What environmental condition is often necessary for the formation of algal blooms?

The formation of algal blooms is commonly associated with high nutrient levels in aquatic environments. When excess nutrients, particularly nitrogen and phosphorus, enter water bodies—typically from sources such as agricultural runoff, wastewater discharge, or nutrient-rich sediments—this nutrient enrichment can lead to rapid algal growth.

Algal blooms occur when conditions are favorable, and high nutrient levels provide the necessary ingredients for algae to proliferate quickly. These blooms can deplete oxygen in the water as the algae die and decompose, which can harm aquatic life. Therefore, the abundance of nutrients is the primary environmental condition that fosters the creation of algal blooms, making this option the most accurate in the context of the question.