What are algal blooms?

Algal blooms refer to the rapid and excessive growth of algae in aquatic environments, often triggered by nutrient overload, particularly phosphorus and nitrogen. This phenomenon typically occurs in water bodies that receive an influx of these nutrients, which can come from sources such as agricultural runoff, wastewater discharge, or fertilizer leaching into streams and lakes.

During an algal bloom, the water can become discolored and may develop a scummy appearance, indicating a proliferation of algae. Some algal blooms can produce toxins harmful to aquatic life, animals, and even humans, leading to environmental and health concerns. Thus, the essence of the correct answer encapsulates both the process (rapid growth) and the cause (nutrient overload), which are central to understanding the nature and implications of algal blooms in ecosystems.