eutrophication, definition of

Enrichment of water, which causes excessive growth of aquatic plants and increasing activity of anaerobic microrganisms. As a result the oxygen levels in the water quickly decline and the water chokes, making life impossible for aerobic water organisms.

• Water-purifying park could save the heart of Helsinki from turning into a swamp
  Töölönlahti Bay suffers from eutrophication, an over-enrichment of water by nutrients commonly caused by fertilizers and factory runoff, starting in the 1800s and persisting to this day due to low water circulation levels...