Water pollution occurs when there are harmful changes to water quality from chemicals, biology, or physics that affect living organisms or make water unsuitable for intended uses. Eutrophication is a natural process where an aquatic ecosystem becomes enriched with nutrients, causing excessive growth of plants. Nutrients come from sources like fertilizers, sewage, and runoff. Increased nutrients promote rapid algae growth, which can block sunlight and reduce oxygen levels in the water. This harms ecosystems, food chains, and increases biochemical oxygen demand, further polluting the water.

1. Biology Form 4 Chapter 9 Title: Water Pollution and Eutrophication Group Member: Lai FookChern Ling Sung Eng Wong Yueh Kai

3. Table of Sources, pollutants, and effects of water pollution

6. Addition of oil destroys life by reducing oxygen and catching fine, destroying ecosystem.

7. Reduced reproduction rate of animals.

8. Increased incidence of diseases.

9. Imbalances created in secondary food chains

11. Eutrophication

13. Sewage treatment plant discharges.

15. Algal blooms endanger the ecosystem in 2main ways. 1, The densely populated algae cover the water surface and block sunlight. Unable to carry out photosynthesis, the aquatic plants die. When these plants die, aquatic animals lose their food sources and habitats. As a result, the food chain and ecosystem change. Algae also reduce the level of dissolved oxygen in the water. 2, When the algae and other aquatic organisms die, decomposing organisms especially saprophytic bacteria use up oxygen to decompose the dead organic materials. This reduce the oxygen content in the water.

16. A depletion in oxygen results in an increase in biochemical oxygen demand (BOD). Eutrophication increase the BOD value in the water. BOD refers to the amount of oxygen utilised by microogranisms to oxidise all organic matter in one litre of water. The higher the BOD value, the more polluted the water as the dissolved oxygen level decrease.

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