In which process does a water body acquire high levels of nutrients, which is a prominent source of water pollution in agricultural areas?

Eutrophication

Explanation:

Eutrophication is referred to the process in which water bodies like lakes and rivers become excessively enriched with nutrients and minerals which cause the production of algae and plants in the lakes. This excessive growth of algae and plants uses enormous amount of oxygen that depletes other water living organisms do not get sufficient oxygen for their survival.  One example of eutrophication is the formation of algal blooms which worsen the water color and quality.

Pollution and Eutrophication:

Eutrophication was considered to be a pollution by many organizations like European and North American by the mid of 20th century. It is because many environmental problems arise from eutrophication like:

Therefore reducing eutrophication is an important concern for environmentalists nowadays.

when it is at an intermediate population density