The typical definition of eutrophication is 'decrease in the levels of oxygen in the water bodies due to effects of excessive use of chemical fertilisers.' This statement clearly tells us all about the cause of the problem of eutrophication. Eutrophication is really a great threat to marine ecosystem an aesthetic value of a water body.
Cause of eutrophication:
The main cause of eutrophication is synthetic fertilisers. Synthetic fertilisers will indirectly decrease the level of oxygen in the water body. It happens in the following manner:
When synthetic fertilisers are used to fertilise the soil on the agricultural land, they usually remain in the soil and keep on showing their fertilising effect for a long time. Usually farmers of the developing countries are not well educated. They think that if they will put more fertilisers in the fields, the yield of the grains will be high. Actually, the plants absorb only that amount of the fertiliser that is needed by them. So the extra amount of the synthetic fertilisers that is put into the soil by the farmers remains in the soil.
Whenever heavy rain occurs, this extra synthetic fertiliser in the soil is washed away by the rain water and is deposited into local water bodies. Eutrophication is usually observed in ponds and lakes where the water is still. When this extra synthetic fertiliser reaches the water bodies, it will start the new process of growth of algae and aquatic plants in the water bodies. The algae and plants will grow in large number due to increased number of nutrients. Soon the whole surface of the lake or pond will be covered with the layer of algae and vegetation called 'algae-bloom'.
These algae will cover the surface of water and will reduce any interaction between the water and the atmosphere. Hence the oxygen and other gaseous levels cannot be kept in equilibrium with the air. Now, when the algae and water plants will die, they will be decomposed within the water body by the action of bacteria and fungus. These microbes will use the dissolved oxygen of the water body to decompose the plants and algae remains. This will result in the depletion in the oxygen concentration in the water. This condition of less oxygen usually persists for a long time and the aquatic body is literally 'dead'.
Effects of eutrophication:
There are many ill effects of eutrophication. These are:
What can be done?
The best way to reduce the instances of eutrophication is by reducing the use of synthetic fertilisers as much as possible. Farmers should be trained to use the fertilisers effectively without much loss. Use of natural ways of fertilising soil should be implemented. Some of these ways are using leguminous plants, crop rotation, mixed farming, etc.
The only way to ensure the theory of sustainable development is by controlled use of all the available resources. Synthetic fertilisers are derived from fossil fuels. Hence, the minimised use of synthetic fertilisers will ensure the safety of the deposits of fossil fuels as well.