Introduction of eutrophication Eutrophicationis the immoderate growth of aquatic plant life due to the increase of inorganicions. Plant growth is usually stimulated when the environment is rich withinorganic ions that may come from the accidental pollution by untreated sewage,run-offs containing animal waste from farmlands into lakes, river or pond andleaching of inorganic fertiliser. Apart from human and animals activities,eutrophication can occur through natural process.Causes of eutrophication Eutrophication is mainlycaused by the immoderate use of inorganic fertiliser. These fertilisersused containing nitrate and phosphate from agricultural land will not all beabsorbed by the crops causing leaching of the fertilisers by rainwater into thesources of water such as rivers, streams, lakes, ponds and oceans. This causesthe increased in the nutrient content in the water.
Ions such as ammonium,nitrate and phosphate can booth the growth of aquatic plants like algae. Duringspring time, the rise in water temperature can also promote the growth of algaeand result in population explosion which is known as algal bloom. ( Figure 1.0shown in Appendices 1 ) they may grow to an extent that the surface of thewater is totally covered by the algae. This will causes the sunlight unable toreach the bottom of the pond.
The plants in the pond will not receivesufficient sunlight that will result in the decrease of the rate of photosynthesis.Thus, aquatic plants will die which leads to the decrease of the amount ofoxygen in the water. Saprotrophic aerobic bacteria will decompose the deadplants and the population of bacteria will increase in size. Consequently, thelimited oxygen in the water will be used up be the bacteria, causing the waterto become deoxygenated and increased in the biochemical oxygen demand, BOD.
This will result in the decaying anaerobic and the formation of hydrogen sulphide.Many of the aquatic plants and marine lives such as fish will die due to thelacking of oxygen and cannot tolerate hydrogen sulphide. Inthe extreme cases, oxygen level continues to drop and the water become completelydeoxygenated. Anaerobic bacteria will grow and release toxic gases such ashydrogen such as hydrogen sulphide. These gases cause the death of the fishes. Eutrophication causes bythe discharged of animal wastes from farmlands into rivers, streams, lakes,ponds and oceans will be the same as the leaching of inorganic fertilisers fromagricultural land.
On the other hand,eutrophication can happen under natural process besides from the activitiescarried out by human or animals. This natural process will take a much longertime to occur. In lowland ponds or lakes, the amount of dissolved nutrientswill increase steadily. In the opposite, the water of mountain lakes and thestreams that are in continuous motion will have a lower amount of dissolvenutrients. The lowland ponds or lakes will become shallow and shallow due tothe washing of sediments from the side of the ponds. In contrast, the side of thestreams is usually stony with poor soil, so the dissolve minerals are little inthe water and less or no aquatic life can be seen. The water would be clear andthe lake bed can be seen. This condition is called oligotrophic.
( Figure 1.1shown in Appendices 1 ) . In the lakes that undergo eutrophication, plants cangrown on the littoral areas when the lakes become shallow enough. As thisnatural process requires a long time to happen, it is also known as lake aging.( Figure 1.2 shown in Appendices 1 ) The natural eutrophication can be varieddue to the climate changes and geology.
