What is the primary source of nutrients that can cause algal blooms in surface waters?

The primary source of nutrients that can lead to algal blooms in surface waters is agricultural runoff containing fertilizers. Fertilizers, particularly those rich in nitrogen and phosphorus, are commonly used in agriculture to enhance crop growth. When it rains, excess fertilizers can wash off fields into nearby streams, rivers, and lakes, significantly increasing the nutrient levels in these water bodies.

This nutrient enrichment creates favorable conditions for certain types of algae to grow rapidly, leading to algal blooms. These blooms can deplete oxygen in the water, block sunlight, and release toxins that can be harmful to aquatic life and human health. The connection between agricultural practices and nutrient loading into surface waters highlights the importance of best management practices in agriculture to mitigate these environmental impacts.

While other sources like industrial waste, urban development, and wildlife waste can contribute to nutrient pollution, agricultural runoff is widely recognized as the most significant contributor to nutrient loading that results in algal blooms.