What is a primary environmental concern associated with phosphorus runoff?

The primary environmental concern associated with phosphorus runoff is water quality degradation leading to algal blooms. When phosphorus enters water bodies through runoff, it acts as a nutrient that fuels the excessive growth of algae, particularly in freshwater systems. This process, known as eutrophication, leads to harmful algal blooms, which can produce toxins harmful to aquatic life, wildlife, and even humans. Additionally, as these algal blooms die and decompose, they consume oxygen in the water, leading to hypoxic conditions that can suffocate fish and other aquatic organisms.

Understanding this relationship between phosphorus, nutrient loading, and water quality is crucial for effective nutrient management strategies aimed at preserving aquatic ecosystems and maintaining safe water supplies. The correct answer reflects a well-documented environmental challenge stemming from agricultural practices, urban runoff, and land management decisions.