American Water College Practice Test

The primary contributor to algae blooms in water bodies is the excessive amounts of phosphorus and nitrogen. These nutrients serve as fertilizers for algae, promoting rapid growth and proliferation in aquatic environments. When levels of phosphorus and nitrogen are elevated, often due to runoff from agricultural land, wastewater discharge, or other human activities, the result can be a dramatic increase in algae populations, leading to blooms.

These blooms can have significant ecological consequences as they may block sunlight from reaching other aquatic plants, disrupt the food chain, and lead to oxygen depletion in the water when the algae die and decompose. This process can create "dead zones" harmful to aquatic life.

While factors such as sedimentation, sunlight, and temperature can also influence algae growth, they do not primarily drive the occurrence of blooms as significantly as the nutrient levels do. Hence, phosphorus and nitrogen are key in determining the prevalence of algae blooms in water bodies.