Eutrophication (from Greek eutrophos, "well-nourished") is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients. It has also been defined as a "nutrient-induced increase in phytoplankton productivity". Water bodies with very low nutrient levels are termed oligotrophic and those with moderate nutrient levels are termed mesotrophic. Advanced eutrophication may also be referred to as dystrophic and hypertrophic conditions. Eutrophication in freshwater ecosystems is almost always caused by excess phosphorus.
