Aquatic Pollution and Coastal Management

Unit 3 : Agricultural wastes and eutrophication

 

3.12.Eutrophication
Aquatic plants and algae gradually fill in freshwater lakes and estuaries over time in a natural process called eutrophication. This process is controlled by low concentrations of certain nutrients (like phosphate and nitrogen) that the plants and algae require to grow. Usually, phosphorus is the limiting nutrient in freshwater and nitrogen in estuaries and salt water. However, when humans release nutrients like phosphate (agriculture ~50%, human metabolism ~20%, industry ~10%, detergents ~10% and natural erosion ~10%), the process of eutrophication is accelerated. In a worst-case scenario, the excess growth of plants and algae can smother other organisms when they die and begin to decay. An eutrophication indictor is derived by converting the different chemical forms of phosphorus and nitrogen into a common or equivalent form. Then, the proportion normally found in aquatic algae is used to weigh the phosphorus and nitrogen. These values are added into an overall indicator.