Algal Bloom - Practice Questions & MCQ

• Human beings have been abusing the water-bodies around the world by using them for disposal of all kinds of waste.
• Due to such activities of human kind the ponds, lakes, stream, rivers, estuaries and oceans are becoming polluted in several parts of the world.
• Realising the importance of maintaining the cleanliness of the water bodies, the Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974 to safeguard our water resources.

Causes of Water Pollution

Domestic Sewage:

• A mere 0.1 percent impurities make domestic sewage unfit for human use.
• Domestic sewage primarily contains biodegradable organic matter, which readily decomposes – thanks to bacteria and other microorganisms, which can multiply using these organic substances as substrates and hence utilise some of the components of sewage.
• It is possible to estimate the amount of organic matter in sewage water by measuring Biochemical Oxygen Demand (BOD). 
• The given figure shows some of the changes that one may notice following discharge of sewage into a river. 
• Microorganisms involved in biodegradation of organic matter in the receiving water body consume a lot of oxygen, and as a result there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. 
• This causes mortality of fish and other aquatic creatures.

• Presence of large amounts of nutrients in waters also causes excessive growth of planktonic (free-floating) algae, called an algal bloom which imparts a distinct colour to the water bodies. 
• Algal blooms cause deterioration of the water quality and fish mortality. 
• Some bloom-forming algae are extremely toxic to human beings and animals.
• Sewage from our homes as well from hospitals are likely to contain many undesirable pathogenic microorganisms, and its disposal into a water without proper treatment may cause outbreak of serious diseases, such as, dysentery, typhoid, jaundice, cholera, etc