Non-Point Source Pollution Envirothon Practice Test

Nutrient overload in water bodies triggers eutrophication, a process where excess nutrients—especially nitrogen and phosphorus—fuel rapid growth of algae and aquatic plants. This bloom can block sunlight and, more importantly, when the extra biomass dies, bacteria decompose it and use up dissolved oxygen in the water. In stratified systems, this oxygen depletion concentrates in deeper layers, creating hypoxic or anoxic conditions that form dead zones where most aquatic life cannot survive. So, the pollutant process most directly linked to dead zones from nutrient overload is eutrophication. Nutrient pollution describes the input of nutrients that starts the chain, but the actual driver of oxygen loss is the eutrophication process. Pathogens aren’t tied to oxygen depletion, and “major NPS pollutants” is a broad category rather than the process itself.