The process by which a water body gradually becomes enriched with nutrients and minerals, mainly phosphorus and nitrogen, leading to enormous growth of algae on the surface of the water, thus decreasing the amount of dissolved oxygen in the water is known as:

Explanation

Eutrophication is an ecological phenomenon occurring when excess agricultural nutrients like nitrogen and phosphorus enter a water body, triggering explosive algal blooms that block sunlight and eventually deplete critical dissolved oxygen upon decomposition.