- Fertilisers contain nitrates and phosphates which are used to increase crop yield.
- Overuse of fertilizers leads to water pollution.
- Excess fertilisers are washed by rainwater into nearby rivers and lakes.
- Nitrates and phosphates encourage abundant growth of algae and water plants. These nitrates and phosphates are used in the synthesis of proteins and nucleic acids. Process is known as EUTROPHICATION.
- Overgrowth of algae and floating water plants prevent sunlight from reaching the submerged plants.
- Sunlight is unable to reach the submerged algae and water plants.
- Algae and water plants die and they are decomposed by aerobic bacteria and fungi.
- As the bacteria feed on the decaying organic matter, they grow and multiply rapidly, using up the oxygen in the water. This causes the death of fish and other organisms.
Some questions to think about.
1. Why is the water in the river green in colour?
2. Do you think the water in the river can support lifeform? Explain your answer.