(Left) Excess nitrogen and phosphorus deposits stimulate the growth of photosynthetic algae, resulting in a characteristic algal bloom. As the algae die off, organic material accumulates and decomposition levels increase, leading to severe hypoxia. These harsh conditions select for efficient anaerobic decomposers. The build-up of the waste product of anaerobic fermentation, carbon dioxide, results in an acidic environment. Ultimately, the severe conditions lead to the local extinction of native species and eventual irreversible ecosystem collapse. (Right) Even in the absence of external stimuli, cancer cells have a high proliferation rate, rapidly expanding to a tumor mass analogous to an algal bloom. As the tumor grows, it quickly outstrips its vascular supply, resulting in a hypoxic microenvironment. To survive, the cancer cells alter their metabolism to utilize relatively inefficient anaerobic glycolysis, exhausting available nutrient sources. The accumulation of lactic acid, the waste product of anaerobic glycolysis, results in an acidic microenvironment. Ultimately, the harsh “cancer swamp” selects for highly lethal cancer superclones. Simultaneously, the toxic conditions lead to increased rates of necrosis, extinction of native host cell types, and eventual organ failure. Oncotarget. 2015 Apr 30; 6(12): 9669–9678.