The frequency, duration, and spatial extent of harmful algal blooms are expanding in aquatic ecosystems worldwide. This project focuses on the socio-environmental system of Lake Victoria, which is beset by cyanobacteria producing harmful algal blooms (cyanoHABs) that threaten the world’s largest lake fishery and the 30 million people it supports. Anthropogenic nutrient loading is driving cyanoHABs, which produce a toxin that accumulates in fish at levels far exceeding guidelines for safe consumption. By altering the base of the food web, cyanoHABs may also reduce the nutritional quality of fish. Fishers, consumers, and markets are expected to respond to awareness of cyanoHABs and nutritional tradeoffs among fish species in diverse ways. In turn, these responses are likely to drive feedbacks affecting the aquatic food web, spatiotemporal dynamics of cyanoHABs, and disparities in human health and wellbeing. We will integrate approaches from ecology, economics, sociology, toxicology, nutritional science, and public health to resolve the following questions: Environmental Change Impacts on the Natural System: (1) Do cyanoHABs affect fatty acid and toxin accumulation differently across fish species? Natural System Impacts on the Human System: (2) How do fishers understand and respond to cyanoHABs? (3) How do fish consumers understand and respond to cyanoHABs? Feedbacks from the Human to Natural System: (4) Do cyanoHABs and market prices redirect fishing effort between habitats? (5) Do human activities drive spatiotemporal variation in cyanoHABs and fish toxins? Socio-environmental System Modeling: (6) As the environment changes, how are impacts distributed across resource-dependent populations?