What is eutrophication associated with?

Eutrophication is a process that typically occurs in aquatic ecosystems, characterized by the excessive growth of algae and aquatic plants due to high nutrient levels, particularly nitrogen and phosphorus. The correct answer, which is associated with excessive plant growth and decay, highlights the key phenomenon of eutrophication.

As nutrient levels rise, usually as a result of agricultural runoff, waste discharge, or other human activities, it leads to an overabundance of nutrients in the water. This nutrient influx encourages the rapid growth of algae, resulting in algal blooms. When these algae eventually die and decompose, the decay process consumes significant amounts of oxygen in the water, leading to hypoxic conditions that can be detrimental to aquatic life. This decay phase is crucial in understanding the lifecycle of eutrophication, as it contributes to a cycle of growth and decline in plant populations and can ultimately deleteriously affect the entire aquatic ecosystem.

In contrast, improvements in water clarity would typically indicate a balanced ecosystem with low levels of nutrient loading, and an increase in fish populations would not occur alongside high levels of decay which deplete oxygen. Reducing nutrient levels could help mitigate eutrophication rather than being associated with the process itself. Thus, the characteristic of excessive plant growth and decay