What phenomenon is eutrophication primarily associated with?

Eutrophication is primarily associated with the excessive enrichment of water bodies with nutrients, particularly nitrogen and phosphorus. This often occurs due to agricultural runoff, wastewater discharge, and other human activities that introduce high levels of these nutrients into lakes, rivers, and coastal areas.

When the nutrient levels are elevated, it leads to an overgrowth of algae, which can create algal blooms. These blooms can have detrimental effects on water quality and aquatic life. As the algae die and decompose, the oxygen levels in the water can drop significantly, leading to hypoxic or anoxic conditions, which can harm or kill fish and other aquatic organisms.

Thus, the phenomenon of eutrophication is fundamentally linked to the excessive nutrient enrichment of water systems, explaining why this choice is the correct answer.