understand the ecological and evolutionary mechanisms triggering harmful cyanobacterial blooms (cyanoHABs) in lake ecosystems, and develop predictive models. We focus on bloom forming cyanobacteria (Oscillatoriales, Nostocales and Chroococcales) in temperate lakes and the production of known toxins and other bioactive metabolites. We are an interdisciplinary team of researchers in ecology, microbiology, environmental chemistry, and dynamical systems theory and together we focus on central questions about the mechanisms triggering cyanoHABs. We study the plankton seasonal progressions in a model lake (Greifensee, Switzerland) that has shown yearly occurrences of cyanoHABs. We test the relative importance and timing of different hypotheses of cyanoHAB drivers (water chemistry and physics, abundances of natural enemies and facilitative species). In parallel, we conductlaboratory experiments to estimate toxin production dynamics and fitness of cyanoHAB taxa relative to competitors in synthetically assembled communities, crossing community composition with environmental factors (e.g., temperature, nutrients, light, grazing). The range of important mechanisms will be constrained by data-analysis and modelling, and tested empirically by mesocosm experiments using natural lake plankton communities. The information acquired will be assimilated into data-driven models to forecast cyanoHABs, and integrated with previous knowledge to develop mechanistic models to predict the probability of cyanoHABs and associated communities based on fitness components and evolutionary strategies, under different environmental conditions (abiotic and biotic).