Eutrophication is an ecological process in which a water body becomes enriched with dissolved nutrients — primarily nitrogen and phosphorus compounds (often from agricultural runoff or sewage discharge).

This nutrient enrichment triggers explosive growth of algae and aquatic plants, known as an algal bloom. The bloom blocks sunlight, depletes dissolved oxygen as the algae decompose, and creates dead zones where aquatic life cannot survive.

Neutralisation of acidic water by minerals describes a buffering process — not eutrophication. Mixing of cold and warm ocean currents describes upwelling or thermohaline circulation. Accumulation of non-biodegradable chemicals at higher trophic levels describes biomagnification (or bioaccumulation), which is a separate phenomenon.

Hence, eutrophication is correctly described as the enrichment of water with nutrients leading to excessive algal growth.