Nutrient input is the addition of nutrients like nitrogen and phosphorus into ecosystems from both natural sources, such as decomposing organic matter, and human activities, such as fertilizer runoff and animal waste. When excess nutrients enter aquatic environments, they can cause eutrophication—an overgrowth of aquatic plants and algae that depletes oxygen levels in the water, ultimately leading to the formation of oxygen-deprived “dead zones” harmful to aquatic life. You can learn more about the causes, impacts, and solutions to Nutrient Input in the below resources!