Eutrophication is the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.)

  • The nutrients can be introduced via leaching from soil by rainfall or released as part of sewage
  • Eutrophication is common around agricultural lands where the use of artificial fertilisers are prevalent

An increase in nutrient supply within waterways will result in several ecological consequences:

  • A rapid growth in algal populations will occur (algal blooms) as a result of the increased availability of nutrients
  • As the algae die, there will be a subsequent spike in the numbers of saprotrophic microbes (decomposers)
  • The high rate of decomposition will result in an increased biochemical oxygen demand (BOD) by saprotrophic bacteria
  • The saprotrophs will consume available quantities of dissolved oxygen, leading to deoxygenation of the water supply
  • Eutrophication will also increase the turbidity of the water, which will reduce oxygen production by photosynthetic seaweeds
  • This will stress the survival of marine organisms, potentially leading to a reduction in biodiversity within the ecosystem