Which nutrient is NOT associated with eutrophication?

Eutrophication is the process by which water bodies become overly enriched with nutrients, leading to excessive growth of algae and subsequent negative effects on aquatic ecosystems. The nutrients most commonly associated with this process are nitrogen and phosphorus, as they are often found in fertilizers and can wash into water systems from agricultural runoff.

Potassium, while essential for plant growth, does not typically contribute to eutrophication. It does not stimulate the same algal blooms that high levels of nitrogen and phosphorus do. Iron, on the other hand, is a micronutrient that can play a role in some aquatic systems, but it is not a primary contributor to eutrophication as it does not lead to the same explosive algae growth as the other two major nutrients.

Thus, potassium is the nutrient that is not associated with eutrophication, as it does not significantly promote the conditions that lead to these harmful algal blooms.