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.
A 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 weight the phosphorus and nitrogen. These values are added into an overall indicator.
To interpret the eutrophication indicator, it is important to realize that the background concentration of the nutrient is the baseline. A similar quantity of added phosphorus at one site may trigger a substantial increase in the level of nutrient, while remaining small at another site. Thus, the actual impact cannot be precisely predicted.
By adding phosphorus, which may affect only freshwaters, and nitrogen, which may affect only saline environments, the connection or relevance of the eutrophication emissions indicator to the environment where it is released is usually lost.
Additional investigation to better understand the environmental meaning of the indicator is suggested.
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.
A 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 weight the phosphorus and nitrogen. These values are added into an overall indicator.
To interpret the eutrophication indicator, it is important to realize that the background concentration of the nutrient is the baseline. A similar quantity of added phosphorus at one site may trigger a substantial increase in the level of nutrient, while remaining small at another site. Thus, the actual impact cannot be precisely predicted.
By adding phosphorus, which may affect only freshwaters, and nitrogen, which may affect only saline environments, the connection or relevance of the eutrophication emissions indicator to the environment where it is released is usually lost.
Additional investigation to better understand the environmental meaning of the indicator is suggested.