Eutrophication refers to the process by which bodies of water become over-enriched with nutrients such as nitrogen and phosphorus. This occurs when agricultural run-off carrying fertilizers and sewage end up in coastal marine ecosystems through rivers and streams.
Excess nutrients cause simple plant organisms (e.g. algae) to grow in abundance. Once the algae die, large populations of bacteria decompose the algae, depleting the water of oxygen needed to support other marine life.
How Was It Measured?
IOLR nitrate mapping (August, 2011) out to 10 km was used to proxy nutrient status. The mean concentrations per district were compared to a background reference value. The trend was calculated as the change in annual nitrogen input from point sources.