What is the process called when excess nutrients lead to algal blooms in water bodies?

The process where excess nutrients, particularly nitrogen and phosphorus, lead to algal blooms in water bodies is known as eutrophication. This phenomenon occurs when runoff from agricultural lands, urban areas, or other sources carries these nutrients into lakes, rivers, and coastal waters. The influx of nutrients stimulates the rapid growth of algae, resulting in dense blooms.

As these algae grow and then die off, their decomposition can deplete oxygen in the water, leading to hypoxic conditions that are detrimental to aquatic life. Eutrophication can significantly disrupt aquatic ecosystems, leading to reduced biodiversity and alter the quality of the water.

In contrast, the other terms listed describe different processes. Oligotrophication refers to the process where water bodies become less nutrient-rich, supporting fewer plants and animals. Thermal stratification is the layering of water in a lake due to temperature differences, and acidification refers to the decrease in pH levels in water bodies, usually due to pollutants like sulfur dioxide or carbon dioxide. These concepts are important in the context of freshwater ecosystems but do not relate to the nutrient-induced algal blooms associated with eutrophication.