Cyanobacteria are photosynthetic microbes and keystone members of aquatic systems, yet in some cases they produce compounds that poison water supplies. The metabolic landscape for freshwater cyanobacteria is complicated. Cyanobacteria persist in environments where short-term changes in temperature, light, and nutrient availability vary during the summer as well as during episodic events (i.e., large storms). This variability leads to many issues for biology, including oxidative stress in photosynthetic organisms. We describe a multidisciplinary research program to quantify the mechanistic role of oxidative stress responses in a model cyanobacterium (Microcystis) to episodic events. Living cells cope with oxidative stress using multiple mechanisms: e.g., all use enzymes to degrade reactive oxygen, while some also employ biologically expensive secondary metabolites (for example, microcystins, which are dangerous liver toxins) for protection. Our goal is to quantitatively demonstrate how more biologically expensive but longer-term coping mechanisms (in this case microcystin) vs. short-term and cheaper strategies (peroxiredoxin enzymes) influence cyanobacteria strain succession and composition in lake communities. Using this data, we will update an existing mathematical model that predicts microcystin production from cell conditions and add a module that predicts growth response, microcystin production, and strain competition due to episodic events. The resulting model has implic