Eutrophication

The process of enrichment of water bodies by nutrients. Eutrophication of a lake normally contributes to its slow evolution into a bog or marsh and ultimately to dry land. Eutrophication may be accelerated by human activities, thereby speeding up the aging process.

The natural aging of a lake or landlocked body of water, which results in organic material being produced in abundance due to a ready supply of nutrients accumulated over the years.


Source: Handbook of water and wastewater treatment plant operations

Wikipedia:  https://en.wikipedia.org/wiki/Eutrophication