IN: the chain that turns Atlantic Ocean conditions into sargassum seaweed blooms washing onto Caribbean and Mexican beaches - nutrient loading, bloom size, beach influx, marina and port fouling, cleanup and barrier operations, rotting-seaweed health effects, tourist arrivals, hotel occupancy and resort revenue, the hospitality and cruise companies exposed to it, AND the four business layers that profit from the blooms: (1) cleanup services - contractor demand, emergency and seasonal contracts, municipal and government cleanup budgets, equipment suppliers, barrier makers; (2) biomass processing - harvesting, treatment of salt and heavy-metal contamination, and valorization into fertilizer and ag inputs, biochar and carbon credits, biogas and biofuel, bioplastics and construction materials; (3) data and prediction services - bloom forecasting, monitoring subscriptions, early-warning products; (4) financial exposure - parametric insurance, remediation contract awards, budget shifts, and demand shifts that benefit unaffected destinations. OUT: open-ocean ecology unrelated to beach landfall, general climate-policy debate, single-name stock trading calls, and non-coastal tourism stories.