To increase the amount of elements, especially nitrogen and phosphorous, in a marine or aquatic ecosystem and the pollution from such sources as sewage effluent or leachate from fertilized fields causes a lake, or pond to become over-rich in organic and mineral nutrients, so that algae and cyanobacteria grow rapidly and deplete the oxygen supply: When water regions eutrophicate, they change in many ways: oxygen disappears from the deep places in water regions first.

When nutrients from the bottom are set free into the water, the process of elements eutrophicate and speed up and because the content of nutrients is rising, the alqae begins to bloom.

When these organic processes eutrophicate in water regions in their natural state, then biological multiplicity decreases, water regions become polluted, and the quality of the environment deteriorates.