Which nutrient is of highest concern regarding eutrophication?

Phosphorus is of highest concern regarding eutrophication because it is a key limiting nutrient in freshwater ecosystems. When phosphorus levels increase due to runoff from agricultural fields, wastewater discharges, or other anthropogenic sources, it can lead to excessive algal blooms. These blooms can deplete oxygen levels in the water, create dead zones, and disrupt aquatic ecosystems. The rapid growth of algae also contributes to the formation of harmful algal blooms, which can produce toxins that affect aquatic life and potentially harm human health.

In contrast, nitrogen, while also a nutrient that can contribute to eutrophication in some contexts, often requires an excess of phosphorus to trigger algal blooms in freshwater systems. Potassium and sulfur do not play significant roles in the process of eutrophication in aquatic environments. Therefore, phosphorus is specifically identified as the primary concern due to its direct association with the acceleration of this ecological issue.