What is the term for a rapid increase in the population of algae in a body of water?

The term for a rapid increase in the population of algae in a body of water is "algal bloom." This phenomenon typically occurs when there are high levels of nutrients, particularly nitrogen and phosphorus, in the water. These nutrients can come from various sources, such as agricultural runoff, sewage discharge, or other pollutants. During conditions favorable for algae growth, such as warm temperatures and ample sunlight, algae can reproduce quickly, leading to large, visible blooms.

Algal blooms can have significant ecological impacts, including reducing light penetration in the water, which can harm aquatic plants and disrupt the balance of aquatic ecosystems. Some algal blooms can also produce toxins harmful to fish, wildlife, and humans. This makes the understanding of algal blooms important for managing water quality and ecosystem health.

The other terms listed do not relate to the rapid increase of algae specifically. Pollution generally refers to the introduction of harmful substances into the environment, overgrowth can refer to many types of excessive growth in different organisms, and deforestation pertains to the clearing of trees, which is unrelated to aquatic algae populations.