What does the term "eutrophication" refer to in aquatic environments?

The term "eutrophication" specifically refers to a process in aquatic environments where there is excessive enrichment of nutrients, primarily nitrogen and phosphorus, leading to an overgrowth of algae and aquatic plants. This nutrient overload can result from various human activities such as agricultural runoff, wastewater discharge, and industrial pollution.

As these nutrients accumulate in the water, they promote algal blooms, which can deplete oxygen levels in the water when the algae die and decompose. This process negatively impacts water quality and can lead to hypoxic conditions, harming aquatic life, disrupting ecosystems, and degrading habitats. Therefore, the core issue associated with eutrophication is that it leads to the deterioration of water quality, making the first choice the most accurate definition of the term.

The other options describe processes that are contrary to the concept of eutrophication, such as reducing nutrient levels, improving ecosystems, or filtering water, none of which accurately encapsulate the effects of nutrient enrichment in aquatic environments.