Eutrophication can be caused by many reasons
Eutrophication can be caused by many reasons. One of them is the leaching of inorganic fertilizers, especially nitrogen and phosphorus from agricultural lands. Farmers are more keen in carrying out agricultural activities nearby the pond or lake. This is because it will be easier for them in terms of water source. Carrying out activities nearby the pond and lake provides the crops with constant water supply thus leading to healthy growth of the crops.
Besides that one of the main reasons is due to input of untreated sewage as well as discharge from sewage treatment plants. This might be due to irresponsible human activity whom are careless and not treating the wastes before letting it flow into the river. This causes enrichment of nutrients in water and therefore causing eutrophication to occur. On the other hand, another main factor is due to the run-offs containing animal wastes from pastures and farmlands into nearby water bodies such as lakes, rivers and also ponds. Animal wastes and agricultural wastes have a large amount of nutrient in them. This causes the water to be rich in nutrients when this wastes is let to flow to the water. These are the main causes of eutrophication.
Draining of excess nutrients from fertilizers and agricultural waste into nearby ponds, lakes and rivers leads to rapid growth of algae and phytoplankton. This is due to increased amount of nutrients in the water, causing these organisms to reproduce. This will further result in a condition known as algal bloom. Algal bloom is a condition where the surface of water is enriched with algae, thus preventing sunlight from penetrating into the water. As a result, aquatic plants will not have sunlight to photosynthesize and therefore they will die.
The products of photosynthesis are glucose and oxygen. When the plans fail to carry out photosynthesis , oxygen will not be produced and therefore oxygen level in the water will be reduced greatly. The dead aquatic plants will undergo decomposition with the aid of aerobic bacteria. This will further cause the amount of oxygen to reduce to a much lower level. When the oxygen content decreases, this will increase the Biochemical Oxygen Demand (BOD) level in the water. Biochemical Oxygen Demand (BOD) refers to the amount of oxygen that is utilized when organic matter in one litre of water is oxidized by living organisms in the water. The level of Biochemical Oxygen Demand can be tested by using methylene blue solution. This solution measures the degree of pollution in a given water sample. When the BOD level is high, the degree of pollution of the given sample is also high.