Artificial eutrophication is where manmade or caused elements are added to water causing reactions like a decrease in oxygen or an increase in plankton. These reactions can be caused by materials in fertilizers, clear cutting of forest and detergents. Even the process of water treatment can ultimately cause eutrophication.
A key player in artificial eutrophication is phosphates. These can be found in fertilizer, runoff from farm, detergents and waste water that has not been fully treated. This can mean that all or a large part of the wildlife in lakes and rivers can be killed or the water become so contaminated that wildlife cannot drink from it and humans can have a hard time treating it to make it drinkable.