What is eutrophication?
Eutrophication is the term to describe an abundance of nutrients in a body of water.
Eutrophication is the term to describe an excessive amount of nutrients, phosphorous and nitrogen, in a body of water. This excess of nutrients causes an increase in plant and algae growth, which in turn depletes the available oxygen in the body of water. With less oxygen available, aquatic organisms die. These organisms then decompose, which in turn uses up even more of the available oxygen. If this process continues for long enough, the ecosystem can be entirely destroyed.
Eutrophication occurs when nutrients from human activities runoff and enter the environment. A main contributor is agriculture. Human activities have significantly increased the amount of nutrients passing into the environment.
You may want to see this related question on eutrophication and its causes in the Biology section.