Which nutrient is primarily associated with eutrophication in water bodies?

Eutrophication is primarily driven by the influx of nutrients into water bodies, particularly phosphorus. This nutrient promotes excessive growth of algae and aquatic plants, leading to algal blooms. When these blooms die and decompose, the decomposition process depletes oxygen in the water, which can create dead zones where aquatic life cannot survive. While nitrogen also contributes to eutrophication, phosphorus is often the limiting nutrient in freshwaters, meaning its availability most directly influences the level of productivity and subsequent eutrophication.

In contrast, potassium and calcium do not significantly contribute to this process. Potassium is important for plant health but does not lead to the same over-enrichment issues as phosphorus. Calcium plays a vital role in various biological and chemical processes in aquatic systems but does not induce algal blooms like phosphorus does. Therefore, phosphorus is rightly identified as the primary nutrient associated with eutrophication.