What causes eutrophication?
The main causes of eutrophication are an increase in the concentration of nutrients in an ecosystem. A distinction is sometimes made between 'natural' and 'cultural' (anthropogenic) eutrophication processes. Natural eutrophication has been occurring for millennia. It is the process of addition of nutrients to water bodies, including lakes, rivers, estuaries and oceans resulting in changes to the primary production and species composition of the community. This process occurs over extended periods of time that are typically geological time scales. Cultural eutrophication is the process that speeds up natural eutrophication because of human activity. These activities come from many diverse sources including agriculture, aquaculture, septic tanks, urban wastewater, urban stormwater runoff, industry, and fossil fuel combustion. Nutrients such as phosphates and nitrates enter aquatic ecosystems via the air, surface water, or groundwater.
