Eutrophication

Hey, everybody, my post's pretty short, but I hope it covers everything we need to know!

Eutrophication refers to an excessive amount of nutrients in a body of water, usually caused by runoff of nutrients (mainly phosphorous in freshwater and nitrogen in saltwater) from the land, which causes a dense growth of plant life, leading to a decrease in oxygen supply, which causes the death of animals.

Causes:

n By man

        -Untreated sewage and agricultural run-off carrying fertilizers

n Natural

        -When nutrients accumulate as sedimentation or when they flow into water bodies for brief periods of time

Effects:

n excessive nutrients in water bodies promote plant growth and decay (mainly in algae and plankton) which leads to

o   a drop in water quality

o   disruption of the natural ecosystem

§  E.g. lack of oxygen for shellfish and marine life (causing a drop in their population). This happens because of algal shading, which is an effect of eutrophication that prevents marine plants from receiving enough sunlight to photosynthesize. The amount of dissolved oxygen thus decreases and many marine animals cannot survive (which is what is happening in the Barnegat Bay Watershed in the USA and the Baltic sea)

o   decrease in the recreational and aesthetic value of water bodies

o   health problems when it occurs in drinking water reserves

o   coral reef decline

§  coral reefs are important as they provide habitats for marine life (which much of the ecosystem depends on) and protect the shore from erosion by storm waves

§  however, they are the most nutrient-sensitive of all habitats, requiring the lowest external inputs to trigger eutrophication

§  this can lead to the death of coral reefs and thus endanger marine reef life

How does this relate to the nitrogen cycle?



Note the eutrophication on the right side occurs due to surface runoff





As mentioned above, one of the nutrients that can cause eutrophication is nitrogen. Therefore, too much nitrogen in the atmosphere can lead to more of it in surface runoffs which go in oceans. This causes eutrophication which leads to the death of marine life due to a decline of oxygen (brought about by excessive algal growth) as well as the death of coral reefs, which are crucial in preventing erosion on shores.

Done by: Chinmayi (: